Fizzy Comet ISON puttin’ on the spritz

These images from NASA’s Spitzer Space Telescope of Comet C/2012 S1 ISON were taken on June 13, when ISON was 310 million miles (about 500 million km) from the sun. Credit: NASA

Holy carbonated comets Batman! NASA’s Spitzer Space Telescope took a look at Comet ISON on June 13 and observed a gassy atmosphere created by frozen carbon dioxide ice slowly fizzing away in sunlight.

Spitzer sees the sky in infrared, a “color” just beyond the red end of the rainbow spectrum. We can’t see infrared with our eyes but our skin senses it as heat. Interstellar dust and comet dust alike give off a warm glow in the infrared.

Artist’s illustration shows the Spitzer Space Telescope orbiting the Sun trailing behind the Earth. To keep its infrared sensors from being swamped by heat from the spacecraft and sun, Spitzer chills them to near absolute zero using liquid helium. Credit: NASA/JPL-Caltech

Spitzer snapped two views ISON; the image on the left was taken through a filter sensitive to the light emitted by warm rock dust and shows a distinct tail blown back from the comet’s head by the pressure of sunlight. The image on the right was made through a slightly longer wavelength filter (deeper in the infrared) that gives us a better view of the comet’s vaporizing gases. Scientists are reasonably certain the gas is carbon dioxide “fizzing” off ISON’s nucleus at the rate of 2.2 million pounds (1 million kg) a day. That’s a lot of champagne bubbles!

Frozen CO2 (dry ice) is a common ingredient found in many comets and one of the first ices to vaporize in the warm sunlight as a comet makes its trek toward the inner solar system. Spitzer’s measurements now prove that ISON’s early brightness surge was most likely due to the gas though frozen carbon monoxide is also a possibility. Thanks to the surge, amateur astronomers Vitali Nevski and Artyom Novichonok discovered the comet when it was still far away between the orbits of Jupiter and Saturn.

All the excitement that makes a comet starts with a small icy-dusty object only a few miles across called the  nucleus. The bare nucleus, which is shrouded in dust and gases, is only visible up close during a spacecraft flyby. Credit: NASA/JPL-Caltech/UMD

Comet ISON is a typical comet composed of various ices – water, CO2, ammonia, methane – and fine rock dust. On approach the sun, a comet’s ice changes directly from solid to gas, a process called sublimation. Dust embedded in the ice goes along for the ride and soon forms a tail behind the comet. Right now, ISON’s blowing off about 120 million pounds of dust every day.

The orbiting ice-ball measures a little under 3 miles (5 km) across and weighs between 7 billion and 7 trillion pounds but already sports a tail 186,400 miles (300,000 km) long. If a glacier could fly, it would resemble a comet … with a few differences. Comets are black as coal; eons of bombardment by solar radiation and cosmic rays have grilled their organic chemicals to a dark pitch.

Comet L4 PANSTARRS still lives! Here we see it on July 17, 2013 when it passed near the galaxy NGC 5678. You can make out typical comet features like the dust tail and coma. Click to supersize. Credit: Gerald Rhemann

“The (Spitzer) observation gives us a good picture of part of the composition of ISON,” said Carey Lisse, leader of NASA’s Comet ISON Observation Campaign. ”We will know even more in late July and August, when the comet begins to warm up near the water-ice line outside of the orbit of Mars, and we can detect the most abundant frozen gas, which is water, as it boils away from the comet.”

After all this comet talk, I’m suddenly in the mood for something cold and fizzy.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

8 thoughts on “Fizzy Comet ISON puttin’ on the spritz

  1. What if someone detects the spectra of hops and barley in this comet? I’m sure we could gin up some support for a retrieval mission!
    Great story!

    • Hi Richard,
      I agree! You wouldn’t believe the surge in popularity of micro-breweries here in Duluth. Probably many other places as well. I’ll bet at the very least alcohol and sugars will one day be found in comets.

    • Edward,
      I’d say not. Carbon dioxide and carbon monoxide sublimation is typical for this distance. Water vapor’s the key now. Let’s see if brightness increases as expected starting later this month and the beginning of August.

      • Bob, this is one from historical sources information about more 1000 years ago. .. “will come the emergence of the tail stars amazing, not like the stars that you see popping up every two-thirds in a decade (ten years), and not even two-thirds that appear in the century, and not even star that appears every century. But it is the star of many centuries, covered the fire, snow, air and land. Elongated tail, velocity, speed time to meet the dawn sunlight. Front end to meet the back end like a giant circle, emitting rays of light in the dark sky as the sun rises. Then the star will return circulating in orbit”.

        • Hi Synur,
          This sounds like a description of a brilliant comet. No one knows for sure if ISON will be become bright or break up and fizzle after it passes closest to the sun in late November. It’s predicted to become a fairly bright comet should it hold together, but I’m very doubtful it will surpass Comet Hale-Bopp (spring 1997) or Comet C/2006 P1 McNaught in Jan. 2007.

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