The halo surrounding the Milky Way is much hotter than previously thought

Halos provide evidence about how galaxies form.


The outer “halo” region of the Milky Way, as with other galaxies, contains the vast majority of the mass of the Galaxy. Yet the exact mass and shape of the halo are not known.

Now, a new study has suggested that the halo surrounding our milky way galaxy is much hotter than scientists once believed.

Past study at Ohio State University suggested that the Milky Way’s halo was at least ten times hotter than anyone had known before.

In this study, scientists found that the extreme temperatures detected in the original analysis up to 10 million degrees Kelvin, or about 18 million degrees Fahrenheit—could be found in the entire halo.

Smita Mathur, professor of astronomy at Ohio State, said“We can’t say for sure that it is everywhere, because we have not analyzed the entire halo. But we know now that the temperatures we saw in the first study are not unique, and that is very exciting.”

“The findings could help astronomers understand more about how the Milky Way and galaxies like it form and grow.”

“We are trying to learn about the elements that form these halos, 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.”

For the study, scientists analyzed the data from an X-ray observatory telescope run by the European Space Agency. That telescope, called XMM-Newton, collects data in X-rays that would have otherwise been blocked by Earth’s atmosphere. The telescope collected that data from within the Milky Way focused in one direction.

Mathur said. “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.”

Anjali Gupta, a visiting astronomy researcher at Ohio State, analyzed data from the Japanese X-ray satellite telescope Suzaku, which collected spectrum from the Milky Way’s halo in four different directions. That analysis confirmed their 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 new findings were presented at a meeting of the American Astronomical Society.


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