Universe Is 30 Times More Run Down Than Thought, Astronomers Find
ScienceDaily (Jan. 27, 2010) — Cars run out of petrol, stars run out of fuel and galaxies collapse into black holes. As they do, the universe and everything in it is gradually running down. But how run down is it? Researchers from The Australian National University have found that the universe is 30 times more run down than previously thought.
Telescope image of the Pleiades star cluster. (Credit: iStockphoto/Paul LeFevre)
"We considered all contributions to the entropy of the observable universe: stars, star light, the cosmic microwave background. We even made an estimate of the entropy of dark matter. But it's the entropy of super-massive black holes that dominates the entropy of the universe. When we used the new data on the number and size of super-massive black holes, we found that the entropy of the observable universe is about 30 times larger than previous calculations," said Mr Egan.
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Chas A. Egan, Charles H. Lineweaver. A Larger Estimate of the Entropy of the Universe. Astrophysical Journal, 2010; (in press
A LARGER ESTIMATE OF THE ENTROPY OF THE UNIVERSE
CHAS A. EGAN
Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australia 1
CHARLES H. LINEWEAVER
Planetary Science Institute, Research School of Astronomy and Astrophysics and Research School of Earth Sciences, Australian National University,
Canberra, Australia
Received 2009, September 22; accepted 2010, January 11.
ABSTRACT
Using recent measurements of the supermassive black hole (SMBH) mass function, we find that SMBHs
are the largest contributor to the entropy of the observable universe, contributing at least an order of magnitude more entropy than previously estimated. The total entropy of the observable universe is correspondingly higher, and is Sobs = 3.1+3.0-1.7 × 10104k. We calculate the entropy of the current cosmic event horizon to be SCEH =2.6±0.3×10122k, dwarfing the entropy of its interior, SCEH int = 1.2+1.1
-0.7×10103k. We make the first tentative estimate of the entropy of weakly interacting massive particle dark matter within the observable universe, Sdm = 1088±1k. We highlight several caveats pertaining to these estimates and make recommendations for future work.
Subject headings: black hole physics — cosmology: miscellaneous — diffusion — elementary particles —
gravitation— neutrinos
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