Orbital observatories such as the Hubble Space Telescope and James Webb Space Telescope (JWST) can see far back into the universe—so far, in fact, that they have revealed some of the earliest galaxies to form in the first 500 million years of our universe’s 13.8-billion-year-history. Much further back, we can see the remnant heat left over from the big bang, the cosmic microwave background (CMB) radiation, which was emitted about 400,000 years into cosmic history. But what about the period after the CMB appeared and before the first stars and galaxies formed, deep in the so-called cosmic dark ages? Is it possible we could witness the birth of some of the first objects in the universe? The task is an almost impossibly tall order with Hubble and JWST: such objects are simply too small and faint. But with a new cadre of gravitational-wave observatories, detecting the stirrings of some early cosmic arrivals—specifically, black holes—should be a cinch.
The best news: those observatories are already being designed. “The era of gravitational waves has arrived,” says Chiara Mingarelli, a gravitational-wave astronomer at Yale University.
Last month the European Space Agency (ESA) approved the latest milestone in this era, a €1.5 billion ($1.6 billion) space observatory called the Laser Interferometer Space Antenna (LISA). Comprising three free-flying spacecraft each separated by 2.5 million kilometers in their orbits around the sun, LISA will search for a specific frequency of gravitational waves unseen by the current crop of ground-based detectors. These are the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo collaboration in the U.S. and Italy—joined by the Kamioka Gravitational-Wave Detector (KAGRA) in Japan, although that observatory’s operation has had setbacks—as well as various pulsar timing arrays such as the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) in the U.S. and Canada, which made its first…
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