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An interstellar mission to a black hole? Astrophysicist thinks it’s possible.
It sounds like science fiction: a spacecraft, no heavier than a paperclip, propelled by a laser beam and hurtling through space at the speed of light toward a black hole, on a mission to probe the very fabric of space and time and test the laws of physics. But to astrophysicist and black hole expert Cosimo Bambi, the idea is not so far-fetched.
Reporting in the Cell Press journal iScience, Bambi outlines the blueprint for turning this interstellar voyage to a black hole into a reality. If successful, this century-long mission could return data from nearby black holes that completely alter our understanding of general relativity and the rules of physics.
“We don’t have the technology now,” says author Cosimo Bambi of Fudan University in China. “But in 20 or 30 years, we might.”
The mission hinges on two key challenges—finding a black hole close enough to target and developing probes capable of withstanding the journey.
Previous knowledge on how stars evolve suggests that there could be a black hole lurking just 20 to 25 light-years from Earth, but finding it won’t be easy, says Bambi. Because black holes don’t emit or reflect light, they are virtually invisible to telescopes. Instead, scientists detect and study them based on how they influence nearby stars or distort light.
“There have been new techniques to discover black holes,” says Bambi. “I think it’s reasonable to expect we could find a nearby one within the next decade.”
Once the target is identified, the next hurdle is getting there. Traditional spacecrafts, powered by chemical fuel, are too clunky and slow to make the journey. Bambi points to nanocrafts—gram-scale probes consisting of a microchip and light sail—as a possible solution. Earth-based lasers would blast the sail with photons, accelerating the craft to a third of the speed of light.
At that pace, the craft could reach a black hole 20 to 25 light-years away in about 70 years. The data it gathers would take another two decades to get back to Earth, making the total mission duration around 80 to 100 years.
Once the craft is near the black hole, researchers could run experiments to answer some of the most pressing questions in physics. Does a black hole truly have an event horizon, the boundary beyond which not even light can escape its gravitational pull? Do the rules of physics change near a black hole? Does Einstein’s theory of general relativity hold under the universe’s most extreme conditions?
Bambi notes that the lasers alone would cost around one trillion euros today, and the technology to create a nanocraft does not yet exist. But in 30 years, he says that costs may fall and technology may catch up to these bold ideas.
“It may sound really crazy, and in a sense closer to science fiction,” says Bambi. “But people said we’d never detect gravitational waves because they’re too weak. We did—100 years later. People thought we’d never observe the shadows of black holes. Now, 50 years later, we have images of two.”
Expert Reaction
These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.
Dr Yvette Perrott, Senior Lecturer in the School of Chemical and Physicals Sciences, Te Herenga Waka - Victoria University of Wellington
"The prospect of sending spacecraft to directly observe black holes is exciting! However, there are many, many engineering challenges which would need to be overcome to actually make it work.
"To name a few: how can we precisely aim nanocraft at such a distant target, when a small starting error in the speed and direction would send them far off-course by the time they get there? Will the nanocraft survive the space environment (micrometeorites, space dust, radiation) over such a long distance? Similar projects such as Breakthrough Starshot envisage a fleet of nanocraft, assuming that many will not make it. How will the nanocraft insert itself into orbit around the black hole once it gets there? This will need to be an autonomous manoeuvre given the distances involved, which will require onboard processing - difficult on a gram-scale satellite. Similarly, how will the instrumentation for doing the required measurements and communicating data back over such vast distances be made small and light enough to fit on the satellite?
"It’s important to dream, but I foresee many lifetimes of work before a mission like this could be practical."
Professor Richard Easther, Department of Physics, University of Auckland
"This story has more plot holes than black holes, unfortunately.
"Firstly, it relies on a potentially optimistic claim that that the Milky Way is home to so many black holes that we are likely to find one within 20 light years of the sun.
"A bigger problem is that it is based on the “Breakthrough Starshot Initiative”, which proposes to use giant lasers to send postage-stamp sized spacecraft to the stars. The author says "there are no specific technical problems to reach 90% of the speed of light” – but there are actually lots of them.
"But the biggest problem of all is that the little spacecraft must slow down and orbit the black hole to make most of the measurements the paper proposes. But even Starshot won’t do that for you – the giant lasers stay behind in our solar system and the chipsats would eventually leave the Milky Way galaxy, just as the Voyager spacecraft left our solar system after zipping by the outer planets. The author acknowledges the issue, but just says "All possible solutions should be considered carefully.” Never a truer word spoken.
"My take: it’s a fun what-if, and this sort back-of-the-envelope calculation is a great workout for a physicist. But it’s more science clickbait than a serious proposal at this point."
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