# parsec

## December 12, 2020

Active galaxies Review

So following on from the post on December 1st this is a quick review of the active galaxies lecture from the Space Telescope Science Institute.

This lecture, presented by Dr Mitchell Revalski, is really interesting, looking at how supermassive black holes, despite their small size compared to the galaxy they reside in.

Energy from these can push away surrounding gas, and heat this up which reduces star formation as gas needs to cool to form stars.

so scales are pretty huge:

First lets look at what a light year is

Citation : spaceplace.nasa.gov

For most space objects, we use light-years to describe their distance. A light-year is the distance light travels in one Earth year. One light-year is about 6 trillion miles (9 trillion km). That is a 6 with 12 zeros behind it!


1 pc = 1 parsec = 3.26 light years

Supermassive black hole < 1pc

Bulge = 1 = 3 kpc (kilo parsec)

disk 30 kpc

circumgalactic area 50kpc

So even though these black holes are very small, they have a big influence on what surrounds them.

We know this is happening thanks to the research that led to the 2020 Nobel prize.

Well worth watching and the link is above.

Next lecture 19th Jan – The Darkest Secrets of the Universe Speaker: Raja Guhathakurta (UC Santa Cruz)