An artistic illustration of the interstellar object known as ‘Oumuamua, the first object ever discovered to be passing through our solar system somewhere behind.
(M. Kornmesser/European Southern Observatory)
An interstellar object that whizzed through our solar system last year is baffling astronomers try to understand how planets, comets and asteroids form.
The object, called ‘Oumuamua, has a composition that suggests it should have formed close to its parent star. But in a twist, the astronomers said that it is difficult to imagine how the object left its parent solar system, because it is difficult to eject an object in orbit to be so close to a star.
‘Oumuamua (pronounced oh-MOO-ah-MOO-ah) was discovered on Oct. 19, 2017, with the help of the NASA-funded Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) at the University of Hawaii. [‘Oumuamua Explained: An Interstellar Visitor in Photos]
After watching ‘Oumuamua with high speed and strongly sloping path through the solar system, the scientists of the International Astronomical Union, the Minor Planet Center concluded that the object is interstellar. The discovery of ‘Oumuamua marks the first time that an interstellar object, which was confirmed in our solar system.
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“This object is probably ejected from a distant galaxy,” said Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center, in a NASA statement.
“What is interesting is that just this one object fly by so quickly can help us with the limit of a number of our planet-formation models,” added Quintana, who is co-author of a new paper in the journal Monthly Notices of the Royal Astronomical Society. The paper, published today (27 March), describes what ‘Oumuamua observations are revealing about the formation of planetesimals, which are small, rocky objects that could come together under gravity, of the pull to the shape of planets.
Observations of ‘Oumuamua suggest that the object is probably pretty dry. Before the discovery, ‘Oumuamua zoomed in than the sun at about 196,000 mph (315,400 km/h). While the object was traveling fast enough to escape our solar system, the speed is somewhat similar to that of a comet along the sun, NASA said.
Comets are loose collections of ice and rock. As she gets closer to the sun, their surface warms, and this release of gas and dust to escape into the space. ‘Oumuamua not behind such a track.
Some scientists have suggested that in a solar-energy system, ‘Oumuamua probably formed in a different region than comets formed in our own neighborhood. But the new paper has a counterargument.
Solar-energy systems, such as our sun and its planets formed from huge clouds of gas, dust and ice. Objects such as comets, which is in the form far away from their parents in the sun can remain icy. If the objects are close to the sun, it is too warm for ice to remain, so that they coincide in objects such as asteroids.
But if ‘Oumuamua formed so close to its star as a meteorite, it is hard to imagine how it was ejected from the vicinity of that zone, the new paper suggests.
“The total real estate that is hot enough, because that is almost zero,” says lead author Sean Raymond, an astrophysicist at the French National Centre for Scientific Research and the University of Bordeaux, in the same statement. “It’s this small, small, circular regions around stars. It is harder for that stuff to get ejected, because it is more gravitationally bound to the star. It is difficult to imagine how ‘Oumuamua might have gotten kicked out of the system if it started as an asteroid.”
“If we understand planet formation is correct, ejected material such as ‘Oumuamua should be mainly icy,” said Thomas Barclay, an astrophysicist at Goddard and the University of Maryland, Baltimore County. “When we see populations of these objects, which are mainly rocky, it tells us we have something wrong in our models.”
How ‘Oumuamua the journey began
While the researchers to examine further, where ‘Oumuamua formed, they have come up with a plausible scenario for how it was ejected. On the basis of simulations of other work, they suggest a gas giant planet — or something that resembles a Jupiter — closer to the skin ‘Oumuamua in the interstellar exile.
If a gas giant plows by small objects such as asteroids, the planet exerts an intense gravitational forces on the objects. In some cases, the gravity breaks the objects apart. In the case of ‘Oumuamua, the gravity of the planet the pressure exerted on the object, placing it in the cigar-like shape observed today.
“The researchers calculated the number of interstellar objects that we need to see, based on estimates that a star system that throws a few of the Earth-mass of material during planet formation,” NASA said. “They estimate that a few large planetesimals will keep most of that mass, but is surpassed by the smaller fragments as” Oumuamua.”
Original article on Space.com.