Using deep X-ray observations from ESA’s XMM-Newton Observatory, astronomers have discovered that Milky Way’s halo — a large cloud of ionized plasma surrounding the Galaxy — has a temperature of 10 million degrees Kelvin (about 18 million degrees Fahrenheit) — about 10 times hotter than previously estimated.
Our Milky Way Galaxy is surrounded by an enormous halo of plasma (seen in blue in this artists’ rendition). Image credit: NASA / CXC / M.Weiss / Ohio State / A. Gupta et al.
“We can’t say for sure that it is everywhere, because we have not analyzed the entire halo,” said Ohio State University’s Professor Smita Mathur, lead author on the research.
“We are trying to learn about the elements that form halos of galaxies, and about the temperatures there.”
“Knowing those things can help us understand more about how galaxies connect with the rest of the Universe, and how they formed and where elements might have come from.”
In the study, Professor Mathur and colleagues analyzed data collected by XMM-Newton.
“It showed us that the halo was much hotter than we had known, but it didn’t show us whether that was the case throughout the Galaxy, or if the telescope had picked up an aberration caused by an unknown force coming from the direction where the telescope was pointed,” she said.
The team also analyzed data from the Japanese X-ray satellite telescope Suzaku, which collected spectrum from the Milky Way’s halo in four different directions.
The analysis confirmed the earlier finding, that the halo is much hotter than had previously been known, and also showed that the other parts of the halo likely are that hot.
The astronomers also wondered if the temperatures they found in the Milky Way’s halo might be found in other galaxies.
They analyzed data for NGC 3221, a Milky Way-like galaxy about 200 million light years away from Earth.
They found that NGC 3221’s halo is about as hot as the halo surrounding our Milky Way Galaxy.
The researchers presented their findings in three separate analyses this week at the 236th Meeting of the American Astronomical Society (AAS).
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S. Mathur. The Hot Circumgalactic Medium of the Milky Way. AAS 236, abstract # 116.01
A. Gupta et al. How Ubiquitous is the Hot Component in the Milky Way CGM? AAS 236, abstract # 306.07
S. Das et al. Evidence for a non-isothermal, extended, massive hot CGM of an L* galaxy: a Suzaku and XMM-Newton discovery. AAS 236, abstract # 205.04
