Black hole-bound gas cloud 'stretched like spaghetti'

The giant gas cloud heading for the
black hole at the centre of our galaxy
has begun its death spiral.
The cloud, known as G2 is now being
stretched out like a piece of spaghetti by
the black hole's extreme gravity.
This gravitational field has caused the
head of the cloud to accelerate around
the black hole and to speed back towards
us.
Astronomers have been closely
observing G2, hoping to catch it being
ripped apart and eaten by the black
hole.
Details of the latest observations are
outlined in the Astrophysical Journal .
The cloud of gas - three times larger than
Pluto's orbit but with a total mass just
three times that of the Earth - was first
spotted on its course toward the galaxy's
centre in 2011.
The mass of the black hole at the centre
of the Milky Way is estimated to be four
million times that of the Sun and is
formally known as Sagittarius A (Sgr A*).
It is the closest known "supermassive"
black hole and is therefore considered
the best places to study these dense
objects in detail.
"The most exciting thing we now see in
the new observations is the head of the
cloud coming back towards us at more
than 10 million km/h along the orbit -
about 1% of the speed of light," said
Reinhard Genzel, from the Max Planck
Institute for Extraterrestrial Physics in
Germany.
"This means that the front end of the
cloud has already made its closest
approach to the black hole."
The origin of the gas cloud remains
unclear, although a variety of ideas have
been proposed.
These range from its recent formation
due to a collision between stellar winds
and the interstellar medium to its origins
as a jet emerging from the galactic
centre to a faint star that is losing
increasing amounts of gas.
The head of the cloud is now travelling
much faster than the tail
The new observations argue against the
cloud possessing a stellar core that
would constantly be supplying new gas.
"We see that the cloud is now being
stretched so much that it resembles
spaghetti. This means that it probably
doesn't have a star in it," said Stefan
Gillessen, also from the Max Planck
Institute, who has been leading the
observing team.
"At the moment we think that the gas
probably came from the stars we see
orbiting the black hole."
Due to the tidal forces stretching G2, the
front of the cloud is now moving about
500 km/s faster than its tail.
The astronomers have been using the
Very Large Telescope (VLT) in Chile to
study G2.
As the gas cloud is stretched its light
gets harder to see. But by staring at the
region close to the black hole for more
than 20 hours of total exposure time
with the VLT's Sinfoni instrument, the
team was able to measure the velocities
of different parts of the cloud as it
streaked past the central black hole.