More than a million asteroids, some of them potential threats to Earth. Asteroids with tails like comets. Interstellar objects that happen to be swinging by our sun. (Could they be alien spaceships?) More distant worlds including, perhaps, a ninth planet, which could fill in the story of our solar system’s turbulent youth.
Those are some of the discoveries that the Vera C. Rubin Observatory in Chile is expected to make in the cosmic neighborhood that is our solar system. (Maybe not the alien spaceships.)
“I think that we’re going to completely transform our view of the solar system and rewrite that textbook over the next few years.” said Meg Schwamb, a planetary scientist at Queen’s University Belfast in Northern Ireland.
Saving the Planet While Stargazing
Rubin’s scans of the night sky will also help make Earth a safer place, spotting potentially dangerous asteroids that have so far eluded detection.
Most asteroids are found in the belt between the orbits of Mars and Jupiter. But some of those space rocks have been deflected onto paths that could cross paths with our planet.
Astronomers are certain that there is nothing the size of the six-mile-wide asteroid that killed the dinosaurs that poses a danger of colliding with Earth anytime soon. But for smaller asteroids, they are not so certain.
There are an estimated 25,000 near-Earth asteroids at least 460 feet wide — large enough to destroy a city — and only 44 percent of them have been found.
By the end of Rubin’s decade-long survey, the tally should reach 70 percent, said Mario Juric, a professor of astronomy at the University of Washington who leads the team putting together Rubin’s strategy for finding asteroids, comets and other solar system objects.
The technique takes advantage of the fact that objects within the solar system move pretty quickly.
“The idea is you observe the same area of the sky, the same pointing in the sky, twice each night within about 20 minutes or so,” Dr. Juric said. “In those 20 minutes, stars remain where they are. Asteroids shift just slightly.”
The slight shift indicates a direction and speed — enough to predict where the candidate asteroid might be three nights later.
If it is not there, then it was not an asteroid. If it is, another prediction is made for three nights later, and if it shows up again, that confirms a bona fide discovery.
The technique was tried for the first time in early May. It worked as expected.
“We found about 1,200 new asteroids,” Dr. Juric said. “Just as a test.”
One of the objects that Rubin spotted appeared to be about two-thirds of a mile wide, and its trajectory would come close to hitting Earth — within 60,000 miles of Earth, or just one-third the distance between Earth and the moon.
“We got both excited and scared at the same time,” Dr. Juric said. But that one turned out not to be a new asteroid, but one that had been discovered by an earlier sky survey, and it will not hit Earth anytime soon.
The 1,200 newly identified asteroids are all in the main asteroid belt far from Earth. “It sounds crude, but it’s that expression, shooting fish in a barrel,” Dr. Juric said. “It feels almost unfair how good this telescope is.”
Ogling Orbital Oddities
The sheer number of objects that Rubin spots will help planetary scientists understand more unusual asteroids because the observatory will find more of them.
Those include active asteroids, which, at least temporarily, possess tails of gas and dust just like comets. Astronomers currently know of about 25 of them, Dr. Schwamb said.
For some, the tails could be debris flying off after an impact with another asteroid. The tails of others appear to contain gases that sublimated from ices on the surface. Those could be comets that were gravitationally pushed toward the sun and were trapped in the asteroid belt.
“This is like a brand-new field of really looking at these things,” Dr. Schwamb said. “Most people aren’t monitoring asteroids, because no one will give us the observing time to do that.”
The same observing technique will also turn up slower-moving, more intriguing bits of rock and ice farther out.
They include small bodies found between the orbits of Jupiter and Neptune known as Centaurs and the Kuiper belt of icy debris beyond Neptune.
“Those bits of the solar system have been relatively unexplored,” Dr. Schwamb said.
The Centaurs are a present-day mystery.
Because Centaurs cross the orbits of one or more of the giant planets, their current orbits are unstable. They will someday pass too close to a planet and get flung somewhere else.
Where did they come from? Where will they go?
“We’re really going to learn more about this population,” Dr. Schwamb said.
Rubin will also reveal the story of the early solar system by mapping out the Kuiper belt, which holds 20 to 200 times the mass of the asteroid belt. Measuring colors of the objects there will tell much about what they are made of.
That information will help astrophysicists who want to understand the chaotic youth of the solar system. Back then, the planets were not where they are now. Gravitational disruptions by Jupiter and Saturn caused an outward migration of Neptune, which snowplowed small icy bodies into what is now the Kuiper belt.
Based on the current understanding of the solar system and the telescope’s planned observing schedule, an international team of astronomers led by Dr. Schwamb predicts that Rubin’s bounty will include 89,000 new near-Earth asteroids, 3.7 million new main-belt asteroids, 1,200 new Centaurs and 32,000 new objects beyond Neptune.
Pursuing Phantoms
There is also the question of Planet Nine.
After the demotion of Pluto in 2006, the solar system has only eight planets. But the discovery of several very distant objects orbiting the sun suggests something might be out there.
These objects are beyond the Kuiper belt. Their elliptical orbits appear to align in a particular direction, and two scientists at the California Institute of Technology, Mike Brown and Konstantin Batygin, argue that points to the gravitational tugging of an unseen planet with several times the mass of Earth — Planet Nine.
So far, searches for Planet Nine have come up empty.
Rubin’s asteroid-finding technique will not flag Planet Nine, because the planet, if it exists, would be so far away that it would appear as an unmoving dot, just like a star, in images taken minutes or days apart.
But careful analysis of the images taken months or years apart might be able to spot it.
“There’s a good chance Rubin will simply just find it,” Dr. Brown said. “If Planet Nine is on the brighter end of our predictions, Rubin will easily find it within the first year of operations.”
If the planet is on the fainter end, Rubin might not see it at all. But regardless, the survey will almost certainly find more of the ultradistant objects. If most of those also align in the same direction, that would be compelling evidence for Planet Nine.
Or it could turn out that the grouping of orbits perceived by Dr. Brown and other scientists is just a mirage.
“We should know that hopefully within the first two years,” Dr. Schwamb said.
The telescope should also find more objects that come from outside the solar system and are just passing through. So far, astronomers have spotted only two: Oumuamua, a cigar-shaped rocket that was discovered in 2017, and Borisov, a comet spotted in 2019 that appeared to be moving fast enough to escape back into interstellar space.
“The predictions are that you could find five or more, 50 possibly,” with the Rubin survey, Dr. Schwamb said. “Or zero. Who knows?”
Avi Loeb, a theoretical physicist at Harvard, has said the elongated shape of Oumuamua indicated it might be artificial in origin — an alien artifact.
Dr. Schwamb does not expect to find aliens, but says that there is a broader question that could be studied scientifically.
“You can actually ask the question: Is anything orbiting in the solar system an alien spacecraft?” she said.
She points out that Elon Musk’s Tesla sports car, the one that was lifted to space during the first launch of SpaceX’s Falcon Heavy rocket, is easy to distinguish from an asteroid. “We can actually see it’s very different colors,” she said.
Similarly, an alien spacecraft would stick out. “That’s actually science we can do along the lines of, ‘Is there alien life?’” Dr. Schwamb said.
Kenneth Chang, a science reporter at The Times, covers NASA and the solar system, and research closer to Earth.
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