Check out this Hubble image of a galaxy 8 billion light-years
away. Notice anything unusual about it? This super bright spot
is not a star in the foreground blocking our view, but is
actually a quasar named 3C186 that’s inside the pictured
galaxy. A quasar is the extremely bright light that’s
emitted by hot gas surrounding a supermassive black hole. A
supermassive black hole is a type of black hole that’s at
least 100-thousand times more massive than our Sun and is at
the center of almost every massive galaxy. But the center
of this galaxy is over here, in this green circle. This galaxy’s
quasar, and therefore its supermassive black hole, for
some reason is more than 35,000 light-years away from the
galaxy’s center, and the redshift, a spectral signature
of the gas in the quasar, shows that the black hole is flying
away from the center at over 1,300 miles per second. [over
2,000 km/s] For reference, our Sun is moving through our galaxy
at about 15 miles per second. [24 km/s] This particular black
hole is over one billion times more massive than our Sun - what
could have possibly moved something so enormous? A team of
astronomers led by Marco Chiaberge at the Space Telescope
Science Institute think they’ve found the most plausible
explanation. Taking a look at the Hubble image, there is some
faint material surrounding the galaxy called tidal tails, and
these are produced by a gravitational tug between two or
more colliding galaxies. If this galaxy is actually two galaxies
that merged, then it’s possible their two central supermassive
black holes also merged. As enormous objects like
supermassive black holes are merging, they create ripples in
the fabric of spacetime called gravitational waves. The two
black holes whirl around each other, getting closer and
closer, and fling out gravitational waves like water
from a lawn sprinkler. If the two black holes are a bit uneven
- maybe one’s more massive, maybe one’s rotating a little
faster - then they fling out these gravitational waves more
strongly along one direction. Once the two black holes finally
collide, the newly merged black hole shoots off in the opposite
direction from the strongest gravitational waves. And that’s
what astronomers think happened to this supermassive black hole.
Based on its enormous mass and velocity, the energy needed to
jettison this black hole was equivalent to something like 100
million supernovas exploding simultaneously. So while this
may not go on your list of the top prettiest Hubble images,
just think - you’re looking at the light emitted 8 billion
years ago from gas orbiting a 1-billion-solar mass black hole
that is flying through its galaxy because it was shot off
like a rocket from the gravitational waves produced by
the merging of two supermassive black holes - and if that’s not
cool, I don’t know what is.
nasa.gov/hubble @NASA_Hubble