We went looking for glowing interstellar gas – and stumbled on 49 unknown galaxies

By Marcin Glowacki, Curtin University

Stars are born from huge clouds of mostly hydrogen gas floating in space. Astronomers like me study this gas because it helps us understand how stars and galaxies form and grow.

Hydrogen gas gives off a faint glow that is invisible to human eyes but can be observed with a telescope tuned to detect radio waves.

Recently, my colleagues and I were using a telescope like this – a radio telescope called MeerKAT, in South Africa – to look for hydrogen gas in a particular galaxy. We were only observing for less than three hours, which is quite a short amount of time since the hydrogen glow is so faint.

When we looked at the results, we were in for a huge surprise. Instead of discovering hydrogen gas in the galaxy we aimed at, we spotted it in no less than 49 previously unknown galaxies. Our findings are published in the Monthly Notices of the Royal Astronomical Society.

Gas in galaxies

The giant clouds of gas in which stars are born are called nebulae. When stars eventually die, they expel their gas into their surrounding environment, where it eventually cools and forms new nebulae.

Galaxies are like huge factories where the life cycle of stars repeats itself over and over. To properly understand galaxies and how they grow and evolve, astronomers need to consider both the stars and the gas making up the galaxy.

One thing we are particularly interested in is “merger events”, when two galaxies collide and merge into a single, larger galaxy. These events can also impact the gas, and kickstart star formation.

Studying gas can often help us understand a galaxy’s history. Gas often extends far further out than the stars in galaxies.

When we see trails of disturbed gas, it is a classic clue that a recent galaxy merger or interaction has occurred.

But we don’t see galactic gas easily with optical telescopes. Thankfully, radio telescopes are a great tool for finding hydrogen gas.

Read Full Story https://theconversation.com/we-went-looking-for-glowing-interstellar-gas-and-stumbled-on-49-unknown-galaxies-226397