Many teams of scientists are preparing themselves to profit from a rare opportunity, watching the sun during a solar eclipse. As “usual”, many studies will be on the sun’s corona, its outermost region whose abnormally high temperature is yet to be explained.

The solar atmosphere or corona, which is normally only visible from the Earth at times of total solar eclipses, has a temperature of 1—2 million degrees Celsius, the sun’s surface being at a mere 5500 degrees. The corona also emits ultraviolet and X-ray radiation, which has been observed with spacecraft such as the ESA/NASA Solar and Heliospheric Observatory (SOHO). But despite more than 60 years of study, the heating mechanism of the corona remains unknown.

The instrument used by the Anglo-Polish team, the Solar Eclipse Coronal Imaging System (SECIS), consists of a double telescope on a driven mount with fast-frame electronic cameras that will form images of the corona during eclipse totality at the rate of 40 frames per second. This is far higher than can be accomplished with spacecraft instrumentation because of telemetry restrictions.

The aim is to search for subtle oscillations in the corona’s light intensity – tell-tale signs of heating by magnetic waves, thought by many to be the main heating mechanism on local scales. The oscillations are likely to have periods of a few seconds or less.

For more information, you can head to NASA’s Eclipse Page and maybe watch the live webcast.

March 27th, 2006 | Physics | No comments

Using Eso’s Very Large Telescope in Chile, an international team of researchers discovered a brown dwarf belonging to the 24th closest stellar system to the Sun. Brown dwarfs are intermediate objects that are neither stars nor planets. This object is the third closest brown dwarf to the Earth yet discovered, and one of the coolest, having a temperature of about 750 degrees Centigrade. It orbits a very small star at about 4.5 times the mean distance between the Earth and the Sun. Its mass is estimated to be some-where between 9 and 65 times the mass of Jupiter.

At a time when astronomers are peering into the most distant Universe, looking at objects as far as 13 billion light-years away, one may think that our close neighbourhood would be very well known. Not so. Astronomers still find new star-like objects in our immediate vicinity. Using Eso’s VLT, they just discovered a brown dwarf companion to the red star SCR 1845-6357, the 36th closest star to the Sun.

“This newly found brown dwarf is a valuable object because its distance is well known, allowing us to de-termine with precision its intrinsic brightness”, said team member Markus Kasper (ESO). “Moreover, from its orbital motion, we should be able in a few years to estimate its mass. These properties are vital for understanding the nature of brown dwarfs.”

(more…)

March 22nd, 2006 | Physics | No comments