To date, astronomers have spotted one asteroid and one comet visiting our planetary neighbourhood from other star systems. In both cases, though, we have only been able to get long-range views of these rare interstellar wanderers as they whip past during fleeting encounters.
Now a group of scientists in the US has been looking at using a solar sailing spacecraft to chase down, and examine up-close, similar objects when they appear in the future. Such a probe would be pushed through space by the pressure of the sun鈥檚 light acting on large, metal-coated sails unfurled from the body of the craft.
The team鈥檚 concept envisages a 50-kilogram spacecraft with six sails spanning some 4000 square metres in total. Once launched, the probe would dive in close to the sun, using our star鈥檚 searing glow to whisk itself out into the solar system at tremendous speeds.
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鈥淲ith the current sail materials, we can approach the sun to about 22-23 solar radii [around 15-16 million kilometres],鈥� says team member Slava Turyshev at NASA鈥檚 Jet Propulsion Laboratory in California. Getting that close to our star could enable the craft to be swept out at velocities as high as 170,000-260,000 kilometres per hour.
Achieving those speeds would be vital for intercepting interstellar objects, which have typically hurtled through our cosmic backyard at around 6 or 7 astronomical units per year 鈥� one astronomical unit being the average distance between the sun and Earth.
听鈥淭he architecture proposed is certainly ambitious and technologically challenging, but I think it is feasible,鈥� says Matteo Ceriotti at the University of Glasgow, UK.
Among the reasons solar sailing spacescraft could be useful for rendezvousing with visiting interstellar objects is that the latter tend to arrive in the solar system on orbits that are inclined to the plane of the planets; if you want to explore them, your space probe has to get onto that tilted trajectory too.
鈥淎 solar sail would allow you to change the inclination of the orbit, a manoeuvre that would require a significant amount of propellant using a traditional thruster, and might be infeasible,鈥� says Ceriotti.
The proposed spacecraft could 鈥渁bsolutely鈥� visit the approaching Oort cloud object Comet Bernardinelli-Bernstein, too, says Turyshev. What鈥檚 more, the project could be done with current technology he says.
鈥淲e are ready to go. Basically everything鈥檚 here. We are looking for the way to actually partner with NASA and with philanthropic organisations, with private industry to start flying those solar sailing missions on very unique trajectories with very exciting scientific objectives,鈥� he says.
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