HUGE sunspot group coming 'round the Sun!

By Phil Plait | July 10, 2012 12:14 pm

[UPDATE: Oh for criminy’s sake. I made a mistake here. The big sunspot group I describe below is actually AR 1515 which has been on the Sun for a while now. AR 1520 can be seen in the full Sun pic on the very left, on the Sun’s edge! It’s still huge, roughly the same size as 1515, and it’s just now coming into view. Most everything I said below about the sunspot group is correct, except it’s about 1515 and not 1520! I’ve corrected the details below. Sorry about the confusion, and thanks to zAmboni in the comments for pointing this out!]

The Sun is at it again: Active Region 1520, a vast sunspot group, is currently blemishing the Sun’s face. Active Region 1515, a vast sunspot group, has been blemishing the Sun’s face for days, and is being joined by Active region 1520, another huge group just now coming around the Sun’s edge.

This Solar Dynamics Observatory image shows AR 1515 on the lower right and AR 1520 on the lower left. A quick measurement shows both are about 200,000 kilometers (120,000 miles) across – fifteen times the width of the Earth! If one end were placed on Earth, it would stretch halfway to the Moon.

Having a hard time grasping that? Let me help: here’s the sunspot cluster AR 1515 zoomed in a bit, with the Earth overlaid pretty much to the same scale:

Holy. Crap. The Sun never does anything small, does it?

In fact, this cluster is so flippin’ big you can see it without a telescope! I just went outside and looked using certified eclipse glasses I got for the last solar eclipse. The sunspot cluster was obvious to my naked eye! It’s even easier to see than Venus was during the transit in June.

[WARNING: Listen folks, never look at the Sun without adequate protection. While looking at the Sun won’t necessarily cause permanent or total blindness, it’s not a good idea, and you should NEVER look at the Sun through binoculars or a telescope unless they are outfitted properly. If you don’t know what you’re doing with astronomical equipment, the best bet is don’t do it. If you don’t have eclipse glasses or the right kind of filter, I suggest using binoculars to project the Sun’s image on a piece of paper (noting this can still damage your binoculars). I have notes on viewing something like this safely on my Transit of Venus page. Read that first before trying anything!]

This cluster should be visible over the next ten days or so as the Sun rotates. While AR 1515 will rotate around to the Sun’s far side in a few days, AR 1520 is coming into view now and will be visible for about two weeks. The magnetic field associated with them will be huge as well, so it wouldn’t surprise me if we get some activity in the form of flares from these guys, too. Since I’ll be at Comic Con for several days starting Thursday, I suggest checking SpaceWeather and Universe Today for updates on any solar activity this cluster might unleash. Maybe we’ll get more aurorae!

Images via and NASA/SDO. Tip o’ the welder’s goggles to Sky and Telescope.

Related Posts:

HUGE sunspots turning toward Earth
First earthward-heading solar flare of the cycle
What a dramatic sunspot!
The birth of a sunspot cluster

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: AR1520, Sun, sunspot

Comments (15)

  1. Cindy

    I’ll run over to my classroom and grab the solar filter! Thanks for the heads up!

    I hope it’s easier to see than the transit of Venus as I had mostly cloudy skies and passing showers. I think I briefly saw Venus through the filter.

  2. Um……Phil.

    I think you have the wrong pictures posted there. That looks to be AR1515 you are showing (a picture from last week). In the picture above, AR1520 is just coming into view in the lower left.

    I was out on Sunday capturing an ISS transit, and was lucky enough to capture the ISS right next to AR1520

    Here is a stack of 25 images and sharpened up a little to show the sunspots in a little more detail (bout the best I can get with my 6″ scope).

  3. KC

    I saw it yesterday…over the next couple of days as it gets away from the limb, its going to look even more prominent.

  4. Arek W.

    “The Sun never does anything small, does it?”

    Yes it does. Neutrinos ūüėõ

  5. Nathan has a good scoop as always too.

    Geez, it almost looks like AR1520 is even larger than 1515.

  6. Matt B.

    Well, now that I have my eclipse shades (they arrived 5 days too late for the T/V), I’ll try to remember to take a look when I get home.

    The great thing about the first picture is that the sun is close to 100 mm wide, so the Earth would be about 1 mm.

  7. MarkV2

    The best solar activity aggregation site I’ve found is it’s pretty awesome. BTW I’m not connected to the site or the site’s owner/operator, other than that I’m also a HAM.

  8. DS1000

    Just to further the eye safety topic, I was taking photos of the Venus transit AT SUNSET and the vision in my left eye is still not quite back to normal.

  9. jearley

    I saw this group on this morning, and grabbed a left over eclipse viewer eye shade and went out to look. The group is just barely naked eye. If I had not known that it was there, I would have missed it.

  10. Daniel J. Andrews

    Saw a note from 3D Sun app about it this a.m. It’s a pretty good app. Except I just tried to open it now and it crashed. Twice. Reboot time. Maybe even delete and reload time. First problem it’s given me in two months though so still recommended for solar watchers.

    Edit: okay, maybe withdraw some of that recommendation. Neither reboot nor delete and install worked and it still crashes now.

  11. Chris

    Listen folks, never look at the Sun without adequate protection.

    I went to my pharmacist and said I need protection. I have no idea how those things are supposed to protect my eyes. Going to need some diagrams.

  12. mike

    I noticed it by chance this morning using viewing glasses that were made redundant during the transit due to inclement weather. Just wondering how big would Venus’s silhouette have been compared to this?

  13. JR

    Safest way I know of oberving the sun:


Discover's Newsletter

Sign up to get the latest science news delivered weekly right to your inbox!


See More

Collapse bottom bar