July 23, 2013
Comet ISON Is Shedding Carbon Dioxide By The Millions
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers say they have observed strong carbon dioxide emissions coming off Comet ISON, giving scientists even more data to help them better understand these space objects.The team captured the images on June 13 using NASA's Spitzer Space Telescope's Infrared Array Camera. The images show carbon dioxide is slowly and steadily "fizzing" away from the so-called "soda-pop comet" in a tail about 186,400 miles long.
"These fabulous observations of ISON are unique and set the stage for more observations and discoveries to follow as part of a comprehensive NASA campaign to observe the comet," said James L. Green, NASA's director of planetary science in Washington. "ISON is very exciting. We believe that data collected from this comet can help explain how and when the solar system first formed."
Carey Lisse, leader of NASA's Comet ISON Observing Campaign and a senior research scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, said they believe ISON is emitting about 2.2 million pounds of carbon dioxide gas and about 120 million pounds of dust every day.
"Previous observations made by NASA's Hubble Space Telescope and the Swift Gamma-Ray Burst Mission and Deep Impact spacecraft gave us only upper limits for any gas emission from ISON," Lisse said. "Thanks to Spitzer, we now know for sure the comet's distant activity has been powered by gas."
The comet was about 312 million miles from the sun when the observations were made, which is about 3.35 times farther than Earth is.
Comet ISON is less than three miles in diameter and is about the size of a small mountain. NASA said the comet weighs between 7 billion and 7 trillion pounds, however its true size and density cannot be determine accurately because it is so far away. ISON is made up of dust and frozen gases such as water, ammonia, methane and carbon dioxide.
According to NASA, Comet ISON is inbound on its first passage from the distant Oort Cloud, which is a collection of comets and comet-like structures that exists in space between one-tenth of a light-year and one light-year from the sun. The comet will be passing within 724,000 miles of the sun at the end of November.
As the comet nears the sun, it warms up gradually, causing gases to heat up to the point of evaporation, which can be detected by instruments from space and on the ground.
"This observation gives us a good picture of part of the composition of ISON, and, by extension, of the proto-planetary disk from which the planets were formed," said Lisse. "Much of the carbon in the comet appears to be locked up in carbon dioxide ice. 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."
NASA released a video at the beginning of July taken by its Hubble Space Telescope of Comet ISON as it makes its approach towards the sun. The video shows observations taken over 43 minutes, as the comet rushes through space at 48,000 miles per hour.