Astronomers Watch As Black Hole Snacks on Companion Star

(Image: Video via  Screenshot/YouTube)

In just fractions of a second astronomers observed a black hole giving off ferocious red flashes, in one of the brightest black hole outbursts in recent years. The discovery was made in June 2015, when the black hole named V404 Cygni was consuming material that it had ripped from an orbiting companion star — the intense brightening continued for about two weeks.

V404 Cygni

V404 Cygni suffers from a stellar identity crisis. The “V” in its name designates it as a variable star (so it gets brighter and fainter). However, at least three times in the 20th century it has produced a bright outburst of energy; therefore it is also a nova. But it does not stop there; it is also known as a soft X-ray transient because it periodically emits short bursts of X-rays.

Armed with this knowledge, astronomers understand that V404 Cygni is a binary system that consists of a black hole and a “normal” companion star. However it also indicates that the black hole is robbing hot gas from its companion star.

V404 Cygni sits about 7,800 light years from Earth, and was the first definitive black hole to be identified in our galaxy. It can also appear extremely bright when it is actively devouring material.

Watch GeoBeats News video on the powerful burst observed by scientists:

The study

The new study, published in the journal Monthly Notices of the Royal Astronomical Society, reported that the black hole had emitted impressive red flashes that lasted just fractions of a second, spewing out material that it could not swallow.

The international team of astronomers had associated the red colour with rapid jets of matter that had been expelled from close to the black hole. The team was led by the University of Southampton, and believes that the observations provide new insights into the construction of these jets and extreme black hole phenomena.

Lead author of the study, Dr. Poshak Gandhi an Associate Professor and STFC Ernest Rutherford Fellow in the University of Southampton’s Astronomy Group, said in a statement:

The observation was made by using the ULTRACAM fast imaging camera mounted on the William Herschel Telescope in La Palma on the Canary Islands.

Watch this video from NASA about the black hole named V404 Cygni:


The red flashes were extremely intense, being comparable to the output of about 1,000 suns. They were also extremely quick in duration (shorter than 1/40th of a second), “about ten times faster than the duration of a typical blink of an eye,” according to the Royal Astronomical Society.

Professor Vik Dhillon of the University of Sheffield and co-creator of ULTRACAM, said in a statement:

V404 Cygni last erupted in 1989 because bright black hole “outbursts” are so unpredictable in nature and are rare, astronomers have a very small window to react. Most upsurges have also been dimmer; however the 2015 event was extraordinarily bright providing an excellent opportunity to study.


The image shows one still image of a red flash observed from the black hole V404 Cygni by the ULTRACAM fast imager on the William Herschel Telescope in the early morning hours of June 26, 2015. The flashes are incredibly short and last less than one second, with some of them being even faster than 1/40th of a second. The flashes are equivalent to a luminosity of about 1,000 times the sun’s power. The background image shows a region of the sky in the Cygnus constellation, with the Cygnus Loop supernova remnant on the bottom left. (Image: DSS2/ et al.)

Dr. Gandhi concluded:

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