The other day we witnessed one of the greatest recent scientific discoveries, when an asteroid from another planetary system – 1I/2017 U1 (`Oumuamua) – was found in our Solar System.
It was the first time we've ever spotted an interstellar visitor, marking a rare event in our history of astronomy. But it begged the question, would it be possible for us to visit the asteroid and study it?
That's what a group called the Insitute For Interstellar Studies (i4is) has been looking into. In a paper published on arXiv, they've looked at the various ways we might be able to catch up to and study this rare object.
"The first definitely interstellar object 1I/’Oumuamua (previously A/2017 U1) observed in our solar system provides the opportunity to directly study material from other star systems," they write. "Can such objects be intercepted?"
Now, the big problem is that this object is speeding out of our Solar System at about 138,000 kilometers per hour (86,000 miles per hour). It's expected to slow down to 95,000 kilometers per hour (59,000 miles per hour), but this still presents a problem.
Our fastest current spacecraft is Voyager 1, which is making its way out of the Solar System at 61,200 km/h (38,000 mph). It took quite a few years for it to reach this speed, though; our fastest spacecraft at launch was New Horizons, at 58,536 km/h (36,373 mph).
These are, of course, not fast enough to catch 'Oumuamua. But i4is looked at a number of current and emerging technologies that might be capable of doing so within five to 30 years.
Using existing chemical propulsion, coupled with a Jupiter flyby, they say it might be possible to catch up to the object. You'd need a lot of propellant, though, so we'd need to use an upcoming heavy-lift rocket like SpaceX's BFR or NASA's SLS to make this work.
"One potential mission architecture is to make use of SpaceX’s Big Falcon Rocket (BFR) and their in-space refueling technique with a launch date in 2025," they write.
"To achieve the required hyperbolic excess (at least 30 km/s [108,000km/h]) a Jupiter flyby combined with a close solar flyby (down to 3 solar radii), nicknamed 'solar fryby' is envisioned."
If this were launched in 2025, a spacecraft using this method at 252,000 km/h (157,000 mph) could intercept Oumuamua in 2039 at a distance of 85 AU (astronomical units, 1 AU is the Earth-Sun distance), twice the orbit of Pluto, going at 70 km/s. At 144,000 km/h (90,000 miles per hour), the object can be intercepted in 2051 at 155 AU.
As it won't be possible to slow down at these speeds and thus orbit the asteroid, i4is suggests the mission could carry an impactor with it to slam into the asteroid. The mother spacecraft could observe the resultant plume of dust to work out what it's made of.
Another intriguing possibility is making use of solar or laser sail technology. The Breakthrough Starshot project is currently looking at the latter to send a tiny probe to our nearest star, Proxima Centauri. Similar technology could be employed here.
Launching in 2021, the researchers say that using a 2.74-megawatt laser beam, they could reach 'Oumuamua in about seven years. This probe would be just one gram in size, so science would be limited, but with a bigger laser, you can send a bigger probe.
"However, with such a laser beaming infrastructure in place, hundreds or even thousands of probes could be sent," they note.
"Such a swarm-based or distributed architecture would allow for gathering data over a larger search volume without the limitations of a single monolithic spacecraft."
This work is only a case study at the moment, so none of these plans are being put into action yet. But i4is plans to pick two or three of the most promising concepts and study them further.
Even if we miss out on 'Oumuamua, astronomers now think an interstellar object passes into our Solar System every year. If we can spot one a bit earlier next time, maybe we can have a mission ready to intercept it.