circumgalactic medium Archives

September 9, 2024September 9, 2024 by Evan Gough

The True Size of Galaxies is Much Larger Than We Thought

Visualisation of the gas shroud of starburst galaxy IRAS 08339+6517. Astronomers struggle to observe this gas clearly, but new research found a way. Image Credit: Cristy Roberts ANU/ASTRO 3D

Ask most people what a galaxy is made up of, and they’ll say it’s made of stars. Our own galaxy, the Milky Way, hosts between about 100 to 300 billion stars, and we can see thousands of them with our unaided eyes. But most of a galaxy’s mass is actually gas, and the extent of the gas has been difficult to measure.

Researchers have found a way to see how far that gas extends into the cosmos.

September 19, 2023September 19, 2023 by Evan Gough

Galaxies Breathe Gas, and When They Stop, No More Stars Form

Artist concept of how a galaxy might accrete mass from rapid, narrow streams of cold gas. These filaments provide the galaxy with continuous flows of raw material to feed its star-forming at a rather leisurely pace. Credit: ESA–AOES Medialab

For most of the history of astronomy, all we could see were stars. We could see them individually, in clusters, in nebulae, and in fuzzy blobs that we thought were clumps of stars but were actually galaxies. The thing is, most of what’s out there is much harder to see than stars and galaxies. It’s gas.

Now that astronomers can see gas better than ever, we can see how galaxies breathe it in and out. When they stop breathing it, stars stop forming.

September 1, 2020September 1, 2020 by Evan Gough

Hubble Shows the True Size of Andromeda

This illustration shows the location of the 43 quasars scientists used to probe Andromeda’s gaseous halo. These quasars—the very distant, brilliant cores of active galaxies powered by black holes—are scattered far behind the halo, allowing scientists to probe multiple regions. Looking through the immense halo at the quasars’ light, the team observed how this light is absorbed by the halo and how that absorption changes in different regions. By tracing the absorption of light coming from the background quasars, scientists are able to probe the halo’s material. Image Credit: NASA, ESA, and E. Wheatley (STScI)

It’s possible that you’ve seen the Andromeda galaxy (M31) without even realizing it. The massive spiral galaxy appears as a grey, spindle-shaped blob in the night sky, visible with the naked eye in the right conditions. It’s the nearest major galaxy to ours, and astronomers have studied it a lot.

Now astronomers have used the Hubble Space Telescope to map out Andromeda’s enormous halo of hot gas.