Sagittarius A*

Sagittarius A*: The Milky Way's supermassive black hole, about 26,000 light years from Earth.

The supermassive black hole at the center of the Milky Way may be producing tiny particles,called neutrinos, that have virtually no mass and carry no electric charge. This Chandra image shows the region around the black hole, known as Sagittarius A*, in low, medium, and high-energy X-rays (red,green, and blue respectively.) Scientists have found a connection to outbursts generated by the black hole and seen by Chandra and other X-ray telescopes with the detection of high-energy neutrinos in an observatory under the South Pole.

Scale: Image is 12 arcmin across (about 91 light years).

Image credit: NASA/CXC/Univ. of Wisconsin/Y.Bai. et al.

Note: For more information, see Sagittarius A*: NASA X-ray Telescopes Find Black Hole May Be a Neutrino Factory.

Virtual Guide to the Milky Way

This virtual journey shows the different components that make up our home galaxy, the Milky Way, which contains about a hundred billion stars.

It starts at the black hole at the center of the Milky Way and with the stars that orbit around it, before zooming out through the central Galactic Bulge, which hosts about ten billion stars.

The journey continues through a younger population of stars in the stellar disc, home to most of the Milky Way's stars, and which is embedded in a slightly larger gaseous disc. Stars in the disc are arranged in a spiral arm pattern and orbit the center of the Galaxy.

The discs and bulge are embedded in the stellar halo, a spherical structure that consists of a large number of globular clusters – the oldest population of stars in the Galaxy – as well as many isolated stars. An even larger halo of invisible dark matter is inferred by its gravitational effect on the motions of stars in the Galaxy.

Looking at a face-on view of the Galaxy we see the position of our Sun, located at a distance of about 26,000 light-years from the Galactic Center.

Finally, the extent of the stellar survey conducted by ESA’s Hipparcos mission is shown, which surveyed more than 100,000 stars up to 300 light-years away from the Sun. In comparison, ESA’s Gaia survey will study one billion stars out to 30,000 light-years away.

Video credit: ESA

Sagittarius A*

Sagittarius A*: The supermassive black hole at the center of the Milky Way.

New evidence has been uncovered for the presence of a jet of high-energy particles blasting out of the Milky Way's supermassive black hole known as Sagittarius A* (Sgr A*). This image of Sgr A* and the region around it contains some of the data used in the study, with X-rays from Chandra (purple) and radio emission from the Very Large Array (blue). Jets of high-energy particles are found throughout the Universe on large and small scales. The likely discovery of a jet from Sgr A* helps astronomers learn more about the giant black hole, including how it is spinning.

Scale: Image is 1.2 arcmin across. (about 9 light years).

Image credit: X-ray: NASA/CXC/UCLA/Z.Li et al; Radio: NRAO/VLA

Note: For more information, see Sagittarius A*: New Evidence For A Jet From Milky Way's Black Hole.

Light Echos from Sagittarius A*

Sagittarius A*: The supermassive black hole about 26,000 light years from Earth at the center of the Milky Way.

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. This image is from a new study of Chandra observations taken over twelve years that shows 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.

Scale: Image is 18.5 arcmin across. (about 140 light years).

Image credit: NASA/CXC/APC/Université Paris Diderot/M.Clavel et al

Note: For more information, see Sagittarius A*: A Glimpse of the Violent Past of Milky Way's Giant Black Hole

The Milky Way's Galactic Center in Infrared

This image, not unlike a pointillist painting, shows the star-studded center of the Milky Way towards the constellation of Sagittarius. The crowded center of our galaxy contains numerous complex and mysterious objects that are usually hidden at optical wavelengths by clouds of dust — but many are visible here in these infrared observations from Hubble.

However, the most famous cosmic object in this image still remains invisible: the monster at our galaxy’s heart called Sagittarius A*. Astronomers have observed stars spinning around this supermassive black hole (located right in the center of the image), and the black hole consuming clouds of dust as it affects its environment with its enormous gravitational pull.

Infrared observations can pierce through thick obscuring material to reveal information that is usually hidden to the optical observer. This is the best infrared image of this region ever taken with Hubble, and uses infrared archive data from Hubble’s Wide Field Camera 3, taken in September 2011.

Photo credit: NASA, ESA, and G. Brammer

Sagittarius A*

Sagittarius A*: The supermassive black hole located 26,000 light years from Earth in the center of the Milky Way.

One of the biggest observing campaigns ever performed by Chandra has provided new understanding into why gas near the giant black hole at the center of the Milky Way is extraordinarily faint in X-rays. The large image contains X-rays from Chandra (blue) and infrared emission from the Hubble (red and yellow). The inset shows a close-up of Sgr A* in X-rays only, covering a region half a light year wide. The diffuse X-ray emission is from hot gas captured by the black hole and being pulled inwards. The new results indicate that less than 1% of the material that is initially within the black hole’s gravitational grasp reaches the event horizon, or, point of no return.

Scale: Wide-field: 1 arcmin across (about 7.5 light years); Close-up: about 4 arcsec (about 0.5 light year).

Image credit: X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI

Note: For more information, see Sagittarius A*: NASA'S Chandra Catches Our Galaxy's Giant Black Hole Rejecting Food.

Hot Gas Falling Into Sagittarius A*

This artist's concept illustrates the frenzied activity at the core of our Milky Way galaxy. The galactic center hosts a supermassive black hole in the region known as Sagittarius A*, or Sgr A*, with a mass of about four million times that of our sun. The Herschel space observatory has made detailed observations of surprisingly hot gas that may be orbiting or falling toward the supermassive black hole.

A dense torus of gas and dust surrounds the galactic center and occupies the innermost 15 light-years of our galaxy. Enshrouded within the disk is a central cavity, with a radius of a few light-years, filled with warm dust and lower density gas.

Part of this gas is being heated by the strong ultraviolet radiation from massive stars that closely orbit the central black hole. Heating also likely results from strong shocks, generated in collisions between gas clouds, or in material flowing at high speeds.

Illustration credit: ESA/C. Carreau

Note: For more information, see:
* Milky Way Black Hole Snacks on Hot Gas
* Galactic Centre
* Herschel Reveals the Milky Way's Warm Heart

Sagittarius A*

Sagittarius A*: The supermassive black hole at the center of the Milky Way galaxy, about 26,000 light years from Earth.

A new study provides a possible explanation of mysterious X-ray flares detected by Chandra over the period of several years. It suggests that there is a cloud around Sgr A* containing trillions of asteroids and comets, stripped from their parent stars. The flares occur when asteroids of six miles or larger in radius are consumed by the black hole. The panel on the left shows a very long Chandra observation of the region around the Sgr A*, while the three panels on the right are artist's impressions of the path that a doomed asteroid would take on its way to the black hole.

Scale: Image is 15 arcminutes across (20 light years)

Photo credit: X-ray: NASA/CXC/MIT/F. Baganoff et al.; Illustrations: NASA/CXC/M.Weiss

Note: For more information, see Sagittarius A*: NASA's Chandra Finds Milky Way's Black Hole May be Grazing on Asteroids