Black-spotted Fever Strikes Again!

This animation, made with photos taken by the SOHO observatory,
show how sunspot group no. 1019, appeared and grew between May 30 and June 2.
Credit: SOHO

A wave of excitement rippled through the community of sun observers this week with the appearance of a new sunspot group. As spots go, it’s very modest, but it’s been many days since we’ve seen one so it’s cause for optimism.

Sunspots are large magnetic disturbances on the blinding white surface of the sun called the photosphere. Surface is a relative term. The sun is a sphere of incandescent hydrogen gas almost a million miles across. As the sun rotates, magnetic energy occasionally bubbles up from beneath the photosphere to form sunspot groups. Sunspots temperatures are about 8000 degrees, several thousand degrees cooler than the photosphere. That’s why they look dark in comparison.

In this photo taken today (June 3), sunspot group 1019 (circled in blue) is modest but easily visible in a small telescope with a safe filter. I’ve marked the magnetic north and south poles. If you could somehow hold a magnet next to the group, the south pole would pull toward the group’s north pole. The Earth is shown to give you an idea of the spots’ sizes. Details: 1400mm at f/14, ISO 50 at 1/5000" and filter. Photo: Bob King

The number of sunspots varies in an 11-year-cycle called the sunspot cycle. We’ve been at the very bottom of the cycle for the past two years with few if any sunspot groups visible. This one excites because it might be the start of an upswing of solar activity leading to the next maximum in 2012-13. Already sunspot group 1019 is kicking up some modest solar flares, raising the potential for auroras.

Iron filings around two magnets (north and south poles shown) outline their invisible but very real magnetic fields. Sunspots groups also have a north and south pole and are places on the sun where its magnetic energy is concentrated. Photo:

We pass from one cycle to the next during the time of minimum. The last was numbered 23, this is 24. Sunspot groups are often split into two parts just like 1019. One half acts just like the north pole of a very powerful magnet, while the other is the south pole. Since poles reverse from one cycle to the next, astronomers can measure a spot’s magnetism and easily figure out to which cycle it belongs. Cycle 23 spots have north on the right side while cycle 24 is on the left. From the photo, you can see that 1019 belongs to the new cycle. New cycle spots are also found further north and south of the sun’s equator than old spots from the last cycle.

A photo taken in ultraviolet light today (June 3) by the SOHO telescope. This particular form of UV shows objects above the photosphere in the sun’s atmosphere that are at a temperature of 2 million degrees. Group 1019 is the brilliant spot left of and above center. Although the spots may be only thousands of degrees, the area around them, especially high in the atmosphere, can be extremely hot. Credit: SOHO

Anyone with a small telescope equipped with a safe (italic) solar filter can watch cycle 24 unfold in the coming months and years. Check out Thousand Oaks Optical, Orion Telescopes and Rainbow Symphony for safe filters that you place over the front end of your scope. Remember to never look directly at the sun. It’s powerful heat can seriously damage your retina, an organ that no skywatcher wants to compromise.

4 Responses

  1. astrobob

    Hi Rhino, for the photo I used a special photo solar filter that allows plenty of light through for photography. For regular visual use, I have a couple different ones — a glass one from Thousand Oaks (works fine) and an older Mylar filter from a company that’s not around any more. Rainbow Symphony makes very nice black plastic mylar glasses for naked eye sun viewing that give a quality image. I haven’t tried their Mylar telescope filters but the price is very good. Both Mylar and glass work fine but glass is sturdier and can’t accidentally get dented or pierced.

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