Comet ISON In Outburst! Brightens A Magnitude Or More Overnight

Just look at how quickly Comet ISON is evolving. Top row (left): on Nov. 3 and 9 (right) it showed a single, prominent dust tail. By Nov. 12 (lower right) it had grown a sharp, narrow gas tail, and on Nov. 14, a multiple tail with streamers. Click to enlarge. Credit: Juanjo Gonzalez

Looks like Comet ISON is finally rubbing the sleep from its eyes. In the past 24 hours the comet has brightened significantly, rising from magnitude 7.5-80 (visible faintly in binoculars) all the way up to 5.5 or brighter than the naked eye limit. That means that despite its rapidly dropping altitude and the moon returning to the morning sky, it should become easier to see. A couple of observers have already spotted it faintly with their bare eyeballs.

Comet ISON shows a bright, dense coma (the bulbous green head) and multiple tail streamers this morning in this photo taken by Mike Hankey of Monkton, Maryland. Click to enlarge

Amateur astronomers report that ISON’s head or coma has become more compact and condensed; the tail has evolved from a single plume-like streak to a complicated tangle of picturesque streamers. Astronomer Emmauel Jehin, a member of the European TRAPPIST (TRAnsiting Planets and Planetesimals Small Telescope) team, shares two pieces of good news. His observations with the group’s 23.6-inch (60-cm) telescope have detected a tenfold increase in dust blasting from the comet’s nucleus as well as additional jet of icy and dust in the past 48 hours. No question about it, an outburst is underway.

The comet is sliding down through the constellation Virgo low in the southeastern sky this week. To find it, face southeast starting about 1 3/4 to 2 hours before sunrise. Use Mars to point you toward Virgo and then drop down toward Virgo’s brightest star Spica. Use the map below to see ISON’s location in more detail now through the weekend. Tomorrow it’s about halfway from Gamma Virginis to Spica. Stellarium

Peering deep into ISON’s coma, Jehin noted that the innermost nuclear region (the small, bright, fuzzy center of the comet) is still intact with no signs of a breakup. So far, so good. ISON’s holding together nicely on its inbound journey. If it keeps it up, we may see a fine comet indeed after perihelion on Nov. 28.

Funny thing – I was out watching ISON on Tuesday with students in my community ed astronomy class at the beginning of the outburst. While the coma’s core glowed brighter compared to a couple days earlier the full effects of the transition had only begun.

Tighter view showing the comet at dawn’s start (CST) through Nov. 19. On the 18th it will sit right next to Spica. Stars shown to magnitude 6.5. Created with Chris Marriott’s SkyMap program

It should come as no surprise that ISON’s leaping to life. Today it’s just under 60 million miles from the sun. The closer the comet gets, the more intense solar heating becomes. Heat vaporizes the comet’s dust-laden ice, and sunlight blows the material back to form a tail.

The sudden brightness jump could very well be from new cracks or fissures developing in icy crust. Exposed to the sun’s heat for the first time, gobs of ice rapidly vaporize and can cause the coma to brighten dramatically.

Comets are very dark objects, reflecting as much light as a chunk of coal. Cracks in the surface expose fresh ice to sunlight which vaporizes and blasts from the comet’s nucleus to form jets. Credit: NASA

I’ve included a couple maps to help you find ISON. It’s in Virgo very low in the southeastern sky just before the start of dawn. Be sure you pick a spot that’s open in that direction. Watch for it beginning about 2 hours before sunrise. At dawn’s first blush, the comet is currently between 15-20 degrees high.

26 Responses

    1. astrobob

      Amazing isn’t it? Comets are cool. I saw Nevski Tues. a.m. at 9.5. Very easy in the scope. So busy here I haven’t even had time to write up Nevski but I plan to do so, along with some interesting fountain features in Lovejoy I saw recently.

      1. Giorgio Rizzarelli

        Yes, and (according Heavens-Above, which seems now correctly updated) there is another one at 8.5, C/2012 T5 Bressi (high at dusk and circumpolar).

        1. astrobob

          T5 Bressi was bright last winter. It’s faded down to around 20th mag. now. Something must still be wrong. Maybe the ICQ uses the most recent actual estimates. No one’s observed Bressi for some time.

        1. astrobob

          Try it now. It was a private e-mail originally. I put the photo up on my public Flickr account, so you should see it now.

          1. astrobob

            Thanks again. It’s so important when something doesn’t work – like the link – or a mistake has been made to let me know. I appreciate that you took the time.

  1. Edward M. Boll

    John Bortle said that within 2 days, ”the comet brightened from 8.5 to 5.4”. A 5.4 would be slightly brighter than Lovejoy. Hopefully the size is a little larger than previous.

  2. Edward O'Reilly

    Great news about Ison,Bob! This outburst is coming at just the right time. Perhaps some of the pessimism that we all felt about the comet’s relatively slow brightening will now be replaced by questions as to just how bright it will become.It seems almost certain now that Ison will be a prominent naked-eye comet. Is it on a path to ‘Great Comet’ territory? I guess we’ll know in a couple of weeks.

  3. Edward M. Boll

    5 potential bright comets but for those not equipped with good star charts, and a good pair of binoculars, the mornings can be frustrating. Nevski , now at magnitude 9, will likely be fading. It is extremely high in late January. Linear X1 seems to be loosing ground, now at 8.5. Encke is extremely hard to see, now in twilight. ISON, though bright is rapidly seeming to follow Encke into the twilight. And Lovejoy right now is in the middle of no where with no bright stars nearby.

    1. astrobob

      While it’s true it can be frustrating to find any of these comets without charts, I have provided what I hope are useful star charts for finding Comets ISON and Lovejoy through Nov. 19 as well as previously providing charts for the other two comets when they were brighter/higher. Anyone who is lacking links to blogs featuring those charts, please let me know. There are also other nice charts available on the Web. You’re right you need a pair of binoculars to see them all, but now even average glass will show ISON and Lovejoy with ease as long as you’ve got a fairly dark sky.

  4. Edward M. Boll

    I was out this morning. I saw Spica and Mercury brightly shining. I aimed my binoculars for ISON but could not for sure see it. It was past 5:45 and the twilight was already showing. I have to assume that the comet is still dimmer than magnitude 5.

    1. astrobob

      ISON’s right at mag. 5. Caught it between clouds in 10x50s and the 15-inch scope. It’s amazing now! Quite bright in binocs and very impressive in the telescope. Too bad the moon returns (for us) tomorrow.

      1. Edward M. Boll

        If it is that bright and keeps brightening even at normal rate, the Moon should not be much of a problem. I will not be able to look again until Monday.

        1. astrobob

          Well worth your time I think even with a moon. That’s probably the next clear morning for us as well. Good luck!

  5. Edward M. Boll

    New Comet discovery, Oukaimeden may make a good binocular sight along with Panstaarrs next September. Unfortunately we lose sight of it in late August in the North Hemisphere.

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