In a landmark study, scientists utilizing NASA’s Hubble Area Telescope have mapped the immense envelope of gas, called a halo, surrounding the Andromeda galaxy, our nearest big galactic neighbor. Researchers were amazed to discover that this tenuous, almost unnoticeable halo of diffuse plasma extends 1.3 million light-years from the galaxy– about midway to our Galaxy– and as far as 2 million light-years in some instructions. This suggests that Andromeda’s halo is currently bumping into the halo of our own galaxy.
They also discovered that the halo has a layered structure, with 2 main nested and distinct shells of gas. This is the most comprehensive research study of a halo surrounding a galaxy.
” Comprehending the huge halos of gas surrounding galaxies is immensely important,” explained co-investigator Samantha Berek of Yale University in New Haven, Connecticut. “This tank of gas consists of fuel for future star formation within the galaxy, as well as outflows from occasions such as supernovae.
” We find the inner shell that encompasses about a half million light-years is even more complex and dynamic,” discussed study leader Nicolas Lehner of the University of Notre Dame in Indiana. “The external shell is smoother and hotter. This difference is a most likely arise from the effect of supernova activity in the galaxy’s disk more directly impacting the inner halo.”
A signature of this activity is the team’s discovery of a large amount of heavy components in the gaseous halo of Andromeda. The halo is then infected with this product from stellar explosions.
The Andromeda galaxy, likewise referred to as M31, is a magnificent spiral of maybe as numerous as 1 trillion stars and comparable in size to our Galaxy. At a range of 2.5 million light-years, it is so near us that the galaxy appears as a cigar-shaped smudge of light high in the fall sky. If its gaseous halo could be seen with the naked eye, it would have to do with three times the width of the Big Dipper. This would quickly be the most significant function on the nighttime sky.
Through a program called Job AMIGA (Absorption Map of Ionized Gas in Andromeda), the research study examined the light from 43 quasars– the very far-off, brilliant cores of active galaxies powered by great voids– situated far beyond Andromeda. The quasars are scattered behind the halo, enabling researchers to probe numerous areas. Checking out the halo at the quasars’ light, the group observed how this light is soaked up by the Andromeda halo and how that absorption modifications in various areas. The immense Andromeda halo is made from really rarified and ionized gas that doesn’t release radiation that is quickly noticeable. Tracing the absorption of light coming from a background source is a much better way to probe this material.
The researchers used the special ability of Hubble’s Cosmic Origins Spectrograph (COS) to study the ultraviolet light from the quasars. Ultraviolet light is absorbed by Earth’s atmosphere, that makes it difficult to observe with ground-based telescopes. The group used COS to discover ionized gas from carbon, silicon, and oxygen. An atom becomes ionized when radiation strips one or more electrons from it.
Andromeda’s halo has been penetrated before by Lehner’s team. In 2015, they found that the Andromeda halo is big and massive.
” Previously, there was extremely little info– just 6 quasars– within 1 million light-years of the galaxy. This brand-new program provides much more info on this inner area of Andromeda’s halo,” discussed co-investigator J. Christopher Howk, likewise of Notre Dame.
Due to the fact that we live inside the Milky Way, scientists can not easily analyze the signature of our own galaxy’s halo. They believe the halos of Andromeda and the Milky Method should be very comparable given that these 2 galaxies are quite comparable.
Researchers have studied gaseous halos of more distant galaxies, however those galaxies are much smaller sized on the sky, suggesting the number of brilliant adequate background quasars to penetrate their halo is typically only one per galaxy. Spatial info is for that reason essentially lost. With its close distance to Earth, the gaseous halo of Andromeda looms large on the sky, permitting a much more comprehensive tasting.
” This is truly a special experiment because only with Andromeda do we have information on its halo along not just one or two sightlines, but over 40,” explained Lehner. “This is groundbreaking for capturing the complexity of a galaxy halo beyond our own Milky Way.”
In truth, Andromeda is the only galaxy in the universe for which this experiment can be done now, and only with Hubble. Just with an ultraviolet-sensitive future area telescope will researchers have the ability to consistently undertake this type of experiment beyond the approximately 30 galaxies making up the Resident Group.
” So Job AMIGA has actually likewise given us a look of the future,” said Lehner.
The team’s findings appear in the Aug. 27 edition of The Astrophysical Journal
The Hubble Area Telescope is a job of international cooperation between NASA and ESA (European Space Firm). NASA’s Goddard Area Flight Center in Greenbelt, Maryland, handles the telescope. The Space Telescope Science Institute (STScI) in Baltimore performs Hubble science operations. STScI is run for NASA by the Association of Universities for Research Study in Astronomy, in Washington, D.C.