Credit: X-ray (NASA/CXC/Univ of Strasbourg/M. Pakull et al); Optical (ESO/VLT/Univ of Strasbourg/M. Pakull et al); H-alpha (NOAO/AURA/NSF/CTIO 1.5m)

NASA recently published a composite multi-wavelength image of a wonderful galaxy, known as NGC 7793. This galaxy, located about 12.7 million light years, is close to our Galaxy, the Milky Way, by the cosmic distance standards. It shows an intriguing phenomenon, termed microquasar. NGC 7793’s microquasar is a luminous object, powered by an active black hole, in the outskirts of the galaxy.

Quasars are the most luminous objects in the universe. A quasar is a galaxy with energetic luminous core, whose activity is driven by an extremely massive black hole, termed supermassive black hole. Micorquasars are miniature versions of quasars.

The image was created by combining X-ray observations, acquired by the Chandra X-ray Observatory (CXO), and optical observations, obtained by two sophisticated ground-based telescopes. The CXO data are represented in red, green and blue, while the visual light ground-based observations, from the Very Large Telescope (VLT), and the CTIO 1.5-m telescope, are colored in light blue and gold, respectively.

The upper inset is a close-up of the X-ray image of the microquasar, which is a system containing a stellar-sized black hole consuming material from a companion star. Gas spiraling into the black hole forms a disk around the black hole. Twisted magnetic fields in the disk generate strong electromagnetic forces that eject some of the gas away from the disk at high speeds, in two jets, forming a huge bubble of hot gas, about 1,000 light years across.

The faint bluish green source near the centre of the upper inset marks the position of the black hole, while the reddish yellow (upper right) and yellow (lower left) sources correspond to spots where the jets are rushing into surrounding gas, and heating it. The lower inset shows the nebula produced by energy from the jets, in light emitted by hydrogen.
The jets in the NGC 7793 microquasar are the most powerful ever detected around a stellar-mass black hole, and the data show that an astonishing amount of energy from the black hole is being released in the jets. The power of the jets is estimated to be about ten times larger than that of the jets of a powerful microquasar in our own Galaxy, designated SS433.

Further Reading

CXO Press Release
http://chandra.harvard.edu/press/10_releases/press_070710.html

NASA-Exploring the Invisible Universe
http://www.nasa.gov/mission_pages/chandra/main/index.html

CXO
http://chandra.harvard.edu/index.html

Aymen Mohamed Ibrahem
Senior Astronomy Specialist