Comet ISON Image of the Week

The Soda-Pop Comet (Aug 12, 2013)

In an observing program led by CIOC Chair Dr. Casey Lisse, the Spitzer Telescope was used in June to take these images of Comet ISON. These images helped the scientists determine that Comet ISON appears to be producing over 50-million kilograms of dust and 1-million kilograms of carbon dioxide every single day!

Formally it's known as C/2012 S1 (ISON) but informally it has been labelled many other things, most recently the "Soda-Pop Comet"! On June 13, 2013, the CIOC's Dr. Casey Lisse led an observing program that had the Spitzer Telescope spend a full 24-hours observing Comet ISON. What Spitzer found does not tell us whether ISON is going to fizzle or sizzle, but certainly tells us that ISON appears at least to be very fizzy!

Many questions remain to be answered about Comet ISON. How large is its nucleus? How bright will it be? Will it survive, or even reach, perihelion in November? It's going to take time and lots of observations for us to answer these questions, but already we've begun to start answering the question of why ISON was so relatively active while still so far from the Sun. The answer is gas!

The images shown above are infrared observations of Comet ISON taken at wavelength of 3.6 (left) and 4.5 microns - wavelengths of light in which the gases carbon dioxide (CO2) and carbon monoxide (CO) tend to reveal themselves in comets. What Spitzer found is that Comet ISON is producing quite a lot of gas from a rather small nucleus. That gas could either be CO2 or CO, but based on similar studies of other comets, CO2 seems much more likely the culprit. Follow-up observations in the coming weeks should resolve this uncertainty.

So just how gassy is Comet ISON? According to the Spitzer observations, it's putting out about 1-million kilograms of CO2 per day! In addition to the gas, it is also producing about 54-million kilograms of dust every day! Numbers like that are hard to grasp, so it's more fun to restate them in terms of something tangible. So the 54-million kilograms of dust is equivalent to producing a Navy aircraft carrier every two days! And the CO2 gas? Well that would be enough to provide the fizz for over 600-million cans of a certain popular cola drink, every day!

Comet ISON is fizzy indeed!

Every week this year we will put up a new image related to Comet C/2012 S1 (ISON). If you have a cool image you'd like us to consider, please send it to, along with a description and any credits you would want applied. We'll contact you if we choose to use your image on the CIOC Website.

See our ISON Image of the Week Archives for earlier picks!