MIT astronomers have identified an extremely bright red spot resembling an ancient enormous star- that also exudes 100 billion times more energy than any known star can produce.
As reported in Nature, the new astrophysical objects were discovered using the James Webb Space Telescope (JWST). The bright red dot was spotted in the very early period of the universe, in the first few hundred million years after the Big Bang.
The high energy output and images suggest that the red spot is a new type of astrophysical object, which the astronomers are calling a “black hole star.” The object is thought to be a hugely dense cloud of gas, not powered by standard nuclear fusion but by a central black hole.
“Our picture of this object is evolving very rapidly,” says lead author Rohan Naidu, a NASA Hubble Fellow and Pappalardo Fellow at MIT’s Kavli Institute for Astrophysics and Space Research (MKI). “We think there is a central black hole that is 100,000 times as massive as the sun. And around this black hole, there would be this very extended envelope of gas that looks like a star the size of the solar system. It’s huge.”
Mirage or Miracle
The survey was originally intended to find the most distant, earliest galaxies. “There’s been this puzzle of many bright galaxies showing up at extremely early times,” Naidu commented. “What we found was that what looks like an extremely bright early galaxy, also known as a ‘miracle,’ in some cases actually could be a ‘mirage.’”
Whilst examining JWST images, a red dot was noticed, called MoM-BH*-1. “Little red dots” have been spotted on the majority of JWST’s deep space images.
“These little red dots seem to be everywhere in the early universe but essentially disappear by the present day,” Naidu says. “What exactly these objects are has been one of the most debated topics of the JWST era.”
“When we see something very red in the universe, we often assume that it is surrounded by dust, like soot or ash,” co-author MKI Director Robert Simcoe explained. “Just as wildfire smoke from Canada recently made the sky in Boston look bright red, astronomical objects can also appear redder than their intrinsic color when you see them through a veil of dust.”
“Truly singular in so many ways”
The dot’s light was extremely bright, except below certain wavelengths, where it disappeared completely.
This phenomenom is known as a “Balmer break” and is traditionally associated with desnse gases absorbing photons in the atmosphere of stars only a few hundred million years old.
“The break we observed in this object is the deepest break we have ever observed in any object, ruling out ‘ordinary’ stars as the source,” Naidu continued. “But it made us wonder if we were seeing a new kind of ‘stellar atmosphere,’ but on a spectacular scale.”
The light emitted from the red dot also contained almost no signature of metals or any elements, bar hydrogen and helium. “It was truly singular in so many ways,” Naidu says.
Recreating the red light
The team ran simulations of various scenarios to better understand MoM-BH*-1.
“We started to ask: Could you make something that red using just hydrogen, without any dust?” Simcoe says. “To our surprise, it turns out you can, if you have an extremely dense screen of hydrogen, so dense that it looks more like the surface of an enormous star than a wispy interstellar nebula.”
The simulations suggested that the red dot could be an energy source surrounded by a very dense shroud of hydrogen, which would explain the lack of metals in the atmosphere and the Balmer break observed. But it would not explain for the extreme brightness of the object.
“You have something that looks a bit like a star but is 100 billion times brighter,” Naidu said. “That means you can’t be powering this by nuclear fusion, which is the energy source that sits at the heart of all the stars we have.”
A black hole is believed to sit at the centre of the star
The researchers knew that black holes can produce energy at a similar scale to the output seen in the object and so adjusted simulations to incorporate an active, accreting black hole at varied masses, as well as with other conditions.
When comparing the brightness from this simulated black hole star to the JWST images, the team concluded that the most likely explaination is that the object contains a central black hole around 100,000 times as massive as the sun. A dense cocoon of hydrogen roughly the size of our solar system surrounds this black hole core.
This research could have implications for the little red dots observed in other JWST imagery, although these objects are not as bright as MoM-BH*-1.
“Every little red dot is consistent with being a black hole star, embedded in a generic early galaxy,” Naidu says. “But what is special about MoM-BH*-1 is, the black hole star is essentially completely outshining its surrounding host galaxy, such that we’re seeing pure black hole star light.”
