G objects
WHAT’S ORBITING
OUR GAL AXY’S
BL ACK HOLE?
Six strange objects have been found in the vicinity of
Sagittarius A* – and there may be moreReportedbyDavidCrookest theheartoftheMilkyWayisa
supermassiveblackholecalled
SagittariusA*.Weknowitis26,000
lightyearsfromEarthandthatit
has 4 milliontimesthemassoftheSun.We
alsofoundoutlastyearthatitissurrounded
byacoolgashaloandisperhapsquieterthan
itscounterpartsinothergalaxiesbecauseof
magneticfields.
Whatwe’relesscertainabout,however,isthe
make-upofsixstrangeobjectsthathavebeen
discoveredrelativelycloseby.Foundtoorbit
SagittariusA*,orSgrA*asitisalsoknown,they
areafewhundredastronomicalunitsawayfrom
the galactic centre and take anywhere between
170 and 1,600 years to complete their circuit.
“These objects look like gas and behave like
stars,” says Andrea Ghez, a professor of physics
and astronomy at UCLA, who co-authored a
recent study into the objects. Yet the exact
identification of what is said to be a new class of
object is still being worked on, and teams coming
up with potential theories appear to be split.
The objects began to truly puzzle astronomers
after one of them, named G2, was seen to makeA
a close approach to the supermassive black hole
in 2014. It had originally been discovered in 2011
by a team based in Germany, and the expectation
was that it would be ripped to shreds and cause a
flash of radiation.
Instead it was observed becoming elongated,
and while much of its gassy outer shell was
torn apart, it survived and continued on its way,
becoming more compact once again. “It went
from being a pretty innocuous object when
it was far from the black hole to one that was
really stretched out and distorted at its closest
approach,” Ghez explains.MYSTE RIE S
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