Black hole explorer mission to probe black holes' secrets Exploring edge of reality

One ambitious project stands out: the Black Hole Explorer (BHEX). Led by a team of pioneering scientists including Alex Lupsasca and Michael Johnson, BHEX aims to venture beyond the confines of Earth and explore the profound complexities of black holes.

Alex Lupsasca aims to expand Earth's largest telescope network beyond the atmosphere with a space-based dish.

This innovation could capture new views of a black hole never seen before, potentially unveiling new insights into physics, Caliber.Az reports citing the foreign media.

The era of black hole imaging began with the landmark release of the first-ever black hole photograph in 2019. This achievement, however, was no small feat—it required a telescope virtually the size of the Earth itself. Yet for scientists like Alex Lupsasca from Vanderbilt University in Tennessee, this initial image wasn't sufficient. Lupsasca and his team are now targeting a more detailed view, necessitating an even larger telescope.

The groundbreaking 2019 image was captured by the Event Horizon Telescope (EHT), a global network of radio observatories strategically placed around the world. Working collaboratively, eight observatories synthesized an image that surpassed what any single dish could achieve in clarity. Lupsasca is part of a group planning to launch the Black Hole Explorer (BHEX) telescope into space, positioned 20,000 kilometers from Earth. This placement would effectively enlarge the telescope beyond the size of the planet, providing the precision needed to observe a mysterious feature of black holes called the photon ring. Specifically, they aim to study the photon ring of M87*, the supermassive black hole in a neighboring galaxy that was prominently featured in the historic 2019 image.

Lupsasca, the deputy project scientist for the BHEX mission, is a theoretical physicist focusing on extreme environments such as the cores of black holes. He believes this mission represents our most promising opportunity to challenge Albert Einstein’s theory of gravity. For Lupsasca, ambitious space missions are crucial for unraveling one of physics' greatest mysteries: the fundamental nature of reality.

Why do we need such a big telescope?

Alex Lupsasca explains that to observe a small object in space, precise resolution of closely spaced rays is essential. A larger telescope dish allows for more precise focusing of these rays. The goal is to capture detailed images of M87*, a nearby supermassive black hole, which appears in the sky as roughly the size of an orange on the surface of the moon. The aim is to observe the black hole's photon ring through high-resolution imaging, requiring a telescope dish larger than the diameter of Earth.

Is the telescope really bigger than Earth?

Imagine you have a large mirrored dish, and you break the mirror into pieces or shards. These shards are then spread far apart, positioned on opposite sides of Earth and even beyond. Each shard captures only a small portion or sliver of the black hole. However, by meticulously recording the data from each shard, it becomes possible to digitally combine or synthesize this information. Through this process, you can reconstruct a complete image of the black hole. With a sufficient number of shards, this synthesized image can achieve nearly the same level of detail and precision as a telescope dish that is larger than the Earth itself.

Has the Black Hole Explorer mission been approved by NASA?

"So far, we haven't achieved it, but in recent months, we've made significant progress toward that objective. We're collaborating closely with NASA’s Goddard Space Flight Center, and we've brought onboard engineers to tackle the remaining technical hurdles. Securing private funding, including seed investment from tech investor Fred Ehrsam, has also been crucial. We're moving forward rapidly to prepare a comprehensive proposal for NASA by next spring. If approved, we aim to launch a satellite in 2031—although that might seem distant, in terms of space missions, it's just around the corner. Hopefully, we'll capture a movie of a photon ring before my hair turns grey."

What is a photon ring?

"Imagine there’s a cloud of hot gas emitting photons near a black hole. Most of these photons curve slightly due to the black hole’s gravity, providing an image of the gas around it, similar to the EHT images of black holes. However, a small fraction of photons, if directed precisely, orbit directly around the black hole’s perimeter, known as its event horizon. This boundary marks the edge of our observable universe—we have little understanding of what happens to particles that cross this boundary, and may never fully comprehend it. The photon ring consists of light that grazes this universal edge and then escapes, carrying crucial information about the space-time structure there."

Why do you want to measure the photon ring?

"We aim to explore gravity under the most extreme conditions conceivable. Gravity is notably the weakest of the four fundamental forces known to us, making it exceedingly challenging to measure. Its effects are subtle and the least understood among these forces.

While we have a robust and internally consistent theory, quantum field theory, for electromagnetism and the strong and weak nuclear forces, it doesn't fully align with Einstein's general theory of relativity, our best model for gravity. Our goal is to develop mathematical equations that unify all these forces. However, integrating these theories reveals a fundamental tension—they don't seamlessly coexist.

To progress, we turn to black holes, which epitomize the most extreme gravitational fields possible. They serve as natural laboratories where we can investigate and glean insights into the deeper layers of fundamental theory. These black holes are ready-made experiments offering intense gravity environments for study, with photon rings serving as distinctive imprints left by their powerful gravitational forces."

Can you describe the signature that the rings contain in more detail?

The first photon ring that the BHEX mission aims to observe originates from light traveling towards a black hole, making half a circuit around its edge before continuing towards telescopes on Earth. This outermost ring is the brightest, surrounded by fainter nested sub-rings categorized by the number of photon orbits around the black hole.

According to general relativity, each ring forms nearly a perfect circle, with slight deviations following a periodic pattern that indicates the ring's diameter at specific angles. This periodicity also reveals precise relationships between these rings. Recently, Michael Johnson of Harvard University, a member of the BHEX team, and I discovered that a single telescope orbiting Earth, observing the photon ring from different angles, can accurately measure its intricate structure. This discovery, which involves mathematical nuances, was recognized with the New Horizons in Physics prize. Other colleagues, such as Sam Gralla and Dan Marrone from the University of Arizona, have also made significant theoretical contributions to this field.

Is the hope that the photon ring will deviate from general relativity?

BHEX’s observations will mark a significant departure from all previous tests of general relativity conducted within the Earth or the solar system. These observations will delve deeply into the realm of strong gravity, offering the potential to discover something entirely revolutionary and unexpected. This is the ambitious aim of BHEX. While there’s a chance we might detect a signature of phenomena diverging from general relativity, I remain cautious about such prospects. Nevertheless, we are certain to gain valuable insights into astrophysics, particularly concerning magnetic fields and the behavior of matter as it approaches a supermassive black hole.