A multinational team of astronomers led by University of Texas researchers has spotted the first visible-light evidence for gravitational waves in a binary system located about 3,000 light-years from Earth.
The binary white dwarf system SDSS J065133.338+284423.37. Image credit: The Sloan Digital Sky Survey (SDSS) Collaboration, www.sdss3.org
“This result marks one of the cleanest and strongest detections of the effect of gravitational waves,” said Dr Warren Brown of the Smithsonian Astrophysical Observatory, co-author of a study to be published in the Astrophysical Journal Letters (arXiv.org version).
Last year, the same team discovered that the two white dwarf stars are so close together that they make a complete orbit in less than 13 minutes, and they should be gradually slipping closer. The system, called SDSS J065133.338+284423.37, J0651 for short, contains two white dwarf stars, which are the remnant cores of stars like our Sun.
“Every six minutes the stars in J0651 eclipse each other as seen from Earth, which makes for an unparalleled and accurate clock some 3,000 light-years away,” said lead author J.J. Hermes, a graduate student at The University of Texas at Austin.
Einstein’s theory of general relativity predicts that moving objects create subtle ripples in the fabric of space-time, called gravitational waves. Gravitational waves should carry away energy, causing the stars to inch closer together and orbit each other faster and faster. The team was able to detect this effect in J0651.
“Compared to April 2011, when we discovered this object, the eclipses now happen six seconds sooner than expected,” explained co-author Dr Mukremin Kilic of the University of Oklahoma.
An artist’s conception of SDSS J065133.338+284423.37 with ripples to demonstrate how the white dwarf pair is emitting gravitational waves (NASA)
“This is a general relativistic effect you could measure with a wrist watch,” Dr Brown added.
J0651 will provide an opportunity to compare future direct, space-based detection of gravitational waves with those inferred from the orbital decay, providing important benchmark tests of our understanding of the workings of gravity.
The team expects that the period will shrink more and more each year, with eclipses happening more than 20 seconds sooner than otherwise expected by May 2013. The stars will eventually merge, in two million years. Future observations will continue to measure the orbital decay of this system, and attempt to understand how tides affect the merger of such stars.
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Bibliographic information: J. J. Hermes et al. 2012. Rapid Orbital Decay in the 12.75-minute WD+WD Binary J0651+2844. Submitted to ApJ Letters; arXiv: 1208.5051v1
