## Friday, April 04, 2008

### NASA: a pocket black hole found

FoxNews
NASA's Chandra Observatory has found the lightest known black hole in the binary system XTE J1650-500 in Ara, a southern hemisphere constellation near Centaurus A (although the latter is 10 million light years away from us).

But don't expect the Hawking radiation to be observed soon. The diameter of the spherical event horizon is 24 kilometers: that's about the wavelength of its would-be thermal radiation. ;-) Using the identity "R = 2GM/c2", you can check that the mass of the black hole equals 3.8 solar masses. The previous record diet black hole in GRO 1655-40 had 6.3 Suns.

We are probably getting to the lower limit on masses that can be naturally produced by the collapse of a star. The boundary is probably somewhere between 1.7 and 2.7 solar masses.

Sorry, I don't have an English version of this videoclip, so here is the Czech one. ;-) They also say that streams of energy are everywhere around. Black holes are born when stars collapse. Light cannot escape. Strong X-rays around help to create stars and they kill all the life that would dare to interfere with their trajectories.