NASA's Nancy Grace Roman Telescope to Hunt for Tiny Black Holes from the Big Bang Era

NASA is gearing up to use its upcoming Nancy Grace Roman Space Telescope to search for minuscule black holes that might date back to the Big Bang. With the telescope set to launch in late 2026, it aims to detect primordial black holes that could be as light as asteroids.

What Are Primordial Black Holes?

When we think of black holes, we usually imagine cosmic behemoths like stellar-mass black holes (with masses tens or hundreds of times that of the sun) or supermassive black holes that anchor entire galaxies. However, scientists believe that there could also be much smaller primordial black holes with masses as low as that of Earth or even large asteroids.

These theoretical black holes are thought to have formed during the early, turbulent days of the universe, around 13.8 billion years ago.

The Hunt Begins

The Nancy Grace Roman Space Telescope will join the search for these elusive, featherweight black holes. William DeRocco, a researcher at the University of California Santa Cruz who led a team studying how the telescope could reveal these ancient black holes, emphasized the potential impact of the discovery:

"Detecting a population of Earth-mass primordial black holes would be an incredible step for both astronomy and particle physics because these objects can't be formed by any known physical process. If we find them, it will shake up the field of theoretical physics."

What Makes Primordial Black Holes Unique?

The smallest confirmed black holes today are stellar-mass black holes, which form when massive stars run out of nuclear fuel and collapse under their own gravity. Stars typically need to be at least eight times the mass of the sun to leave behind a stellar-mass black hole.

However, conditions during the universe's infancy might have allowed much smaller collections of matter to collapse into primordial black holes.

Key Features:

• Event Horizon Size:

• Stellar-mass black holes (30 solar masses) have event horizons about 110 miles wide.

• Primordial black holes with the mass of Earth would have an event horizon no wider than a dime.

• Those with the mass of an asteroid would have an event horizon smaller than a proton.

Hawking Radiation and Black Hole Lifespans

Stephen Hawking's theory of Hawking radiation suggests that black holes "leak" thermal radiation over time. The smaller a black hole is, the faster it leaks this radiation and loses mass, eventually causing it to explode. This has led many scientists to believe that primordial black holes wouldn't have survived for 13.8 billion years.

If the Nancy Grace Roman Space Telescope detects these ancient black holes, it would challenge current physics theories and require a major rethink.

Gravitational Lensing: The Key to Detection

Primordial black holes don't emit or reflect light, making them nearly impossible to observe directly. Instead, the Roman telescope will use a phenomenon predicted by Albert Einstein's general relativity: gravitational lensing.

How It Works:

• Objects with mass warp spacetime, bending the path of light that passes by them.

• When light from a background source is distorted by a massive object (like a galaxy), it creates a lensing effect, making the source appear at multiple locations or appear brighter.

• In the case of primordial black holes, this effect is called microlensing, causing a brief brightening of background sources detectable by the telescope.

Searching for Rogue Planets and Black Holes

Microlensing has already helped scientists find rogue planets (planets not bound to a parent star) in the Milky Way. The Roman telescope aims to increase detections of rogue planets tenfold and potentially distinguish between rogue planets and primordial black holes statistically.

Kailash Sahu, an astronomer at the Space Telescope Science Institute, noted:

"This is an exciting example of something extra scientists could do with data Roman is already going to get as it searches for planets. And the results are interesting whether or not scientists find evidence that Earth-mass black holes exist."

Conclusion

NASA's Nancy Grace Roman Space Telescope could usher in a new era of understanding for both astronomy and theoretical physics. By searching for these ancient black holes, it may provide groundbreaking insights into the early universe and challenge existing theories.

The research was published in January in the journal Physical Review D.