X-ray Surveyor tagged posts

Credit: Harvard-Smithsonian Center for Astrophysics

The center of the Milky Way galaxy is currently a quiet place where a supermassive black hole slumbers, only occasionally slurping small sips of hydrogen gas. But it wasn’t always this way. A new study shows that 6 million years ago, when the first human ancestors known as hominins walked the Earth, our galaxy’s core blazed forth furiously. The evidence for this active phase came from a search for the galaxy’s missing mass.

Measurements show that the Milky Way galaxy weighs about 1-2 trillion times as much as our Sun. About 5/6 of that is in the form of dark matter. The remaining 1/6 of our galaxy’s heft, or 150-300 billion solar masses, is normal matter...