A galactic fossil: Star is found to be 13.2 billion years old

May 10, 2007
The Cosmic Clock
From left: Recent cosmological studies show that the Big Bang occurred 13.7 billion years ago. The metal-poor star HE 1523 formed in our Milky Way galaxy soon afterward, cosmologically speaking: 13.2 billion years ago. The primitive star contained the radioactive heavy elements uranium and thorium, and the amounts of those elements decay over time, each according to its own half-life. Today, astronomer Anna Frebel of the the University of Texas at Austin McDonald Observatory and her colleagues have deduced the star´s age based on the amounts of radioactive elements it contains compared to certain other "anchor" elements, specifically europium, osmium and iridium. The study of the star´s chemical make-up was made using the UVES spectrograph on the Kueyen Telescope, part of ESO´s Very Large Telescope, at Paranal, in Chile. Credit: (c) ESO

How old are the oldest stars" Using ESO's VLT, astronomers recently measured the age of a star located in our Galaxy. The star, a real fossil, is found to be 13.2 billion years old, not very far from the 13.7 billion years age of the Universe. The star, HE 1523-0901, was clearly born at the dawn of time.

"Surprisingly, it is very hard to pin down the age of a star", the lead author of the paper reporting the results, Anna Frebel, explains. "This requires measuring very precisely the abundance of the radioactive elements thorium or uranium, a feat only the largest telescopes such as ESO's VLT can achieve."

This technique is analogous to the carbon-14 dating method that has been so successful in archaeology over time spans of up to a few tens of thousands of years. In astronomy, however, this technique must obviously be applied to vastly longer timescales.

For the method to work well, the right choice of radioactive isotope is critical. Unlike other, stable elements that formed at the same time, the abundance of a radioactive (unstable) isotope decreases all the time. The faster the decay, the less there will be left of the radioactive isotope after a certain time, so the greater will be the abundance difference when compared to a stable isotope, and the more accurate is the resulting age.

Yet, for the clock to remain useful, the radioactive element must not decay too fast - there must still be enough left of it to allow an accurate measurement, even after several billion years.

"Actual age measurements are restricted to the very rare objects that display huge amounts of the radioactive elements thorium or uranium," says Norbert Christlieb, co-author of the report.

Large amounts of these elements have been found in the star HE 1523-0901, an old, relatively bright star that was discovered within the Hamburg/ESO survey [1]. The star was then observed with UVES on the Very Large Telescope (VLT) for a total of 7.5 hours.

A high quality spectrum was obtained that could never have been achieved without the combination of the large collecting power Kueyen, one of the individual 8.2-m Unit Telescopes of the VLT, and the extremely good sensitivity of UVES in the ultraviolet spectral region, where the lines from the elements are observed.

For the first time, the age dating involved both radioactive elements in combination with the three other neutron-capture elements europium, osmium, and iridium.

"Until now, it has not been possible to measure more than a single cosmic clock for a star. Now, however, we have managed to make six measurements in this one star"," says Frebel.

Ever since the star was born, these "clocks" have ticked away over the eons, unaffected by the turbulent history of the Milky Way. They now read 13.2 billion years.

The Universe being 13.7 billion years old, this star clearly formed very early in the life of our own Galaxy, which must also formed very soon after the Big Bang.

Source: European Southern Observatory (ESO)

Explore further: Quest for extraterrestrial life not over, experts say

add to favorites email to friend print save as pdf

Related Stories

Magnetic behavior discovery could advance nuclear fusion

Mar 19, 2014

(Phys.org) —Inspired by the space physics behind solar flares and the aurora, a team of researchers from the University of Michigan and Princeton has uncovered a new kind of magnetic behavior that could ...

New view of supernova death throes

Mar 18, 2014

A powerful, new three-dimensional model provides fresh insight into the turbulent death throes of supernovas, whose final explosions outshine entire galaxies and populate the universe with elements that make ...

NuSTAR telescope takes first peek into core of supernova

Feb 19, 2014

(Phys.org) —Astronomers have peered for the first time into the heart of an exploding star in the final minutes of its existence. The feat by the high-energy X-ray satellite NuSTAR provides details of the ...

How did early Earth protect itself against the cold?

Feb 07, 2014

Earth's Sun was a weakling when it was younger. Around three or four billion years ago, the star's energy was about 20 percent to 25 percent lower than what's experienced today. If that was still true today, ...

Recommended for you

Quest for extraterrestrial life not over, experts say

Apr 18, 2014

The discovery of an Earth-sized planet in the "habitable" zone of a distant star, though exciting, is still a long way from pointing to the existence of extraterrestrial life, experts said Friday. ...

Continents may be a key feature of Super-Earths

Apr 18, 2014

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Exoplanets soon to gleam in the eye of NESSI

Apr 18, 2014

(Phys.org) —The New Mexico Exoplanet Spectroscopic Survey Instrument (NESSI) will soon get its first "taste" of exoplanets, helping astronomers decipher their chemical composition. Exoplanets are planets ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

Ragtime
not rated yet May 09, 2008
This actually means, whole Milky way was created very fast after BigBang by the same way, like other similar gallaxies, which is virtually impossible, even if we consider the qasar formation hypothesis of AWT. This star was probably trapped from some other, much older gallaxy from outside, or the dating is wrong.
Bonkers
not rated yet May 09, 2008
Surely being born just 500 million years after the big bang would make this a first generation star? so where did the heavy elements come from?

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Cosmologists weigh cosmic filaments and voids

(Phys.org) —Cosmologists have established that much of the stuff of the universe is made of dark matter, a mysterious, invisible substance that can't be directly detected but which exerts a gravitational ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...

Airbnb rental site raises $450 mn

Online lodging listings website Airbnb inked a $450 million funding deal with investors led by TPG, a source close to the matter said Friday.