strrong graviational field of the two black holes bends
the light of stars behind them so they are seen distorted around the
black holes. Without the black holes present, the stars would
appear as shown below.
on the video at the very bottom for a movie simulating the
black holes merging.
In this movie, the black holes are near us, in front of a sky
filled with stars and gas and dust. The black regions are the shadows
of the two black holes: no light would reach us from these areas. Light
from each star or bit of gas or dust travels to our eyes along paths
(light rays) that are greatly bent by the holes' gravity and by their
warped spacetime. This is called "gravitational lensing." Because of
this gravitational lensing, the pattern of stellar and gas/dust images
changes in fascinating ways, as the black holes orbit each other, then
collide and merge.
The ring around the black holes, known as an
"Einstein ring," arises from all the stars in a small region directly
behind the holes; gravitational lensing smears their images into the
shape of a ring.
The gravitational waves themselves would not be
seen by a human near the black holes (though they would be felt!) and
so do not show in this video, with one important exception: The
gravitational waves that are traveling outward toward the small region
behind the black holes disturb that region’s stellar images in the
Einstein ring, causing them to slosh around in the ring, even long
after the collision. The gravitational waves traveling in other
directions cause weaker, and shorter-lived sloshing, everywhere outside
the Einstein ring.
September 14, 2015 gravity waves were detected that resulted from the
merger of two black holes 1.3 billion light-years away. One
hole had a mass 29 times that of the mass of our sun, and the other 36
times the mass of the sun. Just before they merged, they were
orbiting each other at half the speed of light and radiating gravity
waves with a power 50 times greater than the light output of all the
stars in the universe. The energy lost amonted to 3 masses of the sun
(using E = mc2
). These waves were
detected by two LIGO
sensors on Earth—one in Louisiana, and the other in Wahington state.
The waveform received is shown below (top). The
of the wave is very small—1/1000 of the diameter of a proton.
This distance, divided by the length of the 2.5-mile tunnel
for the laser beam, gives the strain of just 10–21
The waveform, converted to sound, sounds like this
(The first "chirp" is in vicinity of 150 Hz; the second chirp is the
same sound raised in frequency by a factor of 10 to be heard better.)
The waveform agrees well with that predicted by theory
waveform below). For detailed information read this Physics Review Letter