Traces of rare earth element detected in stars

Herald Globe (IANS) Wednesday 22nd February, 2012

Scientists have detected traces of a rare earth element, tellurium, in three ancient stars located a few thousand light years away, a study reveals.

Traces of this brittle, semiconducting element were found with even heavier elements in the periodic table, for the very first time, possibly originating from a very rare type of supernova during rapid nuclear fusion.

"We want to understand the evolution of tellurium -- and by extension any other element from the Big Bang to today," said study co-author Anna Frebel, assistant professor of astrophysics at Massachusetts Institute of Technology (MIT).

"Here on Earth, everything's made from carbon and various other elements, and we want to understand how tellurium on Earth came about," the Astrophysical Journal Letters reported.

The team analyzed the chemical composition of three bright stars located a few thousand light-years away, "in the halo of the Milky Way," Frebel said, according to a university statement.

Researchers looked at data obtained from the Hubble Space Telescope's spectrograph, an instrument that splits light from a star into a spectrum of wavelengths.

If an element is present in a star, the atoms of that element absorb starlight at specific wavelengths; scientists can observe this absorption as dips in the spectrograph's data.

Frebel and her colleagues detected dips in the ultraviolet region of the spectrum -- at a wavelength that matched tellurium's natural light absorption -- providing evidence that the rare Earth element does indeed exist in space, and was likely created more than 12 billion years ago, at the time when all three stars formed.

The researchers also compared the abundance of tellurium to that of other heavy elements such as barium and strontium, finding that the ratio of elements was the same in all three stars.