When you buy through links on our articles, Future and its syndication partners may earn a commission.An artist’s impression of a window into the heart of a little red dot, revealing the supermassive black hole within. | Credit: NASA/CXC/SAO/M. Weiss; adapted by K. Arcand and J. Major.The discovery of an X-ray signal coinciding with the location of one of the mysterious ‘little red dots’ found by the James Webb Space Telescope (JWST) has strengthened the theory that the dots are ‘black hole stars’ — huge, dense clumps of gas energized by the presence of a growing supermassive black hole within them.The little red dots may be the biggest cosmological discovery made so far by the JWST, and possibly the most important since the discovery of dark energy in 1998. If they are what astronomers think they are, then they would act as a crucial missing link in the formation of not only supermassive black holes but also the galaxies that grow around them.AdvertisementAdvertisementThe newly discovered “X-ray dot” was recognized when the JWST’s observations of an area of sky containing little red dots was compared to archival observations of the same area by NASA’s Chandra X-ray Observatory.”The X-ray dot has been sitting in our Chandra survey data for over ten years, but we had no idea how remarkable it was before Webb came along to observe the field,” said Princeton University astronomer Andy Goulding in a statement.Chandra has identified millions of X-ray sources across the sky, but the importance of this one, catalogued as 3DHST-AEGIS-12014 (AEGIS refers to the All-wavelength Extended Groth Strip International Survey), only became apparent when it was noticed that it was in exactly the same location as a little red dot seen by the JWST. The X-ray source carries an energy not dissimilar to the X-ray energy of quasars, which are galaxies that host an extremely active black hole, often as the result of a galaxy merger stirring up gas and prompting that material to fall towards the black hole.Little red dots are compact, being at most just a few hundred light-years across. They are also very red, meaning they are rather cool — a recent study led by Harvard’s Anna de Graaf identified water vapor in them, the existence of which tells us how cool the little red dots must be, in the range of 3,092 to 6,692 degrees Fahrenheit (1,700 to 3,700 degrees Celsius). This sounds hot to us, but it is cooler than our sun and indeed most stars except for the least massive red dwarfs.AdvertisementAdvertisementFurthermore, little red dots are very distant objects, measured to have existed 12 billion years ago, or even older still. Photometric measurements of 3DHST-AEGIS-12014 by the Hubble Space Telescope tell us that we see this puzzling object as it existed 11.8 billion years ago.The discovery of little red dots potentially also fulfills one of the JWST’s primary science goals, which is to try and trace the origins of supermassive black holes and the galaxies that assemble around them.How supermassive black holes are born has been a mystery that has confounded astronomers. Do they form from the bottom up, as smaller stellar-mass black holes produced in supernova explosions combine with each other? Or, do they form from the top down, via the collapse of a vast gas cloud containing hundreds of thousands or even millions of times the mass of our sun?Little red dots are thought t …
