Our new visitor



The Hubble Space Telescope captured this image of Comet C/2012 S1 (ISON) on April 10, 2013 when the comet was slightly closer than Jupiter’s orbit at a distance of 386 million miles from the sun (394 million miles from Earth). This comet is expected to put on a spectacular display in Earth’s sky – visible from both the Northern and Southern Hemisphere – in late 2013. It might even become a daytime comet!

Even at its current great distance from the Earth and sun, the comet is already active as sunlight warms the surface and causes frozen volatiles to sublimate. A detailed analysis of the dust coma surrounding the solid, icy nucleus reveals a strong jet blasting dust particles off the sunward-facing side of the comet’s nucleus. Preliminary measurements from the Hubble images suggest that the nucleus of ISON is no larger than three or four miles across. This is remarkably small considering the high level of activity observed in the comet so far, said researchers. Astronomers are using these images to measure the activity level of this comet and constrain the size of the nucleus, in order to predict the comet’s activity when it skims 700,000 miles above the Sun’s roiling surface on November 28.

The comet’s dusty coma, or head of the comet, is approximately 3,100 miles across, or 1.2 times the width of Australia. A dust tail extends more than 57,000 miles, far beyond Hubble’s field of view. More careful analysis is currently underway to improve these measurements and to predict the possible outcome of the sungrazing perihelion passage of this comet.

ISON stands for International Scientific Optical Network, a group of observatories in ten countries who have organized to detect, monitor, and track objects in space. ISON is managed by the

Institute of Applied Mathematics, part of the Russian Academy of Sciences.


6 comments on “Our new visitor

  1. This article is interesting because as it said, the coma is not very large but has a lot of activity. It makes you wonder why and how it is going to react when it passes much closer to the sun. It would also be really neat to see a comet during the day.
    -Jared Kruse
    Lab section M03


  2. It is unbelievable how big this comet is. It will be interesting to see how big it really looks once it comes in closer to the Earth, and the fact that I’ve never seen a comet before will make sighting this one even better.


  3. It is absolutely cool to read about this comet since we are learning about it in lecture! I did not know that the coma could be so large and that the dust tail could extend so far. I wonder where this comet came from, the Kupier belt or the Oort cloud. Also, with the coma and dust tail being so large already without being too close to the sun, I can only imagine how giant they will be once they approach closer to Earth/Sun. It will definitely be a site to see!


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