Around 04:00 UTC on Monday morning, January 23, 2012, the Sun let loose a pretty big flare and coronal mass ejection. Although there have been bigger events in recent months, this one happened to line up in such a way that the blast of subatomic particles unleashed headed straight for Earth. It’s causing what may be the biggest space weather event in the past several years for Earth: people at high latitudes can expect lots of bright and beautiful aurorae.

I’ll explain what all that is in a second, but first here’s a video of what this looked like from NASA’s SOHO satellite.

Wow! Make sure you set it to high def.

So what happened here? The sunspot cluster called Active Region 11402 happened.

Sunspots are regions where the magnetic field lines of the Sun get tangled up. A vast amount of energy is stored in these lines, and if they get squeezed too much, they can release that energy all at once. When this happens, we call it a solar flare, and it can be mind-numbing: yesterday’s flare exploded with the energy of hundreds of millions of nuclear bombs!

In the image above, the sunspots are caught in mid-flare, seen in the far ultraviolet by NASA’s Solar Dynamics Observatory (it’s colored green to make it easier to see what’s what). We think of sunspots as being dark (see the image of AR 11402 below), but that’s only in visible light, the kind we see. In more energetic ultraviolet light, they are brilliant bright due to their magnetic activity.

A huge blast of subatomic particles was accelerated by the explosion. The first wave arrived within a few of hours of the light itself… meaning they were traveling at a significant fraction of the speed of light!

But shortly after the flare there was a coronal mass ejection: a larger scale but somewhat less intense event. This also launches particles into space, and these are aimed right at us. The bulk of the particles are traveling at slower speeds — a mere 2200 km/sec, or 5 million miles per hour — and is expected to hit us at 14:00 UTC Tuesday morning or so. That’s basically now as I write this! Those particles interact with Earth’s magnetic field in a complicated process that sends them sleeting down into our atmosphere. We’re in no real danger from this, but the particles can strip the electrons off of atoms high in the air, and when the electrons recombine the atoms glow excite the electrons in atoms high in the air, and when the electrons give up that energy the atoms glow. That’s what causes the aurorae — the northern and southern lights.

If you live in high latitudes you might be able to see quite the display when it’s dark — people in eastern Europe and Asia are favored for this, since this happens after sunset there. But the storm is big enough and will probably last long enough that everyone should check after dark: look north if you live in the northern hemisphere and south if you’re south of the Equator. There’s no way in advance to know just how big this will be; it might fizzle, or it might be possible to see it farther away from the poles than usual. Can’t hurt to look! Also, Universe Today has been collecting pictures of aurorae from the solar blast earlier this week. No doubt they’ll have more from this one as well.

Although big, this flare was classified by NASA as being about M9 class — powerful, but not as energetic as an X class flare. One of those popped off last September, and shortly after that a smaller M flare erupted, which also triggered a gorgeous plasma fountain called a filament on the Sun’s surface.

As I said, we’re in no real danger here on Earth, and Universe Today has a good article describing why the astronauts are probably not in danger on the space station, either. Even if this were larger storm, the astronauts can take shelter in more well-protected parts of the station, too. Bigger storms can hurt us even on Earth by inducing huge currents in power lines which can overload the grid. That does happen — it happened in Quebec in March of 1989 — and it may very well happen again as the Sun gets more active over the next few years. [UPDATE: a ground current surge from today's event was reported in Norway.]

But we should be OK from this one. If you can, get outside and look for the aurorae! I’ve never seen a good one, and I’m still hoping this solar cycle will let me see my first.

Image credit: NASA/SOHO; NASA/SDO

In July of last year, I wrote about a comet that passed extremely close to the Sun. Astronomers have now had a chance to pore over that data, and were able to determine some very cool stuff.

First, here’s the video of the comet’s fiery demise (watch it in HD to make it easier to spot the comet):

See it? It’s faint, but there. Actually, there are a lot of observations from multiple observatories and detectors, which allowed astronomers to find out quite a bit about this doomed chunk of ice and rock.

For one thing, it was screaming along at about 650 kilometers per second (400 miles/second) as it flamed out. To give you an idea of how flippin’ fast that is, it would’ve crossed the entire United States in about eight seconds.

Yeah, I know.

It also passed an incredible 100,000 km (62,000 miles) above the Sun’s surface. Have you ever stood outside on a hot day, and thought the Sun would cook you? Now imagine the Sun filling half the sky. That’s what that comet saw. No wonder it disintegrated.

As it approached the Sun, it was watched by NASA’s Solar Dynamics Observatory. In its final 20 minutes or so, the comet broke up into a dozen pieces ranging from 10 – 50 meters in size (and no doubt countless smaller ones too small to detect), with a tail of vaporized material streaming behind it that went for thousands of kilometers. For that size, it would’ve had a mass of hundreds of thousands of tons — about what a loaded oil tanker weighs on Earth!

We’ve learned a lot about how comets break up and disintegrate by observing this event, but it’s raised further questions: like, why did we see this at all? Comets are faint, and to be able to see it this way against the bright Sun is odd. It was definitely one of the brightest comets seen, but it’s interesting to me that it appears to glow in the ultraviolet, as it did in the above video. That means, at that wavelength, it was brighter than the Sun! It wasn’t like a meteor, burning up as it slammed through material, so some other process must have affected it. I suspect that the Sun’s strong magnetic field may have had something to do with it; in the far ultraviolet magnetism is a strong player. Gas under the influence of intense magnetic fields can store a lot of energy, which is why sunspots — themselves the product of magnetic squeezing — look bright in UV.

Perhaps as the comet broke up, the particles inside got excited by the magnetic fields of the Sun and glowed. I’m no expert, and I’m spitballing here. The thing is, no one is exactly sure. But that doesn’t mean we won’t find out. Nothing makes a scientist’s noggin itch as much as a mystery like this, something apparently misbehaving.

One of the single most important words in science is "yet". We don’t know yet. But we will. Someone’ll figure this out, and we’ll have one more victory in our quest to better understand the Universe.

Science! I love this stuff.

Credits: Credit: NASA/SDO; SOHO (ESA & NASA)

I know I post a lot of pictures I describe as amazing, lovely, breath-taking, jaw-dropping… but that’s only because it’s always true. In this case, though, I think those adjectives fall way, way short in describing the seriously paralyzing beauty of this photograph: Comet Lovejoy, as seen by an astronaut on board the International Space Station:

[Click to encomanate -- and yes. you need to.]

Oh. My.

This stunning photo was taken by astronaut Dan Burbank as the ISS passed over Australia at 17:40 GMT on December 21, 2011 [update: more pix here]. It was early morning over Australia at the time, and you can see the dark limb of the Earth, the thin green line of airglow (atoms in the upper atmosphere slowly releasing the energy they accumulated over the day), some southern hemisphere stars… and of course, the incredible, ethereal, other-worldly beauty of Comet Lovejoy, its tails sweeping majestically into the sky.

Wait, what? "Tails", plural? Yup. Hang on a sec. I’ll get to that.

First, the comet was discovered by amateur astronomer Terry Lovejoy in November. It turned out to be a sungrazer, a comet whose orbit plunges it deep into the inner solar system and very close to the Sun’s surface. It screamed past our star last week, on December 15/16, and, amazingly, survived the encounter. Some sungrazers do and some don’t, but Lovejoy is bigger than usual for such a comet, and that may have helped it remain intact as it passed less than 200,000 km over the Sun’s inferno-like surface.

Now the comet is moving back out, away from the Sun and back to the frozen depths of deep space. But the Sun’s heat, even from its greater distance now, is not to be denied. Comets are composed of rock and ice — the ice being what we normally think of as liquid or gas, like ammonia, carbon dioxide, and even good ol’ water. The heat from the Sun turns that ice directly into a gas (in a process called sublimation), which expands around the solid nucleus of the comet, forming what’s called the coma. Pressure from sunlight as well as the solar wind blows this material away from the comet head, resulting in the lovely tail, which can sweep back for millions of kilometers.
(more…)

Comet Lovejoy was only discovered in late November, but it’s had quite a ride. It was quickly determined to be a Sun-grazer, the kind of comet that plunges down very close to the Sun in its orbit. The date of this solar close encounter: yesterday!

That’s a shot of it using SOHO, a solar observatory orbiting the Sun. The Sun itself is blocked by a mask, and the white circle represents its outline. The comet is obvious enough! The line through the top of it is not real; that’s called blooming and it happens sometimes when a bright object is seen by a digital detector. The electrons in the chip overflow the pixels and leak into adjacent ones. The comet got very bright as it neared the Sun, almost as bright as Venus! This picture, taken on December 15th at 22:36 UT, was shortly before closest approach: a mere 180,000 km (110,000 miles) from the Sun’s searing surface.

Amazingly, after the comet screamed past the Sun, and to the surprise of many, it survived. A lot of comets don’t make it through such an event, but this one did. Here’s a video of the comet reappearing from behind the Sun, as seen by SDO; watch closely or you’ll miss it!

Nifty. But on the way down it had several interesting things happen to it. (more…)

On October 1, a bright comet screamed into the Sun, and apparently disintegrated. This happens pretty often, actually, but in this case, just minutes later, the Sun blew out a pretty hefty coronal mass ejection, a huge explosion of magnetic energy that can release billions of tons of material.

Some people have speculated that these two things are related (including times when this has happened in the past). Are they? We have videos of the event from three different satellites, giving us three angles on what happened, providing clues on what really occurred.

To shed some light on this — haha — I made a short video explaining this, including the footage of the comet collision and CME as seen by the three satellites:

[It helps to set the video resolution to 720p to see the details in the satellite views.]

So my guess is that while it’s possible, it’s not probable. CMEs happen all the time, so I’d expect a few to happen around the same time as comets flying past the Sun just by coincidence. We don’t have any physical reason to think they’re related, and when they are examined more closely, the CMEs usually don’t come from a spot near the Sun where the comet traveled. Still, it’s worth looking into, at least to build up a statistical case on way or the other.

The folks at SOHO — the Solar Heliospheric Observatory — have a post up with more info. Also, if you want to see the three satellite videos on their own, here is the SOHO video
the STEREO A video, and the STEREO B video.

Very special thanks to SungrazerComets on Twitter for making the three original satellite animations. That’s a good stream to follow if you want the latest on comets making death dives onto our star. [UPDATE: @SungrazerComets just posted an excellent and thorough article about this topic, too!]

Image credits: NASA, SOHO, STEREO

Today, June 21, 2001, at 17:16 UTC (1:16 p.m. Eastern US time), the Sun will reach its peak in its northward travels this year. This moment is the summer solstice — I describe this in detail in an earlier post. Technically, that article is for the winter solstice, but the idea’s the same. Just replace "winter" with "summer" and "December" with "June" and "south" with "north". That should be clear enough. It might be easier just to multiply the entire article by -1. Or stand on your head.

Since for the majority of people on the planet this day marks the start (or more commonly the midpoint) of summer, enjoy the gallery below that shows our nearest star doing what it does best: giving us light, giving us beauty, and sometimes, blowing its top.

Use the thumbnails and arrows to browse, and click on the images to go through to blog posts with more details and descriptions.

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Last month, on May 10/11, a bright comet took the Final Plunge, dropping into the Sun. It either broke up and evaporated or actually impacted the Sun, because it wasn’t seen to reappear around the other side. Here’s the video, taken using NASA’s SOHO satellite:

Pretty cool! You can see the Sun erupting with a coronal mass ejection, too. It’s tempting to wonder if the two are related, but in fact the CME let go before the comet had even had a chance to interact with the Sun’s magnetic field (CMEs are essentially magnetic events). I know there are tracts floating around the ‘net about comets causing solar events, but the folks promulgating such ideas never do any actual statistics. They see a comet plunge into the Sun, see a flare or CME, and say they’re related. However, you have to look at how many events happen without comets nearby, and more importantly how many comets hit the Sun and don’t spark an event. Without that, you’re just cherry-picking.

Incidentally, you may have noticed a very short horizontal line going right through the heart of the comet. That’s not real; it’s an artifact of the detector on SOHO. It’s called blooming, and it has nothing to do with Planet X unless you’re willing to turn your back firmly on reality.

Anyway, comets hit the Sun quite often; many have similar orbits and are called Kreutz family comets. It’s funny: many of them get bright enough to technically be seen by the eye, but they’re so close to the Sun they still get washed out.

Actually, now that I think about it, I should mention that SOHO is the greatest comet finder of all time; over 2000 comets have been seen in SOHO images! It seems funny to look to the Sun to find comets, but it’s also amazing to me to think that those 2000 comets have been seen in only 16 years since SOHO’s launch… think about how many comets are out there, in deep space. Millions. Billions. More.

We live in an amazing place, and in an amazing time that we can discover so much about it.

Science! I love this stuff.

Credit: NASA/SOHO