Great Annihilator

This article is about the astronomical object. For the Swans album, see The Great Annihilator.

1E1740.7-2942, or the Great Annihilator,^[3][4] is a Milky Way microquasar, located near the Galactic Center on the sky.^[5][2] It likely consists of a black hole and a companion star. It is one of the brightest X-ray sources in the region around the Galactic Center.^[6]

Great Annihilator

Observation data Epoch J2000      Equinox J2000
Constellation	Ophiuchus
Right ascension	17h 43m 54.83s[1]
Declination	−29° 44′ 42.6″[1]
Astrometry
Distance	16,000 ly (5,000[2] pc)
Database references
SIMBAD	data

The object was first detected in soft X-rays by the Einstein Observatory,^[7] and later detected in hard X-rays by the Soviet Granat space observatory.^[2] Followup observations by the SIGMA detector on board Granat showed that the object was a variable emitter of massive amounts of photon pairs at 511 keV, which usually indicates the annihilation of an electron-positron pair.^[8][9] This led to the nickname, "Great Annihilator."^[10] Early observations also showed a spectrum similar to that of the Cygnus X-l, a black hole with a stellar companion, which suggested that Great Annihilator was also a stellar mass black hole.^[8]

The object also has a radio source counterpart that emits jets approximately 1.5 pc (5 ly) long.^[11] These jets are probably synchrotron emission from positron-electron pairs streaming out at high velocities from the source of antimatter. Modeling of the observed precession of these jets gives an object distance of approximately 5 kpc (or 16,000 ly).^[2] This means that while the object is likely located along our line of sight towards the center of the Milky Way, it may be closer to us than Sagittarius A*, the black hole at the center of our galaxy.