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No black holes after all?
Aug. 11, 2006
Center for Astrophysics
and World Science staff
One of the brightest and furthest known
objects in the universe might not be a black hole as traditionally
believed, but rather an exotic new type of object, a new study suggests.
And the researchers say this raises
doubts as to whether other so-called black holes are really that, either.
|An artist's image of a black hole at the
center of a galaxy. The black hole itself would be hidden at the
center of the disc of swirling gas, with two jets spurting in opposite
directions. In new research, some astronomers claim the central object
is not a black hole, but another type of object that shrinks itself at
an imperceptibly slow rate, forever. (Image Courtesy NASA Goddard
Space Flight Center, A. Kamajian)
The astronomers are elbowing
aside the time-honored concept of the black hole: a large object that
compacts itself, under its own gravity, to an infinitely dense point with such gravitational strength that nothing nearby can escape its
Instead, the researchers are picturing a body with a definite
size, and a surprising property: it gradually crams itself into a smaller
space forever, but never achieves a black hole’s infinitely small size.
In the study, Rudy Schild of the Harvard-Smithsonian Center for
Astrophysics in Cambridge, Mass. and colleagues scrutinized an object of a
stupendously bright type known as a quasar.
Quasars, most astronomers agree, are the centers of
Scientists traditionally picture a quasar’s core as a disc of gas spiraling into a “supermassive” black hole, which sucks it in. The
brilliance comes from the gas, which heats up as it
Some of it also shoots out in two oppositely-directed
Quasars appear only in the furthest reaches of the known cosmos. Astronomers
reason that this is because they existed only long ago. The furthest areas
are those where we see the universe as it was long ago, because it takes
so long for light from those places to reach us.
Quasar-like structures also exist in the more recent, and thus nearby,
universe. They persist as the “black holes” also believed to lie at
the center of most galaxies. But these are dimmer than
quasars. Scientists think this is because they’ve consumed much of the
Theorists have struggled to understand the workings of quasars’ jets and
discs, called accretion discs. It has also
been hard for observers to see the hearts of quasars, because the
regions are so compact and distant.
Schild’s group studied a quasar designated Q0957+561, about 9 billion light-years
away in the direction
of the constellation Ursa Major. A light-year is the distance light
travels in a year.
The quasar holds a
central compact object weighing the equivalent of 3 to 4 billion Suns. Most scientists would call it a
black hole, but Schild said
his findings suggest otherwise:
surprisingly, it’s magnetic, unlike a black hole.
The researchers chose Q0957+561 because it’s associated with a so-called
cosmic lens. Einstein’s Theory of Relativity holds that a galaxy’s
gravity bends space nearby it. It thus also acts
as a sort of lens, bending light. This results in two images of
the distant quasar and magnifies its light. Stars and planets within the
nearby galaxy also affect the quasar’s light, a
related phenomenon called microlensing.
“With microlensing, we can discern more detail from this so-called
‘black hole’ two-thirds of the way to the edge of the visible universe
than we can from the black hole at the center of the Milky Way,” our
Schild. Schild monitored the quasar’s brightness for 20 years, along
with an international consortium of observers at 14 telescopes.
The team studied the quasar’s core, pinpointing a proposed location
where the jets form—something that 60 years of past research have failed
to explain, Schild said.
His team calculated that the jets come from two regions each about 25
times wider than the distance between the sun and Pluto. These lie
directly above the poles of the central compact object, at about 200 times
the Sun-Pluto distance.
Just one proposed scenario can easily explain these locations, Schild said.
The central object is magnetic, and interacts with the disc
through its surrounding magnetic field. As it spins, the field winds up
like a spool. Eventually it winds so tightly that it “breaks”
explosively before re-forming itself in a more relaxed configuration. The
breakages release energy that powers the jets.
But a black hole in an accretion disc can’t have its own magnetic field,
Schild added. This is because normally, a spinning object can be magnetic only if
it carries an electric charge. A black hole can’t sustain
such charge, because any charged hole will immediately suck in
enough oppositely-charged material to cancel out its own charge.
(There are two types of electric charge, positive and negative).
The problem vanishes, Schild and colleagues argue, with the new type of
compact object that they propose, called a Magnetospheric Eternally
Collapsing Object, or MECO.
This body, a variant of an object whose existence was first proposed by the
Indian physicist Abhas Mitra in the late 1990s, is one that not
unlike a black hole, continually shrinks into an ever-smaller space.
But it never becomes a black hole. Instead, its shrinkage slows
down until it becomes imperceptible, but goes on steadily—so slowly, it could go on for many times the
lifetime of the universe. Unlike a
black hole, a MECO also has definite size. Moreover, objects sucked in can theoretically
go back out, albeit with extreme difficulty.
A MECO, essentially a dense ball of plasma, continually generates magnetic
fields through surface currents, explaining the magnetism, Schild said.
His team’s research appeared in the July issue of The Astronomical
It won’t be easy for the MECO theory to gain wide acceptance among
scientists, astronomers say, given that black holes have been the accepted
scenario since Einstein. But Mitra and a few other
theorists claim black holes don’t exist at all—only Eternally
A stringent test might soon be available to resolve the dispute. Within 10
years, astronomers say, technology will let them observe the signature
feature of black holes, the “event horizon.” This is the
area surrounding a black hole, within which no infalling object can ever
Such observations could either confirm black holes’ existence, or raise new
questions over it, if no event horizons show up where they’re expected.
For now, Schild said he’s not disputing the existence of all black
holes. He’s just focusing on Q0957+561. His team wants to avoid “inflated claims,” he wrote in an email, as some critics
might use this to “discredit the entire body of work.”
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R. E. Schild, D.J. Leiter, S. L. Robertson, 2006. Observations Supporting the Existence of an Intrinsic Magnetic Moment Inside the Central Compact Object Within the Quasar
Q0957+561. E-AJ 132, 430-432.
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