The last stargazers

Emily Levesque is a professor in the University of Washington’s astronomy department. Her research program is focused on improving our overall understanding of how massive stars evolve and die.

Her first popular science book, The Last Stargazers, shares the tales and experiences of astronomical observing and comes out on August 4th, 2020! She has also written two academic books: a professional text on red supergiants and a graduate textbook on stellar interiors and evolution written with co-author Henny J. G. L. M. Lamers.

Professor Levesque is the recipient of the 2020 Newton Lacy Pierce prize and the 2014 Annie Jump Cannon award from the American Astronomical Society. She is a 2019 Cottrell Scholar and a 2017 Alfred P. Sloan Research Fellow. From 2010 to 2015 she was a postdoctoral fellow at the University of Colorado at Boulder. She received her astronomy PhD at University of Hawaii in 2010 and her S.B. in physics from MIT in 2006.

https://en.wikipedia.org/wiki/Emily_Levesque

https://depts.washington.edu/astron/profile/levesque-emily/

https://twitter.com/emsque?ref_src=twsrc%5Egoogle%7Ctwcamp%5Eserp%7Ctwgr%5Eauthor

https://www.emlevesque.com/

Introduction

Astronomers journey to some of the most inaccessible parts of the globe while handling equipment worth millions. It is a life of unique delights and absurdities, and one that may be drawing to a close. Soon it will be the robots, not humans, gazing at the sky while we are left to sift through the data.

In this talk, Emily Levesque revealed the hidden world of the professional astronomer. She celebrated an era of ingenuity and curiosity, and asked us to think twice before we cast aside our sense of wonder at the universe.

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The following are notes from the on-line lecture. Even though I could stop the video and go back over things there are likely to be mistakes because I haven’t heard things correctly or not understood them. I hope Professor Levesque and my readers will forgive any mistakes and let me know what I got wrong.

Professor Levesque explained that she wrote her book to give a behind the scenes look at what it is like to be a professional astronomer.

Being new to public science publishing her research told her that the first line of books is very important. So she started her talk by explaining why the first line of her book is “Have you tried turning it off and then on again”. She realised that this would disappoint a lot of people, but it actually refers to something that happened to her when she was doing her PhD.

The time spent on a telescope is just as precious to an astronomer as the money required to fund the studies etc. and Professor Levesque was given one precious night on the Subaru telescope, Mauna Kea Hawaii.

https://subarutelescope.org/en/

https://en.wikipedia.org/wiki/Subaru_Telescope

Subaru Telescope is the 8.2-meter flagship telescope of the National Astronomical Observatory of Japan, located at the Mauna Kea Observatory on Hawaii. It is named after the open star cluster known in English as the Pleiades. It had the largest monolithic primary mirror in the world from its commissioning until 2005 (the largest single piece of glass at that time) and is one of the largest telescopes in the world.

http://www-astro.physics.ox.ac.uk/~pfr/ObsTech/ObsTech5_Tel.pdf

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https://en.wikipedia.org/wiki/Nasmyth_telescope

Most modern research telescopes can be configured into a Nasmyth telescope (i.e. to use the “Nasmyth Focus”).

The telescope and observatory is run by a collaboration of the USA, Japan and other partners.

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Perched at the summit of a dormant volcano on the big island of Hawaii, the Subaru Observatory (left) sits alongside the twin Keck enclosures. Photo credit: National Astronomical Observatory of Japan

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https://twitter.com/SubaruTel_Eng

The size of its primary miror is the most important part of a telescope. It is responsible for focusing light, via the secondary, onto the camera, which then produces the image.

https://en.wikipedia.org/wiki/Primary_mirror

The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective metal (speculum metal up to the mid 19th century), or in later telescopes, glass or other material coated with a reflective layer.

https://twitter.com/astrotweeps/status/1285263534306156546/photo/2

To give some idea of the size of a primary mirror the image below shows professor Levesque standing below the primary mirror of the Gemini Telescope, in Cerro Pachon, Chile

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http://www.gemini.edu/public/pachon.html

https://en.wikipedia.org/wiki/Gemini_Observatory

The Gemini Observatory is an astronomical observatory consisting of two 8.1-metre telescopes, Gemini North and Gemini South, which are located at two separate sites in Hawaii and Chile, respectively. The twin Gemini telescopes provide almost complete coverage of both the northern and southern skies. They are currently among the largest and most advanced optical/infrared telescopes available to astronomers.

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Gemini South in Chile

During her PhD studies professor Levesque needed to use the Subaru telescope to look at distant galaxies where stars had died and formed black holes. She wanted to know how these stars worked and how they died.

In the middle of the night, as a 24-year-old, she heard this warning beep. She asked the person assisting her when the telescope “froze” what does it mean”. The person said “don’t worry the mirror is still on the telescope”. She didn’t realise that not having a mirror was an option.

The primary mirror sits at the bottom of the telescope and suspended high above it is the secondary mirror. It is the secondary mirror that will reflect light from the primary mirror to the camera.

https://en.wikipedia.org/wiki/Cassegrain_reflector

A Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, the main characteristic being that the optical path folds back onto itself, relative to the optical system’s primary mirror entrance aperture. This design puts the focal point at a convenient location behind the primary mirror and the convex secondary adds a telephoto effect creating a much longer focal length in a mechanically short system.

Below is a simple version of a Cassegrain telescope because the Subaru telescope instruments can be mounted at a Cassegrain focus. A camera would be placed at the focal point.

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https://www.astro.caltech.edu/palomar/about/telescopes/hale.html

The secondary mirror is a lot smaller than the primary – about 1m across.

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https://www.naoj.org/jp/about/

https://www.naoj.org/jp/about/features/8.html

The primary has a mass of 22.8 tonnes and the secondary has a mass of around 0.18 tonnes. The secondary is suspended just over 22m above the primary.

It was the secondary mirror that might still be on the telescope.

It was found that some of the supports holding up the secondary had failed and there was a danger that the secondary could fall down onto the primary.

There is an infamous story about the Green Bank telescope

https://en.wikipedia.org/wiki/Green_Bank_Telescope

The Robert C. Byrd Green Bank Telescope (GBT) in Green Bank, West Virginia, US is the world’s largest fully steerable radio telescope. The Green Bank site was part of the National Radio Astronomy Observatory (NRAO) until September 30, 2016. Since October 1, 2016, the telescope has been operated by the independent Green Bank Observatory. The telescope’s name honours the late Senator Robert C. Byrd who represented West Virginia and who pushed the funding of the telescope through Congress.

The telescope began regular science operations in 2001, making it one of the newest astronomical facilities of the US National Science Foundation (NSF). It was constructed following the collapse of a previous telescope at Green Bank, a 90.44 m paraboloid that began observations in October 1961. The previous telescope collapsed on 15 November 1988 due to the sudden loss of a gusset plate in the box girder assembly, which was a key component for the structural integrity of the telescope.

https://public.nrao.edu/gallery/the-collapsed-300foot-telescope/

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https://www.radarpages.co.uk/news/newsimages/300ftbefore.jpg (above left)

https://www.radarpages.co.uk/news/newsimages/300ftafter.jpg (above right)

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The wreckage close up.

At the time it was the biggest telescope in the world, just over 92m from end to end. On the 15th November 1988 it simply collapsed. Luckily nobody was hurt.

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Now professor Levesque was sitting at the top of the observatory knowing she could potentially drop the secondary wondering “what do I do?” How can you plan for something like this? She contacted technical support, who said “have you tried turning it off and on again”.

“Is this actually going to fix the problem? Am I going to lose the data for my thesis?”

Professor Levesque used this story to illustrate what doing professional astronomy is actually like.

People generally love astronomy because of the lovely pictures from the Hubble telescope but they don’t actually know what astronomers actually do. They have no idea of the work that goes into producing the wonderful images.

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Pretty pictures from the Hubble telescope

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The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versatile, well known both as a vital research tool and as a public relations boon for astronomy. The Hubble telescope is named after astronomer Edwin Hubble and is one of NASA’s Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope.

If you ask people what a typical astronomer looks like they would probably describe a man, with a beard, wearing a lab coat, standing next to a little telescope. They are either making notes or looking through a telescope.

Amateur astronomers do spend time looking through relatively little telescopes. Back-yard astronomy,

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I used to teach in an all-girls school and I often got the year 7s (age 11-12) to draw what they thought a scientist looked like. They inevitably drew a man with a beard, wearing a lab-coat.

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The photo above left is a 6-year-old professor Levesque (wearing a NASA T-shirt with a Hubble telescope image). She knew at this young age that she wanted to work in astronomy/space. But she had no actual idea of what the life of an astronomer was actually like. Her understanding of what scientists did came from films. Courtesy of Emily Levesque

https://en.wikipedia.org/wiki/Twister_(1996_film)

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Twister is a 1996 American disaster film directed by Jan de Bont from a screenplay by Michael Crichton and Anne-Marie Martin. Its executive producers were Steven Spielberg, Walter Parkes, Laurie MacDonald and Gerald R. Molen. The film stars Helen Hunt, Bill Paxton, Jami Gertz and Cary Elwes, and depicts a group of storm chasers researching tornadoes during a severe outbreak in Oklahoma.

https://en.wikipedia.org/wiki/Contact_(1997_American_film)

Contact is a 1997 American science fiction drama film directed by Robert Zemeckis. It is a film adaptation of Carl Sagan’s 1985 novel of the same name; Sagan and his wife Ann Druyan wrote the story outline for the film. Jodie Foster portrays the film’s protagonist, Dr. Eleanor “Ellie” Arroway, a SETI scientist who finds strong evidence of extraterrestrial life and is chosen to make first contact.

https://en.wikipedia.org/wiki/Jurassic_Park_(film)

Jurassic Park is a 1993 American science fiction adventure film directed by Steven Spielberg and produced by Kathleen Kennedy and Gerald R. Molen. It is the first installment in the Jurassic Park franchise, and is based on the 1990 novel of the same name by Michael Crichton and a screenplay written by Crichton and David Koepp. The film is set on the fictional island of Isla Nublar, located off Central America’s Pacific Coast near Costa Rica. There, wealthy businessman John Hammond and a team of genetic scientists have created a wildlife park of de-extinct dinosaurs. When industrial sabotage leads to a catastrophic shutdown of the park’s power facilities and security precautions, a small group of visitors and Hammond’s grandchildren struggle to survive and escape the perilous island.

Professor Levesque didn’t know any astronomers growing up which is not surprising considering that out of the world’s population there are only about 50000 of them.

Things didn’t really change until her sophomore year at college when she had the chance to go on her first professional observing trip.

https://en.wikipedia.org/wiki/Sophomore

The term sophomore is used to refer to a student in the second year of college or university studies in the United States; typically, a college sophomore is 19 to 20 years old. In the United States, college sophomores are advised to begin thinking of career options and to get involved in volunteering or social organizations on or near campus.

https://www.noao.edu/kpno/

Professor Levesque’s first observing trip took place at the Kitt Peak National Observatory, Arizona.

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https://en.wikipedia.org/wiki/Kitt_Peak_National_Observatory

The Kitt Peak National Observatory (KPNO) is a United States astronomical observatory located on Kitt Peak of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers west-southwest of Tucson, Arizona. With over twenty optical and two radio telescopes, it is one of the largest gatherings of astronomical instruments in the northern hemisphere.

Kitt Peak National Observatory was founded in 1958. It was home to what was the largest solar telescope in the world, and many large astronomical telescopes of the late 20th century in the United States.

The observatory was administered by the National Optical Astronomy Observatory (NOAO) from the early 1980s until 2019, after which it was overseen by the National Optical-Infrared Astronomy Research Laboratory.

Being at the Kitt Peak Observatory was Professor Levesque’s first chance to see what an observatory was like. Every dome held a telescope. Different sizes for different jobs.

She was given advice by the people there, such as how to stay awake at night. She got to hear stories about unfortunate astronomers, what it was like if you are in a dome when it is struck by lightning.

One story was about an astronomer who got locked in the bathroom.

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Lightning striking an observatory

Another story was about the telescope that got shot.

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The astronomers were introducing her to the life of an astronomer by telling the stories and she wanted to make some of her own.

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The far right picture above is the voice recorder that Professor Levesque used to record her own storie sand the interviews she had with her colleagues and other astronomers. She interviewed over one hundred astronomers to record their experiences for her book, which gives people a behind the scenes look at the life of a professional astronomer.

The books starts by explaining how astronomy started and how it is changing.

It tells the reader about the science and excitement of the astronomers’ discoveries and is built round the stories and adventures of her colleagues.

The astronomers were asked three questions

1) What would surprise people the most about our jobs?

2) What’s your most memorable second/third/tenth-hand observing story?

3) How has astronomy changed since you began observing?

The answers

1) “We don’t look through eye pieces anymore”

It hasn’t been an astronomer’s job for a very long time. Professional astronomers now use cameras to gather data and the nature of cameras has changed dramatically over the years.

They capture what the astronomers want to look at and allow them to analyse the image at a later date.

On occasions astronomers do look through the eyepiece of telescope for recreational purposes.

On one such occasion Professor Levesque was excited to spot Saturn using a small telescope with 1m diameter mirror

https://en.wikipedia.org/wiki/Saturn

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Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine times that of Earth. It only has one-eighth the average density of Earth; however, with its larger volume, Saturn is over 95 times more massive.

She was also able to see eta Carinae

https://en.wikipedia.org/wiki/Eta_Carinae

Eta Carinae (η Carinae, abbreviated to η Car), formerly known as Eta Argus, is a stellar system containing at least two stars with a combined luminosity greater than five million times that of the Sun, located around 7,500 light-years (2,300 parsecs) distant in the constellation Carina. Previously a 4th-magnitude star, it brightened in 1837 to become brighter than Rigel, marking the start of its so-called “Great Eruption”. It became the second-brightest star in the sky between 11 and 14 March 1843 before fading well below naked eye visibility after 1856. In a smaller eruption, it reached 6th magnitude in 1892 before fading again. It has brightened consistently since about 1940, becoming brighter than magnitude 4.5 by 2014.

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(NASA News Release) A huge, billowing pair of gas and dust clouds are captured in this stunning NASA Hubble Space Telescope image of the supermassive star Eta Carinae. Using a combination of image processing techniques (dithering, subsampling and deconvolution), astronomers created one of the highest resolution images of an extended object ever produced by Hubble Space Telescope. The resulting picture reveals astonishing detail. Even though Eta Carinae is more than 8,000 light-years away, structures only 10 billion miles across (about the diameter of our solar system) can be distinguished. Dust lanes, tiny condensations, and strange radial streaks all appear with unprecedented clarity. Eta Carinae was observed by Hubble in September 1995 with the Wide Field Planetary Camera 2 (WFPC2). Images taken through red and near-ultraviolet filters were subsequently combined to produce the colour image shown. A sequence of eight exposures was necessary to cover the object’s huge dynamic range: the outer ejecta blobs are 100,000 times fainter than the brilliant central star. Eta Carinae was the site of a giant outburst about 150 years ago, when it became one of the brightest stars in the southern sky. Though the star released as much visible light as a supernova explosion, it survived the outburst. Somehow, the explosion produced two polar lobes and a large thin equatorial disk, all moving outward at about 1.5 million miles per hour. The new observation shows that excess violet light escapes along the equatorial plane between the bipolar lobes. Apparently, there is relatively little dusty debris between the lobes down by the star; most of the blue light is able to escape. The lobes, on the other hand, contain large amounts of dust which preferentially absorb blue light, causing the lobes to appear reddish. Estimated to be 100 times more massive than our Sun, Eta Carinae may be one of the most massive stars in our Galaxy. It radiates about five million times more power than our Sun. The star remains one of the great mysteries of stellar astronomy, and the new Hubble images raise further puzzles. Eventually, this star’s outburst may provide unique clues to other, more modest stellar bipolar explosions and to hydrodynamic flows from stars in general.

This is a much more massive star than our Sun, maybe 100 times more massive. When viewed it was still “alive” even though the vapour around it indicated it wasn’t. It had “exploded”

This star has puffed out a lot of vapour during its life and astronomers still don’t understand why?

Through the telescope you can see the star through the plumes. It looks red because of glowing hydrogen at the edge of the star.

Images had been taken by the Hubble telescope and cameras but Professor Levesque was very excited to see it herself.

In the first half of the 20th century photographic plates were used to record astronomical images.

https://en.wikipedia.org/wiki/Photographic_plate

Photographic plates preceded photographic film as a capture medium in photography, and were still used in some communities up until the late 20th century. The light-sensitive emulsion of silver salts (silver nitrate solution) was coated on one side of a glass plate, typically thinner than common window glass, instead of a clear plastic film.

https://www.smithsonianmag.com/science-nature/obsolete-art-mapping-skies-glass-plates-can-still-teach-us-180971890/

Silver nitrate darkens when illuminated with visible light.

http://www.royalobservatorygreenwich.org/articles.php?article=1057

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The Astrographic Telescope at Herstmonceux with the Markowitz Moon camera fitted at the breach end. Taken prior to 11 January 1961, the photo also shows the Astrographic’s own plate carrier on the floor by the wall (left). Humphry Smith Photographic Archive

This reflecting telescope is a camera, imaging directly onto glass photographic plates.

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A photographic plate of the 1919 total solar eclipse, taken by Andrew Claude de la Cherois Crommelin and Charles Rundle Davidson during an expedition to Sobral, Brazil. The 1919 eclipse was used by Arthur Eddington, who observed it from the island of Principe off the west coast of Africa, to provide the first experimental evidence of Einstein’s theory of relativity. (Niels Bohr Institute, University of Copenhagen)

Setting up the photographic plates was easier said than done. The glass arrived in a large block and had to be cut to fit the holder for the telescope’s camera.

Baking the plates could speed up the silver nitrate reaction a bit, as could freezing them, rubbing them with lemon juice or bathing them in ammonia. One observatory used hydrogen gas.

Loading the plates had to be done in complete darkness. The astronomers then needed to sit up all night to get the images they wanted then they needed to be able to develop the plates in complete darkness too.

It wasn’t a very comfortable process. Below is an image of Ewin Hubble sitting inside the telescope just in front of the prime focus (primary mirror). The camera was there to collect light from the primary mirror.

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Hubble in the observer’s cage located at the top of the tube of the 200-inch telescope on Palomar Mountain. Astronomers can sit in the cage with their photographic plates to collect light reflected up from the main mirror 55 feet below (American’s don’t seem to like metric). Alternatively, collected light can be directed out of the telescope to a more convenient place, but with loss of light for each additional reflection from a mirror redirecting the light. Image courtesy Mount Wilson and Palomar Observatories.

https://en.wikipedia.org/wiki/Edwin_Hubble

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Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer. He played a crucial role in establishing the fields of extragalactic astronomy and observational cosmology.

You can do a lot of observations from these photographic plates.

In 1912 Henrietta Swan Leavitt worked with glass plates to investigate variable stars, known as Cepheid variables.

https://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt

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Henrietta Swan Leavitt (July 4, 1868 – December 12, 1921) was an American astronomer. A graduate of Radcliffe College, she worked at the Harvard College Observatory as a “computer”, tasked with examining photographic plates in order to measure and catalogue the brightness of stars. This work led her to discover the relation between the luminosity and the period of Cepheid variables. Leavitt’s discovery provided astronomers with the first “standard candle” with which to measure the distance to faraway galaxies

https://en.wikipedia.org/wiki/Cepheid_variable

A Cepheid variable is a type of star that pulsates radially, varying in both diameter and temperature and producing changes in brightness with a well-defined stable period and amplitude.

https://courses.lumenlearning.com/astronomy/chapter/variable-stars-one-key-to-cosmic-distances/

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This light curve shows how the brightness changes with time for a typical Cepheid variable, with a period of about 6 days.

Henrietta worked out that the brighter the stars were, the longer the cycle of intensity. This meant that working out the time for the cycle would indicate the brightness of the star. This proves very useful if a bright star appears dim (a consequence of increasing distance or the presence of materials that could absorb light between the star and Earth)

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How to Use a Cepheid to Measure Distance. (a) Find a cepheid variable star and measure its period. (b) Use the period-luminosity relation to calculate the star’s luminosity. (c) Measure the star’s apparent brightness. (d) Compare the luminosity with the apparent brightness to calculate the distance.

https://en.wikipedia.org/wiki/Period-luminosity_relation

In astronomy, a period-luminosity relation is a relationship linking the luminosity of pulsating variable stars with their pulsation period. The best-known relation is the direct proportionality law holding for Classical Cepheid variables, sometimes called Leavitt’s law. Discovered in 1908 by Henrietta Swan Leavitt, the relation established Cepheids as foundational indicators of cosmic benchmarks for scaling galactic and extragalactic distances. The physical model explaining the Leavitt’s law for classical cepheids is called kappa mechanism.

https://en.wikipedia.org/wiki/Kappa%E2%80%93mechanism

The kappa opacity mechanism is the driving mechanism behind the changes in luminosity of many types of pulsating variable stars.

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Above left: Period-Luminosity Relation for Cepheid Variables. In this class of variable stars, the time the star takes to go through a cycle of luminosity changes is related to the average luminosity of the star. Also shown are the period and luminosity for RR Lyrae stars. Above right: Period-Luminosity relation for Classical Cepheid variables

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Plot from Leavitt’s 1912 paper. The horizontal axis is the logarithm of the period of the corresponding Cepheid, and the vertical axis is its apparent magnitude. The lines drawn correspond to the stars’ minimum and maximum brightness, respectively.

Luminosity is the rate at which a star radiates energy into space.

Apparent brightness is the rate at which a star’s radiated energy reaches an observer on Earth.

Apparent brightness depends on both luminosity and distance.

The inverse-square law relating apparent brightness and luminosity

b = L/(4pd2 )

b = apparent brightness of the star (in watts/metre2)

L = luminosity of the star (in watts)

d = distance to the star (in metres)

p = approximately 3.14159265

So, compare the luminosity of a star with its apparent brightness and this will enable you to work out how far away it is.

Measuring distances in astronomy is incredibly hard (as is trying to explain it to you’re a level physics students).

Edwin Hubble used Henrietta’s law to incredible effect 11 years later.

He was looking at what was then called the Andromeda nebula.

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A 1923 image of the Andromeda galaxy. A cepheid, or variable star (marked VAR!), helped Edwin Hubble determine the vast distance to Andromeda for the first time. Credit: The Carnegie Observatories

His measurements showed that Andromeda was much further than first thought and they demonstrated conclusively that this “nebula” was not a cluster of stars and gas within our own galaxy, but an entirely separate galaxy located a significant distance from the Milky Way. Prior to this work galaxies were known as spiral nebulae. Most 18th to 19th Century astronomers considered them as either unresolved star clusters or anagalactic nebulae, and were just thought as a part of the Milky Way, but their true composition and natures remained a mystery.

Initially these clusters of stars beyond the Milky Way were called island universes, but this term quickly fell into disuse, as the word universe implied the entirety of existence. Instead, they became known simply as galaxies.

Hubble’s work changed the shape of the Universe.

https://en.wikipedia.org/wiki/Andromeda_Galaxy

The Andromeda Galaxy, also known as Messier 31, M31, or NGC 224 and originally the Andromeda Nebula (see below), is a barred spiral galaxy approximately 2.5 million light-years (770 kiloparsecs) from Earth and the nearest major galaxy to the Milky Way.

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The above image of the Andromeda galaxy used modern digital technology, which allows more quantitative analysis.

Still we are not using our eyes but pictures.

Photographic plates have been replaced by electronic imaging in professional and amateur observatories. CCD’s are far more light-sensitive, do not drop off in sensitivity over long exposures the way film does (“reciprocity failure”), have the ability to record in a much wider spectral range, and simplify storage of information. Telescopes now use many configurations of CCD sensors including linear arrays and large mosaics of CCD elements equivalent to 100 million pixels, designed to cover the focal plane of telescopes that formerly used 25–36 cm photographic plates.

https://en.wikipedia.org/wiki/Charge-coupled_device

A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighbouring capacitor. CCD sensors are a major technology used in digital imaging.

In a CCD image sensor, pixels are represented by p-doped metal–oxide–semiconductor (MOS) capacitors. These MOS capacitors, the basic building blocks of a CCD, are biased above the threshold for inversion when image acquisition begins, allowing the conversion of incoming photons into electron charges at the semiconductor-oxide interface; the CCD is then used to read out these charges.

https://upload.wikimedia.org/wikipedia/commons/thumb/6/66/CCD_charge_transfer_animation.gif/250px-CCD_charge_transfer_animation.gif

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The charge packets (electrons, blue) are collected in potential wells (yellow) created by applying positive voltage at the gate electrodes (G). Applying positive voltage to the gate electrode in the correct sequence transfers the charge packets.

In a CCD for capturing images, there is a photoactive region (an epitaxial layer of silicon), and a transmission region made out of a shift register (the CCD, properly speaking).

An image is projected through a lens onto the capacitor array (the photoactive region), causing each capacitor to accumulate an electric charge proportional to the light intensity at that location. A one-dimensional array, used in line-scan cameras, captures a single slice of the image, whereas a two-dimensional array, used in video and still cameras, captures a two-dimensional picture corresponding to the scene projected onto the focal plane of the sensor. Once the array has been exposed to the image, a control circuit causes each capacitor to transfer its contents to its neighbour (operating as a shift register). The last capacitor in the array dumps its charge into a charge amplifier, which converts the charge into a voltage. By repeating this process, the controlling circuit converts the entire contents of the array in the semiconductor to a sequence of voltages. In a digital device, these voltages are then sampled, digitized, and usually stored in memory; in an analogue device (such as an analogue video camera), they are processed into a continuous analogue signal (e.g. by feeding the output of the charge amplifier into a low-pass filter), which is then processed and fed out to other circuits for transmission, recording, or other processing.

Digital colour cameras generally use a Bayer mask over the CCD. Each square of four pixels has one filtered red, one blue, and two green (the human eye is more sensitive to green than either red or blue). The result of this is that luminance information is collected at every pixel, but the colour resolution is lower than the luminance resolution.

2) “We have some surprising adventures…”

In 1980, a grad. Student, Doug Geisler was based at Manastash Ridge Observatory to allow him to study clusters of stars. He was trying to figure out how old they were, their chemistry and what they were made of.

https://en.wikipedia.org/wiki/Manastash_Ridge_Observatory

The Manastash Ridge Observatory (MRO) is an astronomical observatory built in 1972 by the University of Washington. It is located in a remote area approximately 14 kilometres west of Ellensburg, Washington. The observatory features a 0.75 m Ritchey-Chrétien telescope built by Boller and Chivens. Initially used for professional and graduate research, the observatory is now used mostly by undergraduate students for instruction and research.

Like all good scientists Doug kept a log

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Now the date meant nothing to me because it’s forty years ago and I live in the UK. But to American’s who live in Washington state the date reminds them of the day that Mt. St. Helens erupted.

https://en.wikipedia.org/wiki/1980_eruption_of_Mount_St._Helens

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Doug woke up at noon to a weird state where he needed a torch to be able to see. He had no idea what had happened and he did wonder if somebody had dropped a nuclear bomb. He eventually found out what happened by listening to the radio.

Almost one side of the mountain had be blown off sending a plume of ash and debris into the sky over the observatory.

He lost 6 hours but he did spend the time carefully covering and sealing the telescope before he left the observatory. The big mirrors are very precious, they have to be kept polished and clear.

Doug did make a careful log of what had happened.

https://jarphys.wordpress.com/2017/05/19/mt-st-helens-eruption-18-may-1980/

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Doug’s story makes up chapter 4 of Professor Levesque’s book.

Some of the astronomers’ adventures came about because the observatories are in the middle of nowhere with poor weather.

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The above is an actual photograph from one of Professor Levesque’s thesis-critical observing nights.

Wind can be a problem as it can cause debris to enter the observatory and damage the mirror.

If you miss your observation time you may have to wait and entire year you’re your next session

Animals can be a problem too

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Insects can cover equipment and get into electronics

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Astronomers love watching sunsets because they are a good indication of the nights weather.

They will go to extremes to get data:

a) Stick the detectors/cameras on balloons

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https://en.wikipedia.org/wiki/Balloon-borne_telescope

A balloon-borne telescope is a type of airborne telescope, a sub-orbital astronomical telescope that is suspended below one or more stratospheric balloons, allowing it to be lifted above the lower, dense part of the Earth’s atmosphere. This has the advantage of improving the resolution limit of the telescope at a much lower cost than for a space telescope. It also allows observation of frequency bands that are blocked by the atmosphere.

b) Put the telescope in the very cold South Pole

https://en.wikipedia.org/wiki/South_Pole_Telescope

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The South Pole Telescope (SPT) is a 10-metre diameter telescope located at the Amundsen–Scott South Pole Station, Antarctica. The telescope is designed for observations in the microwave, millimetre-wave, and submillimetre-wave regions of the electromagnetic spectrum, with the particular design goal of measuring the faint, diffuse emission from the cosmic microwave background (CMB).

c) Fly around the world to observe total eclipses of the Sun

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Total eclipse of the Sun in north Norway

https://en.wikipedia.org/wiki/Solar_eclipse_of_March_20,_2015

A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby totally or partly obscuring the image of the Sun for a viewer on Earth. A total solar eclipse occurs when the Moon’s apparent diameter is larger than the Sun’s, blocking all direct sunlight, turning day into darkness. Totality occurs in a narrow path across Earth’s surface, with a partial solar eclipse visible over a surrounding region thousands of kilometres wide. This total solar eclipse is notable in that the path of totality passed over the North Pole. Totality was visible in the Faroe Islands and Svalbard.

d) Put a telescope on a 747 and fly it into the stratosphere

https://www.nasa.gov/mission_pages/SOFIA/overview/index.html

https://en.wikipedia.org/wiki/Stratospheric_Observatory_for_Infrared_Astronomy

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SOFIA soars over the snow-covered Sierra Nevada mountains with its telescope door open during a test flight. SOFIA is a modified Boeing 747SP aircraft. Credits: NASA/Jim Ross

SOFIA, the Stratospheric Observatory for Infrared Astronomy, is a Boeing 747SP aircraft modified to carry a 2.7-metre reflecting telescope (with an effective diameter of 2.5 meters). Flying into the stratosphere at 38,000-45,000 feet puts SOFIA above 99 percent of Earth’s infrared-blocking atmosphere, allowing astronomers to study the solar system and beyond in ways that are not possible with ground-based telescopes. SOFIA is made possible through a partnership between NASA and the German Aerospace Centre (DLR).

The observatory’s mobility allows researchers to observe from almost anywhere in the world, and enables studies of transient events that often take place over oceans where there are no telescopes. For example, astronomers on SOFIA studied eclipse-like events of Pluto, Saturn’s moon Titan, and Kuiper Belt Object MU69, the next flyby target for NASA’s New Horizons spacecraft, to study the objects’ atmospheres and surroundings.

During 10-hour, overnight flights, SOFIA observes the solar system and beyond at mid- and far-infrared wavelengths gathering data to study:

Star birth and death

​Formation of new solar systems

Identification of complex molecules in space

Planets, comets and asteroids in our solar system

Nebulas and galaxies

Celestial magnetic fields

Black holes at the centre of galaxies

e) Send the camera to the Moon. This is probably the most extreme expedition

https://en.wikipedia.org/wiki/George_Robert_Carruthers

George Robert Carruthers (born October 1, 1939) is an American inventor, physicist, engineer and space scientist. Carruthers invented the ultraviolet camera/spectrograph for NASA to use when it launched Apollo 16 in 1972. He was working at the US Naval Research Lab. In 1969, Dr. Carruthers was given a patent for “Image Converter for Detecting Electromagnetic Radiation Especially in Short Wave Lengths”. For this and his further work, he received the 2012 National Medal of Technology and Innovation.

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Above left is Dr Curruthers. Above centre is the camera being used on the Moon. Above right shows the telescope developed by Dr. Carruthers on display at the National Air and Space Museum

https://en.wikipedia.org/wiki/Optical_spectrometer

An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify materials.

https://en.wikipedia.org/wiki/Far_Ultraviolet_Camera/Spectrograph

The Far Ultraviolet Camera/Spectrograph (UVC) was one of the experiments deployed on the lunar surface by the Apollo 16 astronauts. It consisted of a telescope and camera that obtained astronomical images and spectra in the far ultraviolet region of the electromagnetic spectrum.

The goals of the Far Ultraviolet Camera/Spectrograph spanned across several disciplines of astronomy. Earth studies were made by studying the Earth’s upper atmosphere’s composition and structure, the ionosphere, the geocorona, day and night airglow, and aurorae. Heliophysics studies were made by obtaining spectra and images of the solar wind, the solar bow cloud, and other gas clouds in the solar system. Astronomical studies by obtaining direct evidence of intergalactic hydrogen, and spectra of distant galaxy clusters and within the Milky Way. Lunar studies were conducted by detecting gasses in the lunar atmosphere, and searching for possible volcanic gasses. There were also considerations to evaluate the lunar surface as a site for future astronomical observatories.

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This is a picture of Earth in ultraviolet light, taken from the surface of the Moon. The day-side reflects a lot of UV light from the Sun, but the night-side shows bands of UV emission from the aurora caused by charged particles.

https://en.wikipedia.org/wiki/Apollo_16

Apollo 16 was the tenth crewed mission in the United States Apollo space program, the fifth and penultimate to land on the Moon, and the second to land in the lunar highlands.

One of the first tasks of the astronauts was to unload the Far Ultraviolet Camera/Spectrograph (UVC), and other equipment, from the lunar module.

3) Do you remember when the telescope got shot

https://en.wikipedia.org/wiki/McDonald_Observatory

The McDonald Observatory is an astronomical observatory located near the unincorporated community of Fort Davis in Jeff Davis County, Texas, United States. The facility is located on Mount Locke in the Davis Mountains of West Texas, with additional facilities on Mount Fowlkes, approximately 1.3 kilometres to the northeast. The observatory is part of the University of Texas at Austin. It is an organized research unit of the College of Natural Sciences.

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https://mcdonaldobservatory.org/news/gallery/smith-telescope-colorful-clouds

Colourful clouds pass behind the open dome of the Harlan J. Smith Telescope. The Hobby-Eberly Telescope is visible atop Mt. Fowlkes in the background at left. Credit: Ethan Tweedie Photography

https://en.wikipedia.org/wiki/Harlan_J._Smith_Telescope

The Harlan J. Smith Telescope is a 2.7 m telescope located at the McDonald Observatory, in Texas, in the United States.

The telescope was the victim of an act of vandalism in February 1970. A newly hired worker suffered a mental breakdown and brought a hand gun into the observatory. After firing one shot at his supervisor, the worker then fired the remaining rounds into the Primary Mirror after demanding that the mirror be lowered. The holes effectively reduced the 2.7 m telescope by about 2.5 centimetres, but did not affect the quality of the telescope’s images because the mirror was very thick, only the amount of light it can collect.

The worker also had a hammer but he was stopped before he could bash the mirror in. The bullets were removed and the holes were covered in with black paint to prevent stray reflections.

https://astroanecdotes.com/2015/03/26/the-mcdonald-gun-shooting-incident/

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“The harm suffered by the mirror from his bullets and his several preliminary blows with a hammer was extraordinarily small.” – Harlan Smith, observatory director.

4) What are the weird signals?

A weird signal is mistaken for something else

https://en.wikipedia.org/wiki/Parkes_Observatory

The Parkes Observatory (also known informally as “The Dish”) is a radio telescope observatory, located 20 kilometres north of the town of Parkes, New South Wales, Australia.

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CSIRO’s Parkes radio telescope in New South Wales, Australia. Image credit: Shaun Amy.

Radio telescopes work in a similar way to light mirror telescopes. They simply use a different part of the electromagnetic spectrum.

https://en.wikipedia.org/wiki/Electromagnetic_spectrum

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. They all have the same speed in a vacuum (3 x 108ms-1)

The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometres down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. The limit for long wavelengths is the size of the universe itself, while it is thought that the short wavelength limit is in the vicinity of the Planck length. Gamma rays, X-rays, and high ultraviolet are classified as ionizing radiation as their photons have enough energy to ionize atoms, causing chemical reactions.

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Radio waves have longer wavelengths and these can bounce off the disk like antennae rather than polished mirrors. The radio waves are focused at the receiver and the data is analysed.

In the early 2000s bright bursts of radio waves were detected at the Parkes observatory which couldn’t be explained. Staff thought the signals were just noise.

http://www.ebpetroff.com/

Dr Emily Petroff decided to investigate

https://www.popsci.com/cosmic-whodunnit-culprit-ismicrowave-ovens/

She looked at the timings of the signals, known as perytons, and found that they clustered around lunchtime from staff buildings. So, she carried out some experiments

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Initially she found that these experiments did not produce the perytons until she noticed that the signals did appear if people opened the oven before the timer had finished controlling the cooking. The microwaves are stopped suddenly when the door is opened.

All the bursts of radio were caused by this except for one fast radio burst. Astronomers don’t know what it is.

The astronomers can now screen out the microwave oven signals

https://en.wikipedia.org/wiki/Peryton_(astronomy)

In radio astronomy perytons are short radio signals having a duration of a few milliseconds, detected only by the 64-meter Parkes radio telescope in Australia since 1998.

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5) How has astronomy changed?

Technology has changed. Now astronomers can take pictures of tiny corners of the Andromeda galaxy and identify individual stars thanks to the Hubble telescope and digital imaging

https://www.nbcnews.com/science/space/hubble-snaps-1-5-billion-pixel-close-up-andromeda-galaxy-n290561

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The largest Hubble Space Telescope image ever assembled provides a sweeping bird’s-eye view of a portion of the Andromeda Galaxy. It’s the sharpest large composite image ever taken of our galactic next-door neighbor.J. Dalcanton, B.F. Williams, L.C Johnson, R. Gendler / UW / PHAT / NASA / ESA / STScI

Mirrors are getting bigger and bigger enabling more light to be gathered. This allows astronomers to look further and further into the Universe.

Procedures and methods have changed.

https://en.wikipedia.org/wiki/Vera_C._Rubin_Observatory

The Vera C. Rubin Observatory, previously referred to as the Large Synoptic Survey Telescope (LSST), is an astronomical observatory currently under construction in Chile. Its main task will be an astronomical survey, the Legacy Survey of Space and Time (LSST). The Rubin Observatory has a wide-field reflecting telescope with an 8.4-meter primary mirror that will photograph the entire available sky every few nights. The word synoptic is derived from the Greek words σύν (syn “together”) and ὄψις (opsis “view”), and describes observations that give a broad view of a subject at a particular time. The observatory is named for Vera Rubin, an American astronomer who pioneered discoveries about galaxy rotation rates.

https://www.lsst.org/about

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In this artist’s rendition, the Rubin Observatory primary mirror is seen through the slit of the dome at sunset.

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A photograph and rendering mix of the exterior of the Vera C. Rubin Observatory building on Cerro Pachón in Chile. Image credit: LSST/NSF/AURA

https://en.wikipedia.org/wiki/Vera_Rubin

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Vera Florence Cooper Rubin (July 23, 1928 – December 25, 2016) was an American astronomer who pioneered work on galaxy rotation rates. She uncovered the discrepancy between the predicted angular motion of galaxies and the observed motion, by studying galactic rotation curves. This phenomenon became known as the galaxy rotation problem, and was evidence of the existence of dark matter.

When the Vera C. Rubin Observatory is built it will look at a large region of the summer sky and take pictures over and over again every few nights for ten years. At the end of this decade there will be a ten-year long movie that shows how the sky changes.

The telescope will be able to discover thousands and thousands of variable stars. A fantastic map of every star changing in the night sky. Locating any asteroids that might be coming our way.

They will discover exploding stars that die and produce supernovae and form things like black holes.

The technology is making astronomers consider where their jobs are going and what this means.

Smaller teams will be needed to operate the telescopes and the digital cameras taking the pictures will run automatically at a large rate.

Astronomers will just need to download the data and work on it. They won’t have to travel to the telescope.

Telescopes will be controlled remotely when astronomers want to look at something in particular.

Plans will be made and the code fed into a computer which will then get the telescope to execute the commands.

About six years ago Professor Levasque became part of a group investigating a new type of star

https://en.wikipedia.org/wiki/Thorne%E2%80%93%C5%BBytkow_object

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A Thorne–Żytkow object (TŻO or TZO), also called a hybrid star, is a conjectured type of star wherein a red giant or supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. Such objects were hypothesized by Kip Thorne and Anna Żytkow in 1977. In 2014, it was discovered that the star HV 2112 was a strong candidate but this has since been called into question.

https://en.wikipedia.org/wiki/Kip_Thorne

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Kip Stephen Thorne (born June 1, 1940) is an American theoretical physicist known for his contributions in gravitational physics and astrophysics.

https://en.wikipedia.org/wiki/Anna_N._%C5%BBytkow

Anna N. Żytkow (born 21 February 1947) is a Polish astrophysicist working at the Institute of Astronomy of the University of Cambridge. Żytkow and Kip Thorne proposed a model for what is called the Thorne–Żytkow object, which is a star within another star. Żytkow in 2014 was part of the team led by Emily M. Levesque which discovered the first candidate for such an object.

A star like ours can last a long time due to the delicate balance between the inward push of gravity and the outward push caused by the nuclear fusion going on inside the star’s core.

http://www.astro.osu.edu/~ryden/ast162_1/notes3.html

The Sun is fairly stable; we don’t see it oscillating wildly in and out, and we don’t see it flickering like a candle about to go out. Moreover, the Sun has been fairly stable for billions of years, allowing the continuous existence of life on Earth.

Gravity has a destabilising effect. The tendency of gravity is to compress the Sun. If the Sun were to collapse inward under its own gravity, it would crunch down to a black hole in the course of a few hours. Obviously, such a catastrophe hasn’t happened. What has kept the Sun from collapsing?

As it turns out, the Sun is kept stable by its internal pressure. Just as pressure increases as you dive deeper and deeper into the Earth’s oceans, so pressure increases as you dive deeper and deeper into the Sun. By the time you reach the Sun’s centre, the pressure has reached a value equal to 340 billion times the air pressure at sea level here on Earth. It’s a general rule that gas flows from regions of high pressure to regions of low pressure. (The pressure difference is what makes air leak out of a punctured tire.) Within the Sun, therefore, pressure creates an outward force, from the high-pressure core to the low-pressure surface. This is in contrast to gravity, which creates an inward force.

When the force due to pressure exactly balances the force due to gravity, a system is in hydrostatic equilibrium. The Sun’s hydrostatic equilibrium is stable and self-regulating; if you tossed a little extra matter onto the Sun, the inward force of gravity would increase. However, the resulting compression would increase the pressure inside the Sun, resulting in an increase in the pressure force just sufficient to balance the increased gravitational force.

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Thorne and Żytkow imagined a star that didn’t quite work like this. A star that outwardly looked normal but inside didn’t have a nuclear fusion core. The process in the star was controlled by quantum physics.

Imagining two stars merging, making a bizarre structure which could be supported against collapse by very exotic quantum physics principles. If these stars did look normal it would be a difficult hypothesis to test.

Astronomers could identify these stars by looking at their chemistry – look for elements that would only be present in a quantum dominated core where a churning effect would drag strange elements to the surface.

https://www.scientificamerican.com/article/bizarre-star-could-host-a-neutron-star-in-its-core/

https://ui.adsabs.harvard.edu/abs/2012ApJ…758…92L/abstract

https://www.space.com/27389-hybrid-star-discovery-thorne-zytkow-object.html

Professor Levesque and colleagues asked for time on the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, to gather data on 62 red supergiants. They found a candidate TZO named HV 2112. The star is a member of the Small Magellanic Cloud, a dwarf galaxy about 199,000 light-years away that is a close neighbour of the Milky Way and easily visible to the naked eye from the Southern Hemisphere.

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The Magellan Telescopes are a pair of 6.5-metre-diameter optical telescopes located at Las Campanas Observatory in Chile. First light for the telescopes was on September 15, 2000 for the Baade, and September 7, 2002 for the Clay. A consortium consisting of the Carnegie Institution for Science, University of Arizona, Harvard University, the University of Michigan and the Massachusetts Institute of Technology built and operate the twin telescopes.

To get the time on the telescope the astronomers needed to put in a proposal with a detailed plan and list of stars they wanted to look at. They were specifically looking for red, bright cold stars.

At the last minute they added a few more stars which was a bit of a problem when instructions had already been fed into the computer.

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An image showing the location of the first suspected Thorne-Zytkow object (TZO), a long-theorized hybrid star thought to form when a red supergiant swallows a neutron star. This likely TZO, known as HV 2112, lies in the Small Magellanic Cloud, about 200,000 light-years from Earth. (Image: © Phil Massey, Lowell Observatory)

A common misconception is that astronomers automatically get lovely space pictures. They don’t. Below is part of an image of Professor Levesque’s data into the study of the chemistry of the stars. The white patches is where there is an atom or molecule might be “glowing” (the arrows are pointing to the patches)

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A colleague, Nidia Morrell, an expert, was immediately interested.

https://en.wikipedia.org/wiki/Nidia_Morrell

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Nidia Irene Morrell (born 3 July 1953) is an Argentine astronomer who is a permanent staff member at the Las Campanas Observatory in La Serena, Chile. She was a member of the Massive Stars research group led by Virpi Niemelä and the Hubble Heritage Project. Professionally, she is known for her numerous contributions related to the astrophysics of massive stars. She participates in the systematic search for variations of brightness in stellar objects, including the observation of a candidate for the Thorne–Żytkow object. She was also a member of the team that discovered the supernova ASASSN-15lh.

It turned out this particular star was one of those stars added at the last minute.

Going through the data months later one of the stars seemed to show the pattern of the weird star predicted – a Thorne and Żytkow object.

Data did indicate that the star had a core supported by quantum physics rather than a fusion core and this was the star mentioned earlier, that had been added at the last minute. They had found the first candidate of a new type of star.

Professor levesque hopes that astronomers won’t lose the chance to do stuff on the spur of the moment.

Astronomers need a whole range of different observatories.

The Vera C. Rubin observatory is one of series of new observatories. These new observatories will include radio telescopes and ones with bigger telescopes

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Astronomers will sometimes still want time with a telescope and sometimes they will want to work from home.

Let the data come in and use curiosity to explain what it means.

People will always be needed to design telescopes and explain how they work.

The role of stargazers will change as the technology is evolving.

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Comet Neowise taken with an Huawei P smart Phone

https://twitter.com/neiltyson/status/1283238175855517697?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembed%7Ctwterm%5E1283238175855517697%7Ctwgr%5E&ref_url=http%3A%2F%2Fspaceexplored.com%2F2020%2F07%2F20%2Fhow-to-find-neowise-comet-iphone%2F

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https://en.wikipedia.org/wiki/C/2020_F3_(NEOWISE)

C/2020 F3 (NEOWISE) or Comet NEOWISE is a long period comet with a near-parabolic orbit discovered on March 27, 2020, by astronomers during the NEOWISE mission of the Wide-field Infrared Survey Explorer (WISE) space telescope. At that time, it was an 18th-magnitude object, located 2 AU (300 million km) away from the Sun and 1.7 AU (250 million km) away from Earth.

NEOWISE is known for being the brightest comet in the northern hemisphere since Comet Hale–Bopp in 1997. It was widely photographed by professional and amateur observers and was even spotted by people living near city centres and areas with light pollution. While it was too close to the Sun to be observed at perihelion, it emerged from perihelion around magnitude 0.5 to 1, making it bright enough to be visible to the naked eye. Under dark skies, it could be seen with the naked eye and remained visible to the naked eye throughout July 2020. By July 30, the comet was about magnitude 5, but binoculars were required near urban areas to locate the comet.

For observers in the northern hemisphere, the comet could be seen on the northwestern horizon, below the Plough or Big Dipper. North of 45 degrees north, the comet was visible all night in mid-July 2020. On July 30, Comet NEOWISE entered the constellation of Coma Berenices, below the bright star Arcturus.

https://en.wikipedia.org/wiki/Neil_deGrasse_Tyson

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Neil deGrasse Tyson (born October 5, 1958) is an American astrophysicist, cosmologist, planetary scientist, author, and science communicator.

Everyone could see the comet.

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https://www.amazon.co.uk/Last-Stargazers-Astronomys-Vanishing-Explorers/dp/1786078236/ref=sr_1_1?crid=Q46T165YUHD1&dchild=1&keywords=the+last+stargazers&qid=1598816241&sprefix=the+last+sta%2Caps%2C154&sr=8-1

The title of Professor Levesque’s book does sound sad but it simply saying the way that we do astronomy is changing

Questions and answers

1) Who do you apply to for telescope time?

Proposals are reviewed by astronomers’ peers. Astronomers need to give detailed reasons for the observations and how much time they will need.

The proposals go to a committee

Some telescopes can be used by anyone and some can only be used by certain consortiums/universities who pay for their running

2) Astronomers don’t operate the telescopes. That is the job of trained telescope operators.

3) What is the difference between astronomy and cosmology?

Astronomy is done by astronomers and astrophysicists and involves looking and investigating stars, planets etc.

Cosmology is a subfield of astronomy and is interested in the big scale of things such as how the Universe began.

4) What is the diffraction limit of a telescope?

http://hosting.astro.cornell.edu/academics/courses/astro201/diff_limit.htm

The minimum angular separation of two sources that can be distinguished by a telescope depends on the wavelength of the light being observed and the diameter of the telescope. This angle is called the diffraction limit.

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https://astronomy.tools/calculators/telescope_capabilities

https://en.wikipedia.org/wiki/Angular_resolution

Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution. It is used in optics applied to light waves,

https://en.wikipedia.org/wiki/Diffraction-limited_system

The resolution of an optical imaging system – a microscope, telescope, or camera – can be limited by factors such as imperfections in the lenses or misalignment. However, there is a principal limit to the resolution of any optical system, due to the physics of diffraction. An optical system with resolution performance at the instrument’s theoretical limit is said to be diffraction-limited.

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Log-log plot of aperture diameter vs angular resolution at the diffraction limit for various light wavelengths compared with various astronomical instruments. For example, the blue star shows that the Hubble Space Telescope is almost diffraction-limited in the visible spectrum at 0.1 arcsecs, whereas the red circle shows that the human eye should have a resolving power of 20 arcsecs in theory, though normally only 60 arcsecs.

http://www.astro.ru.nl/~sluys/Teaching/files/Speckle_AO.pdf

Slow motion image showing the effects of atmospheric turbulence. The atmosphere limits how much detail you can see. Typically, the smallest detail you can see is about 3 or 4 arcseconds, though professional telescopes do better by being built on the top of mountains and using various tricks, like adaptive optics.

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Resulting images are the superposition of many Airy discs at different locations, called speckles. Each Airy disc is defined by the diffraction limit of the telescope

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https://en.wikipedia.org/wiki/Airy_disk

In optics, the Airy disk (or Airy disc) and Airy pattern are descriptions of the best-focused spot of light that a perfect lens with a circular aperture can make, limited by the diffraction of light. The Airy disk is of importance in physics, optics, and astronomy.

https://web.williams.edu/Astronomy/Course-Pages/330/images/distances.pdf

Arcseconds are fractions of a degree, the unit used for angles. It’s connection with distance is explained as follows.

One of the most important (and difficult!) problems in astronomy is the accurate determination of distances to planets, stars, galaxies, etc. Different methods are used at different distances, but most are based on either trigonometry.

When you look at an object, you don’t see its physical size (in, e.g., meters). You see the angle that it occupies, from your vantage point. A full Moon (~ 1/2 degree) looks much smaller than your hand (~ 10 degrees), but only because it is far away. This is called angular size, (or, in the case of the spacing between two objects, angular separation) and it is the only kind of size that any optical imaging system, from your eye to the largest telescope, can measure. The angular size θ of an object depends on its physical size a and its distance d, as shown below.

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and their mathematical relationship is tan θ = a/d .

If you know any two of these numbers, you can calculate the third. In astronomy the angle θ is often rather small, so if θ is expressed in radians θ ≈ a/d .

A complete circle is 2π radians = 360 degrees. Angular sizes or separations may also be measured in arcminutes (60 arcmin = 1 degree) or arcseconds (60 arcsec = 1 arcmin).

https://en.wikipedia.org/wiki/Parsec

The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System. One parsec is approximately equal to 31 trillion kilometres or 210,000 astronomical units, and equates to about 3.3 light-years.

A parsec is obtained by the use of parallax and trigonometry, and is defined as the distance at which one astronomical unit subtends an angle of one arcsecond.

https://en.wikipedia.org/wiki/Parallax

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.

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A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from “Viewpoint A”, the object appears to be in front of the blue square. When the viewpoint is changed to “Viewpoint B”, the object appears to have moved in front of the red square.

https://kalobs.org/more/light-years-and-parsecs/

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The benefit of using the parsec as a unit of distance is its simplicity: determine the parallactic angle of a nearby star in arcseconds and take its reciprocal to get its distance in parsecs. This only works for small angles in a right angle triangle where the length of the hypotenuse is not significantly longer than the length of its long leg.

5) Remote unit telescope?

There are such things but they are pretty small and they will still have operational staff.

Even new telescopes will need operational staff.

6) Will you miss contact with other astronomers if telescopes are used remotely.

No, because important meetings will still occur.

7) How will telescopes cope with extra satellites like starlink (540 rising to 42000)

https://en.wikipedia.org/wiki/Starlink

Starlink is a satellite constellation being constructed by SpaceX to provide satellite Internet access. The constellation will consist of thousands of mass-produced small satellites in low Earth orbit (LEO), working in combination with ground transceivers. SpaceX also plans to sell some of the satellites for military, scientific, or exploratory purposes. The SpaceX satellite development facility in Redmond, Washington houses the Starlink research, development, manufacturing, and on-orbit control operations. The total cost of the decade-long project to design, build, and deploy the constellation was estimated by SpaceX in May 2018 to be about US$10 billion.

Yes, these satellites could cause problems.

8) Can amateurs still contribute?

Yes. You can do great research with small telescopes. Sometimes little telescopes can do things that big ones can’t.

9) Are there any AI controlled observatories.

AI is used in the interpretation of data but we still need human curiosity

10) Is speckle imaging useful?

https://cds.cern.ch/record/1707548/files/978-1-4939-0629-1_BookBackMatter.pdf

https://en.wikipedia.org/wiki/Speckle_imaging

Speckle imaging describes a range of high-resolution astronomical imaging techniques based on the analysis of large numbers of short exposures that freeze the variation of atmospheric turbulence. They can be divided into the shift-and-add (“image stacking”) method and the speckle interferometry methods. These techniques can dramatically increase the resolution of ground-based telescopes, but are limited to bright targets.

Imaging gives us the pictures and spectroscopy sorts out light according to wavelength and are used to identify the materials that make up our Universe.

Speckle interferometry and speckle imaging techniques in astronomy have a significant impact on problems such as stellar formation, stellar masses, and planetary astronomy.

Speckle adaptive optics

https://en.wikipedia.org/wiki/Adaptive_optics

Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effect of incoming wavefront distortions by deforming a mirror in order to compensate for the distortion. It is used in astronomical telescopes and laser communication systems to remove the effects of atmospheric distortion, in microscopy, optical fabrication and in retinal imaging systems to reduce optical aberrations. Adaptive optics works by measuring the distortions in a wavefront and compensating for them with a device that corrects those errors such as a deformable mirror or a liquid crystal array.

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A deformable mirror can be used to correct wavefront errors in an astronomical telescope.

Telescope shoots lasers, the mirror is adjusted to compensate for the atmosphere, slightly longer wavelengths are produced if necessary

11) Are exoplanets imaged directly?

https://exoplanets.nasa.gov/news/1605/observing-exoplanets-what-can-we-really-see/

https://exoplanets.nasa.gov/internal_resources/441

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Four planets are in orbit around a star 129 light-years away in the constellation of Pegasus. Credit: Jason Wang and Christian Marois

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Composite image of an exoplanet (the red spot on the lower left), orbiting the brown dwarf 2M1207 (centre). This photo of the exoplanet 2M1207b is based on three near-infrared exposures (in the H, K and L wavebands) with the NACO adaptive-optics facility at the 8.2-m VLT Yepun telescope at the ESO Paranal Observatory. Credit: ESO

https://www.universetoday.com/140341/what-is-direct-imaging/

Direct Imaging consists of capturing images of exoplanets directly, which is possible by searching for the light reflected from a planet’s atmosphere at infrared wavelengths. The reason for this is because at infrared wavelengths, a star is only likely to be about 1 million times brighter than a planet reflecting light, rather than a billion times (which is typically the case at visual wavelengths).

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope

The James Webb Space Telescope (JWST or “Webb”) is a space telescope that is planned to succeed the Hubble Space Telescope as NASA’s flagship astrophysics mission. The JWST will provide improved infrared resolution and sensitivity over Hubble, and will enable a broad range of investigations across the fields of astronomy and cosmology, including observing some of the most distant events and objects in the universe, such as the formation of the first galaxies.

The James Webb telescope may be able to obtain a spectrum from an exoplanet atmosphere.

https://en.wikipedia.org/wiki/History_of_spectroscopy

Spectroscopy has played and continues to play a significant role in chemistry, physics and astronomy. Fraunhofer observed and measured dark lines in the Sun’s spectrum.

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Solar spectrum with Fraunhofer lines as it appears visually.

https://en.wikipedia.org/wiki/Joseph_von_Fraunhofer

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Joseph Ritter von Fraunhofer (March 1787 – 7 June 1826) was a Bavarian physicist and optical lens manufacturer. He made optical glass and achromatic telescope objective lenses, invented the spectroscope, and developed diffraction grating. In 1814, he discovered and studied the dark absorption lines in the spectrum of the sun now known as Fraunhofer lines.

12) Can you account for dark matter/dark energy in observations?

Dark matter and dark energy can’t be observed directly

Primary evidence for dark matter comes from calculations showing that many galaxies would fly apart, or that they would not have formed or would not move as they do, if they did not contain a large amount of unseen matter.

The evidence for dark energy is indirect but comes from three independent sources:

Distance measurements and their relation to redshift, which suggest the universe has expanded more in the last half of its life.

The theoretical need for a type of additional energy that is not matter or dark matter to form the observationally flat universe (absence of any detectable global curvature).

Measures of large-scale wave-patterns of mass density in the universe.

13) https://phys.org/news/2019-09-china-sky-eye-world-largest.html

China’s Five-hundred-meter Aperture Spherical Radio Telescope, known as FAST, is the world’s most sensitive listening device.

Birds are a problem with radio telescopes, mainly with bird poo but Falcons nested in Jodrell Bank prevents the nuisance of pigeon infestation (by droppings fouling, and their body heat affecting sensitive instrument readings) that some other radio telescopes suffer from.

https://en.wikipedia.org/wiki/Jodrell_Bank_Observatory

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The Jodrell Bank Observatory – originally the Jodrell Bank Experimental Station and from 1966 to 1999, the Nuffield Radio Astronomy Laboratories – hosts a number of radio telescopes, and is part of the Jodrell Bank Centre for Astrophysics at the University of Manchester.

14) Gender problems.

Professor Levesque hasn’t really had problems but she interviewed some women who were not so lucky. 40% doctoral degrees were awarded to women however not many make tenured professor.

She has noticed ambiguous sexism.

https://thelaststargazers.com/

Videos by Professor Levesque

https://www.google.com/search?q=emily+levesque+video&rlz=1C1CHBF_en-GBGB912GB912&sxsrf=ALeKk03UR32ax0wQvoQ_LEXNWcN94kAkeg:1598834584105&source=lnms&tbm=vid&sa=X&ved=2ahUKEwiUrcL7msTrAhWKTBUIHbRMCrkQ_AUoAnoECAwQBA&biw=1463&bih=1016

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