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Possible 22 year old confirmation of gravity waves

Posted by tigerhawkvok on March 04, 2009 17:18 in astronomy , news , IYA

Via Slashdot and the arXiv blog, it turns out that we may have actually detected gravity waves in 1987 associated with SN1987A.

OK, that was a bit of a rush. Let's unpack that a bit. Astrophysicists have been searching for gravity waves for a while now, which are linearized plane wave solutions to the Einstein Field Equations with two polarizations (the other fourteen dropping out). The key bit to this solution is that the coordinate positions of the particles remain constant for all τ, but the fractional change in distance between points A and B changes in an oscillatory manner (as 0.5a sin[ωt+δ] ). Since all but two polarizations drop out, this means that for a plane wave oriented in the z direction, wave effects are restricted to the orthogonal x,y plane.

LIGO

Modern interferometers use long arms with a laser cavity to measure very very small fractional changes in distance via destructive & constructive interference. However, before this, large aluminum cylinders with piezoelectric crystals arranged about it were constructed in an attempt to measure these gravity waves. When SN 1987A went off (Supernova 1987 A, as the first one in 1987), John Weber reported that he detected gravitational waves from the SN detonation. However, calculations of first-order effects (almost always the largest) showed that his detector was insufficiently sensitive to have found any gravitational waves.

However, a new paper (preprint) shows that asymmetries in the 1987 explosion could lead to an enhancement by a factor of 104 in SN1987A, putting these waves right in Weber's detectable range.

So, it seems in retrospect that Weber got the short end of the stick, all things considered. But it's definitely worth re-examining his data to see if he did, in fact, confirm gravity waves 22 years ago.

IYA Entry

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Possible 22 year old confirmation of gravity waves | The Dichotomous Trekkie 2.0

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Possible 22 year old confirmation of gravity waves | The Dichotomous Trekkie 2.0

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Possible 22 year old confirmation of gravity waves | The Dichotomous Trekkie 2.0