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Astronomers think they have traveled for billions of years before crossing our solar system. Astronomers did not know where this "weird" interstellar came from there, but scientists have now reduced their origins to just four stars – out of 1.6 billion.
"Oumuamua is a rock with strange shapes discovered last October by Canadian astronomer Robert Weryk, at the Institute of Astronomy at the University of Hawaii.
The story of Oumuamua is intriguing because one wondered if it was a comet or an asteroid. (The researchers finally determined that it was a comet.)
He is also the first known interstellar visitor and, as a result, astronomers want to understand how and why he was ejected from his star system – which would require a unique set of circumstances.
A diagram that shows the trajectory and location of Oumuamua on December 12, 2017. (NASA / JPL)
"It's a very interesting object that immediately raises the question: where does it come from?" said Timo Prusti, Gaia project scientist at the European Space Agency. "People have tried to solve this problem with the existing data from the very beginning when it was discovered, but the quality of the data available was not enough to really find candidates."
Enter the ESA Space Telescope, Gaia, which has been in orbit since 2013.
Gaia has the unique job of mapping our galaxy into 3D, and one of its features is that it is able to calculate the motion and speed of stars in our galaxy.
Using the first 22 months of Gaia mission data, an international group of scientists reduced the focus of Oumuamua to four small dwarf stars: HD 292249, HIP 3757 and two other unnamed.
The document has been approved for publication in the astronomical journal, but is currently available on arXiv.org.
The current theory is that "Oumuamua was ejected from a binary system – or two stars – during the formation phase of the planet from its star. It is not known yet if any of these four stars is a binary system.
Potentially more candidates
And if 1.6 billion stars seem a lot, it's really a drop of water.
"It sounds like a lot," Prusti said. "But we must always remember that in our Milky Way, it only represents one percent of the stars."
Although there has been only 22 months of data analyzed so far, another batch of data, covering 34 months, will be released in 2021. But if you think that this will help reduce things for Oumuamua, it's not so simple: The new data will add millions of additional stars that could produce new candidates for the comet's home system.
A view of the sky from our Milky Way and nearby galaxies, based on measurements of nearly 1.7 billion stars. The map shows the density of stars, observed by the Gaia space telescope, in each part of the sky between July 2014 and May 2016. The two bright objects in the lower right are the large and small magellanic clouds, two galaxies dwarfs orbiting the sky. Milky Way. (Gaia Data Processing and Analysis Consortium (DPAC) A. Moitinho / A. F. Silva / M. Barros, et al.)
According to Prusti, this might not be a bad thing.
"What could be, is that among the stars, we could have a better candidate, where the velocities – and also the proximity of the meeting – would be better than for those four stars," he said. . "It could be that we are getting a lot more candidates, but one or two of them are very good candidates."
Until now, Gaia has proved invaluable to astronomers who are trying to learn more about our galaxy, which helps them to test theories and better understand the universe.
Last week, a study using Gaia's data revealed that the stars in our galaxy are still facing the effects of a near-galactic collision that occurred between 300 and 900 million years ago.
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