New German telescope stares at the sun

New German telescope stares at the sun
Kiepenheuer-Institut für Sonnenp
Tech Corner

POSTED: Saturday, May 26, 2012 - 9:30am

UPDATED: Saturday, May 26, 2012 - 9:34am

A consortium of German scientists unveiled this week Europe's largest solar telescope, which will give mankind its clearest images of the sun to date.

The telescope, given the appropriately Teutonic name Gregor, is a powerful contraption capable of staring directly into the nearby gas giant.

Until now, scientists were unable to point conventional telescopes at the sun for very long without the mirrors overheating and distorting the image.

But Gregor, built from a sturdy lithium aluminosilicate glass-ceramic, employs reflective surfaces made out of silicon carbide, a material that does not warp under the heat of the sun.

In addition, the telescope, located atop a volcano in the Canary Islands, also boasts a completely open structure, allowing cool ocean breezes to pass through it and further reduce its overall temperature.

And with the help of countless reflectors, spectrometers, etc., Gregor will actually allow astronomers to compensate for any atmospheric distortions, providing crystal-clear images of even small-scale phenomena, like sunspots as small as 70 kilometers in diameter.

"Much about the sun still remains a mystery," said Reiner Hammer, a scientist from the Kiepenheuer Institute for Solar Physics, one of the driving forces behind the project. "So when you're able to look at it with such unprecedented definition, you can't help but hope for progress."

Their new mega-telescope is equipped with a so-called "spectro polarimeter," which the scientists will use to map the sun's atmosphere and magnetic field by analyzing absorptions and emissions within the solar spectrum, according to scientist Rolf Schlichenmaier.

Absorptions within the spectrum are designated by thin black lines and represent light being blocked, or "absorbed," by certain elements in the atmosphere. So-called "absorption lines" can be analyzed to determine the composition of whatever substance the light was passing through.

"The shape of this line tells you about temperature, pressure - all the information we have from the solar atmosphere, we get from those lines," Schlichenmaier said.

"So from the line's width, we can say how hot it is there," he said. "And from the shift in velocity and pressure and density - these are all the physical quantities that we can derive from the shape, the position of such lines."

This becomes even more impressive when you consider the fact that there are some 2,000-3,000 lines in the visible spectrum.

"These lines form at different temperature and heights within the atmosphere," Schlichenmaier said. "So from studying many of those lines we can retrieve the 3D structure of the atmosphere of the sun."

The trick is collecting the data and analyzing it before the section of the sun you're observing changes again. For this, Schlichenmaier says, you need telescopes that are large enough to take in substantial light to minimize exposure times.

When you're talking about taking a picture of something 93 million miles (150 million kilometers) away and analyzing the data before it changes shape and temperature, every second counts.

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