How NASA’s Rome mission will explore ancient black holes

Astronomers have discovered black holes with masses ranging from a few solar masses to tens of billions of masses. Now, a group of scientists has predicted that NASA’s Nancy Grace Roman Space Telescope may be able to discover previously undetectable “featherlight” class black holes. Currently, black holes are formed by the collapse of massive stars or the merger of massive objects. But scientists suspect that smaller “primordial” black holes, including ones with masses similar to Earth’s, formed during the first chaotic moments of the early universe. William DeRocco, a postdoctoral fellow at the University of California, said: “The discovery of a population of proto-Earth-mass black holes would be an astonishing step forward for both astronomy and particle physics, as these objects are bound by known physical processes. Because it cannot be formed.” Dr. Santa Cruz led the research into how Roman was able to expose them. An article describing the results was published in the journal Physical Review D. “If we could discover them, it would shake up the field of theoretical physics.” Original black hole recipe The smallest black holes currently forming occur when a massive star runs out of fuel. When fusion subsides, the external pressure also weakens, and the inward gravitational pull wins the tug-of-war. Stars can shrink and become so dense that they become black holes. But there is a minimum mass, which is at least eight times the mass of the Sun. Brighter stars become white dwarfs or neutron stars. However, conditions in the very early days of the universe may have allowed the formation of much lighter black holes. For instruments that measure the Earth’s mass, the event horizon (the point of no return for incoming objects) would be approximately the width of a dime. Scientists believe that when the universe began, it experienced a brief but intense period known as inflation, during which space was expanding faster than the speed of light. Under these special conditions, a region denser than its surroundings could have collapsed, forming an ancient low-mass black hole. The theory is that the smallest specimens would have evaporated before the universe reached its current age, but specimens with masses similar to Earth may have survived. The discovery of these small objects will have a huge impact on physics and astronomy. “It will affect everything from the formation of galaxies to the amount of dark matter in the universe to the history of the universe,” said Kailash Sahu, an astronomer at the Space Telescope Science Institute in Baltimore. “It will be a lot of work to confirm their identity, and it will take a lot of time to convince astronomers, but it will be worth it.” Evidence of the denizens of the hideout Observations have already revealed evidence that such objects may be lurking in our galaxy. Primordial black holes are invisible, but wrinkles in space-time have helped gather some suspects. Microlensing is an observed effect that occurs because the fabric of space-time is distorted by the presence of mass, like the imprint left when a bowling ball is placed on a trampoline. From our perspective, every time an intervening object appears to be drifting closer to a background star, the light from the star has to traverse the distorted space-time around the object. If the alignment is particularly close, the object acts like a natural lens, concentrating and amplifying the light from the background stars. Using data from MOA (Microlensing Observations in Astrophysics) (a collaborative effort to conduct microlensing observations using the Mount John University Observatory in New Zealand) and OGLE (Optical Gravitational Lensing Experiment), separate groups of astronomers have discovered an unexpectedly large population of Mass object. Theories of planet formation and evolution predict a certain mass and frequency of rogue planets, which are worlds roaming the galaxy without a connection to a star. The MOA and OGLE observations suggest that there are more Earth-mass objects drifting around in the galaxy than models predict. “There’s no way to distinguish between an Earth-mass black hole and a rogue planet on a case-by-case basis,” DeRocco says. But scientists expect Roman to find 10 times as many objects in this mass range as ground-based telescopes. “Roman is going to be very good at statistically distinguishing between the two.”

DeRocco led the effort to determine how many rogue planets exist within this mass range and how many primordial black holes Roman could detect among them. The discovery of a primordial black hole would provide new information about the very beginning of the universe and strongly suggest that the early stages of inflation did occur. Scientists may also be able to explain a small portion of the mysterious dark matter, which makes up most of the mass of the universe but has yet to be identified. “This is an interesting example of what additional scientists can do with the data Roman already has from planetary exploration,” Saf said. “And whether or not scientists find evidence that black holes with the mass of Earth exist, this result is interesting.” Either way, it will enhance our understanding of the universe. ”

source: https://phys.org/journals/physical-review-d/