Roman telescope searches for primordial black holes

NASANancy Grace Roman space telescope It may reveal previously undetected “featherweight” black holes that have masses similar to Earth’s. These primordial black holes, which formed at the beginning of the universe, could greatly impact our understanding of astronomy and particle physics, potentially explaining some of the dark matter in the universe.

Astronomers have discovered black holes with masses ranging from a few times the mass of the Sun to tens of billions. Now a group of scientists has predicted that NASA’s Nancy Grace Roman Space Telescope will be able to find a class of “featherweight” black holes that has eluded discovery until now.

Today, black holes form either when a massive star collapses or when massive objects merge. However, scientists suspect that smaller “primordial” black holes, including some with masses similar to Earth’s, could have formed in the first chaotic moments of the early universe.

“The discovery of a population of Earth-mass primordial black holes would be an amazing step for both astronomy and particle physics because these objects could not have formed by any known physical process,” said William DiRocco, a postdoctoral researcher at UC Santa Fe. Cruz who led a study on how the Romans detected them. A paper describing the results It was published in the magazine Physical review d. “If we find them, it will shake up the field of theoretical physics.”

The discovery of Earth-mass primordial black holes using NASA’s Roman space telescope could change our understanding of the universe and dark matter. Source: NASA Goddard Space Flight Center

Primordial black hole recipe

The smallest black holes that form today are born when a massive star runs out of fuel. Its external pressure diminishes as nuclear fusion declines, so internal gravity wins the tug of war. The star is contracting and may become so dense that it becomes… Black hole.

But there is a minimum mass required: at least eight times the mass of our Sun. The lighter stars will either turn into white dwarfs or neutron stars.

However, conditions in the very early universe may have allowed much lighter black holes to form. A person weighing the mass of the Earth would have an event horizon—the point of no return for falling objects—that is roughly the width of a U.S. dime.

Just as the universe was born, scientists believe it went through a short but intense phase known as inflation when space expanded faster than the speed of light. In these special conditions, regions that were denser than surrounding regions might have collapsed to form low-mass primordial black holes.

While theory predicts that the smallest ones would have to evaporate before the universe reached its current age, those with masses similar to Earth would have survived.

The discovery of these small objects will have a huge impact on physics and astronomy.

“This will affect everything from the formation of galaxies to the dark matter content of the universe to cosmic history,” said Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore, who was not involved in the study. “Confirming their identities will be hard work and astronomers will need a lot of convincing, but it will be worth it.”

Stephen Hawking hypothesized that black holes could slowly contract as radiation escapes. The slow leakage of what is now known as Hawking radiation will, over time, cause the black hole to simply evaporate. This infographic shows the estimated lifetimes and event horizons — the point beyond which falling objects can no longer escape a black hole’s gravitational grip — and the diameters of black holes of different small masses. Source: NASA Goddard Space Flight Center

Hints from hidden homeowners

Observations have already revealed evidence that such objects may be lurking in our galaxy. Primordial black holes may be invisible, but wrinkles in space-time have helped catch some potential suspects.

Microlensing is an observational effect caused by the presence of mass distorting the fabric of space-time, like the imprint left by a bowling ball when placed on a trampoline. Any time an object appears to be drifting close to a background star from our perspective, the star’s light must traverse the warped space-time around the object. If the alignment is particularly close, the object can act as a natural lens, focusing and amplifying the light of the background star.

Separate groups of astronomers found it using data from MOA (Microlensing Observations in Astrophysics) – a collaboration that conducts microlensing observations using the Mount John University Observatory in New Zealand – and OGLE (Optical Gravitational Lensing Experiment). An unexpectedly large number of isolated Earth-mass objects.

Theories of planetary formation and evolution predict certain masses and abundances of rogue planets — worlds roaming the galaxy untethered to a star. MOA and OGLE observations indicate that there are more Earth-mass objects drifting through the galaxy than models predict.

This artist’s concept takes a fantasy approach to imagining tiny primordial black holes. In fact, such small black holes would have difficulty forming the accretion disks that make them visible here. Source: NASA Goddard Space Flight Center

“There is no way to distinguish between Earth-mass black holes and rogue planets on a case-by-case basis,” DiRocco said. But scientists expect that Roman will find a number of objects in this mass range ten times larger than ground-based telescopes. “Roman would be very powerful in distinguishing between the two statistically.”

DiRocco led efforts to determine how many rogue planets would have to be in this mass range, and how many primordial black holes the Romans could distinguish among them.

Finding primordial black holes would reveal new information about the very early universe, and would strongly suggest that an early period of inflation had already occurred. It could also explain a small percentage of the mysterious dark matter that scientists say makes up the bulk of the universe’s mass, but which they have not yet been able to identify.

“This is an exciting example of something more scientists can do with the data that Roman will already have during his planetary search,” Sahu said. “The results are interesting whether or not scientists find evidence of Earth-mass black holes. It would enhance our understanding of the universe either way.”

Reference: “Detecting Earth-mass primordial black holes using the Nancy Grace Roman Space Telescope” by William DiRocco, Evan Frangipani, Nick Hammer, Stefano Profumo, and Nolan Smith, January 8, 2024, Physical review d.
doi: 10.1103/PhysRevD.109.023013

The Nancy Grace Roman Space Telescope is operated at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation from NASA’s Jet Propulsion Laboratory, Caltech/IPAC in Southern California, the Space Telescope Science Institute in Baltimore, and a science team that includes scientists from around the world. Research institutes. Primary industrial partners are BAE Systems, Inc. of Boulder, Colorado; L3Harris Technologies in Rochester, New York; and Teledyne Scientific & Imaging in Thousand Oaks, California.