海角大神

Black holes are a spot in the universe where you won鈥檛 see the sun shine in, to paraphrase that 1960s rock-musical Hair. But speaking of 鈥渉air鈥�, a group of scientists says these singularities may have matter (sometimes referred to as 鈥渉air鈥�) that could affect how they appear.

This is a tangled concept to figure out (so to speak), so let鈥檚 unpack what the new study in Physical Review Letters means.

When black hole understanding was still in its infancy in the scientific literature, physicist John Wheeler wrote a phrase that is now famous among scientists in that field: 鈥淏lack holes have no hair.鈥� His phrase referred to how black holes are defined, which he believed came down to only two factors: their mass, and their angular momentum, or the rotation velocity of the hole. (Some sources also say electric charge was included as a third factor.)

Say you have a black hole that was created out of a huge star that imploded. Even though the star itself had distinctive properties, this theory says they would vanish in a black hole. So to take that to a generality, Wheeler鈥檚 phrase said all black holes are essentially the same.

This understanding of black holes dates back to 1963, arising back to a 鈥渃lean鈥� black hole model first published by Roy Kerr. The new study agrees that Kerr鈥檚 work from 50 years ago works with general relativity, a theory from Einstein that (in very simple terms) says the laws of nature are consistent throughout the universe. (More at聽this past Universe Today article.) As the theory pertains to black holes, strong sources of gravity bend space and time.
Kerr鈥檚 theory, however, does聽苍辞迟听agree with extensions of Einstein鈥檚 work, the scientists said. These extensions are known as scalar-tensor theories and there are several variations on this topic. The physics deals with the interactions between two different types of fields, scalar and tensor. Scalar fields,聽according to this Massachusetts Institute of Technology paper, assign values for every point of space observed. (Think a temperature map of Mars). Tensor fields measure these variables with relation to each other.

The science team included聽Thomas Sotiriou, a聽physicist at the International School for Advanced Studies in Italy.

His team, Sotiriou said in a statement, 鈥渇ocused on the matter that normally surrounds realistic black holes, those observed by astrophysicists. This matter forces the pure and simple black hole hypothesized by Kerr to develop a new 鈥榗harge鈥� (the hair, as we call it) which anchors it to the surrounding matter, and probably to the entire universe.

鈥淎ccording to our calculations,鈥� he added, 鈥渢he growth of the black hole鈥檚 hair is accompanied by the emission of distinctive gravitational waves.鈥�

This model hasn鈥檛 been proved yet in by measurements, so this will be something for astronomical instruments to watch for in the coming decades. It also should be noted that聽other scientists have found different problems with the clean black-hole theory, which you can check out if you鈥檙e so inclined.

In the meantime, you can read the new study聽at this link. There is聽also a prepublished version available.

Source:聽Scuola Internzaionale Superiore di Studi Avanzati

Originally published on Universe Today.

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Elizabeth Howell (M.Sc. Space Studies '12) is an award-winning freelance space journalist living in Ottawa, Canada. She reported on three shuttle launches, including the first launch "tweetup" during STS-129. Besides Universe Today, she regularly writes for SPACE.com, the Space Exploration Network and All About Space, among other publications. You can follow her on Twitter @howellspace or contact her at聽her website.