Eclipse Sunspots Signal Increased Activity

Sun sunspots show up during the recent annular eclipse. Credit: Shehal Joseph and Romayne Anthony

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Astrophotographers capturing the recent annular solar eclipse on January 15, 2010 got an added bonus: upon closer inspection, they found sunspot 1040 also showed up on their images, too. “We didn’t mean to catch sunspots in our Jaffna Eclipse expedition, nor did we plan to,” said Prasanna Deshapriya, one of the members of the Eclipse Hunt 2010 crew, featured in our eclipse photo and video collection. “But surprisingly this is what really happened.”

SOHO image of sunspot 1040 on January 15, 2010. credit: SOHO/MDI

The rather big sunspot 1040, which was also captured by the SOHO spacecraft on Jan. 15 has just disappeared over the sun’s western limb, currently leaving the visible disk of the sun blank once again in this uncharacteristically long solar minimum. But our old friend, sunspot 1039 should be showing up soon, as the sun rotates around. We know it is still there, because the STEREO spacecraft can show us what is going on the sun’s far side. Sunspot 1039 should emerge for direct viewing from Earth within the next 48 hours. Spaceweather.com encourages those amateur astronomers with solar telescopes to monitor the Sun’s east limb for developments.

STEREO B captures the largest solar flare in two years. Click for larger movie.

Additionally on Jan. 19th at 1340 UT, STEREO-B recorded the strongest solar flare in almost two years. Click the image to see the action on an ultraviolet movie of the blast. The M2-class eruption came from sunspot 1039, so that sunspot is likely still very active.

Spaceweather.com said that considering the sunspot was not even visible from Earth at the time of the eruption, the flare was probably much stronger than its M2 classification would suggest. This active region has produced at least three significant eruptions since Jan. 17th and it shows no signs of cooling off.

Sources: Eclipse 2010 blog, Spaceweather.com from 01/19/2010 , Kanabona.com

Unprecedented Images Show Betelgeuse Has Sunspots

Caption:The surface of Betelgeuse in near infrared at 1.64 micron in wavelength, obtained with the IOTA interferometer (Arizona). The image has been re-constructed with two different algorithms, which yield the same details, of 9 milliarcseconds (mas). The star diameter is about 45 milliarcseconds. Credit: Copyright 2010 Haubois / Perrin (LESIA, Observatoire de Paris)

An international team of astronomers has obtained an unprecedented image of the surface of the red supergiant Betelgeuse, in the constellation Orion. The image reveals the presence of two giant bright spots, which cover a large fraction of the surface. Their size is equivalent to the Earth-Sun distance. This observation provides the first strong and direct indication of the presence of the convection phenomenon, transport of heat by moving matter, in a star other than the Sun. This result provides a better understanding of the structure and evolution of supergiants.

Betelgeuse is a red supergiant located in the constellation of Orion, and is quite different from our Sun. First, it is a huge star. If it were the center of our Solar System it would extend to the orbit of Jupiter. At 600 times larger than our Sun, it radiates approximately 100,000 times more energy. Additionally, with an age of only a few million years, the Betelgeuse star is already nearing the end of its life and is soon doomed to explode as a supernova. When it does, the supernova should be seen easily from Earth, even in broad daylight.

But we now know Betelgeuse has some similarities to the Sun, as it also has sunspots. The surface has bright and dark spots, which are actually regions that are hot and cold spots on the star. The spots appear due to convection, i.e., the transport of heat by matter currents. This phenomenon is observed every day in boiling water. On the surface of the Sun, these spots are rather well-known and visible. However, it is not at all the case for other stars and in particular supergiants. The size, physical characteristics, and lifetime of these dynamical structures remain unknown.

Betelgeuse is a good target for interferometry because its size and brightness make it easier to observe. Using simultaneously the three telescopes of the Infrared Optical Telescope Array (IOTA) interferometer on Mount Hopkins in Arizona (since removed), and the Paris Observatory (LESIA) the astronomers were able to obtain a numerous high-precision measurements. These made it possible to reconstruct an image of the star surface thanks to two algorithms and computer programs.

Two different algorithms gave the same image. One was created by Eric Thiebaut from the Astronomical Research Center of Lyon (CRAL) and the other was developed by Laurent Mugnier and Serge Meimon from ONERA. The final image reveals the star surface with unprecedented, never-before-seen details. Two bright spots clearly show up next to the center of the star.

The analysis of the brightness of the spots shows a variation of 500 degrees compared to the average temperature of the star (3,600 Kelvin). The largest of the two structures has a dimension equivalent
to the quarter of the star diameter (or one and a half the Earth-Sun distance). This marks a clear difference with the Sun where the convection cells are much finer and reach hardly 1/20th of the solar radius (a few Earth radii). These characteristics are compatible with the idea of luminous spots produced by convection. These results constitute a first strong and direct indication of the presence of convection on the surface of a star other than the Sun.

Convection could play an important role in the explanation of the mass-loss phenomenon and in the gigantic plume of gas that is expelled from Betelgeuse. The latter has been discovered by a team led by Pierre Kervella from Paris Observatory (read our article about this discovery). Convection cells are potentially at the origin of the hot gas ejections.

The astronomers say this new discovery provides new insights into supergiant stars, opening up a new field of research.

Sources: Abstract: arXiv, Paper: “Imaging the spotty surface of Betelgeuse in the H band,” 2009, A&A, 508, 923″. Paris Observatory

Solar Activity is Picking Up

The current solar cycle (24) has been pretty boring, but a new sunspot — 1035 — is growing rapidly and now is seven times wider than Earth. Solar astronomers are predicting it could grow to be the largest sunspot of the year. There’s not been a lot of competition for the biggest sunspot, though: for 259 days (or 74%) of 2009, the sun has been spotless. But maybe the (solar) tide is turning. There’s been other action recently besides the new sunspot. A long-duration C4-class solar flare erupted this morning at 0120 UT from around the sunspot, which hurled a coronal mass ejection (CME) towards Earth. (See below for image of the CME that blasted off the sun on Dec. 14) Observers at high-latitude could see some aurora action when the CME arrives on or about Dec. 18th. Keep cheering; maybe the sun will come out of its doldrums.

CME on Dec. 14, 2009.  Credit: NASA, SoHO
CME on Dec. 14, 2009. Credit: NASA, SoHO

Remember, don’t look at the Sun directly to try and see the sunspot. NASA has a great site that gives real-time data and updated images of the Sun from SoHO (Solar and Heliospheric Observatory.) Or check out Spaceweather.com, which also provides updates. And if you have a safe way of observing and imaging the sunspot, feel free to post images here, or send to Nancy.