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Home / Science / The DNA of 350,000 stars is interrogated in search of the sun's lost siblings

The DNA of 350,000 stars is interrogated in search of the sun's lost siblings



HERMES, the new spectrograph built at AAO, uses volume phase holographic (VPH) gratings to generate different optimized spectra in blue, green, and red light band in infrared light. HERMES spectra allow astronomers to study the chemical composition of stars to understand their formation and evolution. A spectrum of the sun shows many dark features due to various chemical elements in sunlight. Credit: N.A. Sharp, NOAO / NSO / Kitt Peak FTS / AURA / NSF.

An Australian group of astronomers working with European collaborators has discovered the "DNA" of more than 340,000 stars in the Milky Way to help them find the siblings of the sun that are now scattered across the sky.

This is an important announcement of an ambitious Galactic Archeology study called GALAH, which was launched in late 2013 to uncover the formation and evolution of galaxies. Upon completion, GALAH will examine more than a million stars.

The GALAH study used the HERMES spectrograph at the Australian Astronomical Observatory's (AAO) 3.9 meter long Anglo-Australian telescope near Coonabarabran, NSW, to collect spectra for the 340,000 stars.

The GALAH survey today publishes its first large public data.

The "DNA" traces the origins of stars and shows astronomers how the universe of hydrogen and helium – after the Big Bang – became a reality Englisch: www.mjfriendship.de/en/index.php?op…d=26&lang=en. 01 & Itemid = 37

"No other study could measure as many elements for as many stars as GALAH," Dr. Gayandhi De Silva from the University of Sydney and AAO, the HERMES instrument scientist who led the groups working on today's data release.

"These data will enable such discoveries as the galaxy 's original star clusters, including the birth chart of the Sun, and so on. There is no other dataset ever collected anywhere in the world, said Dr. De Silva. Sarah Martell of UNSW Sydney, who directs GALAH survey observations, said the sun, like all stars, was born in a group or cluster of thousands of stars.

"Every star in this cluster will have the same chemical composition, or DNA – these clusters are rapidly being pulled apart from our Milky Way galaxy and are now scattered all over the sky." Martell.




Each astronomical object has a unique spectrum or "rainbow fingerprint" that allows astronomers to determine their galaxy, content, age, formation history, movement through space, temperature, and more! The AAO continuously builds innovative spectrographs for the 4-meter AAT and UK Schmidt telescopes to collect spectral data from hundreds of thousands of stars and galaxies. This video, first released in 2015, shows the way the light from distant astronomical objects travels through the optics of the telescope to divide the light into its rainbow spectrum. Credit: AAO and Dr. Amanda Bauer

"The goal of the GALAH team is to create DNA matches between stars to find their long-lost sisters and brothers."

For each star, this DNA is the amount they contain of nearly two dozen chemical elements such as oxygen, aluminum, and iron.

Unfortunately, astronomers can not collect the DNA of a star with a mouth swab, but instead use starlight with a technique called spectroscopy.

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

Associate Professor Daniel Zucker of Macquarie University and the AAO said that astronomers have measured the locations and sizes of dark lines in the spectra to determine the amount of each element in a star.

"Each chemical element leaves a unique pattern of dark bands of specific wavelengths, such as fingerprints, in these spectra," he said.

Dr Jeffr Simpson of the AAO said that it takes about an hour to gather enough photons to light each star, but "fortunately, we can observe 360 ​​stars simultaneously with fiber," he added.

The GALAH team has spent more than 280 nights at the telescope since 2014 to collect all the data.

The GALAH survey was conducted by Professor Joss Bland-Hawthorn of the University of Sydney and the ARC Center of Excellence for all three-dimensional sky astrophysics (ASTRO 3D) and Professor Ken Freeman of the Australian National University (ANU). It was designed more than a decade ago to decipher the history of our Milky Way. the HERMES instrument was designed and built by the AAO specifically for the GALAH study.

Schematic representation of the HERMES instrument showing the light path of starlight from the telescope AAT is divided into four different channels. Credit: The Australian Astronomical Observatory (AAO)

Measuring the abundance of each chemical in so many stars is a huge challenge. GALAH has developed sophisticated analysis techniques.

PhD student Sven Buder of the Max Planck Institute for Astronomy, who wrote the scientific article on the GALAH data release, is part of the project's analysis work, in collaboration with PhD student Ly Duong and Professor Martin Asplund of ANU and ASTRO 3D

Mr. Buder said, "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 calculate the amount of each element for all Ms. Duong noted that "The Cannon is named after Annie Jump Cannon, a pioneering American astronomer who has classified the spectra of some 340,000 stars several decades ago over several decades." Our code analyzes that many stars in less than a second are more detailed day. "

The GALAH Survey data is timed to coincide with the massive release of data on April 25 from the European Gaia satellite, which maps more than 1.6 billion stars in the Milky Way has – and is by far the largest (19659005) In combination with speeds of GALAH, Gaia data does not just give the Positions and distances of the stars, but also their movements within the galaxy.

Professor Tomaz Zwitter (University of Tübingen) of Ljubljana, Slovenia) said that today's results of the GALAH survey would be crucial in interpreting the results of Gaia: "The accuracy of the speeds we achieve with GALAH is for such a great survey unprecedented. " [19659005 Sanjib Sharma of the University of Sydney concluded, "For the first time, we will be able to get a detailed understanding of the history of the galaxy."


Further information:
Archeology of a million stars to decipher the evolution of galaxies

Provided by:
University of Sydney


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