By now, many of us have heard of gravitational wave detection. Many have even heard about the combined gravitational wave and electromagnetic detection and observation of a neutron star merger last year -- the first of its kind to make use of synergistic data from more than one path of information about an event, and which marked the official birth of "multi-messenger astronomy".
But we're not done. not by a long shot.
@JWilliams The neutron star merger (GW170817) gave us a wealth of data that we couldn't have acquired without both sources of information. because we knew that the event WAS the merger of two neutron stars, and because we knew basically in what direction to look, optical, radio, and gamma-ray observatories didn't have to start from scratch in their observations.
@JWilliams When the gamma ray signal was received at nearly the same time as the gravitational wave signal, it confirmed important predictions in General Relativity, and disproved others. we now know with great certainty that gravity as a force, and gravitational waves, travel at the speed of light.
We also have a pretty good idea now that merging neutron stars are at least one cause of gamma-ray bursts.
@JWilliams But I said we're not done, right? Rainer Weiss, who shared the 2017 Nobel Prize in Physics for his work on gravitational wave detection, says that (among other things) astronomers would love to have multi-messenger signals from supernovae, and magnetars (neutron stars with phenomenally powerful magnetic fields, which are another potential source of gamma ray bursts).
And with significant advances in the sensitivity of gravitational wave detectors, it should happen.
@JWilliams In fact, with planned upgrades to the NSF-funded LIGO observatories and the VIRGO observatories, we should be able to obtain multi-messenger data from much weaker signals closer to home--in our own solar system.
And that's STILL not the end. the 2020's/2030's should see the launch of the LISA satellites which will be sensitive to gravitational waves of different frequencies than LIGO/VIRGO can detect. LISA should see supermassive black hole mergers.
@JWilliams And combined LISA and LIGO/VIRGO observations would have detected the run up to a neutron star merger *months* in advance.
Even more exciting: there's only so far back in time that optical astronomy can go. Gravitational wave observations should let us gather data right back to the Big Bang, and solve some big mysteries.
@JWilliams It's an incredibly cool time.
It's been said that the "low-hanging fruit" in astronomy has been picked, and the important things already discovered. The first is kind of true: observatories (gravitational wave and electromagnetic) capable of making these discoveries are not cheap or simple. But you get what you pay for: today's telescopes could detect a half-watt cellphone signal from more than .01 light year away (750 times the distance from the Earth to the sun).
@JWilliams And considering the mysteries yet to be solved, "big discoveries" most definitely remain.
/fin
@JWilliams A clarification to the above: GW170817 did not disprove General Relativity predictions. But it DID do damage to some theories that involved modified gravity. Some such theories predicted gravitational waves would travel much more slowly than light.
@JWilliams Whoa, nice thread
@JWilliams We could also put boundaries on the optical signal. when the received light shifted from blue to red over time, it confirmed we were seeing heavy element production.
Since the gravitational wave signal indicated "neutron star merger", we now know with high certainty that such mergers produce a large amount of the heavy elements in the universe--including the stuff that makes up your jewelry.
#CoSoScience