Telescope to watch ”dancing” stars

Washington, May 16 (ANI): After spending billion of years twinkling and shining, some stars in the heavens appear to “dance” as they wind down.

Now, for the next 14 days, the Whole Earth Telescope, an international network of cooperating astronomical observatories led by the University of Delaware, will be continuously monitoring three of these stars to try to figure out what”s going on inside their luminous masses of cooling plasma.

The primary target is a white dwarf star known as GD358 in the constellation Hercules. It”s made of helium and has a surface temperature estimated at around 19,000 Kelvin.

“We recently discovered that this star is pulsating a little strangely, and we are looking for signs that it is spinning like a top,” says Judi Provencal, assistant professor of physics and astronomy at the University of Delaware and director of the Delaware Asteroseismic Research Center.

A primary mission of the center, which is sponsored by Mt. Cuba Observatory in Greenville, Del., and UD, is to coordinate the activities of the Whole Earth Telescope.

A white dwarf is a “dead” star that doesn”t generate its own energy like the sun does, Provencal says.

“The sun will one day become a white dwarf star, which is why we”re interested in knowing more about them and what happens to any planets the original star might have had,” Provencal notes.

The Whole Earth Telescope”s second target star is the rapidly pulsating PG1325+101 in the constellation Virgo, which is suspected of having one or more planets in orbit around it. The international team will be working to confirm that suspicion, observing the star in collaboration with colleague Roberto Silvotti, leader of the observing group in Italy.

The third target star, WD1524, in the constellation Serpens, was observed during the Whole Earth Telescope”s 2009 international campaign. The star was a high-amplitude pulsator until right before the observing run started, when it mysteriously became a small-amplitude pulsator.

“How stars pulsate depends on their structure and composition,” says Provencal. “Last year, WD1524 completely changed how it was pulsating. Imagine ringing the Liberty Bell and having it sound like a hand bell. That would be hard to do. We don”t understand how this happens with our pulsating stars. We now know that this star has changed yet again, so we are trying to understand how that can happen. Our current theoretical models of white dwarfs don”t predict this sort of behavior.”

There are thousands of white dwarfs in our galaxy; however, only about 30 percent are bright enough for scientists to study using the science of stellar seismology or asteroseismics, which can determine the age, temperature, and composition of a star from its oscillations and brightness.

A white dwarf star pulsates or quakes as waves of energy travel through it. The star”s outer surface sloshes from side to side, like waves on the ocean, Provencal says.

From the shape of these pulses, scientists can measure how the atmosphere is moving around in these pulsating stars and figure out what”s going on inside them, and determine whether an external object like a planet is influencing the star.

The scientific goal of the Whole Earth Telescope is to obtain uninterrupted time-series measurements of “variable stars” — stars whose brightness changes over time — and then construct theoretical models from which their fundamental astrophysics can be derived. The approach, which has been extremely successful, according to Provencal, has placed the fledgling science of “star quakes” at the forefront of stellar astrophysics. (ANI)

Human-induced land cover changes can influence regional climate

Washington, August 9(ANI): Scientists have analyzed seven different climate models to come to the conclusion that human-induced land cover changes (LCCs), such as the clearing of forests for farming, can affect climate.

To study the regional and global effects of LCC, A. J. Pitman from Climate Change Research Centre, University of New South Wales, Sydney, analyzed seven different climate models.

Each model simulation was run several times, with prescribed land cover reflecting conditions in 1870 and in 1992.

The researchers found that in all models, LCC has a statistically significant regional effect on latent heat flux and near-surface temperature.

Furthermore, they found that LCC affect temperature only in the region where the land cover change took place, not in remote regions.

While all models show significant regional effects, these vary across models for several reasons arising from differences in the implementation of the LCC, different land surface models, and different ways of representing the landscape.

The researchers concluded that it is essential to include LCC in future regional and global climate studies but that it is not feasible to impose them in a common way across multiple models for the next Intergovernmental Panel on Climate Change assessment. (ANI)

CO2 not only reason for curious spike in Earth’s temperature 55 million years ago

Washington, July 16 (ANI): A new research has left scientists puzzled as it indicates that something other than carbon dioxide (CO2) was also responsible for a curious spike in Earth’s temperature 55 million years ago.

Over the past couple of decades, researchers have been gathering data about a mysterious event known as the Paleocene-Eocene Thermal Maximum (PETM).

The data, derived from drill cores brought up from the deep seabed in the Atlantic and Pacific Oceans, show that the surface temperature of the planet rose by as much as 9 degrees Celsius within 10,000 years during the PETM, which itself started out warmer than our current world.

Temperatures stayed at this elevated level for nearly 100,000 years.

On the surface, the culprit appeared to be CO2. For reasons unknown, atmospheric concentrations of the gas rose by about 700 parts per million, from 1000 ppm to 1700 ppm.

That was more than four times higher than today’s level of 385 ppm – during the PETM.

That much of an infusion of the well-established greenhouse gas should have been plenty to spike temperatures.

But a new analysis doesn’t fully support this scenario.

Oceanographer Richard Zeebe of the University of Hawaii, Manoa, and colleagues ran carbon-cycle simulations of the oceans and atmosphere based on the data yielded by the sediment cores.

They even simulated what would happen to global temperatures when they increased the atmosphere’s sensitivity to doubling CO2 levels – to 2000 ppm – during the PETM.

The most they could achieve was a warming of 3.5 degrees Celsius, they reported.

That means some other phenomenon must have pushed up temperatures by as much as 5.5 degrees C, the team said.

So at present, the unexplained warming represents a gap in understanding about what causes significant and rapid climate change.

“It’s possible that other greenhouse gases such as methane could have contributed to the (PETM) warming,” Zeebe said.

It’s also possible that the models are underestimating the climate response to CO2 increases.

If that’s the case, it “would mean our understanding of the climate system is incomplete,” said Zeebe.

Zeebe’s team is now looking at smaller warming events that occurred within several million years after the PETM.

“We’re currently trying to find out whether or not they were caused by the same mechanism,” he said. The idea is to determine whether the PETM warming was unique “or a universal feature,” he added. (ANI)