This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A few hundred million years after the Big Bang, the first stars ignited—literally the "let there be light" moment for the universe. Now known to astronomers as Population III, or Pop III, stars, these giants were very different from the stars we know today.
They formed from pristine hydrogen and helium, with almost no "metal" (i.e., other elements) holding them back. They were also huge, growing to tens to hundreds of times larger than the sun. And they died young, in many cases collapsing into the universe's earliest black holes.
Some of those black holes even partnered up, eventually colliding with one another and creating gravitational waves that, if we have instruments sensitive enough, we could potentially detect. A new study posted to the arXiv preprint server led by astrophysicist N.V. Krishnendu of the University of Birmingham and colleagues shows just how much we can learn about them with the new suite of gravitational-wave detectors about to come online.
Current gravitational-wave observatories, such as LIGO in the U.S., Virgo in Italy and KAGRA in Japan, have proven themselves very capable. They've detected around 400 events, with the first one occurring only about 11 years ago. However, they're limited by distance—which also means time when talking about space.
Because of their high-frequency limitations, they can see back only about 8 billion years. Still impressive, but not enough to capture any data on Pop III stars. Two projects are set to take over the next round of gravitational-wave astronomy.
Cosmic Explorer (CE), based in the U.S., is a planned L-shaped facility similar to LIGO, with arms stretching up to 40 km (25 miles). The Einstein Telescope (ET), on the other hand, is a planned underground facility on Sardinia, built in a 10-km (6-mile) triangle. While these new observatories are planned to be very capable, trying to sort out what a black hole from near the beginning of the universe would look like is hard.
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