Scientists are about to spot more cosmic collisions than ever before
Add Axios as your preferred source to
see more of our stories on Google.
/2023/05/29/1685372946270.gif?w=3840)
Illustration: Aïda Amer/Axios
The search for ripples in space and time sent out by extreme cosmic collisions is entering a new phase with more and faster detections.
Why it matters: These ripples — called gravitational waves — carry information about crashes between dense objects like black holes and neutron stars that scientists use to test long-held theories about the universe.
What's happening: Two gravitational wave detectors — in Washington State and Louisiana — are now back online after three years of upgrades to improve their sensitivity.
- It's possible that once the detectors that make up the Laser Interferometer Gravitational-wave Observatory (LIGO) are at full strength, they will detect a gravitational wave signal every two or three days.
- Previous observations have netted between 90 and 100 detections since LIGO clocked its first gravitational wave in 2015, astronomer Chad Hanna of Pennsylvania State University tells Axios, adding, "It's quite likely that we will add several hundred more."
- More observations mean more opportunities to see the rarest events in the universe, Hanna added.
How it works: LIGO makes use of a laser that sends a beam of light down the arms of the L-shaped instrument. That light bounces off the end of the arm and back to the middle, always arriving at precisely the predicted time.
- However, if a gravitational wave passes through Earth's part of space, it slightly bends the fabric of space-time, imperceptibly warping every piece of matter it passes through, including the detector. That creates a very slight change in the time that light reaches the middle of the detector.
- By having multiple detectors operating at once, scientists are able to more precisely track signals to the parts of space they originate from, Katerina Chatziioannou, physics professor at CalTech, tells Axios.
The intrigue: Astronomers think LIGO's improved sensitivity could allow them to more readily see light and other signals like radio waves emitted during crashes between two neutron stars and possibly other objects as well.
- Gravitational waves from two neutron stars colliding have been detected before, but seeing the light also emitted by them poses a logistical challenge with multiple instruments needing to be tasked quickly.
- LIGO scientists are hoping to make use of the observatory's newfound sensitivity to quickly localize the part of the sky where a given gravitational wave signal originates, allowing other light-detecting telescopes to turn toward the source of the waves.
- This kind of "multi-messenger" detection with gravitational waves and light has only been done once before, in 2017, when two neutron stars collided.
Between the lines: If researchers see more multi-messenger collisions, it could help them piece together a better understanding of the objects that produced them.
- For example, the 2017 detection confirmed that some gamma-ray bursts are caused by neutron star collisions.
- Multi-messenger detections also have the potential to help measure the expansion of the universe in a new way, possibly helping to settle a growing debate about the measurement known as the Hubble Constant.
What to watch: Two other gravitational wave facilities are slated to collaborate with LIGO during this observing run.
- The KAGRA detector in Japan is online now, but it will go offline in about a month for some upgrades. Virgo, in Italy, will also be back online after upgrades and will join LIGO's observing run.
- India and the U.S. are also building a gravitational wave detector that is expected to be online and collaborating with the other observatories by 2030.
