Tag: filament

Purple shag Sun

By Phil Plait | November 1, 2012 10:05 am

The great astrophotographer Andre van der Hoeven sent me a shot he took of the Sun a few days ago. Looks like either Barney or the Grape Nehi folks paid it a visit:

[Click to envioletenate.]

Pretty cool. First, of course, the purple color is not real. It’s just the color Andre chose for this picture when he processed it. Second, he used an Hα filter, which lets through a very narrow slice of light (actually in the red part of the spectrum). This color is emitted by warm hydrogen, and is preferentially under the influence of the Sun’s magnetism. You can see arching prominences – huge towers of gas – off the edge of the Sun. The long stringy bits on the face of the Sun are called filaments, and are actually the exact same thing as prominences! Prominences are filaments we see from the side, instead of looking down on them. The terminology is a holdover from when astronomers first started observing the Sun, and we’re kinda stuck with it.

Also, Andre inverted the picture, so what looks black is actually very bright, and what looks bright is very dark. Those bright white blotches? Sunspots. For some reason, our brains can pick out detail better that way, and it also gives an eerie 3D sense to the image. He made a close-up mosaic of his pictures, too, which is actually a bit creepy. It’ll keep the Halloween spirit going for another day, at least!

Image credit: Andre van der Hoeven, used by permission.

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CATEGORIZED UNDER: Astronomy, Pretty pictures

A HUGE solar filament erupts into space

By Phil Plait | September 10, 2012 11:45 am

On August 31, the Sun threw a major tantrum. It started with a vast arc of material towering over its surface, a stream of plasma flowing between two sunspots. Sometimes these collapse back down to the Sun’s surface, but this one exploded, blasting hundreds of millions of tons of material out into space.

SDO captured this ridiculously awesome picture of the arc just before it erupted:

Holy solar hissy fit! [Click to enfilamentenate.]

This picture is a combination of two images, both in the extreme ultraviolet part of the spectrum (30.4 and 17.1 nanometers, to be specific), where magnetic activity is easy to spot. The bright spot to the upper left is a sunspot, which are normally dark in optical light, but shine brightly in the UV. The filament, as the arch is called, is so big it’s hard to comprehend: it was something like 300,000 kilometers (nearly 200,000 miles) across! That’s nearly enough to extend from the Earth to the Moon.

Having a hard time picturing that? Yeah, me too. Happily, NASA provided an image with the Earth for comparison. Yegads. And there are more images of the event on the NASA/Goddard Flickr page.

Stephen Ramsden is an astronomer who runs the Charlie Bates Solar Astronomy Project, and he saw it while at Dragon*Con! I was at D*C but totally missed this, but he got a very cool picture too. As you can see in this picture, it was erupting when he caught it. I’m kicking myself to have missed the solar observing at the con, and next year I’ll be sure to take a look. I’d hate to miss something like this again!

For his non-profit Charlie Bates Solar Astronomy Project, Stephen takes solar telescopes across his region and uses them to teach people (including kids!) about the Sun and its effect on us. I’ll note he accepts donations to help him do this. Hint hint.

Finally, I’ll add that this amazing solar eruption traveled outward at about 1500 kilometers per second (900 miles/second) and nicked the Earth’s magnetic field on September 3, sparking aurorae in extreme latitudes. This had little real impact on us, but I gently remind you the Sun is still not at its peak. It’ll reach the max of its cycle next year sometime, and the biggest flares and other storms tend to happen a few months after the peak. It’s hard to say if this will do any damage – loss of satellites and power blackouts are possible, though no direct harm to humans on Earth can happen – but we’ll see. The most likely outcome is aurorae, so keep your browser tuned to the NOAA Space Weather Prediction Center and SpaceWeather. If we do get aurorae, those are great places to let you know.

Images credit: NASA/GSFC/SDO; Stephen Ramsden

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CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures
MORE ABOUT: filament, SDO, solar storm, Sun

Awesomely blemished inverted solar beauty

By Phil Plait | September 2, 2012 7:01 am

Alan Friedman’s photos are no stranger to this blog; I’ve posted a lot of his amazing pictures of the Sun (See Related Posts, below). So many, in fact, that one needs to be surpassingly cool to add to the lineup.

So, yeah:

[Click to ensolarnate.]

Yegads. He took this on July 29, 2012. Because the image is inverted – dark things appear bright, and vice-versa – sunspots are intense white patches, bright plages appear dark, and towering filaments are whitish-gray.

Note how the Sun’s face gets darker toward the center and brighter toward the edge – meaning in reality the center is bright and the edge dimmer. This is called limb-darkening (the opposite of limb-brightening seen in some gas clouds), and occurs because gas around the Sun absorbs its light. We look through more of it near the edge than toward the center, so there’s less light coming from the limb of the Sun.

I’ll note that only the face of the Sun is inverted, though. Everything outside that is normal, so the leaping prominences of gas on the edge are bright, as they should be. That might be a bit confusing, but it does make for a dramatic picture.

And given how volatile our local star, you don’t have to go very far to get drama out of it.

Image credit: Alan Friedman

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Desktop Project Part 21: Dancing in the dark filaments

By Phil Plait | April 15, 2012 7:00 am

[My Desktop Project — clearing off the cool astropix from my computer’s desktop by posting one each day — is getting close to being done soon; I’m down to my last few pictures!]

It’s funny how different the Sun looks at different wavelengths of light. In visible light, you can see all sorts of surface features like sunspots, granules (rising and falling packets of gas convecting like a pot of water on a stovetop), and more.

But when you have eyes sensitive to the ultraviolet, the Sun takes on an entirely new appearance. That’s where the effects of the Sun’s active and crazy magnetic field claim dominion, and you see vast arcs, loops, and towers of incredibly hot plasma. To be fair, you can see this in visible light too, but it’s not quite so… dynamic. Cue NASA’s Solar Dynamics Observatory, and its UV detectors:

This image was taken by SDO on March 28, 2012, and shows the limb of the Sun at a wavelength of 19.3 nanometers — well into the UV. What you’re seeing is plasma — gas so energetic it’s had electrons ripped right off its atoms, putting it under the sway of the Sun’s fierce magnetism. The plasma flows along the magnetic field lines, arcing high off the surface into space before coming back down.

Usually, those arcs are hot and bright, like the tight loops you can see on the left (within hours, those loops got bigger and brighter, making dozens of well-defined glowing coils). But you can also see a dark arc in the center, going from just below the center of this picture, curving to the upper left, then heading up and over to the right, off the face of the Sun. For some reason, the plasma there wasn’t quite as hot, and so instead of glowing at this wavelength it appears dark, absorbing the light from material behind it.

I took this shot using Helioviewer.org — if you click the picture it will take you there. You can then play with the controls on the left and watch this dark filament change, grow, dance, and playfully flow from one arc base to the other. It’s mesmerizing. SDO has a page with some pre-made animations, too.

I love how we see the Sun pretty much every day, but in many ways it is as unfamiliar as any distant star. Happily, though, our drive to explore and understand has led us to the point where we can investigate our nearest star, and learn more about it. Given that it’s the main driver of life on Earth, this is probably a smart idea.

Image credit: NASA/SDO/Helioviewer.org

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Desktop Project Part 8: From filament to prominence

By Phil Plait | April 2, 2012 7:00 am

[Over the past few weeks, I’ve collected a metric ton of cool pictures to post, but somehow have never gotten around to actually posting them. Sometimes I was too busy, sometimes too lazy, sometimes they just fell by the wayside… but I decided my computer’s desktop was getting cluttered, and I’ll never clean it up without some sort of incentive. I’ve therefore made a pact with myself to post one of the pictures with an abbreviated description every day until they’re gone, thus cleaning up my desktop, showing you neat and/or beautiful pictures, and making me feel better about my work habits. Enjoy.]

Sometimes, what you see depends on how you see it.

For example, take the Sun. Imagine it as a ball of ionized gas 1.4 million kilometers in diameter, churning and roiling, with intense magnetic fields piercing its surface and causing vast eruptions of material 150,000 km across.

OK, you don’t have to imagine that, since a) that’s the way the Sun really is, and 2) I can show you a picture of it! Like this one, from astrophotographer Ted Wolfe:

That shows the Sun as it was on November 25, 2011. That towering arc is plasma — gas that has had one or more electrons stripped from its atoms — being guided by the crazy strong and complex magnetic fields looping into and out of the Sun’s surface. This picture is interesting, since this loop of plasma is nearly aligned with our line-of-sight. One foot of it is on the near side of the Sun, and it arcs over across the Sun’s limb to the other side!

What’s funny is that when you get one of these on the face of the Sun it’s called a filament. When it’s seen projected against the black of space, it’s called a prominence. This terminology is a holdover from a long time ago, but we still use it. To be fair, the terminology comes up because usually filaments look very different than prominences. If you use a regular filter (one that just blocks light) to take pictures of the Sun, filaments look dark; they are cooler than the Sun’s surface and absorb the light from coming up from beneath (much like sunspots). But they’re still plenty hot, and look bright when seen against the black of space. You can see examples of this here and here.

This picture from Ted Wolfe is different. He used a special Hα filter, which doesn’t just darken the Sun but picks out a very specific color of light (in the red part of the spectrum) and isolates that, letting it through while blocking everything else. Warm hydrogen (like in the filament) emits that color, so if you use that filter the loop of plasma looks pretty much the same against the Sun as it does against the sky. It’s a bit of a trick, but is useful in showing that filaments and prominences are just two different views of the same structure.

So what do we call this thing in Ted’s picture? We see it against the Sun and against space! A filanence? A prominent? Beats me. But it’s pretty cool either way.

Credits: Tom Wolfe, used by permission.

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MORE ABOUT: filament, prominence, Sun

The Sun roils over Mexico

By Phil Plait | August 23, 2011 6:00 am

Yesterday, "amateur" astronomer César Cantú took an amazing mosaic image of the Sun, showing our star boiling and writhing under its own dynamic forces:

[Click to unGdwarfenate.]

That hardly looks like the Sun, does it? That’s because he used a filter that blocks all the light we see except for a very narrow slice of color in the red part of the spectrum. That filter lets through only light from warm hydrogen, at just the right temperature to allow the electrons in the hydrogen atoms to drop from the third energy level to the second. You can picture the electron in an atom like it’s on a staircase, and only allowed (by quantum mechanics) to sit on a step, or move from one to the other. It takes energy to move it up a step, and gives off energy when it moves down. When it jumps down from the third to the second, it emits a photon — a particle of light — at a wavelength of 656.3 nanometers, and astronomers call this light (H alpha).

The gas on the Sun’s surface emitting Hα is under furious stirring due to magnetic fields and other forces, and you can see that in the twisted, roiling appearance in this photo. I particularly like the dark arc just left of center: that’s a filament, an eruption of gas off the surface. It’s about 150,000 kilometers (90,000 miles) long! It’s a bit cooler than the surface material, so it’s darker, and we see it in silhouette. When those happen on the limb of the Sun they’re called prominences, and you can see several of those in this picture too.

Amazingly, this picture (which is really a mosaic of six separate shots) was taken using a telescope with only a 90 mm (3.5 inch) lens. The Coronado 90 mm telescope is a favorite of sidewalk astronomers, since it shows the Sun in amazing detail, but is totally safe to look through since it blocks almost all the Sun’s light. It’s common to see them at planetaria and museums, set up where passers-by can get a quick glimpse of the Sun. For most, it’s the first time they ever see the might and power of a star only 150 million kilometers away.

And if you want a sense of scale here, in the picture above the Sun is about 450 pixels across. On the same scale, our entire planet Earth would be only about 4 pixels across.

Just in case you were feeling big and important today.

Credit: Image used by permission of César Cantú.

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CATEGORIZED UNDER: Astronomy, Pretty pictures

SDO's first year in space with bonus voting

By Phil Plait | April 26, 2011 7:00 am

NASA’s phenomenal Solar Dynamics Observatory has spent just over a year in space. During that time it has ceaselessly observed the Sun, returning incredibly detailed and exquisite images and videos. In high resolution we’ve seen sunspots, flares, coronal mass ejections, filaments, prominences, and towering loops of magnetic plasma.

To celebrate, the folks at SDO put together this video featuring 12 of their favorite clips. I’ve written about several of these myself in the past year (see Related Posts below). Make sure you set the resolution to 720p!

You can go to the SDO page to get a list of what you’re seeing.

In a related bit of news, NASA is asking people to vote on their favorite short video from SDO. Many of those clips are also in the above video, but they’re also listed separately on the NASA contest page. I know which one is my favorite… but I’m not telling.

The voting closes May 5th.

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The Sun blasts out a flare and a huge filament

By Phil Plait | November 13, 2010 7:00 am

Never forget: the Sun is a star, a mighty ball of ionized gas, and when a star throws a tantrum, even a small one is epic.

And the Sun just sent us a little reminder: NASA’s Solar Dynamics Observatory caught this amazing sequence of a sunspot blasting out a flare, then shooting out a long streamer of plasma:

[Direct link to YouTube video here]

Wow! So what are we seeing here?

SDO views the Sun in many wavelengths, and in this case we’re looking at ultraviolet light form the Sun so energetic it’s almost X-rays. The bright spot is actually a sunspot! They’re dark in the kind of light we see with our eyes* but can be very bright at other wavelengths. Sunspots are regions of intense magnetic field concentration; magnetic loops arc out of the spot, reach into space, then head back down. They seethe with vast amounts of energy, which can be released explosively under some conditions.

That’s what happened here. Read More

The return of sunspots! Maybe!

By Phil Plait | December 16, 2009 10:42 am

After a very long absence, it looks like the Sun may finally be kick-starting its magnetic cycle. A big ol’ group of sunspots has just appeared on our nearest star:


A quick comparison to the Sun’s disk (done with Photoshop, so don’t quote me extensively!) indicates this group of spots is about 10 times the width of the Earth, making it decently hefty. It’s the biggest group we’ve seen since the solar minimum a couple of years ago.

The Sun’s face has been almost entirely devoid of spots for some time, and it’s been getting a little weird. There was some activity earlier this year, but it didn’t seem to be gaining any footing. And while this new group of spots doesn’t mean the new solar cycle has finally gotten started, it’s a good sign.

As a quick refresher: the Sun is a variable star. Its magnetic activity strengthens and weakens over a roughly 22 year cycle. It’s actually two 11 year cycles: the field rises in strength over 5 or so years, peaks, then dips back down over the next 5 or so years. When it begins to rise again, the polarity (north/south) is reversed. To be clear, it’s not the actual spin of the Sun that flips, just the magnetic field poles. Also, it’s not exactly 5.5 years every time; the length of the cycle itself can change a bit.

When the Sun’s magnetic field is at its strongest, we see lots of sunspots, which are areas on the surface of the Sun where the local magnetic field lines constrain the movement of the Sun’s gas. The gas cools and dims, looking dark against the hotter gas. Normally, convection (like boiling water) would drag the cooler material down into the Sun’s interior, but the magnetic field prevents that, so sunspots can persist for days or weeks.

Mind you, it’s all far more complicated than this, but hopefully this gives you the idea.

Right now we’re at the minimum of the Sun’s magnetic cycle, and normally we would have seen a rise in magnetic activity more than year ago. But for some unknown reason the Sun has been slow to return to its usual business. No one is really sure what would happen if the minimum were prolonged for years, though there is a weak tie between sunspot activity and the Earth’s temperature (and no, not enough to account for global climate change).

solarfilament_dec2009In the face of all these unknowns, I’ll be honest and say I’d like to see the Sun getting back on the stick and producing spots again! So this new grouping is a tentative relief. Hopefully we’ll be seeing more spots soon.

Also, I’ll note that this grouping comes just a few days after a nice filament erupted from the Sun, as seen here by the STEREO spacecraft.

You can monitor the Sun in real time by going to the SOHO spacecraft website, where they frequently update pictures from the solar observatory.

Image credits: STEREO, SOHO, NASA/ESA

CATEGORIZED UNDER: Astronomy, Pretty pictures

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