- News Home
17 April 2014 12:48 pm ,
Vol. 344 ,
Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
- About Us
A Shortcut for Detecting Alien Worlds
12 November 2009 (All day)
Finding new alien worlds may become a lot easier. Astronomers have discovered that stars containing low amounts of the element lithium tend to host solar systems, a result that could dramatically reduce the time it will take to detect another Earth-like planet.
Thus far, attempting to determine whether other stars play host to planets has required great patience and painstaking measurements. Astronomers scan the skies for two stellar phenomena. One is the barely perceptible but regular dimming of a star's brightness that occurs when an orbiting planet passes between the star and Earth. The other is the regular but minuscule variation in a star's radial velocity--its speed through the galaxy relative to Earth's speed--which indicates that the star is being tugged by an orbiting planet's gravity. Astronomers casually refer to the two phenomena as blink and wobble. Efforts to detect planets via these methods can take months--and they often come up empty.
Enter lithium. Some young stars form inside a small rotating disk of dust and gas, whereas others coalesce inside a much larger rotating disk, called a protoplanetary disk. Astronomers think that in the former case, the star rotates much faster because it isn't subject to the gravitational drag imposed by the larger disk. This faster rotation, the thinking goes, pushes the star's lighter elements, such as lithium, closer to the surface, where they can persist for billions of years. The presence of a protoplanetary disk, on the other hand, could hinder the star's rotation, thereby causing lithium and other lighter elements to sink deep inside the star's nuclear furnace, where they are consumed. If these scenarios are correct, stars with low levels of lithium should be more likely to host planets.
That's what astronomers have found. In today's issue of Nature, a team led by Garik Israelian of the Instituto de Astrofisica de Canarias in Spain's Canary Islands surveyed 46 stars in our galactic neighborhood that host planets, along with 116 stars where so far no planets have been detected. Analysis of the light from the 46 stars showed low lithium content, the team reports, whereas the 116 stars all had higher levels of lithium--with over half sporting about 10 times more than the planet-hosting stars.
Physicist Dejan Vinković, of the University of Split in Croatia calls the paper exciting, but he says it's still unclear exactly why stars that host planets have low lithium levels. It's possible, he says, that something other than the protoplanetary disk is contributing to the chemical's loss.