Primordial Mega-Stars May Have Seeded the First Supermassive Black Holes
At the center of many galaxies, there exists a supermassive black hole, but scientists still aren't sure how they're formed.
However, we may soon witness how they formed in the very early universe, thanks to a team of international scientists who just predicted that distant supermassive stars explode into extreme supernovae — the possible progenitors of supermassive black holes, according to a recent study published in the journal Monthly Notices of the Royal Astronomical Society.
Whether the supernovae spawn supermassive black holes or not, calculations suggest the James Webb Space Telescope will be in prime position to observe them, once it's launched later this year.
Origin story of supermassive black holes baffles scientists
The study of supermassive black holes is a crucial one in contemporary astrophysics. Consensus says supermassive black holes were forged in the violent finality of the ancient deaths of the first colossal stars — very early in the universe's lifespan — which then grew to present-day size by swallowing untold volumes of matter for most of cosmic history.
However, this theory has faced new scrutiny as most massive stars seen in the local universe are roughly one or two times our sun's mass. If the first stars of a few hundred solar masses became the seeds of the first black holes, they'd need to maintain uncommonly high accretion efficiency to form the supermassive black holes we know exist today — something very difficult to keep up.
In other words, the black holes would have to continually eat a lot of matter for billions and billions of years to grow supermassive — without throwing too much matter away.
Early supernovae may be visible from our solar system
In his 2014 paper, Assistant Research Fellow Ke-Jung Chen of ASIAA Taiwan suggested a relativistic instability supernova could happen when a primordial supermassive star — which is 10^4 to 10^5 solar masses — dies in the right conditions.
"There may be a small number of the first stars in the early universe with tens of thousands of solar masses. They are likely to be the progenitors of supermassive black holes in galaxies," said Chen, according to a Phys.org report. "Because the more massive [...] the black hole seed, the more efficient it is [at swallowing] the surrounding matter."
"The black holes don't need to maintain a high accretion rate to grow quickly," Chen added.
Commonsense says observing ancient supermassive stars would prove difficult — since they have purportedly already exploded, and spent most of the universe's history becoming present-day supermassive black holes. But using Chen's model, the research team behind the present study created a new radiation hydrodynamics simulation — predicting how radiation of non-visible wavelengths from the ancient supermassive supernovae might reach us.
The James Webb Space Telescope could observe the birth of a supermassive black hole
And, incredibly, they discovered that the forthcoming James Webb Space Telescope mission might have a shot at capturing a "long-lasting" plateau phase from this kind of supernova. Critically, the ongoing explosion could serve as a scientific survey lasting decades.
"The plateau phase lasts for decades when it appears at high redshifts and it will likely be observed as a persistent source in the future deep near-infrared imaging surveys," read the study.
In other words, we may soon get confirmation of the origin story of supermassive black holes from a distant galaxy — as a supermassive star transforms into one of the first supermassive black holes.
With the James Webb Space Telescope's forthcoming mission, a window to the ancient behavior of the early universe may be about to open, offering us the first-ever empirical evidence of and explanation for the birth of a supermassive black hole. But for now, all we can do is wait, and hope the worst for dying, supermassive stars of the early universe.
Why do we do it, how can we stop it, and who else is at it?