By NASA // September 8, 2020
The invisible light of the expanded plasma extends from the galaxy to 1.3 million light years
(NASA) – In a landmark study, scientists using NASA’s Hubble Space Telescope mapped an enormous gas envelope called the halo that surrounds our nearest large galaxy, the Andromeda Galaxy.
Scientists are amazed that this delicate, almost invisible stream of expanded plasma extends from the galaxy to 1.3 million light-years — up to half our Milky Way — and in some directions to 2 million light-years.
This means that the halo of Andromeda is already bursting into the halo of our own galaxy.
They found that the hollow had a layered structure, with two main clusters and distinct gas shells. This is the most comprehensive study of a halo around a galaxy.
Samantha Berek, a fellow researcher at Yale University in New Haven, Connecticut, explained. “It is important to understand the massive gases that surround galaxies.
“This gas reservoir will provide fuel for future galaxy formations in the galaxy, as well as coming out of events such as supernovae.
“We found the inner shell to be very complex and dynamic, stretching back half a million light years,” explained Nicholas Lehner, study leader at the University of Notre Dame in Indiana.
“The outer shell is soft and warm. This difference affects the internal flow more directly due to the effect of supernova activity on the galactic disk. ”
The signature of this activity is the discovery of large amounts of massive elements in the airflow of Andromeda. Massive elements are cooked inside the stars and then emitted into space — sometimes violently when the star dies. Halo is then contaminated with this material from stellar explosions.
The Andromeda Galaxy, also known as M31, is probably the majestic spiral of 1 trillion stars and comparable to our Milky Way.
At a distance of 2.5 million light-years, the galaxy appears to be high in cigar-shaped light in the autumn sky.
If its airflow could be seen with the naked eye, it would be three times the width of the Big Dipper. This is the biggest feature of the night sky.
Through a program called Project AMIGA (Absorption Map of Ionized Gas in Andromeda), the study examined light from 43 quasars — the most distant, spectacular cores of active galaxies driven by black holes — beyond Andromeda.
Quasars are scattered behind the halo, allowing scientists to explore multiple areas. Looking through the halo at the quasars light, the team observed how this light is perceived by the Andromeda halo and how that absorption changes in different areas.
The enormous Andromeda Hollow is made up of highly verified and ionized gas that does not emit easily detectable radiation. Therefore, absorbing light coming from a background source is a good way to investigate this material.
The Lehner team examined Andromeda’s halo beforehand. In 2015, they discovered that the Andromeda Hollow was large and massive. But there is little hint of its complexity; Now, it has been mapped in more detail, leading to a more accurate determination of its size and mass.
“Previously, the galaxy had very little information in just 1 million light-years — only six quasars.
“It is important to examine the gas in this radius, because it represents the sphere of gravity to Andromeda.”
Because we live inside the Milky Way, scientists cannot easily understand the signature of the halo of our own galaxy. However, they believe that the haloes of Andromeda and the Milky Way are very similar because these two galaxies are so similar.
The two galaxies are in a collision course and form a large elliptical galaxy beginning 4 billion years from now.
Scientists have studied the air currents of galaxies farther away, but those galaxies are so small in the sky that the number of background quasars bright enough to observe their flow is usually only one per galaxy.
Therefore spatial information is inevitably lost. Due to its proximity to Earth, Andromeda’s airflow is large in the sky, allowing for a much wider pattern.
“It’s really a unique experiment, because with Andromeda we have not only one or two scenes but more than 40 information on its flow,” Lehner explained. “It’s amazing to capture the complexity of the galaxy halo beyond our own Milky Way.”
In fact, Andromeda is the only galaxy in the universe, this experiment can be done now, and only with Hubble.
Only with the ultraviolet-sensitive future space telescope can scientists routinely carry out this type of experiment beyond the approximately 30 galaxies that make up the native cluster.
“So Project AMIGA gave us a glimpse into the future,” Lehner said.
The team’s results appear in the August 27 issue of The Astrophysical Journal.