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Black hole “baldness” reflected in more everyday objects: physicist
Feb. 24, 2009
Courtesy Washington University in St. Louis
and World Science staff
New research from a Washington University in St. Louis physicist may help scientists find spinning black holes orbited by smaller black holes in space. A mathematical
representation of a small black hole orbiting a larger one. Physicist
Clifford Will hopes to learn more about how these orbits play out, where the relativist Carter constant plays a key role.
(Illustration by Don Davis)
A black hole is an object so dense that its field of gravity permanently imprisons anything that come too close, even light. Ordinary laws of physics also break down in its vicinity.
Einstein’s general relativity theory implies that rotating black holes have only two
observable properties: mass and spin. This simplicity is sometimes
summed up by a saying, “black holes have no hair.”
A small object theoretically orbiting a rotating black hole is more complex. It traces a twisting rosette pattern with no discernible regularity, though two
quantities associated with the satellite—called energy and angular momentum—would remain fixed over time.
In 1968, theoretical physicist and cosmologist Brandon Carter found that such a particle’s gyrations also hold a third variable fixed. The meaning of this quantity, dubbed the “Carter constant,’’ remains somewhat mysterious.
Now Clifford M. Will at Washington University has found that even among objects that follow laws of gravity, arrangements can exist whose gravitational field admits a Carter-like constant of motion. Variations in the gravitational field shape are determined by equations identical to those for rotating black holes, also called Kerr black holes.
One ordinary gravitational, or “Newtonian,” system featuring this property is surprisingly simple: two equal point masses resting a fixed distance apart, Will wrote in a paper in the Feb. 12 issue of the research journal
Physical Review Letters.
“I was completely stunned when I saw that the Newtonian condition for a
Carter constant was identical to the condition imposed by the black hole no-hair
theorems,” Will said. “Do I know why this happens? So far, not a clue. But what I really hope is that insights gained about this strange constant in the simpler Newtonian context will teach us something about how small black holes orbit around rotating massive black holes in general relativity, where the relativistic Carter constant plays a key role.”
This has implications for astronomy, he said, because signals from such events may be detectable via exotic emissions predicted by Einstein known as gravitational waves, ripples in the fabric of space and time. Human-built detectors such as the Laser Interferometer Gravitational Wave Observatory (LIGO) in the United States and the proposed Laser Interferometer Space Antenna (LISA) may be able to pick up these fluctuations, he added.
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New research from a Washington University in St. Louis physicist may help scientists find spinning black holes orbited by smaller black holes in space. A black hole is an object so dense that its gravitatational field permanently imprisons anything that come too close, even light. Ordinary laws of physics also break down in its vicinity. Einstein’s general relativity theory implies that rotating black holes have only two observable properties: mass and spin, a simplicity sometimes summed up by the saying “black holes have no hair.” A small object theoretically orbiting a rotating black hole is more complex. It traces a twisting rosette pattern with no discernible regularity, though two quantities associated with the satellite—called energy and angular momentum—would remain fixed over time. In 1968, theoretical physicist and cosmologist Brandon Carter found that such a particle’s gyrations also hold a third variable fixed. The meaning of this quantity, dubbed the “Carter constant,’’ remains somewhat mysterious. Now Clifford M. Will at Washington University has found that even among objects that follow laws of gravity, arrangements can exist whose gravitational field admits a Carter-like constant of motion. Variations in the gravitational field shape are determined by equations identical to those for rotating black holes, also called Kerr black holes. One ordinary gravitational, or “Newtonian,” system featuring this property is surprisingly simple: two equal point masses resting a fixed distance apart, Will wrote in a paper in the Feb. 12 issue of the research journal Physical Review Letters. “I was completely stunned” by the equations’ similarity, Will said. “Do I know why this happens? So far, not a clue. But what I really hope is that insights gained about this strange constant in the simpler Newtonian context will teach us something about how small black holes orbit around rotating massive black holes in general relativity, where the relativistic Carter constant plays a key role.” This has implications for astronomy, he said, because signals from such events may be detectable via exotic emissions predicted by Einstein known as gravitional waves, ripples in the fabric of space and time. Human-built detectors such as the Laser Interferometer Gravitational Wave Observatory (LIGO) in the United States and the proposed Laser Interferometer Space Antenna (LISA) may be able to pick up these fluctuations, he added.