Sagittarius A* at the Center of Our Galaxy


A black hole called Sagittarius A* (pronounced A-star) lies at the center of our Milky Way Galaxy, only 27,000 light-years away. Its mass is roughly 4 million times the mass of the Sun. Our galaxy’s black hole is mild-mannered compared to the central black holes in some other galaxies, much more calmly consuming material around it. However, it does sometimes flare-up. An flareup lasting several hours is documented in this series of X-ray images from the orbiting Nuclear Spectroscopic Telescope Array (NuSTAR). NuSTAR is the first instrument to provide focused views of the area surrounding Sgr A* at X-ray energies higher than those accessible to the Chandra and XMM observatories. The flare sequence is shown in the panels on the right. The images cover a two-day span. X-rays are generated in material heated to over 100 million C and traveling at nearly the speed of light as it falls into the black hole. The center X-ray image spans about 100 light-years. Its bright white region is the hottest material closest to the black hole; the pinkish cloud probably belongs to the remnant of a nearby supernova. Click the picture to embiggen it.

Sgr A* is monitored on a daily basis by the X-ray telescope of the Swift satellite. I made contributions to the design of the power and thermal control systems of the Burst Alert Telescope instrument on Swift.

Image Credit: NASA

At the Core


SagA*quietThere’s a supermassive black hole at the center of our Milky Way galaxy. It’s known as Sagittarius A* and shown in the center of this infrared (red and yellow) and X-ray (blue) composite image. Data from observations taken in orbit by Chandra‘s X-ray telescope was used to create an image the diffuse emission surrounding the black hole. See the close-up inset. The inset’s field of view covers an area about 1/2 light-year across the galactic center some 26,000 light-years away. These X-ray emissions originate in hot gas drawn from the winds of massive young stars near the galactic center. The Chandra data indicate that only 1% or so of the gas within the black hole’s gravitational influence ever reaches the event horizon after losing enough heat and angular momentum to fall into the black hole. The rest of the gas escapes in an outflow. This explains why the Milky Way’s black hole is so quiet, much fainter than might be expected in energetic X-rays.

Note: All data is subject to future verification. Beowulf Shaeffer was unavailable for comment.

Image Credit: NASA

Looking at an Asteroid and Seeing a Black Hole


This animation simulates an X-ray outburst from a black hole MAXI J0637-043 that was detected by the REXIS instrument aboard the OSIRIS-REx spacecraft, as the black hole moved through REXIS’s line of sight. The outburst is initially intense, but it gradually fades. The animation was constructed using data collected by the X-ray spectrometer while observations were being made of the space around asteroid Bennu on 11 November, 2019.
Image Credits: NASA / Goddard / University of Arizona / MIT / Harvard

A Black Hole on Edge


When viewed almost on edge, the disk of gas spinning around a black hole takes on a odd double-humped appearance. The black hole’s extreme gravity deflects the paths of light coming from different parts of the disk, producing the warped image. What the observer sees depends on his viewing angle. The greatest distortion occurs when viewing the system nearly edgewise.
Animation Credit: NASA / Jeremy Schnittman

A Microquasar


This is SS 433, a microquasar located about 18,000 light-years away in the constellation Aquila. This image at submillimeter wavelengths is special because it shows the jets emitted by a hot, swirling disc of material around the black hole at SS 433’s center. The jets’ corkscrew shapes are created by a phenomenon known as precession. The two jets are slowly wobbling about their spin axes in the same manner as a spinning top as it slows down. The corkscrew is enormous—5000 times the size of the Solar System.

Image Credit: ESO

Magnetism and a Black Hole


The dusty streamlines in this image highlight the magnetic fields around the Milky Way’s massive black hole. The Y-shaped structure is warm material falling toward the black hole, which is located near the intersection of the the two arms of the Y. The streamlines reveal that the magnetic field closely follows the shape of the dusty structure surrounding the black hole. Each of the blue arms has its own field that is distinct from the rest of the ring which is shown in pink. The dust and magnetic fields are from data taken by SOFIA and have been overlaid on a visible light image from Hubble.
Image Credit: NASA

A Black Hole


A black hole and its shadow have been captured in an image for the first time, a historic feat by an international network of radio telescopes called the Event Horizon Telescope. The black hole at the center of galaxy M87 is outlined in the image by emission from hot gas swirling around it under the influence of the strong gravity near the event horizon.

Image Credit: Event Horizon Telescope collaboration et al.

NGC 3201


NGC 3201 is an oddball among the 150-or-so globular star clusters in the Milky Way. It is moving very rapidly through the galaxy, and its motion is retrograde, that is, it’s orbiting around the galactic core in the opposite direction of most of the stars in the galaxy. That’s led to speculation that it may have come from outside and have been captured.

Also, it contains a black hole which was revealed by the strange movements of a star being quickly flung around the massive, invisible singularity.

Image Credit: ESA / NASA

Fornax A


Fornaxgiant_radioFornax A is a galaxy with a very active black hole in its core. That black hole is send out huge jets of radio waves. The white glow in the center of this picture is the visible galaxy NGC 1316. There’s another, smaller galaxy just above it. These two galaxies are merging, and as gas and dust are stripped out of the small galaxy and poured into the center of NGC 1316. The huge radio lobes (shown as orange blobs in this multi-wavelength image) to either side of this merger are signs that a black hole is being fed more than it can handle and spinning some of the material out into intergalactic space.

Image Credit: NRAO

X Marks the Core


M51 X in CoreThis Hubble Space Telescope image of the core of the spiral galaxy M51 shows a dark “X” silhouetted across the galaxy’s nucleus. The “X” is caused by absorption of light by dust and marks the position of a black hole which may have a mass about one-million times the mass of the Sun. The darkest bar may be an edge-on view of a dust ring 100 light-years in diameter. It blocks the black hole its accretion disk as seen from Earth. The second bar of the “X” could be a second disk seen edge on, or it might be rotating gas and dust in M51 intersecting with the jets and ionization cones from the black hole.

Image Credit: NASA