On November 15, the Sun had a minor eruption on its surface that launched a prominence — a towering arc of ionized gas — into space. Sometimes these prominences collapse back down to the surface, and sometimes they wind up ejecting that material into space. This one did a little of both:

The animation was made from images taken over the course of 13 hours by the Solar Dynamics Observatory. The images are false-color; what you see as orange is really ultraviolet light, where the energized gas glows brilliantly. This particular event sent some gas more or less toward Venus, where probably not much will happen. This isn’t like a major flare or coronal mass ejection… but it’s still cool.

Prominences occur all the time (click the picture here to see a gorgeous one from last year), and generally don’t wind up affecting us here on Earth. Still, it’s fascinating to watch the gas — which is hot enough to have its electrons stripped off its atoms, so it follows the Sun’s magnetic field as strongly or even more strongly than it does the Sun’s gravitational field — writhe and seethe under these tremendous forces.

Credit: NASA/GSFC/SDO

Take a look at the image displayed here [click to redshiftenate]. Every object you see there is a galaxy, a collection of billions of stars. See that one smack dab in the middle, the little red dot? The light we see from that galaxy traveled for 12.9 billion years before reaching the ESO’s Very Large Telescope in Chile. And when astronomers analyzed the light from it, and from a handful of other, similarly distant galaxies, they were able to pin down the timing of a pivotal event in the early Universe: when the cosmic fog cleared, and the Universe became transparent.

This event is called reionization, when radiation pouring out of very young galaxies flooded the Universe and stripped electrons off of their parent hydrogen atoms. An atom like this is said to be ionized. Before this time, the hydrogen gas was neutral: every proton had an electron around it. After this: zap. Ionized. This moment for the Universe was important because it changed how light flowed through space, which affects how we see it. The critical finding here is that reionization happened about 13 billion years ago, and took less time than previously thought, about 200 million years. Not only that, the culprit behind reionization may have been found: massive stars.

OK, those are the bullet points. Now let me explain in a little more detail.

Young, hot, dense, and chaotic

Imagine the Universe as it was 13.7 billion years ago. A thick, dense soup of matter permeates space, formed in the first three minutes after the Big Bang. The Universe was expanding, too, and cooling: as it got bigger, it got less dense, so the temperature dropped. During this time, electrons and protons were whizzing around on their own. Any time an electron would try to bond with a proton to form a neutral hydrogen atom, a high-energy photon (a particle of light) would come along and knock it loose again.

During this period, the Universe was opaque. Electrons are really good at absorbing photons, so light wouldn’t get far before being sucked up by an electron. But over time, things changed. All those photons lost energy as things cooled. Eventually, they didn’t have enough energy to prevent electrons combining with protons, so once an electron got together with a proton they stuck together. Neutral hydrogen became stable. This happened all over the Universe pretty much at the same time, and is called recombination. It occurred about 376,000 years after the Big Bang.

(more…)

450 million light years away are two interacting galaxies. Both spirals, they are caught in each other’s gravitational claws. Already distorted and bound, eventually, to merge into one larger galaxy in a few million years, the view we have of them from Earth is both amazing and lovely… and hey: they’re punctuating their own predicament!

[Click to exclamatenate.]

Looking a lot like an exclamation point, the two galaxies together are called Arp 302 (or VV 340). This image is a combination of pictures from the Chandra X-Ray Observatory (purple) and Hubble (red, green, and blue). The bottom galaxy is a face-on spiral, while the upper one is seen more edge-on, giving the pair their typographical appearance.

(more…)

Scott Wiessinger produces video for NASA’s Goddard Space Flight Center — my old stomping ground, and I did some work with the video folks while I was there, too — and he sent me links to two very cool videos he put together recently.

In early June the Sun erupted, letting loose a huge plume of plasma from its surface which then fell back down along magnetic field lines in a display the likes of which I had never seen before. I created a video (at the link above) which was far and away the most popular I’ve ever done, garnering nearly 1.5 million views as I write this.

But Scott’s video of the event is much, much cooler:

[Don't forget to set the resolution as high as possible!]

Breathtaking, isn’t it? The video is greatly sped up; the whole event took many hours to complete. All the different animations were taken in the ultraviolet, where the highly-energetic plasma erupting from the Sun emits strongly. You can really see that the plasma does not fall along ballistic trajectories (the usual arcs due to gravity) but instead moves along the magnetic field lines, sometimes twisting around in non-intuitive ways. Beautiful, graceful, and stunning.

And I love the music^*.

The second video is from a camera mounted on a sounding rocket, a rocket that goes essentially straight up and back down. At its highest point it goes up nearly 300 km (180 miles), well into space. It was carrying an instrument to observe the Sun in the ultraviolet.

(more…)

I recently wrote about a mind-boggling event: astronomers capturing what are apparently the final moments in a star’s life as it was literally torn apart by a black hole.

Today, NASA has released some new pictures of the event, including this Hubble Space Telescope shot:

[Click to embiggen.]

I know, it may not look like much at first. But remember what you’re seeing: the violent death of a star ripped apart by the gravity of a black hole… and it’s happening 3.8 billion light years away! That’s about 40,000,000,000,000,000,000,000 kilometers, so the fact that we can see it at all is pretty amazing. And terrifying.

In this false-color Hubble image, the galaxy and explosion are marked. Pretty much everything you see in the picture is a distant galaxy, a billion of more light years away. Normally, the host galaxy itself would appear as a dot, at best with some small amount of fuzz around it, the glow of billions of stars reduced by the incredible distance. But the dying light of the star increased the galaxy’s brightness by a lot. A whole lot.

This image (click to greatly embiggen!) is a combination of visible light (white), ultraviolet (purple), and X-rays (yellow and red) from NASA’s Swift observatory, the satellite that first detected the explosion. While the spikes are not real — they’re just an optical effect from the telescope itself — it still speaks to the drama of what we’re seeing.

And so just what are we seeing?
(more…)

The Sun is getting back into the swing of things: a big active region on its limb erupted yesterday (October 10), sending out a small storm of subatomic particles into space. We weren’t in the line of fire, but over the next few days the rotation of the Sun will bring Active Region 11112 closer to the center of the Sun’s disk, and if that region erupts it may send a storm our way.

Here’s a recent image of the Sun from the Solar Dynamics Observatory:

This shows the Sun in ultraviolet (where activity can manifest itself) from around 23:00 UT (19:00 Eastern US time) on October 11. The active region is pretty obvious there to the lower left.

A magnetogram, which shows magnetic activity, makes the region obvious as well. A recent one (shown here on the left) from around the same time as the image above again shows the active region has a lot of magnetic activity going on.

The Sun’s magnetic field lines can contain a huge amount of energy. As the gas in the Sun roils and swirls, the field lines get tangled together. If they connect, bang! They can explode, sending that energy out into space. (more…)

NASA’s Swift satellite is a modern success story: designed to peer at the Universe in ultraviolet, X-rays, and gamma rays, it is on constant lookout for gamma-ray bursts, explosions so vast they are second only to the Big Bang itself.

Swift scans the skies, constantly observing, always on its toes for that fleeting blast of high-energy light. But it also does other science as well; an orbiting camera like that has many uses. For three months in 2008, astronomers used Swift to target the nearest major spiral galaxy like our own: M31, the Andromeda Galaxy. And what they got was this gorgeous picture:

Wow. You absolutely want to click that to embiggen it most cromulently — you’ll get a whopping 4400 x 200 pixel version.

This image is incredible, both scientifically and logistically. It is the combination of 330 images, totaling 24 hours of solid observations, and amounted to a hefty 85 gigabytes of data. It covers three UV wavelengths: 192.8, 224.6, and 260 nanometers, which are just outside the range the human eye can see.

The image is huge; the full Moon would just fit over the apparent size of the central bulge of the galaxy. Over 20,000 individual sources of ultraviolet light can be found. Some science can be seen just with just a glance: for example, the light coming from the spiral arms is clumpy, and from the bulge it’s smooth. The arms are where you find patches of giant gas clouds forming newly born stars; the most massive of these blast out UV light and fierce winds which make the clouds themselves glow in UV.

But the bulge at the core is smooth, because stars there are old; star formation long ago ceased in the galactic center. The UV glow is mostly from tightly packed stars, not from gas. There are so many stars that the individual sources blend together into what looks like a continuous glow (not unlike a digital image itself, where individual pixels blend together to make what looks like a smooth picture).

This image is the most detailed ever taken of our big neighbor in the ultraviolet, and I have no doubt it will be used as an atlas for higher-resolution cameras aboard Hubble and future spacecraft. Pictures like this are scientifically incredibly useful; they are roadmaps we can use to plan out our travels ahead.

And they are also just very, very cool.

Image credit: NASA/Swift/Stefan Immler (GSFC) and Erin Grand (UMCP)