Ripples in space-time could squeeze and stretch the sun and Jupiter, forming a gigantic gravitational-wave detector in our own celestial backyard.
Einstein鈥檚 theory of general relativity predicts the existence of space-time ripples聽鈥撀�gravitational waves聽鈥撀燽ut none have yet been detected directly. One way to find them might be by watching stars for vibrations caused by a passing gravitational wave, but these oscillations would be small compared to the star鈥檚 intrinsic fluctuations. Spotting similar signals in stars in the same cluster would help to distinguish waves from internal effects, but the nearest star clusters are too far away for existing instruments to check.
Closer to home, however, we have Jupiter and the sun, which are large enough and near enough to oscillate in concert. 鈥淲hatever happens to the sun due to gravitational waves, similar things must happen to Jupiter,鈥� says of Bogazi莽i University in Istanbul, Turkey. Studying the oscillations of the two together could help to detect gravitational waves, he suggests.
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Could we have already found them? Astronomers use a spectrometer called to study Jupiter鈥檚 heaving surface, and several space-based instruments watch the sun鈥檚 oscillations. In 2011, in frequency to within 10聽microhertz. Semiz went 鈥渙ut on a limb鈥� and speculated that the oscillations may have been due to gravitational waves.
SYMPAthetic scientists
Patrick Gaulme of New Mexico State University in Las Cruces, who is on the SYMPA team, points out that the error bars in their measurements are too high for such detections. 鈥淭he signal we detected with SYMPA cannot be explained by gravitational waves,鈥� he says. Nonetheless, he thinks the idea has merit. The trick would be to observe Jupiter and the sun over many days, so that any signal can rise above the noise. Such a signal would have to come from a long-lived gravitational wave source, such as the slow inward spiral of two neutron stars or a neutron star and a black hole.
Il铆dio Lopes at the University of Lisbon, Portugal, an expert on the effect of gravitational waves on stars, says we first must understand Jupiter鈥檚 internal oscillations before using it as a detector. Once we do that, then 鈥渞ather than build instruments on Earth, you can use the universe around to see gravitational waves鈥�, he says.
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