Stars’ ‘DNA’ can ‘find’ Sun’s lost siblings

Sydney: With the aim to find the lost siblings of the Sun, now scattered across the sky, a team of astronomers has collected the "DNA" of more than 340,000 stars in the Milky Way.

The "DNA" can help trace the ancestry of stars, showing astronomers how the universe went from having only hydrogen and helium -- just after the Big Bang -- to being filled today with all the elements we have here on Earth that are necessary for life.
The research, detailed in the journal Monthly Notices of the Royal Astronomical Society, is based on the Galactic Archaeology survey, called GALAH, launched in late 2013 as part of a quest to uncover the formulation and evolution of galaxies. 

When complete, GALAH will investigate more than a million stars.The GALAH survey used the HERMES spectrograph at the Australian Astronomical Observatory's (AAO) 3.9-metre Anglo-Australian Telescope near Coonabarabran in New South Wales to collect spectra for the 340,000 stars.

"No other survey has been able to measure as many elements for as many stars as GALAH," said Gayandhi De Silva of the University of Sydney and AAO. 

"This data will enable such discoveries as the original star clusters of the Galaxy, including the Sun's birth cluster and solar siblings -- there is no other dataset like this ever collected anywhere else in the world," De Silva said.

The Sun, like all stars, was born in a group or cluster of thousands of stars, explained Sarah Martell from the University of New South Wales (UNSW) Sydney who leads the GALAH survey observations.

"Every star in that cluster will have the same chemical composition, or DNA - these clusters are quickly pulled apart by our Milky Way Galaxy and are now scattered across the sky," Martell said.

"The GALAH team's aim is to make DNA matches between stars to find their long-lost sisters and brothers," she added.For each star, this DNA is the amount they contain of each of nearly two dozen chemical elements such as oxygen, aluminium and iron.
Unfortunately, astronomers cannot collect the DNA of a star with a mouth swab but instead use the starlight, with a technique called spectroscopy.

The light from the star is collected by the telescope and then passed through an instrument called a spectrograph, which splits the light into detailed rainbows, or spectra.