STEREO catches an eruptive prominence

By Phil Plait | October 15, 2012 12:27 pm

Via Jenny Winder on Google+ I saw this way cool video of an eruptive prominence on the Sun: a towering arc of plasma held aloft by the Sun’s magnetic fields. Sometimes these field lines are unstable, and the plasma can blast away from the Sun and out into space:

This video was taken by one of NASA’s twin STEREO spacecraft; a pair of probes with one orbiting well ahead and the other behind the Earth. They stare at the Sun, literally giving us an angle on it we can’t get from our planet. Specifically this was from the STEREO Ahead spacecraft, and combines an ultraviolet view of the Sun itself together with a visible light portion that shows the Sun’s outer atmosphere, called the corona.

You can see the prominence form, rise up, and then erupt away into space over the course of one day, on October 6-7, 2012. Sometimes this material rains back down to the surface, and sometimes it escapes entirely. When it does the latter, it can flow outward, impact the Earth, and cause a geomagnetic storm. Usually those do us no harm, though if they get big they can disrupt satellites and potentially cause power outages. More likely they just create gorgeous aurorae which can be photographed from the ground.

It’s actually rather amazing how many space-based eyes we have on the Sun and the amount of data they send back. The Sun is a feisty beast, and getting feistier as we approach the maximum part of its magnetic cycle. The more we observe it, the more we learn, and learning is always good.

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CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

Lovejoy lives!

By Phil Plait | December 16, 2011 7:00 am

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. Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

October's solar blast, seen from the side

By Phil Plait | November 3, 2011 11:34 am

Speaking of solar storms causing gorgeous auroral displays

In late October, a coronal mass ejection (CME) — a violent explosion of subatomic particles erupting from the Sun at high speeds — blasted away from our star, impacting the Earth, and setting off aurorae seen as far south as Arkansas. It was cloudy here in Boulder, but from space, the view is always clear. NASA’s STEREO spacecraft are twin machines, one ahead of the Earth, one behind, both staring at the Sun 24/7. They are currently roughly 100° around the Earth’s orbit, so they are essentially seeing the Sun "from the side".

STEREO A, ahead of the Earth in its orbit, captured images of the Sun during October’s solar hissy fit, and got dramatic footage of the explosion:

Yegads. [Make sure you click the HD button to see this in all its glory.]

The Earth is off to the left, well off-screen, in this animation. The Sun is blocked by a circular mask, so fainter things can be seen (its disk is represented by the white circle). The big CME occurred early on October 22 and is followed by others.

Read More

CATEGORIZED UNDER: Astronomy, Cool stuff, Pretty pictures

The comet and the Coronal Mass Ejection

By Phil Plait | October 4, 2011 9:30 am

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

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Solar storm tracked all the way from the Sun to Earth

By Phil Plait | August 20, 2011 7:00 am

Yesterday I wrote about scientists being able to see sunspots as they form deep inside the Sun, well before they rise to the surface.

Around the same time, more news about the Sun was released as well. And I was ready to write up a fancy schmancy post talking all about it, I really was. It would be about how my old friend Craig DeForest used data from NASA’s Solar TErrestrial RElations Observatory (aka STEREO) to track a coronal mass ejection (CME) — a huge blast of subatomic particles chock full o’ magnetic energy — all the way from the solar surface to the Earth… but then those folks at NASA’s Goddard Space Flight Center put together this terrific video explaining it really well, saving me the effort!

Very very cool. Here is a still from the actual animation of the blast:

[Click to embiggen.]

In this graphic, the Sun is on the right and the Earth on the left. The horizontal scale is logarithmic, which means it’s highly compressed; as you get farther away from the Sun (that is, looking more to the left) the step size gets bigger. That allows a lot of space to be shown in a relatively small graphic. The green arrow shows the location of the CME, still well before it hit the Earth (if you click to get the complete image, you’ll see several frames as the CME headed our way; the planet to the right of Earth is a representation of Venus).

It’s hard to overstate just how faint this thing is; it took a huge amount of detailed processing to tease out the weak signal from the much brighter background of stars, the Milky Way, and other sources. Now let me phrase this next bit carefully. I know a lot of scientists, and many of them are the best of the best. Geniuses. I’ve known Craig for a while now (we used to work down the hall from each other at Goddard), and so when I tell you he is among the smartest people I have ever met, then hopefully you will understand the full import of this.

So this work is fantastic. Not only is it really beautiful and simply cool, it is also very important. A big CME carries a heckuva whallop with it, and can damage or destroy satellites and cause blackouts here on Earth. Nailing down their arrival times is extremely important, and has always been difficult. Craig’s process using STEREO data can potentially reduce that uncertainty, and in the process save a lot of cash and grief. In this game, minutes count.

As the Sun ramps up its activity toward the peak in 2013 and 2014, this technique, and STEREO itself, will come in handy, I’d wager. But then, that’s why we do this stuff!

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CATEGORIZED UNDER: Astronomy, Cool stuff, Science, Top Post

Summer solstice 2011

By Phil Plait | June 21, 2011 6:30 am

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.


CATEGORIZED UNDER: Astronomy, Pretty pictures

STEREO sees an ethereal solar blast

By Phil Plait | April 18, 2011 5:25 pm

On March 19, 2010, the Sun’s magnetic field erupted, launching a billion tons of plasma into space in an event called a coronal mass ejection. This particular CME headed right for Earth, but had no effect on us (except perhaps sparking some aurorae). It was captured from the side by NASA’s STEREO spacecraft — actually, two spacecraft, labeled A and B, which are far ahead and behind the Earth in its orbit around the Sun. A pretty nifty video of the STEREO A observations of this CME has just been released:

[Note: I suggest upping the resolution to 1080, and then making this full screen.]

The Sun is off to the right, and you can see the loops and glow from the plasma as it left the Sun at high speed — about 350 km/sec (210 miles/sec). That’s fast enough to reach us here on Earth in about 5 days. And yup, those are stars you’re seeing in the background. At the distance to the CME, the scale of the video is about 48 million km (30 million miles) across.

On its way to Earth, this CME plowed past a satellite called ACE, designed to study subatomic particles ejected by the Sun (as well as from galactic and extragalactic sources, too). This means that CMEs like this one can be studied as they erupt, have their internal structures traced as they expand, and then studied as they impact us as well. As more are observed, we’ll learn about how these giant eruptions are formed, and what impact they have on Earth.

The goal too is to understand them well enough to be able to predict their impact on us. A big CME can damage satellites and cause power grid outages on Earth, which can result in billions of dollars in economic loss. If they can be accurately predicted, it can potentially save us a lot of grief.

Video credit: Anthony Williams / NASA / Richard Harrison

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CATEGORIZED UNDER: Astronomy, Pretty pictures

STEREO scoping

By Phil Plait | February 7, 2011 12:01 pm

On Sunday I posted about NASA’s twin STEREO spacecraft, which are now 90° ahead and behind the Earth in its orbit. From their vantage point, over 200 million kilometers away, they can together see the entire far side of the Sun and beam the images back to Earth, providing us with real time data impossible to get from home.

While I was going through old blog posts to look at entries I had written about STEREO, I found one showing some STEREO data that I thought was worth showing everyone again. Putting it in Sunday’s article would’ve made it too long, so here it is on its own.

Let me interject a personal note first. I was at NASA’s Goddard Space Flight Center working on Hubble when STEREO was first being put together as a mission. I remember thinking how cool it would be to see the entire Sun at the same time, and what it would mean to my friends over at the heliospheric physics section. I have a decent imagination, but still there was no way I could’ve ever foreseen some of the things STEREO has brought us — Nature is always more clever than any one of us. And my favorite of all of them, sent back while the two spacecraft were still relatively near the Earth, is this incredible animation showing something that can never be seen from Earth: the tiny disk of the Moon transiting the Sun:

From Earth, that would be a solar eclipse, where the black disk of the Moon would look the same size as the bright Sun. But from well over a million kilometers away — the distance STEREO B was when it took these images — the Moon is smaller, providing this eerie and beautiful view that is a stunning reminder that humans are a spacefaring species, and the views we get from there expand our world.

MORE ABOUT: eclipse, Moon, STEREO, Sun, transit

The Whole Sun Catalog

By Phil Plait | February 6, 2011 10:26 am

Scientists are now having their day in the Sun… a day that will last 8 years.

In October 2006, NASA launched a pair of twin spacecraft into space. Called STEREO — Solar TErrestrial RElations Observatory — they traveled in opposite directions, one ahead and the other behind the Earth in its orbit around the Sun. The goal was to get a wide, stereoscopic view of the Sun which would provide 3D information on our star.

Today they reached that goal. After traveling a combined 470 million kilometers (290 million miles) relative to the Earth, they are now on opposite sides of the Earth’s orbit, staring down at opposing faces of the Sun.

This image [click to ensolenate], taken just four days ago, is the result: the far side of the Sun! If you could bore straight through the center of the Sun in this image, plunging through nearly 1.4 million kilometers of solar fire, out the other side, and straight on for another 150 million kilometers, you’d be back at the Earth.

Mind you, the STEREO spacecraft reached their 180° separation today, and this image was taken just before that happened. The black line represent the small amount of solar real estate still invisible to the twin probes last week, but which can now be seen (I expect we’ll get that image from NASA pretty soon). The images are slightly fuzzy around that line because to the two spacecraft that’s the edge of the Sun where their view is distorted by perspective. However, that’s a minimal issue, and this is the first time we’ve ever seen the actual entire far side of the Sun!

I’ll note that there is no real, permanent far side of the Sun like there is for the Moon. Read More


One solar piece of flare

By Phil Plait | March 26, 2010 7:08 am

The Sun is displaying its individuality — I guess the manager at Chochkies finally got through to it — by showing a nice little flare the other day:


This image, taken by the STEREO spacecraft (for Solar Terrestrial Relations Observatory), shows the Sun in the far ultraviolet, almost at X-ray energies. The bright flare is on the left. The slightly tilted elongated diamond is not real; it’s what happens when an electronic detector gets flooded with light. Detectors like this convert photons of light into electrons, and if too many photons hit it, the electrons leak out and "bloom" into nearby pixels.

Flares happen when the magnetic field lines of the Sun get tangled up. A huge amount of energy is stored in those lines! If the magnetic field gets too entangled, they can suddenly reconnect and release that energy. In my book, I make the analogy to a bunch of bed spring coils all under tension and thrown into a bag. If one snaps back, it hits the others which then snap, and you get a very quick and very violent release of energy. For the Sun, that means a solar flare is released. The one shown here is little, but big ones can release as much as 10% of the Sun’s total energy! They roar out, vast and powerful across the electromagnetic spectrum, from radio waves to gamma rays, and unleash a flood of subatomic particles as well.

If you look to the right of the flare, you’ll see some arcs extending up from the Sun’s surface. Those are also loops of magnetic energy, and a little time after this image was taken they too snapped, releasing a coronal mass ejection; it’s spread out more than a flare, so it’s less intense, but CMEs can blast out huge amounts of energy as well.

Images like this, and more observations by STEREO, help astronomers understand our nearest star better. And this isn’t just academic knowledge: flares and CMEs can damage or even destroy satellites, which represent billions of dollars of assets. The government and private companies take this threat very seriously indeed, of course. Just imagine the number of TPS reports they’d have to fill out!

Image credit: NASA, STEREO

CATEGORIZED UNDER: Astronomy, NASA, Pretty pictures

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