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

A Wide Spectrum Look at M101


It’s one of the last entries in Charles Messier’s famous catalog, but M101 is definitely not one of the least. The galaxy is big—roughly 170,000 light-years across, almost twice the size of our own Milky Way Galaxy. This multiwavelength view is a composite of images recorded by space-based telescopes. Color coded from X-rays to infrared wavelengths (high to low energies), the image data was taken from the Chandra X-ray Observatory (x-rays, purple), the Galaxy Evolution Explorer (ultraviolet, blue), the Hubble Space Telescope (visible light, yellow), and the Spitzer Space Telescope (infrared, red). While the X-ray data shows the multimillion degree gas around M101’s exploded stars and neutron star and black hole binary star systems, the lower energy data shows the stars and dust that define M101’s grand spiral arms. Known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major. It’s about 25 million light-years away.

Image Credit: NASA

Mergers and Acquisitions


Galaxy clusters are the largest objects in the universe held together by gravity. They can contain hundreds or thousands of galaxies held together in vast clouds of multi-million-degree gas glowing in X-rays.

The system known as Abell 2384 is the result of the collision of a pair galaxy cluster hundreds of millions of years ago. This composite image was put together using x-ray data from the Chandra X-ray Observatory and XMM-Newton (blue) and radio data from the Giant Metrewave Radio Telescope in India (red). It shows the superheated bridge of gas running through Abell 2384 and reveals the effects of a jet from a supermassive black hole in the center of a galaxy in one of the clusters. The jet is so powerful that it bends the shape of the 3 million light-year long gas bridge which has the mass of about 6 trillion Suns.

Image Credit: NASA

Inside the Flame Nebula


NGC 2024Stars are often born in clusters, in giant clouds of gas and dust. This composite image shows one such cluster, NGC 2024, which is found in the center of the Flame Nebula about 1,400 light years from Earth. X-rays from the Chandra X-ray Observatory are shown in purple, and infrared data from the Spitzer Space Telescope are colored red, green, and blue.

Image Credit: NASA

A Multi-Wavelength Crab


This composite view of the Crab Nebula uses data from the Chandra X-Ray Observatory (blue and white), the Hubble Space Telescope (purple), and the Spitzer Space Telescope (pink). The nebula is the remnant of a supernova that was seen on Earth in AD 1054.

It’s powered by a pulsar, a quickly spinning neutron star  formed when a original star ran out nuclear fuel and collapsed. The combination of rapid rotation and a strong magnetic field in the Crab generates jets of matter and anti-matter moving away from the pulsar’s poles and an intense stellar wind flowing out of its equator.

Image Credit: NASA