Artistic depiction of a comet by UCSB | A/2017 U1 (Previously C/2017 U1 (PANSTARRS)) is an extremely hyperbolic comet discovered on October 18, 2017 by the Pan-STARRS telescope when the object was 30,000,000 km from Earth.
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Scientists Observe First-Known Interstellar Comet

Science Section Staff
26 October, 2017

Telescopes only picked it up a week ago, but it’s likely been traveling through interstellar space for millions of years. {Have they not looked at the heaven above them – how We structured it and adorned it and [how] it has no rifts?} [Surat Qaf 50:6].

For centuries, skywatchers have chronicled the comings and goings of thousands of comets. Everyone of them has come from someplace in our own solar system. Either the Kuiper Belt beyond Neptune or the much more distant Oort Cloud at the fringes of the Sun’s realm.

But an object swept up just a week ago by observers using the PanSTARRS 1 telescope atop Haleakala on Maui, Hawaii has an extreme orbit. It’s on a hyperbolic trajectory that doesn’t appear to be bound to the Sun.

Preliminary findings, published on October 25, 2017 by the International Astronomical Union’s Minor Planet Center (MPC), suggest that we are witnessing a comet that escaped from another star.

“Further observations can confirm the unusual nature of this orbit. It may be the first clear case of an interstellar comet,” Gareth Williams, the MPC’s associate director told Kelly Beatty in an interview for SkyAndTelescope.

Designated previously as C/2017 U1, Comet PanSTARRS was a dim, 20th-magnitude blip when first spotted on October 18. That’s after having zipped within 37,600,000 km of the Sun on September 9.

Now it flys out of the solar system, never to return. It passed closest to Earth on October 14th at a distance of about 24,000,000 km. Astronomers worldwide have been tracking it in the hopes of divining its true nature; especially whether it’s displaying any cometary activity.

Why Unique?Interstellar Comet

What gives A/2017 U1 away as an interstellar visitor wasn’t its very high inclination (122°) with respect to Earth’s orbit. But, more critically its extreme hyperbolic eccentricity (1.19).

Check out the comet’s pass through the inner solar system using JPL’s interactive Horizons app (requires Java).

“Comet PanSTARRS appears to have entered the solar system from the direction of the constellation Lyra,” dynamicist Bill Gray told Beatty.

This object entered the solar system moving at 26 km per second. At that speed, in 10 million years it would traverse 8,200,000,000,000,000 km; more than 850 light-years.