The Sun Just Killed a Comet
One of the brightest sungrazing comets discovered played "chicken" with the sun... and lost.
The sun is the most dominant force in the solar system. It provides its family of planets with heat (even supporting life on one of them), gives gravitational stability and shines like a beacon across thousands of light-years. Though our nearest star is beautiful and life-giving, don't mistake its altruism for weakness.
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Unfortunately for one "sungrazer" comet, it didn't take heed of the warnings and decided to play a game of "chicken" with that massive ball of superheated plasma. Needless to say, it didn't turn out so well for the comet:
This animation shows observations made by the NASA/ESA Solar and Heliospheric Observatory (SOHO) spacecraft that is constantly looking at the sun and its surrounding environment. And you see that bright object streak into view on the right of the frame? Yep, that's a soon-to-be ex-comet.
Key to SOHO's mission is the close monitoring of space weather phenomena, such as coronal mass ejections and the solar wind. But shortly after SOHO's launch in 1995, it became clear that it wasn't only a solar mission, it was an ace comet hunter. However, SOHO's comets aren't your run-of-the-mill "we're going to keep a safe distance from that burning ball of stellar matter" comets, these comets are sungrazing comets, the ultimate icy thrillseekers with a death wish.
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Sungrazers, also known as "Kreutz sungrazers" after the astronomer who first studied them, are fragments of a massive comet that broke apart hundreds of years ago. These fascinating objects regularly streak in front of SOHO's field of view, but none of the smaller chunks, usually only measuring a few meters across, survive close approach (known as perihelion). A few larger Kreutz comets do have the fortitude to survive the sun's violent heating at perihelion, such as C/2011 W3 (Lovejoy), but the majority fizzle and vaporize fast as they plunge deep into the sun's atmosphere, the corona.
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This most recent sungrazer is one of the brightest examples to be spotted by SOHO, but just as it was discovered, astronomers knew its fate was sealed.
"That was the total destruction of a 600 km/s snowball, witnessed exclusively by SOHO," said Karl Battams of the Naval Research Lab in Washington DC. in a tweet. "My good friend and colleague Matthew Knight estimated the comet peaked at ~mag -0.5, putting it squarely in the top ten (five?) of SOHO's brightest Kreutz sungrazers."
Though it was one of the brightest, its fame was short-lived; it didn't stand a chance against the sun's intense heat. Its water vapor and dust are now scattered through the corona, blowing in the constant breeze of the solar wind.
Farewell brave unnamed sungrazer, we hardly knew ye.
GALLERY: The Weird and Wonderful SOHO Observations
SOHO, or the Solar and Heliospheric Observatory, just celebrated 20 years in space with a main goal of learning more about the sun's activity. The spacecraft has seen some neat things, including comets, planets and unexpected solar activity. Here, based on a video recently produced by NASA, are some of the more unusual things SOHO has witnessed.
Because the planets periodically pass nearby the sun from SOHO's perspective, the spacecraft can see them in its viewfinder. They look a little overexposed because they are so bright (compared with the wispy clouds of plasma in the solar wind), but they still provide a unique view of our neighbors in space. This congregation pictured here took place in 2000 and includes Venus, Mercury, Jupiter and Saturn -- as well as a famous star cluster called the Pleiades. "Such congregations of planets are rare events, and they cannot be seen from the ground when close in the sky to the dazzling sun. But the LASCO C3 instrument on SOHO uses a mask to blot out direct sunlight, and it has a wide enough field of view (15 degrees) to take in the four planets in the same picture," the SOHO website wrote at the time.
Is that a snowstorm in space? No, it's actually energetic particles hitting the viewfinder of SOHO. These are caused by fast-moving protons coming from the sun, and you can see the view can get rather ... intense at times. This particular image happened in January 2012 during one of the strongest radiation storms since 2005. These storms are more frequent when the sun reaches its maximum, which last happened in roughly 2013-14. NASA is interested in these storms not only because they are awesome to watch, but also to monitor their effects on Earth. Solar storms can cause blackouts in radio communications, satellites and power lines if they are strong enough. Part of SOHO's role is to provide better predictions of the sun's activity and how Earth's environment will react to it.
SOHO was not designed to look for comets, but the sun happens to be a great place to look for them. The massive gravitational attraction of the star periodically pulls comets very close to its vicinity. Most of these so-called "sungrazers" do not survive their closest approach, called perihelion, but at least we can see their remains in pictures. Comet count so far? More than 3,000. This is a particularly spectacular example from 2003, when Comet NEAT made a close approach while the sun was quite active. "The LASCO pictures and movies of this comet are quite out of the ordinary, with a sizeable tail and a very bright (saturated) comet nucleus," the SOHO website wrote at the time. "We even got a nice coronal mass ejection (CME) off the west limb close to perihelion time, putting the icing on the cake!"
The sun has a fairly routine cycle of activity that lasts roughly 11 years between maximum and maximum. But it's not always a clear shot as to when you're going to see a big flare. In 2003, the sun became extremely active long after its expected peak in 2001, which shows us how much more scientists have to learn. "Some of the most intense activity that we saw was in the fall of 2003," said Joe Gurman, the U.S. project scientist for SOHO, in a NASA video posted on Twitter. "This was bit of a surprise as it was a couple of years after the maximum of the 11 year cycle."
This was a surprise discovery for SOHO. The spacecraft's observations reveal a sort of pulse that takes place during coronal mass ejections -- those particle-laden explosions from the sun. It's a neat find because it shows us more about how the inner workings of the sun create the activity that you can see in pictures of CMEs. "Think of an underwater explosion: you will get water forced upwards as a great spray, but you will also get a wave on the surface of the water that travels outwards from the explosion site," SOHO wrote on an educational website. "The waves on the sun are similar, although in this case the explosion occurs just above the surface rather than below it."