A Big Sunspot Is Staring Us In The Face

The sun through high clouds this morning at 10 a.m. Central Time. With my #14 welder’s glass I could easily see the big sunspot, dubbed active region 2738, with the naked eye. A paler penumbra surrounds the dark umbra. The filter tints the sun green. If you look closely at the spot, you’ll see that the umbra is split in two by a narrow light bridge crossing its center. Easier to see in the picture below. Bob King

Sunspots have been meager this year. As we approach the minimum of the 11-year sunspot cycle, solar activity is ebbing. That’s why it’s so exciting to see a big sunspot blemish the sun’s face these past few days. Amateur astronomer Giorgio Rizzarelli of Trieste, Italy sent along his photos to share the news when it was too cloudy to view the sun from my area. Now that it’s clear, I can see it myself.

In this photo taken by Giorgio Rizzarelli on April 13, 2019, you can better see the light bridge splitting the spot’s umbra in two. Giorgio Rizzarelli

I used a #14 welder’s glass and with only a little effort, spotted a pinhead-sized dot on an otherwise blank sun this morning. If you still have your eclipse glasses from the August 2017 eclipse, put ’em on and have a look. A clear sky is best, but it should still be visible if you have high, thin clouds like I did. Cup your hands around the glasses to block any stray light and concentrate your vision. It will appear very tiny but distinct. Always use a safe, approved filter when viewing the sun. If you see the spot or not, please share your observation by leaving a comment.

A close-up of the spot taken at 11:15 a.m. April 14 shows the umbra, penumbra, the light bridge and thousands of tiny granules around the spot. Each is a small cell of gas the size of Texas bubbling up from below (via convection). NASA / Solar Dynamics Observatory

Although the sunspot looks like a little bug in the photos, it’s truly gigantic with a diameter about three times that of the Earth. Slicing across its middle is a skinny light bridge 12,400 miles (20,000 km) long and about 500 miles (800 km) wide or a bit shy of the length of Nebraska.

The bright appeared a couple days ago and threatened to split the spot in half. That may yet happen or the gap could close. Light bridges typically form during the breakup of sunspots. It should make for fun and instructive viewing the next few days to watch which way the core trends.

Sunspots are regions where concentrated magnetic fields deep within the sun rise to its surface and insulate and chill the area. Spots appear only dark because they’re several thousand degrees cooler than the blinding white surface. If you could see a sunspot apart from the sun it would glow with a brilliant orange-red light.

The dark umbra makes a depression in the sun’s surface like a valley. A light bridge then is literally a bridge of fire (hot like the rest of the bright solar surface) crossing a dark, colder abyss — an awesome thing to contemplate and even better to see for yourself.

This graph shows the progress of Cycle 24, the current solar cycle, and a preliminary forecast for the next based on sunspot numbers. Time runs along the bottom of the graph with sunspot number at left. NOAA

Solar activity like flares and sunspots rises and falls in a cycle that averages 11 years. Right now, we’re near the bottom of that cycle, one of the reasons it’s exciting to see the big spot. Minimum is expected to occur sometime between July 2019 and Sept. 2020 with the next maximum due in 2023-2026. The coming minimum may last years so get ready for a lot of “blank suns.”

NASA’s Solar Dynamics Observatory captured this photo of the big spot and the active region around it in far ultraviolet light this morning (April 14). Solar plasma (gas) is swept up in the spot’s powerful magnetic field to create these magnificent swirls several dozen times larger than Earth. NASA

The last maximum in 2012-2014 was pretty wimpy as maxima go, and the next isn’t expected to be much better. While that may be good news for satellites and power grids, which can be adversely affected by powerful solar storms, aurora watchers prefer stormy times.  That doesn’t mean auroras will dry up and go away. Coronal holes — openings in the sun’s magnetic canopy — are more common at minimum and produce auroras, too. But there’s nothing like a huge flare to spark a wicked display.

Meantime, we’ll be keeping an eye on the current spot. It will be nicely placed for viewing for the next 5 days or so. While it has produced minor B-class flares, it may have more in the offing.

7 Responses

  1. kevan hubbard

    You say you use a welders glass. I use to use ”thousand oaks’film as it is more durable than the baader film but I haven’t looked at the sun through an optical aid for a while. I would love to invest in a proper solar telescope, probably if I did the coroando PST,but even the cheapest are really pricey (excluding the various white light scopes which are cheap but offer no advantage over solar film on a normal telescope except I suppose from a safety point of view as theres no film to fall off).also I have seen second hand PST’s but they had a problem with ‘rusting’filters coatings a few years back, corrected now,but you could be buying one of those older PST’s second hand.

    1. astrobob

      Kevan,
      You can get any old refractor or small reflector and fit it with a glass or mylar filter (in a cap to fit model / make) and see lots of great stuff in white light. The PST is only for H-alpha, which is fine but a bit tricky and the image scale is small.

  2. Jake Skywatcher

    I made a pair of filters from ‘thousand oaks’ film and a couple pill bottle caps that happen to be the right size to fit in my binocular objectives. The sunspot shows up quite well Thanks for the head’s up!

      1. Jake Skywatcher

        After the look with the binoculars I pulled out my SLR film camera (Canon AE-1P) and a 500 mm f8 reflector lens with a doubler – making a 1000 mm f16. I also had made a filter holder for this one, using a peanut butter lid. Did some bracketing of the exposures, we’ll see what develops…

  3. kevan hubbard

    The strange thing about the pst is that it is supplied with a very low quality Kellner eye piece,12mm if I recall, which is strange considering the price of the thing.of course most people who buy a PST are going to have their own quality eye pieces as it’s not the sort of thing a beginner pops out to buy as a first telescope. I doubt that the Kellners ever get used? I believe that the PST is only 30mm or 35mm in appeture so the field will be very narrow at higher powers if however you drop in something like a 20mm eye piece, providing you can bring it to focus considering the star diagonal,you would increase the field but obviously drop magnifying power but as the sun is so big even 6x will give you a fine view.with these short focal small appeture telescopes often star diagonals cause focusing problems. I know as I have a 25mm Japanese pocket Borg,which is astronomical rather than solar but if a star diagonal is added you can’t focus no matter what eye piece unless you add a Barlow too then the field of view is tiny.this 25mm has a huge field of view at 8x wider than 10×50 binoculars!but you have to look through it as a through and through.

    1. astrobob

      Kevan,
      The main issue with the PST is that it’s only H-alpha, not white-light viewing. I’ve looked through a couple PSTs, and the H-a images are fine, but I’ve seen much better, so it wouldn’t be my first choice for an H-alpha scope.

Comments are closed.