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Neighbor Star May Help Explain Mystery Of Sun’s Bizarre Temperatures

February 20, 2013
Image Credit: ESA One of the great curiosities in solar science is that our Sun’s outer atmosphere – the corona – is heated to millions of degrees when its visible surface is ‘only’ about 6000 degrees. Even stranger is a curious temperature minimum of 4000 degrees lying between the two layers, in the chromosphere. Now, using ESA’s Herschel space observatory, scientists have made the first discovery of an equivalent cool layer in the atmosphere of the Sun-like star, Alpha Centauri A.

Michael Harper for redOrbit.com — Your Universe Online

As it turns out, studying our Sun can be rather difficult. It´s not the distance so much that keeps scientists guessing — although that certainly doesn´t help. The Sun´s intense heat also keeps scientists at bay, leaving them to make some of their observations and predictions based purely on context and far away measurements.

One thing astronomers have been able to observe is a significant difference in temperatures between the Sun´s atmosphere and surface. This difference has perplexed them for many years, but a recent discovery by the European Space Agency (ESA) has given these scientists another, separate example of this unusual temperature differential to study and understand.

The Alpha Centauri system is our Sun´s closest neighbor, located only four to five light years away. According to the ESA, their Herschel Space Observatory has just discovered an atmospheric makeup similar to that of our Sun surrounding the star Alpha Centauri A. This star is a virtual twin to our Sun in terms of age, chemical composition, mass and temperature. As such, it has become an important object of observation for astronomers who wish to know more about the Sun.

As we all know and learned from a very early age, the Sun is hot — very hot. What scientists have been unable to figure out, however, is why the Sun´s wispy outer atmosphere is the hottest part — even hotter than the temperatures found directly on its surface. Known as the corona, this outer layer produces temperatures upwards of one million degrees Celsius, while the surface of the Sun remains in the relatively tame ballpark of about 6,000 degrees Celsius.

Even more perplexing is the difference in temperature between the lowest part of the Sun´s atmosphere, called the lower chromosphere, and the upper chromosphere. Whereas the surface of the Sun is around 6,000 degrees, the lower chromosphere is roughly 2,000 degrees cooler. However, the upper chromosphere shoots back up to a scorching 10,000 degrees Celsius, creating a 4,000 degree temperature difference between the surface and the upper chromospheres with only a few hundred miles of space between them.

For many years astronomers have assumed that the Sun´s atmosphere is so heated due to the magnetic energy that swirls and snaps through these layers, launching a tremendous amount of energy into the depths of space. These solar flares can send waves of magnetic energy throughout the Solar System and are occasionally even so powerful that they cause telecommunication disruptions here on Earth.

While scientists have been able to account for the increase in heat, they have not yet been able to explain why the lower chromosphere — which rests snuggled between two hotter regions — is a relatively cool 4,000 degrees Celsius. However, the ESA astronomers have now discovered a similar phenomenon in the atmospheres of Alpha Centauri A and plan to study it further in search of an explanation.

“The study of these structures has been limited to the Sun until now, but we clearly see the signature of a similar temperature inversion layer at Alpha Centauri A,” explains René Liseau of the Onsala Space Observatory in Sweden. Liseau is also the lead author of a newly published paper explaining the findings.

“Detailed observations of this kind for a variety of stars might help us decipher the origin of such layers and the overall atmospheric heating puzzle.”

Astronomers recently discovered a small planet with a mass similar to that of Earth orbiting around Alpha Centauri B. While the surface temperature on this so-called “Second Earth” is likely too hot to support life, some scientists believe that the existence of a planet so similar to Earth and so close in our galactic neighborhood could be a good indication that there are even more planets out there like ours. Some have even suggested that one of these planets may be able to support life.


Source: Michael Harper for redOrbit.com – Your Universe Online



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