An interstellar object roaring through our solar system last year confuses astronomers trying to understand how planets, comets, and asteroids form.
The object, called Oumuamua, has a composition that suggests that it should have formed near its parent star. But in one turn, astronomers said it's hard to imagine how the object left its mother-solar system because it's difficult to eject an object so close to a star.
& # 39; Oumuamua (pronounced oh-moo-ah-moo-ah) was discovered on October 19, 2017, with the NASA-funded Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) at the University of Hawaii. [‘Oumuamua Explained: An Interstellar Visitor in Pictures]
After looking at Oumuamua's high speed and the steeply inclined path through the solar system, scientists from the International Astronomical Union's Minor Planet Center concluded that the object was interstellar. The discovery of & # 39; Oumuamua marks the first time that an interstellar object has been confirmed in our solar system.
"This object was probably ejected from a distant star system," Elisa Quintana, astrophysicist at NASA's Goddard Space Flight Center, said in a NASA statement.
"Interestingly, only this one object that passes so quickly can help us confine some of our planetary formation models," added Quintana, the co-author of a new paper in the journal The Monthly News of the Royal Astronomical Society , The paper published today (March 27) describes what Oumuamua's observations reveal about the formation of planetesimals, which are small, stony objects that could fuse into planets under the gravitational pull of gravity.
Observations by & # 39; Oumuamua suggest that the object was probably quite dry. Before its discovery, Oumuamua zoomed by in the sun at about 196,000 miles per hour (315,400 km / h). While the object traveled fast enough to escape our solar system, its velocity was similar to that of a comet passing the sun.
Comets are loose collections of ice and rocks. As they approach the sun, their surface warms up and this releases gas and dust to escape into space. & # 39; Oumuamua has not left such a trail.
Some scientists have suggested that Oumuamua in its own solar system was probably formed in a region other than comets formed in our own neighborhood. But the new paper has a counter-argument.
Solar systems such as our Sun and its planets are formed by large clouds of gas, dust and ice. Objects like comets, which form far from their mother's sun, can remain icy. When the objects are near the sun, it is too hot for the ice to remain so that they merge into objects like asteroids.
But if Oumuamua has formed as close to its star as an asteroid, it is hard to imagine how it was thrown out of that zone,
"The whole property that is hot enough for that is almost zero, "said senior author Sean Raymond, an astrophysicist at the French National Center for Scientific Research and the University of Bordeaux, in the same statement. "It's these small, small, circular areas around stars that make it harder for these things to be expelled because they are more tied to the star, and it's hard to imagine how Oumuamua could be thrown out of his system if it does An asteroid started. "
" If we understand the planet formation properly, ejected material like "Oumuamua should be predominately frosty," added Thomas Barclay, an astrophysicist at Goddard and the University of Maryland, Baltimore County. "If we see populations of these objects that are predominantly rocky, it tells us that we have something wrong in our models."
How & # 39; Oumuamua's Journey Begins
While researchers continue to investigate where & # 39; Oumuamua was formed, they have found a plausible scenario for the ejection. Based on simulations from other work, they suggest that a gas giant planet – similar to a Jupiter – flung Oumuamua into interstellar exile.
While a gas giant plows at small objects such as asteroids, the planet exerts intense gravitational forces on the objects. In some cases, gravity breaks apart the objects. In the case of & # 39; Oumuamua, the planet's gravity put pressure on the object and forced it into the cigar shape we are seeing today.
"Researchers calculated the number of interstellar objects we should see, based on estimates from a star system, likely casts a few pieces of earth material during planet formation," NASA said. "They estimated that some large planetesimals will hold most of this mass, but smaller fragments like" Oumuamua "will outnumber them.
Original article on Space.com.