December 2010 Archives

Agence France-Presse

PARIS--Astronomers have for the first time analysed the atmosphere of a "super-Earth," the name given to rocky exoplanets only a few times larger than our own, according to a study released Wednesday.

The breakthrough is a key step in the quest to identify planets in other solar systems that could potentially host forms of life we might recognise, the researchers said.

"We've reached a milestone on the road toward characterising these worlds," said lead author Jacob Bean, a professor at the Harvard-Smithsonian Center for Astrophysics.

The exoplanet in question, dubbed GJ 1214b, is some 42 light years -- four hundred trillion kilometers, or 250 trillion miles -- from our corner of the universe, with a radius about 2.6 times that of Earth.

Discovered last year, GJ 1214b circles a small, faint star, making it that much easier for scientists to tease out data about the atmosphere by analysing starlight as it passes the rim of the planet on its way to us.

Depending on the chemical composition and weather of the atmosphere, specific signature wavelengths of light are absorbed.

Using the European Space Agency's Very Large Telescope in Chile, Bean and colleagues were able to narrow the range of possibilities from three to two.

The first is that GJ 1214b is shrouded by water which -- given the nearness to its star -- would be in the form of steam.

It could also be a rocky world with an atmosphere consisting mostly of hydrogen, but with high clouds or haze obscuring the view.

What the exoplanet is not, the observations prove, is a "mini-Neptune" with a small rocky core and a deep, hydrogen-rich atmosphere.

"Although we can't say yet exactly what that atmosphere is made of, it is an exciting step forward to be able to narrow down the options for such a distant world to either steamy or hazy," said Bean.

In either case, it is more than unlikely that GJ 1214b hosts life forms.

"This planet is much too hot to be considered habitable," Bean told AFP. "In the regions of the atmosphere with pressures similar to what are seen at sea level on Earth, the temperatures are estimated to be more than 500 degree Celsius (930 degrees Fahrenheit)."

It circles its star every 38 hours at a distance of only two million kilometers, seventy times closer than Earth's orbit of the Sun.

Despite this, GJ 1214b is smaller, cooler and more Earth-like than any other known exoplanet.

Most of the more than 500 exoplanets discovered to date are "hot Jupiters", so-called because of their large, gaseous masses and extreme temperatures.

But as observational tools become more powerful, astronomers have begun to identify more and more rocky orbs similar to our own.

"We are working to discover and eventually characterise the atmospheres of planets that would be habitable," said Bean.

"We aren't there yet, but the goal is obtainable within the next decade," he said by email.

No exoplanet discovered so far falls within its solar system's "Goldilocks zone," where temperatures are not so hot that water evaporates, nor so cold that it freezes, but just right for the stuff of life to exist in liquid form.

Earth's atmosphere is 78 percent nitrogen, 21 percent oxygen and one percent other gases, including carbon dioxide.

Agence France-Presse

PARIS--Women instinctively shun their fathers when they are most fertile, even as they seek out the companionship of their mothers, a new study has shown.

The reasons, say the researchers, is evolution. Females in other species have also been observed to give a wide birth to male kin during periods of maximum fertility.

"The behaviour has long been explained as a means of avoiding inbreeding and the negative consequences associated with it," explained lead author Debra Lieberman, a professor at the University of Miami.

"But until we conducted our study, nobody knew whether a similar pattern occurred in women."

Lieberman and colleagues examined cell phone records of 48 women in their reproductive years, noting the date and duration of all calls with their fathers and, separately, their mothers over the course of a billing period.

They found that women called their dads less frequently during the days when the were ovulating, and would hang up sooner if the calls came the other way.

Overall, daughters were half as likely to ring up papa during high fertility days compared to the period of menstruation. What's more, the conversations that did occur lasted about half as long.

The researchers checked to be sure that the women were not giving their dads the slip in order to meet male suitors.

Nor were they simply trying to evade parental control: even when hormones were working overtime, the women were far more, rather than less, likely to give mom a ring.

Women have hard-wired mechanisms that protect against the risk of less healthy children, which tend to occur when close genetic relatives mate, the researchers concluded.

"It makes sense that women would reduce their interactions with male genetic relatives, who are undesirable mates," Lieberman said.

At the same time, when women are in their most fertile phase they are attracted to men with "masculine" qualities such as husky voices and competitive personalities, previous research has shown.

The study was published in the peer-reviewed journal Psychological Science.