NASA Maps Massive Halo Around The Andromeda Galaxy Using Hubble Telescope

NASA has used the Hubble Space Telescope to map a complex, layered structure with two nested gas shells that surround the Andromeda spiral galaxy. Andromeda nearest major galaxy to the Milky Way. While Andromeda can be seen in the nighttime sky during autumn in the northern hemisphere, we can't see is a vast halo of hot, rarefied gas that surrounds the galaxy.

If we could see that halo of gas, it would stretch out from the Andromeda galaxy the width of three Big Dippers. NASA has conducted a comprehensive study of the halo of gas using the Hubble space telescope. Scientists have discovered the nearly invisible and diffuse plasma extends 1.3 million light-years from Andromeda, or about halfway to the Milky Way.

Researchers discovered that the halo has a layered structure with two main nested and distinct shells of gas during the study. This is the most comprehensive study of a halo surrounding a galaxy performed to date. Researcher Samantha Barrick from Yale says that understanding the huge halos of gas surrounding the galaxy is "immensely important." She says the gas reservoir contains fuel for future star formation within the galaxy and outflows from events like supernovae.

This massive reservoir of gas has clues regarding the past and future evolution of the galaxy, and NASA has been able to study in great detail for the first time. The inner shell extends about half a million light-years and is described is far more complex and dynamic than the outer shell. The outer shell is smoother and hotter. The difference likely results from the impact of supernova activity in the galaxy's disk more directly affecting the inner halo.

Andromeda galaxy is also known as M31and is a spiral with as many as 1 trillion stars comparable in size to the Milky Way. The program NASA operates to study the gas cloud is called Project AMIGA standing for Absorption Map of Ionized Gas in Andromeda. The study examined the light from 43 very distant quasars.

The quasars are the brilliant cores of active galaxies powered by black holes. The team is able to observe how the light from the quasars is absorbed by the handle of gas and how that absorption changes in different regions. The Hubble Cosmic Origins Spectrograph was used to study the ultraviolet light from those quasars.