Remarkable flares from the galactic center

Sagittarius A* (Sgr A*), the supermassive black hole at the center of our Milky Way Galaxy, is 100 times closer to us than any other SMBH and therefore a prime candidate for studies of how matter radiates as it accretes onto black holes. SgrA* has been observed for decades and rapid fluctuations reported from X-ray to the near infrared wavelengths (intervening dust reduces optical light signals by a factor of over a trillion) and at submillimeter and radio wavelengths.

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Credit: X-ray: NASA/CXC/UMass/D. Wang et al.; Optical: NASA/ESA/STScI/D.Wang et al.; IR: NASA/JPL-Caltech/SSC/S.Stolovy

A multiwavelength view of the field around the Milky Way's galactic center seen from the X-ray (blue) through the infrared (red). Astronomers have measured flaring events at multiple wavelengths coming from the supermassive black hole at the very center.

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Astronomers have discovered evidence for thousands of black holes located near the center of our Milky Way galaxy using data from NASA's Chandra X-ray Observatory.

This black hole bounty consists of stellar-mass black holes, which typically weigh between five to 30 times the mass of the Sun. These newly identified black holes were found within three light years — a relatively short distance on cosmic scales — of the supermassive black hole at our Galaxy's center known as Sagittarius A* (Sgr A*).

A black hole by itself is invisible. However, a black hole — or neutron star — locked in close orbit with a star will pull gas from its companion.

Astronomers call these systems "X-ray binaries". This material falls into a disk and heats up to millions of degrees and produces X-rays before disappearing into the black hole. Some of these X-ray binaries appear as point-like sources in the Chandra image.

Researchers have found evidence that the normally dim region very close to the supermassive black hole at the center of the Milky Way galaxy flared up with at least two bright outbursts in the past few hundred years.

These images are from a study of Chandra observations taken over twelve years that show rapid variations in the X-ray emission from gas clouds surrounding the supermassive black hole.

The phenomenon, known as a "light echo," provides astronomers an opportunity to piece together what objects like Sgr A* were doing long before there were X-ray telescopes to observe them.

A new study using data from NASA's NuSTAR space telescope suggests that the most luminous and massive stellar system within 10,000 light-years, Eta Carinae, is accelerating particles to high energies -- some of which may reach Earth as cosmic rays.

Cosmic rays with energies greater than 1 billion electron volts (eV) come to us from beyond our solar system. But because these particles -- electrons, protons and atomic nuclei -- all carry an electrical charge, they veer off course whenever they encounter magnetic fields. This scrambles their paths and masks their origins.

Eta Carinae, located about 7,500 light-years away in the southern constellation of Carina, contains a pair of massive stars whose eccentric orbits bring them unusually close every 5.5 years. The stars contain 90 and 30 times the mass of our Sun.