The Sciences

First, a big chunk of the Sun seemingly goes missing; then a satellite sees a Sun-grazing comet plunge to its death

ImaGeo iconImaGeoBy Tom YulsmanAug 7, 2016 5:56 PM

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All the action was captured live and in color by spacecraft. Here's what it looked like — and what's going on.

What took a huge bite out of the Sun? (Source: NASA, ESA and JAXA) Check out the image above, acquired by NASA's Solar Dynamics Observatory spacecraft. It almost seems like something took a big bite out of the Sun, right? And if that weren't enough, here's what happened a day later:

This screenshot from an animation of images from the Solar and Heliospheric Observatory spacecraft (SOHO) shows a comet zooming toward the sun on Aug. 3rd and 4th, 2016. Click the image to watch the animation on Youtube. (Source: U.S. Naval Research Laboratory) That bright streaking object is a comet plunging toward the Sun at nearly 1.3 million miles per hour before getting torn to shreds and vaporized, as witnessed by the Solar and Heliospheric Observatory, or SOHO spacecraft. Meanwhile, at the same time the comet was on its death plunge, the Sun belched, letting loose a gargantuan eruption of hyper-hot plasma into space. You can see it in the video — it's that bolus of bright white stuff spewing out on the left. (Not to worry. It wasn't directed toward us on Earth...)

SEE ALSO: What's up with that huge dark hole in the Sun?

Quite an interesting couple of days in the neighborhood of the Sun, eh? First, let's deal with the chunk of the Sun that seemed to go missing. If you are rolling your eyes and thinking it was just an ordinary solar eclipse, you're on the right track. But you're not entirely correct. A solar eclipse occurs when the Moon obscures the Sun. Nothing like that actually occurred on Aug. 2nd — at least not from our vantage point here on Earth. (As NASA's eclipse website shows). But a more unusual eclipse did occur — from another point of view: the one held by the Solar Dynamics Observatory spacecraft in its inclined geosynchronous orbit more than 20,000 miles above Earth's surface. For about an hour starting at 7:13 a.m. EDT, the Moon passed between SDO and the Sun. And that's what darkened a chunk of the Sun in images sent by SDO back to Earth. The phenomenon is known as a lunar transit, and it happens two to three times each year. Here's an animation of SDO images showing what the recent one looked like: http://imgur.com/YeiX91n You may have noticed that the Moon's horizon is strikingly sharp in this animation. That because the Moon has no atmosphere around it to distort the light from the sun. You may also be wondering why the animation stops abruptly before the Moon completes its transit across the Sun's face. That's because SDO actually went on the fritz — it stopped sending imagery back to Earth before the eclipse ended. The spacecraft is now on the mend, according to the SDO mission blog:

I had forgotten how nice it was to see the Sun each morning in all of the different ways SDO provides. It took longer then we expected, but as of the end of the Friday work day [Aug. 5], SDO is in science mode and all three instruments are returning science data.

Even so, the spacecraft is not yet back to full health. It is running an older version of its flight software. The SDO doctors are working on it... Next up: The comet that took that deep dive — and didn't survive to tell the tale. Here's a closeup view, posted to Instagram by NASA: https://www.instagram.com/p/BIsoDAeDyHf/ The caption provides most of the details — except for one thing: Where's the dang Sun? You can see the comet streaking in, as well as the bright material exploding out into space on the left. (More about that in a minute.) But the Sun is blacked out. Why's that? The LASCO instrument aboard SOHO consists of three telescopes that employ a solid disk, called an “occulter,” to cover up the Sun. This blocks direct sunlight, thereby allowing the Sun’s dimmer corona — it’s extended atmosphere — to be seen. It also means that Sun-grazing comets can be recorded for posterity as well. Thanks to the occulting disk, LASCO is able to capture beautiful imagery of coronal mass ejections — unimaginably huge explosions of magnetic field and super hot plasma that blow out into space from the Sun's corona.

SEE ALSO:

Here's an even closer view that shows the coronal mass ejection on August 3rd and 4th in all its glowing glory: http://imgur.com/87uwwC0 And here's a quick explanation of CMEs from NOAA's Space Weather Prediction Center:

Close-up videos capture big, beautiful explosions on the Sun

CMEs originate from highly twisted magnetic field structures, or “flux ropes”, on the Sun, often visualized by their associated “filaments” or “prominences”, which are relatively cool plasmas trapped in the flux ropes in the corona. When these flux ropes erupt from active regions on the Sun (regions associated with sunspots and very strong magnetic fields), they are often accompanied by large solar flares...

If you're as fascinated by the Sun as I am, check back here at ImaGeo often. I'm always looking out for compelling imagery of what's happening on the Sun and in its environs.

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