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Astronomers Pinpoint How Milky Way Was Formed

By Dave Reneke

Astronomers have produced the clearest picture yet of how our galaxy formed more than 13.5 billion years ago.

The world’s largest filled single dish radio telescope began operation in September, and it relies on a piece of Western Australian innovation. The telescope, known as FAST, uses a data system developed at the International Centre for Radio Astronomy (ICRAR) in Perth and the European Southern Observatory to manage the huge amounts of data it generates.

The software is called the Next Generation Archive System (NGAS), and will help astronomers using the telescope to search for rotating neutron stars and look for signs of extraterrestrial life. FAST, or the Five Hundred Metre Aperture Spherical Telescope, is so large it had to be built into a valley in Guizhou province in south-west China.

The NGAS data system will help to collect, transport and store about three petabytes of information per year from the telescope. “That’s 100,000 32GB iPods filled every year,” said Prof Andreas Wicenec, who heads up ICRAR’s ICT program and helped design the data system.

Getting that kind of capacity is not too hard, especially in this day and age, but the main challenge is transporting so much data and having the network bandwidth to move it around.

FAST will be one of the most sensitive telescopes ever built. The huge amounts of data produced will allow astronomers to map hydrogen gas in the Milky Way, hunt for rotating neutron stars known as pulsars, and look for signals from extraterrestrial intelligence.

It is an official pathfinder to the multi-billion dollar Square Kilometre Array (SKA) telescope to be built in Western Australia and South Africa. China marks the latest conquest for the NGAS data system, which is already used by the Murchison Widefield Array in outback Western Australia.

Astronomers Pinpoint How Milky Way Was Formed
Using colours to identify the approximate ages of more than 130,000 stars in the Milky Way’s halo, astronomers have produced the clearest picture yet of how our galaxy formed more than 13.5 billion years ago.

The astronomers, based at the University of Notre Dame, are part of JINA-CEE – the Joint Institute for Nuclear Astrophysics Centre for the Evolution of the Elements – which is headquartered at Michigan State University.

“We haven’t previously known much about the age of the most ancient component of the Milky Way, which is the halo system,” said Prof Daniela Carollo of the Notre Dame Department of Physics. “But now we have demonstrated conclusively for the first time that ancient stars are in the centre of the galaxy and the younger stars are found at longer distances.”

The new results confirm predictions of models that suggest the Milky Way was formed by the merging and accretion of small “mini halos” containing stars and gas. In these models, the centre of the galaxy forms first and therefore contains the oldest stars, while younger stars and small galaxies that were drawn in by gravity over the course of billions of years are found farther from the centre.

Using data from the Sloan Digital Sky Survey, the scientists identified more than 130,000 “blue horizontal” branch stars, which burn helium in their cores and exhibit different colours based on the amount of time that a star has been alive. This allows their age to be estimated.

These new research results will allow JINA-CEE collaborators to develop improved computer simulations of the formation and evolution of Milky Way like galaxies. These models provide a basis for stellar astrophysicists and nuclear scientists to implement data from nuclear experiments at facilities like Notre Dame.

“This result gives critical clues to the formation of the Milky Way’s stellar halo, and presents us with the only way to directly determine when the Milky Way’s progenitors formed,” Prof Brian O’Shea of Michigan State University. “It will be invaluable for informing our computational models of galaxy evolution that we are developing.”