In our night sky, towards the constellation of Sagittarius, lies the center of our galaxy.
The core of our galaxy has always been obscured from us, hiding behind a thick veil of interstellar
gas and dust some 26,000 light years from Earth.
Wavelengths of light shorter than those in the visible range cannot get through to us.
Photons are absorbed and scattered as they travel from stars in the core out to the spiral arms where
we live - and it is only recently that we have had the proper telescopes in place that allow us to peer behind this curtain
Using instruments like the Very Large Telescope at the European Southern Observatory and the
Keck Telescope on Mauna Kea in Hawai'i, astronomers have begun imaging the galactic center in
infrared wavelengths. These longer wavelengths are able to pass right through the gas and
dust strewn throughout the galaxy and illuminate our detectors, showing us for the first time
the center of our home galaxy.
And what they've found there is astonishing.
These are actual infrared observations of stars near the galactic core orbiting an unseen
and massive object, this is something we could never have seen just a decade ago.
Now, by carefully observing the motions of these stars over several years, astronomers
have been able to infer the existence of a black hole, these stars are doomed, eventually
destined to be devoured in the black hole's powerful gravitational field.
There is a darkness in the heart of our galaxy, and there is probably one at the center of
every other galaxy. These supermassive black holes in the cores of galaxies are among the
most colossal objects in the universe, ranging in size from millions of times the size of
our Sun to the largest weighing in at over 10 billion times that amount.
Supermassive black holes are devouring stars at a prodigious rate and emitting vast quantities
of energy in the form of x-rays and gamma ray in the process.
They are among the most luminous objects ever seen. The brightest of these active galactic nuclei can emit more
energy than all the other stars in their galaxy combined.
They are called quasars.
These active galaxy centers, powered by supermassive black holes, have only recently come under
close scrutiny and it's only over the past decade or so that astronomers have been able
to carefully map and measure the activity in the center of our galaxy.
These stars betray the black hole to us, while we can't see it directly, the orbits of these
doomed stars tell us right where it is.
They also tell us how large it is: the black hole at the center of our galaxy is four million
times larger than our Sun.
But there's more. In December 2011, using observations taken over the course of several
years, a massive cloud of hydrogen gas was discovered heading directly towards the black hole.
The hydrogen cloud is about three times the mass of the Earth and is made visible from
the glow of nearby stars as it passes. It is travelling at 8 million kilometers per hour.
Sometime over the next few years, this cloud will pass very close to the black hole, allowing
astronomers to see for the first time, a direct collision of a gas cloud with a black hole.
Just a few short decades ago, astronomers thought black holes were theoretical objects
existing only in mathematical models and obscure theories. Now, not only do we know them to
exist, but we have direct observational evidence of it. What's more, these dark harbingers
of destruction, while emitting no light of their own, are the driver for some of the
brightest and brilliant objects ablaze in the cosmos.