The James Webb Area Telescope has noticed objects within the early universe that is likely to be a brand new type of star — one powered by darkish matter.
These “darkish stars” are nonetheless hypothetical. Their identification in JWST photos is much from sure. But when any of the three candidates — reported within the July 25 Proceedings of the Nationwide Academy of Sciences — change into this new kind of star, they might provide a glimpse of star formation within the early universe, trace on the nature of darkish matter and probably clarify the origins of supermassive black holes.
First proposed in 2007 by cosmologist Katherine Freese and colleagues, darkish stars may need been among the first kinds of stars to kind within the universe (SN: 1/1/08). Although darkish stars have but to be noticed, they’re regarded as powered by warmth from darkish matter interactions slightly than by nuclear fusion reactions like within the solar.
Darkish stars “could be very bizarre trying,” says Freese, of the College of Texas at Austin. The hypothetical stars would have shaped from clouds of hydrogen and helium that drew in domestically plentiful darkish matter as they coalesced. Although the true nature of darkish matter isn’t identified — its presence is inferred largely by way of its impact on how stars transfer inside galaxies — it’s potential that darkish matter particles can work together with themselves, annihilating one another after they collide and producing huge quantities of sunshine and warmth (SN: 7/7/22). That warmth would maintain the cloud of hydrogen and helium from condensing right into a dense, scorching core like the celebrities that exist at this time.
As a result of the warmth from darkish matter annihilations would maintain the gasoline cloud from condensing, darkish stars might develop to gargantuan measurement. Theoretically, darkish stars might be 10 instances as large as Earth’s orbit across the solar. They is also hundreds of thousands of instances as large because the solar and shine billions of instances brighter — vivid sufficient, probably, to be noticed by JWST.
To see if any darkish stars are lurking in knowledge from the orbiting observatory, Freese and colleagues pored over photos from a JWST survey of early galaxies. In such photos, JWST has up to now found over 700 objects which will have originated within the first few hundred million years of the universe — the epoch when darkish stars would have emerged (SN: 12/16/22). Gentle from these distant objects is stretched, or redshifted, because the universe expands. So Freese and colleagues zeroed in on 4 objects already confirmed to be extremely redshifted, making them among the oldest objects seen up to now.
These objects are at the moment regarded as small galaxies from the universe’s relative infancy. However as a result of they’re so distant, JWST can’t resolve them properly sufficient to find out whether or not they’re really galaxies or giant, ultrabright stars, the researchers say.
The workforce ran pc simulations of how a lot mild a hypothetical darkish star would possibly produce at numerous wavelengths. They in contrast these spectra to mild from photos collected by JWST at completely different wavelengths for every of the 4 objects. JWST knowledge from three of these objects are in step with the simulated darkish star patterns, Freese and colleagues report.
Some scientists are skeptical. Identified kinds of stars might additionally create the noticed mild from the three candidates, says Sandro Tacchella, an astrophysicist on the College of Cambridge. And figuring out any of the objects as a darkish star would require that the simulated patterns match properly to extra detailed spectra, says Brant Robertson, a theoretical astrophysicist on the College of California, Santa Cruz.
If darkish stars have been to be discovered, although, “that will be revolutionary,” says research coauthor Cosmin Ilie, an astrophysicist at Colgate College in Hamilton, N.Y.
Detecting darkish stars would affirm the existence of a darkish matter particle and trace at the way it works (SN: 7/7/22). “Simply having the data that [dark matter] is one thing that might annihilate could be actually, actually highly effective,” says Tracy Slatyer, a theoretical physicist at MIT who was not concerned within the research. That data might assist scientists search for darkish matter elsewhere within the universe, she says.
Darkish stars might additionally assist clarify the formation of supermassive black holes (SN: 3/16/18). As soon as the darkish matter contained in the star has annihilated itself, the remaining hydrogen and helium — hundreds of thousands of instances the mass of the solar in a comparatively compact house — would collapse in on itself and kind a black gap. These black holes might merge over time into black holes like those on the facilities of most galaxies, hundreds of thousands or billions of instances as large because the solar.
Future experiments, like in search of brighter or dimmer mild at sure wavelengths, might assist affirm whether or not any of the three objects are darkish stars. Freese additionally expects to search out extra darkish star candidates in future JWST knowledge, she says. However for now, whether or not darkish stars really exist stays a thriller.
