WRAL WeatherCenter Blog

Comet, space station should be visible early Monday

Posted November 25, 2013

If you’ve not yet seen Comet ISON, you may be running out of time.

Imagery from the Hubble Space Telescope less show ISON’s core to be less than two miles across. Its nearly 5 million-mile-long tail is made up of water – ice leaving the comet’s surface. Bad Astronomy author Phil Platt and the Comet ISON Observing Campaign estimated that enough water to fill an Olympic-size swimming pool is leaving the comet about every three minutes. The comet reaches a critical point in its life later this week.

ISON will reach perihelion, the closest point in its swing through the solar system, on Thanksgiving Day. Before then ISON will be visible before sunrise. After it will be most visible after sunset, if the comet survives that long.

Comets are made of rock and dust and ice and it's the ice that holds them together. Temperatures in a comet’s core can rise beyond 5000 degrees Farenheit, hot enough to melt iron much less ice, during that solar encounter. Large chunks of ice can break away in a process called “calving.” The sun’s energy may disintegrate or even evaporate its icy visitor. There is no way to predict what will happen though the appearance of a second tail has led to concerns about possible fissures within the core.

Monday looks be our last opportunity in central North Carolina to see ISON before perihelion. Clear skies are expected while overcast skies will likely spoil the view on Tuesday and Wednesday. Bundle up because temperatures will be in the teens before sunrise.

ISON will rise shortly after 6 a.m. and reach 10 degrees above the horizon (the width of your fist held at arm’s length) by sunrise at 7 a.m. Look to the southeast low on the horizon for a fuzzy green dot. Look for ISON’s dimmer tail pointing away from the sun and toward the quarter moon.

A triangle of stars above just above ISON will serve as a guidepost as well. Actually only the dimmer star on the right is actually a star – Zubenelgenubi, the brightest star in the constellation Libra. The brightest of the small triangle is Mercury (top) with slightly dimmer Saturn on the left.

If a pair of planets and a comet aren’t enough to get you out of bed a bit early, the International Space Station will make an appearance in the northwest at 6:44 a.m. rising about 1/3 up the sky setting six minutes later in the east right into the rising sun. What a way to begin the week.

If you miss ISON Monday morning, hope for the best for survival on Thursday. The comet will be visible after sunset through December and into January. Christmas night looks promising with visibility comfortably above the northwest horizon and another bright ISS pass beneath the comet.


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  • Tony Rice Nov 28, 2013

    Not looking good for Comet ISON. Images as it approaches the sun suggest that ISON is breaking up. Coma is gone from these images, tail is smearing out.

  • Tony Rice Nov 28, 2013

    Word from astronomers monitoring ISON via NASA's SOHO spacecraft is that it brightened A LOT over night but in the last hour dimmed again. Still not able to determine if the nucleus is intact. Check the latest blog post here for a link to a Google+ hangout with NASA scientist this afternoon as the comet travels closest to the sun.

  • Tony Rice Nov 27, 2013

    wlm, Should ISON survive tomorrow, it will be visible both before sunrise and after sunset (though it will still be a bit better in the morning) but we'll need to give it a week to 10 days to move away from the sun's glare. Even if the comet breaks up, we'll likely still be able to see debris.

    I'll post another blog next week with more details.

  • wlm Nov 26, 2013

    Tony, I wish this article had been posted earlier, but maybe you can answer my questions, to help later this week. When will the comet switch from morning to evening viewing? Where would one look starting this Thursday? Thanks.

  • Tony Rice Nov 25, 2013

    @cdiezel, the ISS will be passing over each morning this week. Tue & Wed are probably out due to cloudy conditions. Thu it will pas at 5:55 from the NNW, Fri at 5:08 at 5:08 from the NE

    Twitter users can follow @isspassraleigh (https://twitter.com/isspassraleigh) for a heads up for passes that take the weather into consideration.

  • cdiezel Nov 25, 2013

    Hey Tony- Did we miss the space station as well?? Thanks for clarifing where & when that will be visible since we missed the comet viewing window.....nice

  • bru333 Nov 25, 2013

    Typical. Posting an article after the event.

  • uhlersoth Nov 25, 2013

    So this article was posted roughly 20 minutes before the end of the window of visibility? Wouldn't it have been a bit more useful to post it last night?