Most of the history of astronomy consists of observing electromagnetic radiation from outside our planet. That includes the light which shines off the sun and reflects from bodies in the solar system, as well as radio waves produced by phenomena around the universe including pulsars.
Now that we also have neutrino detectors and gravitational wave detectors like LIGO we can receive signals of other kinds from around the universe, helping us to understand it all better. One neat trick: since the universe did not allow the transmission of light for the first 400,000 years there is a limit to how far back we can look by electromagnetic means.
You can sign up for neutrino burst warnings, in case they indicate something great happening in the sky that you may wish to observe by other means.
LIGO itself is due for another upgrade within the next few years. This will almost double its sensitivity, permitting it to observe with the same rigour a volume of space seven times larger than now. Beyond that, the European Space Agency’s Laser Interferometer Space Antenna (LISA), scheduled for 2034, will be the first orbiting gravitational-wave instrument. Its detectors will be arranged in an equilateral triangle with sides 2.5m kilometres long. lisa will be sensitive to low-frequency waves that currently get lost in the noise.
Looking still further ahead, another generation of ground-based observatories is competing to take over once ligo’s useful life is at an end. Europe is offering the Einstein Telescope, a proposed interferometer with three arms arranged in an equilateral triangle buried underground and cooled to within ten degrees of absolute zero, to improve its sensitivity. America proposes the Cosmic Explorer, a version of ligo with arms 40km long. Either would be able to spot black-hole mergers almost anywhere in the universe.
“When a star goes supernova (like, say, Betelgeuse), subatomic particles called neutrinos shoot out from its collapsing core before the explosion’s light is visible. A network of detectors is watching for those neutrinos and you can see them in real time https://nusoft.fnal.gov/nova/public/ ”
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