The Vera Rubin Observatory's Legacy Survey of Space and Time (LSST) will revolutionize solar system science by discovering a population of previously undiscovered interstellar comets and asteroids passing through our cosmic neighborhood
Many undiscovered interstellar objects exist throughout our Milky Way galaxy: comets and asteroids ejected from their home star system. Some of these objects pass through our solar system, and bring valuable information about how planetary systems form and evolve. So far only two interstellar visitors have been discovered: Omoamua and 2I/Borisov. The upcoming LSST will show us many more of them.
We have learned a lot about the largest and brightest objects in our solar system using the instruments and telescopes available. But astronomers like Michelle Bannister of the University of Canterbury in Aotearoa, New Zealand, and a member of the Solar System Science Collaboration between the Rubin Observatory and LSST, want to look deeper for small, faint bodies that originate in planetary systems very far from our own.
These interstellar bodies – thrown from their home systems into interstellar space – are so faint that they are virtually undetectable. But with the old survey of the upcoming space and time, which is carried out with the Vera C. Observatory. Robin in Chile, the scientists are expecting a period of many discoveries when these faint bodies are first seen.
Mitzpe Rubin is jointly funded by the National Science Foundation and the US Department of Energy. Robin is a program of the Foundation's NOIRLab, which will operate Robin together with the SLAC National Accelerator Laboratory.
The origin of our solar system is a giant swirling cloud of gas and dust that collapsed to form new stars, one of which is our sun. The stars swallowed most of the cosmic components, but around each star the remaining components formed the small building blocks of the planets - the planetesimals - which range in size from tens of meters to several kilometers. Some of them merged into planets and their moons and rings, but trillions of planetesimal remnants continued to orbit their host stars.
Using observations of our solar system and computer simulations, scientists hypothesize that the gravity of the large planets and nearby passing stars often launch most of these remaining planetesimals from their home system into their own galaxy. They move through space when not bound to any star and are now called interstellar objects.
"A planetary system is a place of change and development, of sculpting and reshaping," Bannister said. "And planets are like active reporters in that they can propel trillions of tiny planetesimals into galactic space."
If the planets are the reporters, the interstellar objects are the telegrams containing valuable information about distant planetary systems and how they formed. And for a short while, some of these messages from afar are right in our cosmic backyard. "A rock from another solar system is a direct probe that shows how planetesimals formed on another planet," said Bannister. "So it's really great that they come to us."
Although astronomers think that many interstellar objects exist, and probably pass through our solar system regularly, only two have been confirmed: Omoamua in 2017 (also known as 1I/2017 U1) and Comet 2I/Borisov in 2019. They were discovered thanks to excellent timing, a lot of work and a bit of luck - these small, faint travelers can only be seen when they are close enough, and when our telescopes are aimed at the right place at the right time.
"According to our calculations there are a lot of these small worlds in our solar system right now," Bannister said. "We just can't find them yet because we don't see such faint objects."
Mitzpe Rubin will change that. Using an 8.40 meter diameter telescope equipped with a digital camera with the highest resolution in the world, Robin will detect fainter objects than we have ever seen. "It's like suddenly going from a small boat bobbing in the beautiful shallow water near the shore to the middle of the big, deep ocean when you can see into that space for the first time," Bannister said.
In addition, Robin's fast-moving telescope can scan the entire visible sky every few nights, capturing a fleeting glimpse of interstellar objects on their rapid journey through our solar system.
We do call Omoamoa and 2I/Borisov interstellar objects, but they differ in almost every way we can measure. What will the third or twentieth interstellar object look like? In the first year of the 2025-year LSST at the Rubin Observatory, scheduled to begin in XNUMX, scientists hope to get an idea. "We will go from the study of two specific objects to the study of a population or at least dozens," Bannister said. Because interstellar objects can come from stars throughout the Milky Way, this numerical increase will allow scientists to directly study how planetary systems form on distant stars throughout our galaxy's history—including ancient stars that no longer exist.
Meanwhile, scientists can only predict imprecisely how many interstellar objects Robin will detect. Bannister jokingly bets on 21, but says we really have no idea yet. Whatever the outcome, Robin is about to revolutionize the study of the solar system - along with many other fields in astronomy and astrophysics. "This will be one of the gifts Robin gives," she said. "A new history of the solar system and a better understanding of where we came from".
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