GRS 1915+105
What is GRS 1915+105?
Black holes & quasars· Distance 28,000 ly. A “mini-quasar” inside our own galaxy. In 1994 its jets appeared to move faster than light — the first time this had been seen within the Milky Way.
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Its place in the sky
A black hole, in the direction of Aquila.
Mass, distance, nature
| Mass | ~12 Suns |
|---|---|
| Distance | ~28,000 ly |
| Companion | K-type giant, 33.5-day orbit |
| Jet speed | >90% of light speed, apparently superluminal |
| How the mass is measured | the companion star’s Doppler-measured orbit, its tilt and the companion’s mass |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Discovery and name
A microquasar found in 1992 — the first superluminal jet motion seen inside our galaxy.
GRS 1915+105's X-ray flicker and its spinning black hole
The X-rays of GRS 1915+105 flicker regularly, from tens to more than a hundred times a second. Scientists think this flicker is linked to gas orbiting closest to the black hole. Its X-ray brightness also rises and falls in more than ten different patterns over seconds to minutes, which is read as the inner disk emptying and refilling again and again.
Careful study of the disk's light also reveals how fast the black hole spins, because how close the gas disk can get to a black hole depends on its spin. The results put this black hole's spin close to the fastest rate theory allows. Since 2018, however, thick gas has hidden the system and its X-rays have weakened greatly, and scientists are watching to see what happens next.
The black hole in depth
GRS 1915+105 is a black hole and star pair about 28,000 light-years away toward Aquila. A black hole of about 12 solar masses and a swollen old star circle each other every 33.5 days. Russia's Granat satellite discovered it in X-rays in 1992. Gas flowing from the old star built a large disk around the black hole, and the system stayed bright in X-rays for many years after its discovery.
In 1994 radio observations showed clumps of gas from it seeming to cross the sky faster than light. They are not really faster than light. When gas moves at more than 90 percent of light speed at a slant toward us, differences in when its light arrives make it appear to move faster than light. The effect had been seen only in distant quasars, so this object became the classic “microquasar”.
So much dust lies between us and it that even the companion star cannot be seen in ordinary light, so it is studied in infrared, radio and X-rays. In the Sky view it appears in northern Aquila, in the middle of the summer Milky Way. Hidden inside that faint glow visible to the naked eye is an object like this.
Frequently asked
- What is the mass of GRS 1915+105?
- The mass of GRS 1915+105 is ~12 Suns.
- How far is GRS 1915+105 from Earth?
- The distance of GRS 1915+105 is ~28,000 ly.
- How fast is GRS 1915+105 travelling?
- The jet speed of GRS 1915+105 is >90% of light speed, apparently superluminal.
- Where in the sky is GRS 1915+105?
- GRS 1915+105 lies in the direction of Aquila.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.