05 November 2018
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Astronomers have found what could be one of the universe’s oldest stars, a body almost entirely made of materials spewed from the Big Bang.
The discovery of this approximately 13.5 billion-year-old tiny star means more stars with very low mass and very low metal content are likely out there — perhaps even the universe’s very first stars. The star is unusual because unlike other stars with very low metal content, it is part of the Milky Way’s “thin disk” — the part of the galaxy in which the Sun resides. And because this star is so old, researchers say it’s possible that our galactic neighbourhood is at least 3 billion years older than previously thought. The findings were published today in The Astrophysical Journal.
Co-study author Dr Andrew Casey, a lecturer in the School of Physics and Astronomy at Monash University said the research team had discovered an ancient star unlike any other, which suggests that some of the first stars to form in the university may still exist today. “The findings are significant because for the first time we have been able to show direct evidence that very ancient, low mass stars do exist, and could survive until the present day without destroying themselves,” Dr Casey said.
Scientists find elusive star, 2MASS J18082002–5104378 B
Lead author Assistant Professor Kevin Schlaufman, from the Johns Hopkins University Physics and Astronomy Department, said this star may be one in ten million. “It tells us something very important about the first generations of stars,” Assistant Professor Schlaufman said.
The universe’s first stars after the Big Bang would have consisted entirely of elements like hydrogen, helium, and small amounts of lithium. Those stars produced elements heavier than helium in their cores and seeded the universe with them when they exploded as supernovae. The next generation of stars formed from clouds of material laced with those metals, incorporating them into their makeup. The metal content, or metallicity, of stars in the universe increased as the cycle of star birth and death continued.
This star’s extremely low metallicity indicates that in a cosmic family tree, it could be as little as one generation removed from the Big Bang. Indeed, it is the new record holder for the star with the smallest complement of heavy elements – about the same heavy element content as the planet Mercury. In contrast, our Sun is around 100,000 generations down that line and has a heavy element content equal to 14 Jupiters. Astronomers have found around 25 ancient, ‘ultra metal-poor’ stars with the approximate mass of the Sun. The star Schlaufman and his team found is only 14 percent the mass of the Sun. They found the tiny, almost invisibly faint “secondary” star after another group of astronomers discovered the much brighter “primary” star and measured its composition by studying a high-resolution optical spectrum of its light. Those astronomers also identified unusual behaviour in the star system that implied the presence of a neutron star or black hole. Schlaufman and his team found that to be incorrect, but in doing so they discovered the visible star’s much smaller companion. The existence of the smaller companion star turned out to be the big discovery. As recently as the late 1990s, researchers believed that only massive stars could have formed in the earliest stages of the universe — and they could never be observed because they burn through their fuel and die so quickly.
But as astronomical simulations became more sophisticated, they began to hint that in certain situations, a star from this time period with particularly low mass could still exist, even more than 13 billion years since the Big Bang. Unlike huge stars, low-mass ones can live for exceedingly long times. Red dwarf stars, for instance, with a fraction of the mass of the Sun, are thought to live to trillions of years.
The discovery of this new ultra metal-poor star, named 2MASS J18082002–5104378 B, opens up the possibility of observing even older stars.
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Monash University is an Australian public research university based in Melbourne, Australia. Founded in 1958, it is the second oldest university in the State of Victoria. Monash is a member of Australia’s Group of Eight and the ASAIHL, and is the only Australian member of the influential M8 Alliance of Academic Health Centers, Universities and National Academies. Monash is one of two Australian universities to be ranked in the The École des Mines de Paris (Mines ParisTech) ranking on the basis of the number of alumni listed among CEOs in the 500 largest worldwide companies. Monash is in the top 20% in teaching, top 10% in international outlook, top 20% in industry income and top 10% in research in the world in 2016.
Monash enrolls approximately 47,000 undergraduate and 20,000 graduate students, It also has more applicants than any university in the state of Victoria.
Monash is home to major research facilities, including the Australian Synchrotron, the Monash Science Technology Research and Innovation Precinct (STRIP), the Australian Stem Cell Centre, 100 research centres and 17 co-operative research centres. In 2011, its total revenue was over $2.1 billion, with external research income around $282 million.
The university has a number of centres, five of which are in Victoria (Clayton, Caulfield, Berwick, Peninsula, and Parkville), one in Malaysia. Monash also has a research and teaching centre in Prato, Italy, a graduate research school in Mumbai, India and a graduate school in Jiangsu Province, China. Since December 2011, Monash has had a global alliance with the University of Warwick in the United Kingdom. Monash University courses are also delivered at other locations, including South Africa.
The Clayton campus contains the Robert Blackwood Hall, named after the university’s founding Chancellor Sir Robert Blackwood and designed by Sir Roy Grounds.
In 2014, the University ceded its Gippsland campus to Federation University. On 7 March 2016, Monash announced that it would be closing the Berwick campus by 2018.