It has been five years since astronomers spotted our first confirmed interstellar visitor, but even with the benefit of hindsight, no one is exactly sure what ‘Oumuamua was. This mysterious visitor is too far away to investigate, but it might be possible to prepare for the next one. A new study proposes a plan for intercepting future interstellar objects, which could confirm important details about their composition and origins. And who knows, maybe we’ll find something decidedly technological.
The discovery of ‘Oumuamua as it zipped past Earth captured the attention of astronomers all over the world. It was the first time we were able to track something that originated in another solar system. Scientists now believe ‘Oumuamua is roughly pancake-shaped, but its composition remains a mystery. Initially, everyone assumed it was a comet that got ejected from the edge of a neighboring solar system. However, there was no hazy coma around it as you’d expect for a comet. And yet, it showed slight acceleration associated with comet-like outgassing. Some follow-up analyses have suggested ‘Oumuamua was something exotic and previously unseen, like a hydrogen iceberg. But we just don’t know!
Because interstellar objects are traveling at incredible speeds relative to Earth, we can’t just decide to chase one down after it’s been discovered — we need to prepare. That’s the subject of a new study from Harvard astrophysics student Amir Siraj, who led the team behind the new paper. You can read the full study (PDF), which has been submitted to the Journal of Astronomical Instrumentation, on the arXiv preprint server.
Also on the team is Harvard astronomer Avi Loeb, who has been outspoken about the possibility that ‘Oumuamua may have been a piece of alien technology. The pair have collaborated in the past, including the apparent confirmation that another interstellar object fell into the ocean in 2014. Loeb is hoping to go looking for fragments of that one, but that’s another story. The analysis in the new paper definitely acknowledges the possibility that an ‘Oumuamua-like object could turn out to be technological in origin.
To rendezvous with an interstellar object, you have to plan ahead. According to the study, the initiative starts with the right instrumentation. It calls for a spectrometer sensitive to the wavelength range of 0.4 to 2.5 µm. This should be capable of differentiating between various natural and artificial materials from a distance of several hundred miles. The team believes the spectra of extrasolar materials could vary dramatically compared to the materials in our solar system.
Timing is also key to success. With something a few hundred meters across like ‘Oumuamua, you’d be lucky to have a couple of months to get into position. Something smaller and dimmer might not be spotted until a matter of weeks before it passed out of range — again, if you’re lucky. The solution may be to design and build a spacecraft, launch it, and then leave it lying in wait at the Earth-Sun L2 Lagrange point for something interesting to pass. This region, which is also home to the James Webb Space Telescope, is an area of gravitational equilibrium where the probe could hibernate until it’s time to jet off on an intercept course.
Currently, this is just a general outline based on the limits of physics, according to Siraj, but both NASA and the ESA have shown interest in the idea of checking out interstellar visitors. There are no firm plans at this time, but the temptation might prove too great as we detect more of these mysterious travelers.