Imagens - Porto - Portugal (2)

O Porto foi eleito o melhor destino europeu de 2017, ficando à frente de Milão e de Gdansk, no pódio das três cidades mais votadas

Foto Pedro Granadeiro/global Imagens

Astronomy picture of the day - 2011 September 11 - X-Rays Indicate Star Ripped Up by Black Hole

X-Rays Indicate Star Ripped Up by Black Hole 
Illustration Credit: M. Weiss, CXC, NASA

Explanation: What could rip a star apart? A black hole. Giant black holes in just the right mass range would pull on the front of a closely passing star much more strongly than on the back. Such a strong tidal force would stretch out a star and likely cause some of the star's gasses to fall into the black hole. The infalling gas has been predicted to emit just the same blast of X-rays that have recently been seen in the center of galaxy RX J1242-11. Above, an artist's illustration depicts the sequence of destruction (assuming that image-distorting gravitational-lens effects of the black hole are somehow turned off). Most of the stellar remains would be flung out into the galaxy. Such events are rare, occurring perhaps only one in 10,000 years for typical black holes at the center of typical galaxies.