Paul M. Sutter is an astrophysicist at SUN Stony Brook and the Flatiron Institute, host of “Ask a spaceman” and “space station, “and the author of”How to die in space. “ Sutter contributed this post to Space.com Expert Opinion: Op-Ed & Insights.
On October 19, 2017, Robert Weryk, an astronomer at the University of Hawaii at Manoa, discovered a fascinating new object with the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) in Hawaii. From the moment it was discovered, it was a strange object – strange orbit, strange speed, strange properties.
Foreign object, later named ‘Ouamuamua, is the first known interstellar object to visit the solar system. But astronomers were only able to observe the odd guest for 11 days before it appeared too small and too dim to be detected. Considering the meager information gleaned from such a short window of observation, the true nature of ‘Ouamuamua remains a mystery, even to this day.
‘Oumuamua, a Hawaiian word that roughly translates to “guide”, is a fitting name; the object is a messenger, a representative of some distant (and unknowable) star system. It has wandered in the cold, empty interstellar depths of Galaxy for hundreds of millions, or maybe billions of years, before encountering Sun.
‘Oumuamua is not big; its largest face is 10 to 100 meters (33 to 330 feet) wide; it can fit comfortably inside a football field.
Sunlight reflected from ‘Oumuamua continuously dimmed and brightened, telling astronomers that the object was tumbling every few hours. Based on that change in light, the astronomers determined that ‘Oumuamua is much longer than it is wide, by a factor of 5 to 10, meaning it is shaped like a cigar or a pancake.
By the time ‘Oumuamua was discovered, it was already on its way out solar system. Given the object’s incredible speed and steep angle relative to the rest of the system, ‘Oumuamua is not gravitationally bound to the sun.
Astronomers tracked ‘Oumuamua using multiple ground- and space-based observatories for about 11 days. That’s it: 11 days. Those observations were all the information we had about this mysterious visitor; ‘Oumuamua is too far away and too dim to be seen with our most powerful instruments, and no rocket can hope to catch it.
It’s gone, forever.
Hidden numbers known
‘Oumuamua is probably the strangest object we’ve ever seen inside the solar system. No one else knows small planet or extreme-shaped comets (although, to be fair, our catalog of objects 100 meters or more is not exact). ‘Oumuamua has a dusty red color, similar to the color of other deep objects in the solar system. But it doesn’t work like a comet, a small object most common at those distances from the sun.
The interstellar traveler entered the solar system at a velocity very close to the local standard of rest, which is the average velocity of the stars in our vicinity. However, most of those stars have much larger specific velocities. So why should ‘Oumuamua be so close to the mean? It is still a mystery.
Finally, on its way out of the solar system, ‘Oumuamua gave astronomers one more colossal mystery: It appeared to be accelerating, moving away from the sun at a slightly faster rate than each day. pass. This wouldn’t be the strangest thing for comets, which can have unusual acceleration profiles due to escaping materials. But ‘Oumuamua’s observations showed no such activity.
In the years since its original discovery, only another interstellar traveler were detected. And that object, called 2I/Borisov, looks and behaves like any other comet. Nothing like ‘Oumuamua has ever been seen before or since.
So what is ‘Oumuamua? The debate continues; Speculation is ripe in such a data-poor environment. Harvard astronomer Avi Loeb used the lack of data to suggest that ‘Oumuamua is an alien spaceship. But considering intelligent aliens might be capable of doing whatever they want, this could be the explanation for quite a few observations.
Astronomers have also come up with a variety of non-alien explanations. An opinion that perhaps ‘Oumuamua is a nitrogen ice Pluto-like object chipped long ago. However, Loeb and his colleague Amir Siraj, a Harvard student, said it was impossible because pure nitrogen is rare on Pluto and in the universe at large. They calculated that the mass of exo-Plutos needed to make pure nitrogen ‘Oumuamua was surprisingly high.
Other researchers have suggested that perhaps ‘Oumuamua is a solid block of hydrogen, formed on the outskirts of a giant molecular cloud as a by-product of the process that created the solar system. Others suggested that ‘Oumuamua was after all a comet – an alien was kicked off from its natural solar system by a gravitational interaction, or an interaction that formed here, in our own solar system, and then moved outward before turning inward. final jump.
In the end, we’ll never know. And maybe, like that stranger, we should move on.
Learn more by listening to the podcast “Ask a Spaceman”, available on iTunes and askaspaceman.com. Ask your own question on Twitter using #AskASpaceman or follow Paul @PaulMattSutter and facebook.com/PaulMattSutter.
https://www.space.com/oumuamua-first-interstellar-visitor-true-nature-mystery Will we ever know the true nature of ‘Oumuamua, the first interstellar traveler?