Small asteroid or comet 'visits' from beyond the solar system

October 26, 2017, NASA
A/2017 U1 is most likely of interstellar origin. Approaching from above, it was closest to the Sun on Sept. 9. Traveling at 27 miles per second (44 kilometers per second), the comet is headed away from the Earth and Sun on its way out of the solar system. Credits: NASA/JPL-Caltech

A small, recently discovered asteroid - or perhaps a comet - appears to have originated from outside the solar system, coming from somewhere else in our galaxy. If so, it would be the first "interstellar object" to be observed and confirmed by astronomers.

This unusual object - for now designated A/2017 U1 - is less than a quarter-mile (400 meters) in diameter and is moving remarkably fast. Astronomers are urgently working to point telescopes around the world and in space at this notable object. Once these data are obtained and analyzed, astronomers may know more about the origin and possibly the composition of the object.

A/2017 U1 was discovered Oct. 19 by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala during the course of its nightly search for Near-Earth Objects for NASA. Rob Weryk, a postdoctoral researcher at the University of Hawaii Institute for Astronomy (IfA), was first to identify the moving object and submit it to the Minor Planet Center. Weryk subsequently searched the Pan-STARRS image archive and found it was present in images taken the previous night, but was not initially identified by the moving object processing.

Weryk immediately realized this was an unusual object. "Its motion could not be explained using either a normal solar system asteroid or comet orbit," he said. Weryk contacted IfA graduate Marco Micheli, who had the same realization using his own follow-up images taken at the European Space Agency's telescope on Tenerife in the Canary Islands. But with the combined data, everything made sense. Said Weryk, "This object came from outside our solar system."

"This is the most extreme orbit I have ever seen," said Davide Farnocchia, a scientist at NASA's Center for Near-Earth Object Studies (CNEOS) at the agency's Jet Propulsion Laboratory in Pasadena, California. "It is going extremely fast and on such a trajectory that we can say with confidence that this object is on its way out of the solar system and not coming back."

The CNEOS team plotted the object's current trajectory and even looked into its future. A/2017 U1 came from the direction of the constellation Lyra, cruising through interstellar space at a brisk clip of 15.8 miles (25.5 kilometers) per second.

The object approached our solar system from almost directly "above" the ecliptic, the plane in space near where the planets and most asteroids orbit the Sun, so it did not have any close encounters with the eight major planets during its plunge toward the Sun. On Sept. 2, the small body crossed under the ecliptic just inside of Mercury's orbit and then made its closest approach to the Sun on Sept. 9. Pulled by the Sun's gravity, the object made a hairpin turn under our solar system, passing below Earth's orbit on Oct. 14 at a distance of about 15 million miles (24 million kilometers)—about 60 times the distance to the Moon. It has now shot back up above the plane of the planets and, travelling at 27 miles per second (44 kilometers per second) with respect to the Sun, the object is speeding toward the constellation Pegasus.

"We have long suspected that these objects should exist, because during the process of planet formation a lot of material should be ejected from planetary systems. What's most surprising is that we've never seen interstellar objects pass through before," said Karen Meech, an astronomer at the IfA specializing in small bodies and their connection to solar system formation.

The small body has been assigned the temporary designation A/2017 U1 by the Minor Planet Center (MPC) in Cambridge, Massachusetts, where all observations on small bodies in our solar system—and now those just passing through—are collected. Said MPC Director Matt Holman, "This kind of discovery demonstrates the great scientific value of continual wide-field surveys of the sky, coupled with intensive follow-up observations, to find things we wouldn't otherwise know are there."

Since this is the first object of its type ever discovered, rules for naming this type of object will need to be established by the International Astronomical Union.

"We have been waiting for this day for decades," said CNEOS Manager Paul Chodas. "It's long been theorized that such objects exist - asteroids or comets moving around between the stars and occasionally passing through our solar system - but this is the first such detection. So far, everything indicates this is likely an interstellar object, but more data would help to confirm it."

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TrollBane
1 / 5 (1) Oct 26, 2017
Just keep it away from Jules Pierre Mao and we'll be fine.
rrwillsj
1 / 5 (4) Oct 26, 2017
Moving pretty slow at approx. 54,000 MPH?

Must be looking for a parking space!
BubbaNicholson
1.5 / 5 (4) Oct 27, 2017
Perhaps another alien probe.
NoStrings
1 / 5 (1) Oct 27, 2017
25.5 km/sec in interstellar space. Must be a low tech space colony using the Sun for a course change without expanding much energy. I wonder what is in the constellation of Pegasus for them.
:-)
mauldred
3 / 5 (1) Oct 27, 2017
Greg Benford's fans will immediately think about the Snark.
rrwillsj
1 / 5 (3) Oct 27, 2017
Myself? I'm a fishing for the boojum from my boat made of unobtanium.
mreedb
not rated yet Oct 27, 2017
This is the first hyperbolic orbit they have seen? I have a hard time with that...
wduckss
1 / 5 (1) Oct 28, 2017
The first time they watched. This is just another confirmation of earlier discoveries.
"The only possible specificity is for that object (the errant objects, incoming from outside the Solar system) to arrive vertically onto one of the poles and to hit the opening of a cyclone that exists on the poles of stars." http://www.svemir...html#12b
"Opposite to the process of rotation there is the approaching of an object to the poles of a central object, where there are no orbits created, but only collisions of the incoming objects with the central object. These objects also have a speed, just as the objects that approach straight or with an inclination towards the equator do, but these speeds neither create orbits, nor there are observations to support such claims. If there is no rotation, there is also no orbit, no matter what the speed of the incoming object is." https://www.acade...Universe
rrwillsj
1.7 / 5 (3) Oct 28, 2017
NS thanks for correcting my math. I had done in my head, off the cuff. A pose that is certain to result in a bungle.
torbjorn_b_g_larsson
not rated yet Oct 29, 2017
"It's been a long road, getting from there to here.
It's been a long time, but my time is finally near."

Actually it took so long that astronomers have long seen comets around other stars (rather, diving into them).

This is the first hyperbolic orbit they have seen? I have a hard time with that...


The first that is falling in with a hyperbolic orbit, I take it. I read somewhere this week on this topic that astronomers have seen comets that fall in on parabolic orbits originating from the Oort cloud and exit on hyperbolic - system ejection - tracks after gravity assist when passing Sun.

If we see more of those ejected than visiting we can conclude that a local density of comets such as the Oort cloud exist. (Well, duh.)

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