ESA NASA Hubble Images: Changes in a black-hole-powered jet of hot gas

This sequence of images, taken over a 13-year span by NASA's Hubble Space Telescope, reveals changes in a black-hole-powered jet of hot gas in the giant elliptical galaxy M87. 

The observations show that the river of plasma, traveling at nearly the speed of light, may follow the spiral structure of the black hole's magnetic field, which astronomers think is coiled like a helix. 

The magnetic field is believed to arise from a spinning accretion disk of material around a black hole. 

Although the magnetic field cannot be seen, its presence is inferred by the confinement of the jet along a narrow cone emanating from the black hole. 

The visible portion of the jet extends 5,000 light-years. M87 resides at the center of the neighboring Virgo cluster of roughly 2,000 galaxies, located 50 million light-years away. 

The images are part of a time-lapse movie that reveals changes in the jet over more than a 13-year period. 

They were taken by Hubble's Advanced Camera for Surveys in 2006 and Wide Field Planetary Camera 2 in 1995, 1998, 2001, and 2007. 

Credit: NASA, ESA, E. Meyer, W. Sparks, J. Biretta, J. Anderson, S.T. Sohn, and R. van der Marel (STScI), C. Norman (Johns Hopkins University), and M. Nakamura (Academia Sinica)

The Milky Way is surrounded by a massive halo of hot gas

An international team of astronomers has combined data from NASA's Chandra X-ray observatory, ESA's XMM-Newton space observatory and Japan's Suzaku satellite to suggest that our galaxy may be surrounded by a halo of hot gas extending in all directions for hundreds of thousands of light-years. 

The finding also offers clues as to why more than half of the ordinary matter in early galaxies has seemingly disappeared without leaving a trace.

Protons and neutrons are classified as "baryons," a type of subatomic particle that interacts strongly to form the nuclei of atoms. Taken together, baryons make up nearly all of the ordinary matter in our universe.

But if you were to tally the number of atoms in the universe, you'd find that something doesn't quite add up.

Astronomers have observed that entire galaxies seem to lose over half of their atoms compared to when they first formed.

All of this matter couldn't have simply disintegrated, so where has it gone? This decade-old question is known as the problem of the "missing baryons."

Now, a team of astronomers led by Dr. Anjali Gupta may have just found the answer, at least for our galaxy.

The baryons, says Gupta, haven't disappeared from the Milky Way. Rather, a mass of up to sixty billion suns – well in excess of the matter contained in the entire galactic disk – is spread out over a halo of hot gas stretching all around us for hundreds of thousands of light-years.

This gas is reaching temperatures in the millions of degrees, and with a density so low that, even if it were present in other galaxies, we would probably have no way of detecting it.

"With reasonable assumptions, our observations imply a huge reservoir of hot gas around the Milky Way," said co-author Smita Mathur of Ohio State University in Columbus.

"It may extend for a few hundred thousand light-years around the Milky Way or it may extend farther into the surrounding local group of galaxies. Either way, its mass appears to be very large."

A paper detailing the study was published on The Astrophysical Journal.