Year 13 Astronomy day at the Royal Greenwich Observatory

The final activity of the day was a lecture by Dr Olivia Johnson on – How black holes shape the universe.

http://en.wikipedia.org/wiki/Black_hole

A typical galaxy contains 100 billions of Suns and has a size of about 100000 light years.

A galaxy cluster contains about 10 trillions of Suns and has a size of about 10 million light years.

The size of a black hole is proportional to galaxy size. A black hole may stop a galaxy growing. There are three types of black holes.

Supermassive black holes (see http://en.wikipedia.org/wiki/Supermassive_black_hole)

A supermassive black hole is the the largest type of black hole in a galaxy. Its mass is equivalent to billions of our Suns and its size is about 1 light year. It is too small to see but it is extremely powerful. Until recently they were thought to be very rare but we now know that they hide inside every galaxy. They are a phase not an oddity.

About 1% of galaxies contain an Active Galactic Nucleus (AGN) which consists of a supermassive black hole feeding on the gas from the galaxy and emitting huge quantities of radiation. It is thought that all galaxies go through an AGN phase.

Supermassive black hole = 2.74 light hours across and galaxy is 325000 light years across. This is like saying the SMBH is a grain of sand and the galaxy is the Earth.

All three types of black hole (stellar, supermassive and miniature) evolved together. Jets from black holes may be due to spinning.

Well tested theories tell us how the universe formed and how it has evolved. Gravity is involved.

The first galaxies were believed to have formed 200 million years after the big bang. Our Sun formed 9 million years ago.

Computer simulations can be used to model the creation of the universe but the properties of simulated galaxies and clusters don’t always match the observed universe.

http://hubblesite.org/

http://en.wikipedia.org/wiki/Hubble_Ultra-Deep_Field

The Hubble Ultra-Deep Field is an image of a small region of space in the constellation Formax and allows us to see far back in time when the galaxies first appeared after the big bang.

http://www.pbs.org/deepspace/timeline/

Anish, Arjun, Devan, Dr Johnson, Abdi, Anthony and Dinesh at the end of the lecture.

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