A Different Kind of Sunspot

Here’s the European Southern Observatory’s description of this animation—

Spots on extreme horizontal branch stars (right) appear to be quite different from the dark sunspots on our own Sun (left), but both are caused by magnetic fields. The spots on these hot, extreme stars are brighter and hotter than the surrounding stellar surface, unlike on the Sun where we see spots as dark stains on the solar surface that are cooler than their surroundings. The spots on extreme horizontal branch stars are also significantly larger than sunspots, covering up to a quarter of the star’s surface. While sunspots vary in size, a typical size is around an Earth-size planet, 3000 smaller than a giant spot on an extreme horizontal branch star.

Video Credit: ESO

Go here for information about extreme horizontal branch stars.

Watching a Sunspot

Here’s NASA’s description of the video—An active region on the sun — an area of intense and complex magnetic fields — has rotated into view on the sun and seems to be growing rather quickly in this video captured by NASA’s Solar Dynamics Observatory between July 5-11, 2017. Such sunspots are a common occurrence on the sun, but are less frequent as we head toward solar minimum, which is the period of low solar activity during its regular approximately 11-year cycle. This sunspot is the first to appear after the sun was spotless for two days, and it is the only sunspot group at this moment. Like freckles on the face of the sun, they appear to be small features, but size is relative: The dark core of this sunspot is actually larger than Earth.

Video Credit: NASA

Coronal Loops

Coronal LoopsThe Atmospheric Imaging Assembly instrument aboard the Solar Dynamics Observatory images the solar atmosphere in 10 wavelengths every 10 seconds. Its data is used to link changes in the surface to interior changes in the Sun.In this image the Sun’s magnetic field can be readily visualized through bright strands called “coronal loops”. Loops are shown here in a blended overlay with the magnetic field measured by SDO’s Helioseismic and Magnetic Imager shown underneath. Blue and yellow represent the opposite polarities of the magnetic field.

Image Credit: NASA


One of my hobbies is amateur radio, and one of the things that many of us ham radio geeks keep an eye on is sunspots. Sunspots are darker, cooler regions on the Sun created by intense magnetic fields breaking through the surface. As that solar activity increases, the Sun’s effect on the Earth’s ionosphere generally improves the propagation of shortwave radio signals. The Sun showed a substantial increase in sunspots over the first part of this month. This movie and still (assembled from data taken by the Solar Dynamics Observatory) show the Sun in filtered white light. It’s dotted with more and larger sunspots than we have seen for quite a while, and I’ve noticed improved radio propagation, occasionally extending to VHF bands. The Sun is supposed to have passed the peak for this 11-year sunspot cycle, but it will still be producing more sunspots and solar storms during the rest of this solar cycle.

[youtube http://youtu.be/B5mEnfusn4Q]

Video Credit: NASA

Sunspot Loops in UV

sunspotloops_traceFrom time to time, it is the pleasure of Hogeman, Internet Astronomer, to feature amazing views of the Sun as seen in ultraviolet light by the Solar Dynamics Observatory satellite operated by NASA. Today’s picture comes from the earlier TRACE mission and was taken in 2000 during the last solar cycle. It shows a quiet day on the Sun, but, even on slow days, the Sun’s surface is a busy place. The relatively cool dark regions have temperatures of thousands of degrees Celsius. A large sunspot group called AR 9169 can be seen as the bright area near the horizon. The bright glowing gas flowing around the sunspots has a temperature of over one million degrees Celsius. We’re not sure of the reason for the high temperatures, but the best guess is that it’s related to the rapidly changing magnetic field loops that channel solar plasma. Large sunspot group AR 9169 moved across the Sun during the autumn of 2000 and decayed within a few weeks.

Image Credit: NASA

Sunspots and Solar Flares

NASA’s Solar Dynamics Observatory (SDO) captured this image of an M7.9 class flare on 13 March 13, 2012 . It is shown here in the 13.1 nanometre wavelength (particularly useful for seeing solar flares) colorized in teal. This was in the same active region that produced flares and coronal mass ejections the entire week. The region has been moving across the face of the sun since 2 March and will soon rotate out of Earth view.

A solar flare is an intense burst of radiation coming from the release of magnetic energy associated with sunspots. They are the solar system’s most massive explosions. They appear as bright areas on the sun and can last from a few minutes or several hours.

We classify solar flares according to their x-ray brightness. There are 3 categories: X-, M- and C-class. X-class flares are the strongest. Even though M-class flares are medium-sized, they can cause brief radio blackouts that affect Earth’s polar regions. C-class flares are small with few noticeable consequences on Earth.

Image Credit: NASA/SDO