Astronomers can infer what kind of star interstellar objects like ‘Oumuamua come from, and therefore something about their composition, based on their speed as they enter our solar system, new research suggests.
So far, astronomers have found only two confirmed interstellar objects (ISOs) in our solar system. ‘Aumuamua And 2I/Borisov. They couldn’t have been more different from each other: ‘Aumuamua had no comet tail of any kind, but Borisov looked like a normal one. comet.
However, the characteristics of their home planetary systems are imprinted on both, said Matthew Hopkins, a grad student at the University of Oxford in England, who conducted the new research and presented it at the UK’s National Astronomical Meeting in early July.
related to: ‘Oumuamua: The Solar System’s First Interstellar Visitor Explained in Photos
“Because they come from other stars, their properties will be correlated with those stars,” Hopkins told Space.com.
Although we’ve only found two ISOs to date, expect thousands of ISOs to cross our path solar system At any given time, it is too far away from us to detect. However, most or all ISOs likely began life as comets around other stars, before encountering a Jupiter-sized planet or perhaps a fly-by star, ejecting them into interstellar space.
In our solar system, “for every comet Thursday (And Neptune) pushed inwards Oort CloudThat’s 10 fully ejected, and there are a trillion objects in the Oort cloud,” Hopkins said. Doing the math, it’s easy to come to the conclusion that ISOs are “the most objects.” The Milky Way Galaxy.”
Moving groups of interstellar objects
Each star moves around the galaxy at its own speed, and together they form moving groups relative to their origin that match their internal chemistry.
Stars with the heaviest elements like ours the sun, lives in the galaxy’s “thin disc,” a plane in the spiral arms 400 light-years thick. The “thick disk” that surrounds it can extend up to 1,000 light-years above the galactic plane and consists mostly of old stars with lighter elements.
The populations of stars belonging to each disc have different velocity distributions. Because the ISOs they emit share similar velocities relative to the Sun as their parent star, they tend to stick to the same moving groups, but these moving groups always cross the path of the Sun.
“The sun is essentially running into them,” Hopkins said. This means that we should prefer to see ISOs coming from the “solar apex”, which is the direction of the Sun’s motion relative to other nearby stars.
“‘Aumuamu’a was very close to the peak of solar energy,” Hopkins said. “Borisov was a bit further away but very close (to the solar apex) and that’s where we expect most of them to come from.”
Coming from this direction means they will be closest to the Sun when they are in the Southern Hemisphere sky, where they are easier to spot. Vera Rubin Observatory The survey will be conducted. Vera Rubin is expected to be there Discover hundreds of new ISOs.
Related: Vera Rubin: The Astronomer Who Brought Dark Matter to Light
Slow ISOs have less water
The lower the relative velocity of an ISO compared to the Sun, the more likely it is to fall into the inner Solar System that we can detect; Faster ones will pass quickly without being pulled too much by the Sun’s gravity. The relative velocity of an ISO is related to the relative velocity of its parent star, depending on whether that star comes from a thin disk with more heavy elements or a thick disk with fewer heavy elements.
“My results show that the velocity of an ISO is related to its composition, and because of this, we can get a handle on the types of stars they might have formed from,” Hopkins said.
Low-velocity ISOs (compared to the Sun) are expected to come from a thin disk, where stars and their accompanying planetary systems form from gas and dust containing heavier elements. The disks of gas and dust that form planets and comets have heavier elements, and an ISO has a smaller fraction of water.
That’s because a protoplanetary disk rich in heavy elements contains a lot of carbon, and carbon (as well as iron, magnesium, silicon, and sulfur) is adept at snapping up all the free oxygen atoms two at a time to form molecules. Carbon dioxide. Water forms only from any remaining oxygen atoms, meaning that the ISOs that form within these discs generally contain only a small fraction of water.
Could this lack of water explain why ‘Aumuamu’a does not display a comet tail?
“Because it has a slower speed compared to the Sun, it came from a thin disk star with heavier elements,” Hopkins said. However, he is keen to point out a caveat that we do not know the history of ‘Aumuamu’a – it would have lost its water and other volatiles in some other way. They may be annihilated by cosmic rays as they travel through interstellar space, for example, or by very close passes to their parent star before being ejected.
Borisov, on the other hand, was in the middle of the water based on spectral observations of its tail.
As there are currently only two examples of ISO, it is difficult to draw too many conclusions. However, once the Vera Rubin Observatory is up and running later this decade, the hundreds of ISOs it should detect can provide a complete picture of where they come from and what their chemical properties are.
“We would expect to see more ISOs from the thin disk if there is a bias towards ISOs that move similarly to the Sun falling into the inner Solar System,” Hopkins said.
That means we’ll see more ‘Oumuamua-like objects than Borisov. Time will tell how true that prediction is.