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10 Things: Mysterious ‘Oumuamua

10 Things: Mysterious 'Oumuamua

The interstellar object ‘Oumuamua perplexed scientists in October 2017
as it whipped past Earth at an unusually high speed. This mysterious
visitor is the first object ever seen in our solar system that is known
to have originated elsewhere. 

Here are five things we know and five things we don’t know about the first
confirmed interstellar object to pass through our solar system.

1. We know it’s not from around here.

 The object known as 1I/2017 U1 (and nicknamed ‘Oumuamua) was traveling too fast
(196,000 mph, that’s 54 miles per second or 87.3 kilometers per second)
to have originated in our solar system. Comets and asteroids from
within our solar system move at a slower speed, typically an average of 12 miles per second (19 kilometers per second) . In non-technical terms, ‘Oumuamua is an “interstellar vagabond.”


Artist impression of the interstellar object ‘Oumuamua. Credit: ESA/Hubble, NASA, ESO, M. Kornmesser

2. We’re not sure where it came from.

‘Oumuamua entered our solar system from the rough direction of the constellation Lyra, but it’s impossible to tell where it originally came from.
Thousands of years ago, when ‘Oumuamua started to wander from its
parent planetary system, the stars were in a different position so it’s
impossible to pinpoint its point of origin. It could have been wandering
the galaxy for billions of years.


3. We know it’s out of here.

‘Oumuamua is headed back out of our solar system and won’t be coming back.
It’s rapidly headed in the direction of the constellation Pegasus and
will cross the orbit of Neptune in about four years and cover one light
year’s distance in about 11,000 years.

4. We don’t really know what it looks like.

We’ve only seen it as a speck of light through a telescope (it is far
away and less than half a mile in length), but its unique rotation
leads us to believe that it’s elongated like a cigar, about 10 times
longer than it is wide. We can’t see it anymore. Artist’s concepts are
the best guesses at what it might look like.

5. We know it got a little speed boost.

A rapid response observing campaign allowed us to watch as ‘Oumuamua got an unexpected boost in speed. The acceleration slightly changed its course from earlier predictions.

“This additional subtle force on ′Oumuamua likely is caused by jets
of gaseous material expelled from its surface,” said Davide Farnocchia
of the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Laboratory. “This same kind of outgassing affects the motion of many comets in our solar system.”

6. We know it’s tumbling.

Unusual variations in the comet’s brightness suggest it is rotating on more than one axis.


This illustration shows ‘Oumuamua racing toward the outskirts of our
solar system. As the complex rotation of the object makes it difficult
to determine the exact shape, there are many models of what it could
look like. Credits: NASA/ESA/STScI

7. We don’t know what it’s made of.

Comets in our solar system kick off lots of dust and gas when they get close to the Sun, but ‘Oumuamua did not, which led observers to consider defining it as an asteroid.

Karen Meech, an astronomer at the University of Hawaii’s Institute of
Astronomy, said small dust grains, present on the surface of most
comets, may have eroded away during ′Oumuamua’s long journey through
interstellar space. “The more we study ′Oumuamua, the more exciting it
gets.” she said. It could be giving off gases that are harder to see
than dust, but it’s impossible to know at this point.

8. We knew to expect it.

Just not when. The discovery of an interstellar object has been anticipated for decades.
The space between the stars probably has billions and billions of
asteroids and comets roaming around independently. Scientists understood
that inevitably, some of these small bodies would enter our own solar
system. This interstellar visit by ‘Oumuamua reinforces our models of
how planetary systems form.


9. We don’t know what it’s doing now.

After January 2018, ’Oumuamua was no longer visible to telescopes,
even in space. But scientists continue to analyze the data gathered
during the international observing campaign and crack open more
mysteries about this unique interstellar visitor.

10. We know there’s a good chance we’ll see another one…eventually.

Because ′Oumuamua is the first interstellar object ever observed in
our solar system, researchers caution that it’s difficult to draw
general conclusions about this newly-discovered class of celestial
bodies. Observations point to the possibility that other star systems regularly eject small comet-like objects
and there should be more of them drifting among the stars. Future
ground- and space-based surveys could detect more of these interstellar
vagabonds, providing a larger sample for scientists to analyze. Adds,
Karen Meech, an astronomer at the University of Hawaii’s Institute of
Astronomy: “I can hardly wait for the next interstellar object!“

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