Predicted by Einstein's theory of general relativity, black holes are the extremely dense remnant cores of a massive dead star. Think of a star, more than 10 times the size of our own sun, squeezed down to a sphere that would fit very comfortably inside the space between Raleigh and Fayetteville.

That is a lot of mass in a very small space, which makes black holes do some interesting and destructive things. Escape velocity inside that sphere exceeds the speed of light earning black holes their name.



In June of last year, NASA’s X-Ray detecting Swift mission detected V404 Cygni, a black hole 10+ times the mass of our solar system, orbited by a star slightly smaller than our own, waking up from a 26-year nap. The Monitor of All-sky X-ray Image (MAXI) instrument aboard the International Space Station saw it too.



V404’s black hole is siphoning off gas from the star. As enough gas builds up in a ring around the black hole, it rapidly falls in, or accretes. Friction caused by the rapid increase of gravity heats up that accretion material. That heat is detectable by in the x-ray portion of the spectrum by instruments such as Swift and MAXI.



You can find where this binary black hole is in the constellation Cygnus the Swan. Cygnus is one of the more recognizable constellations, rising shortly before sunset and is visible in the western sky until setting just before 9 p.m. Look for the bright star Vega, then directly above for the slightly dimmer star, Deneb. Deneb forms the swan’s tail with a line of stars down and to the left forming the neck. Look to the lower wing for where V404 is located.

This week, researchers in Japan, led by Mariko Kimura of Kyoto University, published a paper in the journal Nature reporting on flashes of visible spectrum light coming from the black hole observed since June. Telescopes as small as eight inches, within the reach of many amateur astronomers, observed these flashes lasting from several minutes to a few hours.

Local astronomy clubs volunteer a number of telescopes large enough to catch a glimpse of this twinkling black hole at sky watching session sponsored by the Morehead Planetarium and Science Center. The next session is Saturday, Jan. 16, from 6 to 8 p.m.