It’s the first confirmed visitor from another star system to enter our solar system.
This unique interstellar traveler appears to be a rocky, cigar-shaped object with a reddish tint, unlike anything we’ve seen before in our cosmic neighborhood.
Named ‘Oumuamua, meaning “a messenger from afar arriving first” in Hawaiian, this object is about a quarter-mile (400 meters) long and is highly elongated—about ten times longer than it is wide.
This shape is much more stretched out than any asteroid or comet we’ve seen in our solar system.
Its unusual form could provide new insights into the formation of other solar systems.
Journey Through the Galaxy
Before arriving in our solar system, ‘Oumuamua had been wandering the Milky Way, not attached to any star system, for hundreds of millions of years.
Its unexpected encounter with our solar system allowed astronomers to study it closely.
After its discovery, telescopes worldwide, including the European Southern Observatory’s (ESO) Very Large Telescope in Chile, quickly began observing it to determine its orbit, brightness, and color.
Unique Characteristics
Astronomers, led by Karen Meech from the Institute for Astronomy in Hawaii, used multiple telescopes and filters to study ‘Oumuamua.
They discovered that it spins on its axis every 7.3 hours, causing its brightness to vary by a factor of 10.
No known asteroid or comet in our solar system shows such a large variation in brightness, suggesting ‘Oumuamua is highly elongated and has a complex shape.
Meech’s team also found that ‘Oumuamua has a reddish color, similar to objects in the outer solar system, and it lacks any dust around it.
This suggests it is a dense object made of rock and possibly metals, with no water or ice, and its surface has been reddened by cosmic radiation over millions of years.
Tracking ‘Oumuamua
As ‘Oumuamua moved away from Earth, astronomers continued to track it using large ground-based telescopes, as well as NASA’s Hubble and Spitzer space telescopes.
It travels at about 85,700 miles per hour (38.3 kilometers per second) relative to the Sun.
Its path takes it above the plane of the planets orbiting the Sun, and it will eventually leave our solar system, heading toward the constellation Pegasus.
Preliminary calculations suggest that ‘Oumuamua came from the direction of the star Vega in the constellation Lyra.
However, it took so long to make the journey that Vega wasn’t in the same position when ‘Oumuamua passed by roughly 300,000 years ago.
A Rare Discovery
Astronomers believe that interstellar objects like ‘Oumuamua pass through the inner solar system about once per year.
However, they are often too faint to detect.
Only recently have powerful survey telescopes, like Pan-STARRS1, been able to spot these rare visitors.
“This is an incredible discovery,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object Studies.
“It’s a strange visitor from a distant star system, shaped like nothing we’ve ever seen in our solar system.”
Discovery and Naming
‘Oumuamua, officially named 1I/2017 U1 by the International Astronomical Union (IAU), was discovered on October 19, 2017, by the Pan-STARRS1 telescope in Hawaii.
Funded by NASA’s Near-Earth Object Observations Program, this telescope finds and tracks asteroids and comets near Earth.
Initially thought to be a comet, ‘Oumuamua showed no signs of cometary activity after it passed the Sun on September 9, 2017, at a speed of 196,000 miles per hour (87.3 kilometers per second).
It was briefly classified as an asteroid until astronomers noticed it was slightly accelerating, behaving more like a comet.
Conclusion
‘Oumuamua’s visit to our solar system has given scientists a unique opportunity to study an object from another star system up close.
Its unusual shape and characteristics continue to intrigue astronomers and may provide valuable clues about the formation and behavior of objects in distant star systems.