The solar storm that erupted from the Sun yesterday reached the Earth today at about 15:00 UTC (10:00 a.m. Eastern US time). The wave of subatomic particles has been impacting the Earth’s magnetic field, and we’re starting to see some auroral activity:

Isn’t that lovely? That was taken at 18:00 UTC today from a webcam in Abisko, Sweden. Can you see the handle of the Big Dipper right below the green curtain? [More aurora webcam sites are listed below.]

The two biggest questions I’m getting on Twitter and Google+ are 1) is there any danger to this storm, and b) can I see the aurora from [my location]?

First, no, we’re not in any danger from this event. Even though it sounds terrifying — an explosion the equivalent of billions of nuclear weapons launching hundreds of millions of tons of subatomic particles Earthward at speeds of million of kilometers per hour! — we’re pretty well protected down here on the surface. The Earth’s magnetic field catches the particles, and most of those get dumped harmlessly in our upper atmosphere. That can create the aurora displays, but won’t dose everyone with radiation and give them superpowers.

Sorry. [UPDATE (19:00 UTC): a ground current surge was reported in Sweden, but so far that's the only physical impact I've heard of.]

But the aurorae are pretty cool, and that brings us to the second question. The answer depends on where you are, and when it’s dark out. As I write this, activity is on the rise. Here are some live webcams for aurorae, some of which are showing spectacular activity! Note they only show views when it’s nighttime locally:

Lapland

Fairbanks, Alaska

Yellowknife, Canada

Tromso, Norway

As for seeing them wherever you are, that’s tough to say. The Geophysical Institute has a map showing predicted activity for North America, for example, and NOAA’s Space Weather Prediction Center has a continuously updated map showing auroral activity for both hemispheres. Universe Today has a guide on how to see the aurorae, and Astronomy magazine has a discussion of aurorae, too.

I’m getting conflicting info on potential aurorae tonight; the webcams in Scandinavia listed above are showing strong (and gorgeous) activity, but the prediction for Canada and the US appear moderate at best. But don’t let that discourage you! If you have clear skies, go outside once it’s good and dark and take a look. Even if there’s no aurora, you can see Venus and the thin crescent Moon to the west right after sunset, and that’s always a plus. And if things perk up, you might get a nice light show to the north, too!

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

Apparently I could do nothing but post incredible time lapse videos all the time. Watch this staggeringly beautiful video, "Yosemite", and be in awe.

[YES, make it full screen and HD!]

The video was made by Sheldon Neill and Colin Delehanty, and the music? "Outro", by a group called M83.

Ha! That’s the name of a spiral galaxy I’ve written about once or twice before. Even thrice. And it’s appropriate, given how prominently our own galaxy features in this video.

The shots of the park during the day aren’t too shabby, either.

I’ve lived out west for twelve years now, and I’ve never made it to Yosemite park. Maybe it’s time to change that.

Tip o’ the piton to Chris Perriman.

As a scientist, I can guarantee that the closest a solid object can be to a liquid state is a cat snoozing on a staircase in the sunshine.

If anyone tells you the Earth isn’t warming up…

… tell them they’re full of it.

2011 was the ninth hottest year on record, and those records go back 130 years.

And then they might say, well, sure, but that could be coincidence. Then you look them straight in the eye, and you say:

Nine of the ten hottest years on record have been since 2000.

The map above shows changes from average (where the average is from 1951 to 1980). You see clearly that temperatures over land have increased almost universally. Most of the ocean temperatures have gone up as well; the one big cooler region in the eastern Pacific is due to the La Niña last year, so it’s a temporary effect. Even with La Niña dropping temperatures, the overall effect is an increase in temperature. I’ll note that sunspot numbers were low last year as well, which (if anything) should result in a (very) slight cooling effect too.

Climate change deniers will gnash and froth — I expect the comments to this post to reflect that, as they always do — but the bottom line is this. The Earth is getting hotter. Human beings are at least partly to blame, and the evidence has piled up that we are mostly to blame. Not the Sun, not cosmic rays, not orbital oscillations. Humans.

As I’ve said before, here are the facts:

The Earth is warming up. The rate of warming has increased in the past century or so. This corresponds to the time of the Industrial Revolution, when we started dumping greenhouse gases into the atmosphere. Greenhouse gases warm the planet (hence the name) — if they didn’t we’d have an average temperature below the freezing point of water. Carbon dioxide is a greenhouse gas which is dumped into the atmosphere by humans to the tune of 30 billion tons per year, 100 times the amount from volcanoes. And finally, approximately 97% of climatologists who actually study climate agree that global warming is real, and caused by humans.

Given the vast amount of evidence supporting all this, denying it is fantasy. Again, that won’t stop deniers: they will obfuscate, blow smoke, and nitpick details to make them seem important. But what they’re doing is fiddling while Earth burns.

One of these things is not like the others:

The Cassini spacecraft took this lovely image in December 2011, during a close pass of Saturn’s moon Dione. Ignoring Saturn’s rings slashing through the picture, we see, from left to right, the moons Dione, Prometheus, and Epimetheus. Which is the odd moon out?

Here’s a hint: Dione is 1100 km (700 miles) across, Prometheus 86 km (53 miles) along its longest axis, and Epimetheus 113 km (70 miles). Got it now?

Yeah, sure, Dione is far larger than the other two! But that’s not my point: Dione is round, while the other, smaller moons are lumpy and rather potato-shaped. Why?

Size matters. In this case, a bigger moon means more mass, and that means more gravity. In general, the force of gravity points toward the center of an object. As you add more mass to an object, gravity gets stronger. On a small moon, a big lump of rock like a mountain feels very little force downward, while on a more massive moon the force would be larger. If the moon has enough mass, and enough gravity, the force will be more than the internal strength of the rock itself, and the mountain crumbles.

So moons that are big and massive enough will tend to flatten their surface, or, more accurately, shape them into spheres. Dione is big enough to do that. Prometheus and Epimetheus are not. Dione is a big ball, the other two are spuds.

Note that gravity’s not the only thing that can make objects spherical. Water has surface tension, for example, caused by the electrostatic attraction between water molecules. In space, without gravity, drops of water are spherical. Random processes can generate round objects too: I bet if we could get a super-duper close look at Saturn’s rings, we’d see the trillions of chunks of ice that make up the rings are round too. But that’s from collisions; there are enough of those bits of ice that they smack into each other. Since they spin and tumble, over time any part of a chunk will have gotten hit by some other chunk, and that will tend to make them round.

So how big does an object have to be before it starts to become round via gravity? That’s complicated, and depends on its composition — a ball of ice the same size as a ball of iron will have far less gravity since it’s so much less dense, and will have lower mass. But for a ball of ice and rock — like Dione — that size is clearly no bigger than 1100 km across. And if you’re wondering how this might play into our concept of what a planet is, then you might want to read this. I’m way ahead of you!

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)