Advancing Basic Science for Humanity
07/08/2020 - How the Universe Washes Over Us Earthlings: Astrophysics Highlights
By Adam Hadhazy
The Dark Energy Spectroscopic Instrument, which will map millions of galaxies in 3D from a mountaintop in Arizona, has reached its final milestone toward its startup. Photo credit: P. Marenfeld & NOAO/AURA/NSF
Many sciences have an "agency" to them, whether it's documenting new species in the wild, studying how our bodies work, or devising incredible new machines; in essence, we go find it, examine it, or build it. Astronomy and astrophysics operate differently, however. Much of their science is instead dependent on the universe coming to us, rather than us going to it. Sure, we have physically gone to the Moon and retrieved a bunch of lunar rocks. And yes, we've made dozens of forays into the solar system via robotic probes to visit other worlds and send back data on a vast range of phenomena—even out into the fringes of interstellar space, thanks to the twin Voyager spacecraft. But for the most part, to conduct astronomy and astrophysics, we must build observatories and then sit back and collect what the cosmos incidentally sends our way. That includes light from all the stars in existence, including the Sun, which of course we cannot physically encounter. Our observatories are further bathed in the radiation streaming from phenomena as diverse as hot exoplanets, re-emitting light they absorbed from their host stars, to black hole jets smashing particles together and releasing immense energies. We detect the particles blasted out by numerous astrophysical happenings, locally by the Sun and from galaxies far beyond our own. Most recently, we've learned to register the passing through our planet of great ripples in the fabric of the cosmos itself, the gravitational waves unleashed by objects such as black holes cataclysmically coalescing. It's amazing to think about how much cosmically washes over us here on our mote-like Earth, and what we're able to learn about the wider universe because of it generously arriving right at our doorstep.
A federal advisory board has formally declared the completion of the Dark Energy Spectroscopic Instrument, or DESI. A next-generation explorer of dark energy, the enigmatic force speeding cosmic acceleration, DESI will gather light from tens of millions of galaxies, building a 3D cosmic map. Numerous researchers at the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) at Stanford University have been involved with the project since its nascency. DESI should begin observations late this year or early next.
Scientists at the Massachusetts Institute of Technology's Kavli Institute for Astrophysics and Space Research (MKI) and colleagues have discovered a young brown dwarf surrounded by a dusty disk located only about 330 light-years away—the closest such object of its kind. Brown dwarfs are "failed" stars, essentially, possessing not quite enough mass to ignite a fusion furnace in their cores. The dusty disk around the brown dwarf is—when around stars, at least—a planetary breeding ground. Studying the disk further will help advance our understanding of the kinds of worlds that could possibly emerge in orbit around failed stars.
Studying exoplanets is normally the purview of substantially sized telescopes on both the ground and in space. Now a spacecraft merely the size of a briefcase has successfully spotted an exoplanet. The spacecraft, called ASTERIA, was a technology demonstration led in part by researchers from MKI. The spacecraft has shown how small, low-cost spacecraft can offer a helping hand with the science tasks normally allocated to bigger vessels.
The science of black hole mergers is one of the hottest areas in astrophysics currently, thanks to the accumulating record of these cataclysmic events being compiled by the LIGO and VIRGO gravitational wave detectors. The biggest merger detected so far involved a black hole with a staggering 50 times the mass of the Sun—far bigger than theoretically expected. Researchers at the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) have now helped solve the mystery of this monster black hole's origin. In a recent study, the researchers detailed an evolutionary path by which a colossal star with more than 80 times the mass of the Sun could undergo a particular kind of supernova explosion, ultimately leaving behind a remarkably hefty black hole.
One of the newest kids on the block in terms of documented astrophysical phenomena is fast radio bursts—typically few-millisecond-short blasts of radio waves that, astonishingly, can outshine a whole galaxy in terms of raw power. Besides a few random repeaters, most of the 100 or so FRBs discovered in the last 13 years are one-off events. Now a team of researchers, including MKI members, has cataloged the first FRB that repeats in a pattern, which lasts 16 days. This finding should help in locking down the sources of some FRBs, thought to involve super-dense neutron stars.