Astronomers at the University of Texas at Austin have done something rather remarkable: They’ve identified a nearby star that was birthed from the same cluster as our own Sun. If that wasn’t cool enough, the lead author also says that — because the Sun and this sibling star were once relatively close and may have bumped uglies — there is a “small, but not zero” chance that planets orbiting this star could host extraterrestrial life.
This new star, HD 162826, is about 110 light years away in the constellation Hercules. It’s about 15% larger than our Sun, but even so you’ll need some binoculars or a simple telescope to see it.
110 light years, in interstellar terms, is very close; the galactic center of the Milky Way, by comparison, is around 25,000 light years distant; Sirius, the brightest star in the night sky is around 9 light years away.
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| HD 162826's location in the northern night sky, in the constellation Hercules |
To identify HD 162826 as a sibling star, Ivan Ramirez and friends from UT Austin used high-resolution spectroscopy to analyze the elemental composition of a bunch of stars. When they found a star that matched our Sun’s chemical makeup, they then looked at its orbit, to see where the star had been, and where they’re currently heading. By combining both of these calculations, the astronomers ended up with just one star: HD 162826.
As luck would have it, the McDonald Observatory Planet Search project has actually been watching the star for the last 15 years. Their observations have ruled out any giant planets orbiting close to the star, but there could still be some smaller planets. To find out more, we’d need to take a look at the star with a proper planet-spotting telescope, such as Kepler, or its successor the Transiting Exoplanet Survey Satellite.
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| NGC 2035, also known as the Dragon’s Head Nebula. Our Sun and its new-found sibling would’ve been birthed in a similar nebula 4.5 billion years ago. |
For now, though, we can certainly do some educated guessing about the history of our Sun and its new-found sister. As far as we can tell, both stars were probably born around the same time — 4.5 billion years ago — in the same birth cluster (nebula). We’re not entirely sure which nebula we were born in, or if that nebula still exists — we may have drifted out of the nebula, or the nebula may have dissipated, we just don’t know.
In any case, Ramirez speculates that, back when the Sun, HD 162826, and all of its fellow siblings were close together, it was probably quite common for asteroids to knock a chunk off a planet, which then traveled to a nearby planet. If one of those planets harbored life, it’s possible that life could’ve been seeded on other planets in other solar systems. “… It could be argued that solar siblings are key candidates in the search for extraterrestrial life,” Ramirez said.
Moving forward, the plan is to identify more of the Sun’s siblings. There could’ve been thousands or millions of stars in our Sun’s birth cluster, and they’re probably all over the Milky Way by now. If we can locate enough sister stars, we should be able to backtrack their orbits to find out where they once all coexisted: our Sun’s birthplace.
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