Researchers from
the U.S. Department of Energy’s Los Alamos National Laboratory and the
University of South Carolina have provided a hypothesis that "black
holes" in space are not holes at all, but instead are more akin to
bubbles.
Researcher Emil Mottola of Los Alamos’ Theoretical Division today presented
a new explanation for black holes at the American Physical Society annual
meeting in Albuquerque, N.M. Pawel Mazur of the University of South Carolina
is Mottola’s co-author. The researchers’ explanation redefines black holes
not as "holes" in space where matter and light inexplicably
disappear into another dimension, but rather as spherical voids surrounded
by an extremely durable form of matter never before experienced on Earth.
Mazur and Mottola call the extraordinary objects Gravastars.
The Gravastar explanation for black holes helps provide answers to some
of the daunting questions raised by traditional black-hole descriptions.
Based on earlier-held astrophysical explanations, black holes form in
space when stars reach the end of their lives and collapse in on themselves.
According to black hole theory, the matter from these dying stars occupies
a tiny amount of space — a mere pinpoint — and creates a mind-boggling
gravitational field so powerful that nothing can escape, not even light.
Mottola and Pawel suggest that while some degree of collapsing does take
place in a dying star, the collapse proceeds only to a certain point.
At that point, the intense gravity of the dying star transforms the star’s
matter into an entirely new phase. Mottolla describes this phase as similar
to a Bose-Einstein condensate, a phase of matter recently observed in
a laboratory setting and the subject of scientific excitement in the past
few years.
On Earth, a Bose-Einstein condensate forms when matter is plunged to
very low temperatures approaching Absolute Zero, the theoretical temperature
at which all atomic motion — the motion of electrons, protons and
all other subatomic particles within an individual atom — is believed
to cease. When matter is cooled sufficiently to become a Bose-Einstein
condensate, the atoms that make up the matter enter a strange new phase.
The atoms all reach the same energy state, or quantum state, and they
coalesce into a blob of material called a "super atom." The
properties of Bose-Einstein condensates are the subject of intense study
and many physicists are working to understand them.
Mottola and Mazur believe that dying stars collapse to the "Event
Horizon" — in essence the point of no return for objects entering
the gravitational field of a black hole. At this point, the matter in
the dying star transforms to a new state of matter that forms a Gravastar.
According to the two researchers, the dying star’s matter c16es an ultra-thin,
ultra-cold, ultra-dark shell of material that is virtually indestructible.
The new form of gravitational energy in the interior is akin to a Bose-Einstien
condensate, although it appears on the inside to be a bubble of vacuum,
hence the term Gra (vitational) Va (cuum) Star, or Gravastar.
"Since this new form of matter is very durable, but somewhat flexible,
like a bubble, anything that became trapped by its intense gravity and
smashed into it would be obliterated and then assimilated into the shell
of the Gravastar," Mottola said. "However, any matter in the
vicinity that fell onto the surface could be re-emitted as another form
of energy, which would make Gravastars potentially much more powerful
emitters of radiation than black holes, which simply swallow the material."
The space trapped inside the Gravastar’s shell is a similarly uncanny
conceptually. The interior of the Gravastar would be totally warped space-time
(the traditional three dimensions plus time). According to the researchers,
this interior space would exert an outward force on the shell, adding
to its durability.
Although unconventional, Mottola and Mazur’s Gravastar explanation for
black holes does solve at least one serious quandary created by black
hole theory. Under a black-hole scenario, the amount of entropy created
in a black hole would become nearly infinite. Physicists have struggled
for years to account for the huge entropy of black holes, and largely
have failed. Unlike their black hole counterparts, Gravastars would have
a very low entropy.
Mottola and Mazur continue to refine their theory and are working on
a concept behind rotating Gravastars. They even suggest that the universe
we now know and live in may be the interior of a Gravastar.
"These are fascinating concepts to think about," Mottola said.
"I look forward to exploring this hypothesis further."
Los Alamos National Laboratory is operated by the University of California
for the U.S. Department of Energy.
