& i thought they were referring to Gov. Chris Cristie's presidential announcement.
-Daniel aka Obsidian
By Jessica Orwig
June 30, 2015 6:07 PM
Lurking
8,000 light years from Earth is a black hole 12 times more massive than
our sun. It's been peacefully sleeping for 26 years. But on June 15, astronomers detected something signaling that it had woken up. Now, scientists around the world are using highly sophisticated
instruments to learn as much as they can about this mysterious beast of
nature before the black hole returns to its slumber, which will be soon.
Black holes are very dense, massive objects in space that have an
immensely powerful gravitational field that traps anything and
everything that comes too close, including light. But on occasion
they'll spit out material as well as suck it in. On
June 15, one of NASA's satellites picked up a torrent of x-rays all coming from a single source: the black hole.
"Relative to the lifetime of space observatories, these black hole
eruptions are quite rare," said Neil Gehrels, the principal investigator
for Swift, the NASA satellite that first identified the eruption in a
NASA press release.
"So when we see one of them flare up, we try to throw everything we
have at it, monitoring across the spectrum, from radio waves to gamma
rays."
A deadly companion
This black hole is just one half of a two-body system called V404
Cygni. Its partner is a star slightly smaller than our sun, and it's
been nourishing the black hole for at least 77 years. The x-rays that
astronomers observed on June 15 were the heated guts from the companion
star that had spiraled into the mouth of the black hole.
When black holes in binary systems, like V404 Cygni, feed, they do so
by gravitationally attracting a single thread of gas from the star. The
black hole is 12 times more massive than its companion and therefore
has a much stronger gravitational grip which slowly pulls gas from the
star as the star orbits around it, like in the animation below:
As the gas gets pulled in, it orbits around the black hole, forming a
disc. The closer the gas gets to the black hole, the stronger
gravitational force it feels and so the faster it moves, heating up to
searing-hot temperatures. When the gas reaches temperatures of more than
1.7 million degrees Fahrenheit,
it emits a jet of high-energy particles, which satellites like NASA's
Swift instrument then detect — albeit 8,000 years later because of the
time it takes light to travel from the V404 Cygni to Earth.
But there isn't always a steady stream of gas falling into the black
hole, which is why it takes such long naps in between feedings. That disc has two regions: and inner, hot region, and an outer
cool region. You need a lot of gas to provide enough pressure and push
to cross this barrier, which takes time to generate. Once the black hole
has consumed all of the gas in the inner region, which it does in a few
days, it has to wait for more. But scientists don't understand the
details of how much gas is necessary or exactly how long it takes to
build up.
That's why this event is so exciting because it gives
astronomers a chance to better understand the mechanism that's driving
these eruptions.
A once-in-a-professional-lifetime opportunity
(European Southern Observatory on Flickr) V404 Cygni's black hole has erupted before.
However, when astronomers first saw the outbursts more than 77
years ago, in 1938, they didn't have half of the instruments that are
around today. The black hole erupted again in 1956, and then again in
1989.
While the eruption of 1989 was studied with a handful of instruments,
the outburst wasn't studied in half the detail compared to this year's
event. Outbursts like this usually only last for a few weeks
to months, so astronomers have culminated a total of nine instruments in
space and on the ground to study the black hole in all wavelengths,
from very low energy like radio waves to the most energetic like gamma
rays, before time runs out.
Some of the instruments they're using include the Chandra X-ray
Observatory, the European Space Agency's INTEGRAL satellite, Japan's
MAXI, and the 10.4-meter Gran Telescope Canarias operated by Spain in
the Canary Islands.
"It is definitely a 'once in a professional lifetime' opportunity," said Erik Kuulkers, the INTEGRAL project scientist in the
NASA press release.
