September 8, 2012

Astrophysicists Using VLT To Look At Cosmic Lithium In Magellanic Clouds

April Flowers for — Your Universe Online

A team of astrophysicists from the Center for Astrophysics at the University of Notre Dame are exploring a discrepancy between the amount of lithium predicted by the standard models of elemental production during the Big Bang and the amount of lithium observed in the gas of the Small Magellanic Cloud.

The Small Magellanic Cloud is a dwarf galaxy with a diameter of about 7,000 light-years.  It contains several hundred million stars, and is one of the Milky Way's nearest neighbors.

J. Christopher Howk, Nicolas Lehner and Grant Mathews published a paper this week in the journal Nature titled "Observation of interstellar lithium in the low-metallicity Small Magellanic Cloud."

"The paper involves measuring the amount of lithium in the interstellar gas of a nearby galaxy, but it may have implications for fundamental physics, in that it could imply the presence of dark matter particles in the early universe that decay or annihilate one another," Howk says. "This may be a probe of physics in the early universe that gives us a handle on new physics we don't have another way to get a handle on right now."

Using observations from the European Southern Observatory's (ESO) Very Large Telescope (VLT), the team measured the amount of lithium in the interstellar gas of the Small Magellanic Cloud, which has far fewer star-produced heavy elements than the Milky Way.  Scientists believe that conditions immediately following the Big Bang led to the formation of some elements, including a small amount of lithium.  This is in addition to the production of elements by fusion in the core of stars.

ESO's VLT is located Chile and is the flagship facility for European ground-based astronomy.  It consists of four Unit Telescopes with main mirrors of 8.2 meters in diameter and four movable 1.8-meter diameter Auxiliary Telescopes.  The telescopes can work together, or each can be used separately.  The VLT has such precision that it can reconstruct images with an angular resolution of milliarcseconds, equivalent to distinguishing the two headlights of a car at the distance of the Moon.

Big Bang predictions expect about four times more lithium on the surface of stars that is present in the Milky Way.  Some scientists argue that stellar activity might destroy lithium, or the element might sink from the surface through lighter hydrogen.  The ratio from star to star is remarkably consistent, however, challenging this view.

Observations of gas in the Small Magellanic Cloud revealed the amount of lithium that predictions say would have been produced at the Big Bang, but leave no room for subsequent production of the element.

One explanation could be a novel kind of physics operating at the Big Bang that left less lithium than the Standard Model predicts. To pursue this possibility, the team will conduct three nights of observations on the VLT in November. They will look for the lithium isotope 7Li in the Large Magellanic Cloud and 6Li in both the Large Magellanic Cloud and the Small Magellanic Cloud. The standard model predicts that no 6Li was created at the Big Bang.