NASA / SOHO
Comet Lovejoy skimmed across the sun's edge about 140,000 km above the surface late Dec. 15 and early Dec. 16, 2011, furiously brightening and vaporizing as it approached the sun. This SOHO spacecraft image shows the comet during that time.
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updated 4/4/2012 11:53:27 AM ET 2012-04-04T15:53:27

Comets skimming past the sun may seem like ill-fated cosmic snowballs, and a team of scientists is trying to figure out what makes some fizzle and others explode as they make their solar death dives.

Research into these doomed comets may yield clues on the origins of the solar system, as well as shed light on the potential risks the comet deaths on the sun could pose for us on Earth, scientists say.

In recent decades, astronomers have witnessed even dramatic interactions between comets and the sun, with thousands seen falling near or into our closest star. Now researchers are analyzing how these so-called sun-diving comets lose their mass and energy depending on how close they get to the star.

"In modeling how icy comets behave in this extreme environment, we really are starting to understand what happens to these 'supersonic snowballs in hell' when they make a close approach to the sun," said study lead author John Brown, Astronomer Royal for Scotland.

"Such data can show us for the first time what is inside a comet," Brown told Space.com. "All other data to date, apart from Jupiter impacts like Shoemaker-Levy 9, are only from the surface layers."

Whether these comets fizzle or explode appears to depend on whether they stray deep into the sun's lower atmosphere. This lies about 4,350 miles (7,000 kilometers) above the top of the photosphere, the sun's brightest visible layer. [ Photos of Comet Lovejoy's Dive Through Sun ]

The researchers found that "sun-skimmer" comets — ones that dive toward the sun but not into its lower atmosphere — can slowly get vaporized by sunlight in deaths that last hundreds to thousands of seconds, depending on their mass. During such demises, the scientists calculated that the comets should emit weak but detectable extreme ultraviolet radiation.

In contrast, "sun-plunger" comets that get even closer to the sun will meet their demise in only a few seconds, as they collide with the dense layers of the sun's lower atmosphere. The resulting explosions typically generate effects similar to those of solar flares, such as sunquakes on the solar surface. If the most massive comets smashed into the sun, they would produce dramatic explosions just above the photosphere, the researchers said.

To create their model, the scientists looked at the first direct observations of sun-skimmer comets, captured last year by NASA's sun-watching Solar Dynamics Observatory (SDO). The first comet, C/2011 N3, was completely destroyed after passing about 62,000 miles (100,000 km) above the photosphere.

The second and larger comet, Lovejoy (C/2011 W3), survived a close approach to a similar distance of 87,000 miles (140,000 km), although it lost a significant fraction of its mass in the process. Both events were in line with the predictions of the researchers' new model.

Comet Lovejoy did pass through the sun's million-degree corona, but its survival was not miraculous, Brown said. The corona is hot, but its density is so small that the heat Lovejoy experienced "would be quite safe even on our skin," he explained.

Comets might help serve as probes of the sun's atmosphere and magnetic field, helping to uncover its secrets. They are also thought to date back to the formation of the sun and the planets — as such, ones that dive toward the sun could, in their death throes, reveal important details not only about themselves, but also the early history and composition of the solar system.

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"The two sun-skimmers seen last year have already given us a new insight into the sun's atmosphere and it's only a matter of time before we see the flare from a sun-plunger with a low enough orbit to reach the lower atmosphere of the sun," Brown said. "When that happens we will be able to analyze the light from the resulting 'cometary flare' and find out even more about the composition of the interiors of comets."

The cometary flares that the very largest comets might release if they slammed into the sun can be 100 times more energetic than the largest solar flares ever observed, "and so could be dangerous not only to spacecraft and power lines and communications, but even to our atmosphere," Brown said. "Such comets are, however, very, very rare today, though they may have been commoner in the early system."

Brown and his colleagues detailed their findings Friday at the National Astronomy Meeting in Manchester, England.

Follow Space.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.

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Photos: Month in Space: January 2014

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  1. Southern stargazing

    Stars, galaxies and nebulas dot the skies over the European Southern Observatory's La Silla Paranal Observatory in Chile, in a picture released on Jan. 7. This image also shows three of the four movable units that feed light into the Very Large Telescope Interferometer, the world's most advanced optical instrument. Combining to form one larger telescope, they are greater than the sum of their parts: They reveal details that would otherwise be visible only through a telescope as large as the distance between them. (Y. Beletsky / ESO) Back to slideshow navigation
  2. A balloon's view

    Cameras captured the Grandville High School RoboDawgs' balloon floating through Earth's upper atmosphere during its ascent on Dec. 28, 2013. The Grandville RoboDawgs’ first winter balloon launch reached an estimated altitude of 130,000 feet, or about 25 miles, according to coaches Mike Evele and Doug Hepfer. It skyrocketed past the team’s previous 100,000-feet record set in June. The RoboDawgs started with just one robotics team in 1998, but they've grown to support more than 30 teams at public schools in Grandville, Mich. (Kyle Moroney / AP) Back to slideshow navigation
  3. Spacemen at work

    Russian cosmonauts Oleg Kotov, right, and Sergey Ryazanskiy perform maintenance on the International Space Station on Jan. 27. During the six-hour, eight-minute spacewalk, Kotov and Ryazanskiy completed the installation of a pair of high-fidelity cameras that experienced connectivity issues during a Dec. 27 spacewalk. The cosmonauts also retrieved scientific gear outside the station's Russian segment. (NASA) Back to slideshow navigation
  4. Special delivery

    The International Space Station's Canadian-built robotic arm moves toward Orbital Sciences Corp.'s Cygnus autonomous cargo craft as it approaches the station for a Jan. 12 delivery. The mountains below are the southwestern Alps. (NASA) Back to slideshow navigation
  5. Accidental art

    A piece of art? A time-lapse photo? A flickering light show? At first glance, this image looks nothing like the images we're used to seeing from the Hubble Space Telescope. But it's a genuine Hubble frame that was released on Jan. 27. Hubble's team suspects that the telescope's Fine Guidance System locked onto a bad guide star, potentially a double star or binary. This caused an error in the tracking system, resulting in a remarkable picture of brightly colored stellar streaks. The prominent red streaks are from stars in the globular cluster NGC 288. (NASA / ESA) Back to slideshow navigation
  6. Supersonic test flight

    A camera looking back over Virgin Galactic's SpaceShipTwo's fuselage shows the rocket burn with a Mojave Desert vista in the background during a test flight of the rocket plane on Jan. 10. Cameras were mounted on the exterior of SpaceShipTwo as well as its carrier airplane, WhiteKnightTwo, to monitor the rocket engine's performance. The test was aimed at setting the stage for honest-to-goodness flights into outer space later this year, and eventual commercial space tours.

    More about SpaceShipTwo on PhotoBlog (Virgin Galactic) Back to slideshow navigation
  7. Red lagoon

    The VLT Survey Telescope at the European Southern Observatory's Paranal Observatory in Chile captured this richly detailed new image of the Lagoon Nebula, released on Jan. 22. This giant cloud of gas and dust is creating intensely bright young stars, and is home to young stellar clusters. This image is a tiny part of just one of 11 public surveys of the sky now in progress using ESO telescopes. (ESO/VPHAS team) Back to slideshow navigation
  8. Fire on the mountain

    This image provided by NASA shows a satellite view of smoke from the Colby Fire, taken by the Multi-angle Imaging SpectroRadiometer aboard NASA's Terra spacecraft as it passed over Southern California on Jan. 16. The fire burned more than 1,863 acres and forced the evacuation of 3,700 people. (NASA via AP) Back to slideshow navigation
  9. Where stars are born

    An image captured by NASA's Spitzer Space Telescope shows the Orion Nebula, an immense stellar nursery some 1,500 light-years away. This false-color infrared view, released on Jan. 15, spans about 40 light-years across the region. The brightest portion of the nebula is centered on Orion's young, massive, hot stars, known as the Trapezium Cluster. But Spitzer also can detect stars still in the process of formation, seen here in red hues. (NASA / JPL-Caltech) Back to slideshow navigation
  10. Cygnus takes flight

    Orbital Sciences Corp.'s Antares rocket rises from NASA's Wallops Flight Facility on Wallops Island, Va, on Jan. 9. The rocket sent Orbital's Cygnus cargo capsule on its first official resupply mission to the International Space Station. (Chris Perry / NASA) Back to slideshow navigation
  11. A long, long time ago...

    This long-exposure picture from the Hubble Space Telescope, released Jan. 8, is the deepest image ever made of any cluster of galaxies. The cluster known as Abell 2744 appears in the foreground. It contains several hundred galaxies as they looked 3.5 billion years ago. Abell 2744 acts as a gravitational lens to warp space, brightening and magnifying images of nearly 3,000 distant background galaxies. The more distant galaxies appear as they did more than 12 billion years ago, not long after the Big Bang. (NASA / NASA via AFP - Getty Images) Back to slideshow navigation
  12. Frosty halo

    Sun dogs are bright spots that appear in the sky around the sun when light is refracted through ice crystals in the atmosphere. These sun dogs appeared on Jan. 5 amid brutally cold temperatures along Highway 83, north of Bismarck, N.D. The temperature was about 22 degrees below zero Fahrenheit, with a 50-below-zero wind chill.

    Slideshow: The Year in Space (Brian Peterson / The Bismarck Tribune via AP) Back to slideshow navigation
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