A quasar Milky Way six million years ago?As the first human ancestors walked the Earth, our galaxy’s central black hole might have been in the process of blasting away most of the galaxy’s normal matter.
In recent decades, astronomers have learned that the center of our home galaxy, the Milky Way, contains a four-million-solar-mass black hole. For the most part, this supermassive black hole is inactive, although it’s known to swallow sips of hydrogen gas occasionally. But, if astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) are correct, the Milky Way recently (by cosmic standards) went through a quasar stage in its evolution. The astronomers say it happened when the Milky Way’s central black hole swallowed a huge amount of gas, creating a shock wave that has now crossed 20,000 light-years of space. They say that event left behind a million-degree gaseous fog, a sort of “bubble” that extends from the Milky Way’s core two-thirds of the way to Earth. It’s this “bubble” that the astronomers say they’ve now observed, via data from an X-ray spacecraft. Thus, according to their August 29, 2016 statement, six million years ago:
The CfA study – which has been accepted for publication by the Astrophysical Journal – was led by Fabrizio Nicastro, who holds joint appointments at CfA and the Italian National Institute of Astrophysics. The study is based on a search for the galaxy’s missing mass. Nicastro explained:
The CfA statement explained the missing mass as follows:
Nicastro and his group analyzed archival X-ray observations – older data that had been stored – from ESA’s XMM-Newton spacecraft in their search for the Milky Way’s missing mass. Their statement said they found:
The astronomers used the amount of absorption to calculate how much normal matter was there, and how it was distributed. They applied computer models but learned that they couldn’t match the observations with a smooth, uniform distribution of gas. Instead, they found that there is a “bubble” in the center of our galaxy that extends two-thirds of the way to Earth. Their statement explained:
The astronomers say this timeline is corroborated by the presence of 6-million-year-old stars near the Milky Way’s center. They said they believe those stars formed from some of the same material that once flowed toward the black hole. They also said the observations and associated computer models show that the hot, million-degree gas can account for up to 130 billion solar masses of material. That’s a lot of mass, but the Milky Way’s missing mass is also alot. Their statement said the numbers add up and that their ideas:
Their statement also spoke of a concept for a next-generation space mission known as X-ray Surveyor:
Bottom line: Astronomers at the Harvard-Smithsonian Center for Astrophysics believe that our galaxy’s central black hole might have been in a quasar phase of activity six million years ago. Via the Harvard Smithsonian Center for Astrophysics
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