Our Sun is Not Alone

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The star performer which always takes the center stage in our solar system is the Sun. So what if the sun had a twin brother? Well, scientists have found one which even though is light years away from us, it shares the same properties like that of the Sun. Astronomers have always known that the Sun isn’t an only child. Now they may have tracked down one of its siblings. The Sun was born nearly five billion years ago in a giant cloud of interstellar gas and dust. Over time, gravity pulled this material together until the temperature rose enough for stars to ignite.

This cosmic nursery would have played host to as many as 10,000 new stars, all siblings of the Sun. Those stars have since spread out, migrating deeper into the galaxy, making them harder to track down.

But thanks to some clever detective work, a team led by Dr. Ivan Ramirez of the University of Texas at Austin, in the US, claim to have located one – a star named HD 162826 some 110 light years from us. Probing this star’s shared history with the Sun requires the astronomical equivalent of a DNA test, looking at its chemical composition.

If the star was born from the same cloud as the Sun, it should be made of the same stuff.

If the star was born from the same cloud as the Sun, it should be made of the same stuff. Yet working out what a star is made from is labour-intensive, so first Ramirez needed a shortlist to work with. Previous work had selected 30 possible siblings based on the way those stars move around the galaxy. “We knew they were good candidates,” he says.

Spectroscopy works by breaking up starlight into its constituent colours, in a similar way to a prism.

Armed with that list, Ramirez used spectroscopy to assess which elements each star was made of. Spectroscopy works by breaking up starlight into its constituent colours, in a similar way to a prism. That spectrum contains dark gaps where specific hues are absent – that light was swallowed by different chemical elements in the star itself. So the gaps act like the markings on a fingerprint, betraying the elements that make up the star. “We went through element by element and compared them to what’s in the Sun,” says Ramirez.

Find enough (sibling stars) and they can trace their motions back to their common place of origin – the birthplace of the Sun.

“Time and again this star gave a near perfect match, even down to rarer elements like barium and yttrium.” Now that one sibling has been found, researchers have a way to find more. Find enough and they can trace their motions back to their common place of origin – the birthplace of the Sun. “If we can figure out where in the galaxy the Sun formed, we can say something about what the early Solar System was like,” says Ramirez.

Knowing what the Sun and Earth were like in their infancy could provide valuable clues to the conditions necessary for life, and help astronomers target their search for living planets elsewhere in the galaxy. But astronomer Dr Victor Debattista of the University of Central Lancashire, in the UK, urges caution. “This could be a sibling, but if I had to put my money on it I’d say it wasn’t,” he tells Science Uncovered.

Their apparent similarity could be down to chance, but Gaia could help us find out..

His hunch is that extended to a bigger sample of stars, this method of ‘chemical tagging’ would claim more siblings than could have possibly been in the Sun’s birth cloud. “Their apparent similarity could be down to chance, but Gaia could help us find out,” he says. Gaia is a space telescope launched by the European Space Agency with the intention of accurately charting the position and orbits of a billion stars in the Milky Way.

Researchers will then be able to sift that trove of data for other stars with the potential to be solar siblings. So whether or not our star’s family tree is set to grow is still an open question.

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