Until recently, black holes were
thought to come in only two sizes: Small stellar varieties that are several
times heavier than our sun, and supermassive black holes that pack the
gravitational punch of many million suns—large enough to swallow our entire solar
system. Notorious for ripping apart and swallowing stars,
extra-large black holes live exclusively in the hearts of most galaxies,
including our own Milky Way. The new middleweight black hole is between these
two types—equal to the matter of about 90,000 suns.
New Black Hole Relics of the Early
Universe?
An international team, who
discovered HLX-1 "almost by accident" in 2009, noticed the object was
pumping out copious amounts of x-rays and radio flares—not from within the core
of its host spiral galaxy, but some 12,000 light years beyond.
"Our observations from 2009
and 2010 showed that HLX-1 behaves similarly to the stellar [low] mass black
holes, so we worked out when we should be expecting to see radio flares from
HLX-1, and when we made more observations in August and September 2011, we
did," said study leader Natalie Webb, of the Centre d'Etude Spatiale des Rayonnements in
France. The origin of these intermediate black holes may lie in centers of
globular clusters, where hundreds of thousands of stars are densely packed
together by gravity.
Alternatively, the middleweights may be true
ancient relics of the universe,
formed by the very earliest stars, said Webb, whose study appears tomorrow in
the journal Science. "At
the dawn of the universe, very massive stars may have existed—maybe as much as
ten thousand times the mass of our sun—and these stars would have
a very
short lifetime and end their lives as intermediate mass black
holes,"
Webb said.
Middleweights May Explain Black Hole
Giants
The very existence of middleweight
black holes may also be key in solving how their supermassive cousins formed. For
instance, Webb suspects the middleweights may in fact be the supermassive black
holes' progenitors. These giants may either form when a single intermediate
black hole gobbles enough matter to grow into a supermassive black hole
with at least a million solar masses.
Or, a number of intermediate
black holes "merged in the early universe to form the supermassive
black holes we see today," Webb said.Either way, without further surveys,
it's impossible to tell how common middleweight black holes are across the
universe.
"It's difficult to assess observationally,
as [HLX-1] is the only good candidate," Webb said.
"But some people think that there may be
hundreds in each and every galaxy."
No comments:
Post a Comment