Finding lost siblings of the Sun

In a huge galactic archaeology project, astronomers have revealed the “DNA” of more than 340,000 stars in the Milky Way, which should help them find the siblings of the Sun, now scattered across the sky.

Our galaxy, the Milky Way. Image: Shutterstock
Our galaxy, the Milky Way. Image: Shutterstock

UNSW scientists in collaboration with European scientists demonstrated that the “DNA”, or spectra, of more than 340,000 stars in the Milky Way could aid them to search the siblings of the Sun, now scattered across the sky.

Scientists actually are working on project GALAH, the survey observations for the ambitious galactic archaeology project- which launched in late 2013 as part of a quest to uncover the formulation and evolution of galaxies. Scientists gathered the data from HERMES spectrograph at the Australian Astronomical Observatory’s (AAO) 3.9-metre Anglo-Australian Telescope near Coonabarabran in NSW to collect spectra for the 340,000 stars.

The data shows that how the Universe went from having just hydrogen and helium soon after the Big Bang to being loaded with every one of the components show now on Earth that is fundamental forever.

Astronomers mapped almost 1.6 billion stars in the Milky Way, making it by far the biggest and most accurate atlas of the night sky to date.

Dr. Martell, from the UNSW School of Physics, says the Sun, like all stars, was born in a group or cluster of thousands of stars. 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.”

“The GALAH team’s aim is to make DNA matches between stars to find their long-lost sisters and brothers.”

For each star, the DNA shows to the amount they contain almost two dozen chemical elements, for example, oxygen, aluminum, and iron.

A schematic of the HERMES instrument showing how star light from the telescope AAT is split into four different channels. Credit: The Australian Astronomical Observatory.
A schematic of the HERMES instrument showing how star light from the telescope AAT is split into four different channels. Credit: The Australian Astronomical Observatory.

Astronomers thus gather starlight, utilizing a technique called spectroscopy.

The light from the star is gathered by the telescope and after that went through an instrument called a spectrograph, which parts the light into definite rainbows, or spectra.

Dr. Gayandhi De Silva, of the University of Sydney and AAO – the HERMES instrument scientist who oversaw the groups working on today’s major data release – says: “No other survey has been able to measure as many elements for as many stars as GALAH.

“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.”

Associate Professor Daniel Zucker, from Macquarie University and the AAO, says astronomers measure the locations and sizes of dark lines in the spectra to work out the amount of each element in a star.

“Each chemical element leaves a unique pattern of dark bands at specific wavelengths in these spectra, like fingerprints,” he says.

Dr. Jeffrey Simpson of the AAO says it takes about an hour to collect enough photons of light for each star: “Thankfully, we can observe 360 stars at the same time using fiber optics.”

It was considered over 10 years prior as an approach to disentangle the historical backdrop of our Milky Way galaxy. The HERMES instrument was composed and worked by the AAO particularly for the GALAH overview. Estimating the wealth of every synthetic in such a significant number of stars is a gigantic test. To do this, GALAH has created advanced investigation methods.

Ph.D. student Sven Buder of the Max Planck Institute for Astronomy, Germany, who is lead writer of the logical article portraying the GALAH information discharge, is a piece of the examination exertion of the undertaking, working with Ph.D. understudy Ly Duong and Professor Martin Asplund of ANU and ASTRO 3D.

Mr. Buder says: “We train [our computer code] The Cannon to recognize patterns in the spectra of a subset of stars that we have analyzed very carefully, and then use The Cannon’s machine learning algorithms to determine the amount of each element for all of the 340,000 stars.“

Ms Duong says: “The Cannon is named for Annie Jump Cannon, a pioneering American astronomer who classified the spectra of around 340,000 stars by eye over several decades a century ago. Our code analyses that many stars in far greater detail in less than a day.”

In combination with velocities from GALAH, Gaia data will give not just the positions and distances of the stars, but also their motions within the Galaxy.

Professor Tomaz Zwitter of the University of Ljubljana in Slovenia says today’s results from the GALAH survey will be crucial for interpreting the results from Gaia: “The accuracy of the velocities that we are achieving with GALAH is unprecedented for such a large survey.”

Dr. Sanjib Sharma from the University of Sydney says: “For the first time we’ll be able to get a detailed understanding of the history of the Galaxy.”