“comets are like cats: they have tails, and do whatever they want to do”


In the BBC’s science news preview of 2013, reporter Jason Palmer highlights a couple of astronomical events worth keeping an eye out for.

In mid-February we will get another reminder we live in a (potentially) violent cosmos – asteroid 2012 DA14 will make a harmless but attention-grabbing pass near the Earth, at a distance just a tenth that of the Moon. Exactly what happens then will determine how near the asteroid’s next pass will be, in 2026. (Don’t worry, signs are pretty good so far.) Late in the year, a comet called Ison might make a dramatic appearance in the night skies, brighter than the full moon – if it doesn’t burn up as it gets nearer.

As the JPL Near Earth Object Program noted back in March 2012, the Near-Earth Asteroid 2012 DA14 will pass extremely close to Earth, but, thankfully, will be otherwise unspectacular. 

Discovered by the LaSagra observatory in southern Spain, the small asteroid 2012 DA14 will pass within about 3.5 Earth radii of the Earth’s surface on February 15, 2013. Although its size is not well determined, this near-Earth asteroid is thought to be about 45 meters in diameter. Asteroid 2012 DA14 will pass inside the geosynchronous satellite ring, located about 35,800 km above the equator. Its orbit about the sun can bring it no closer to the Earth’s surface than 3.2 Earth radii on February 15, 2013. On this date, the asteroid will travel rapidly from the southern evening sky into the northern morning sky with its closest Earth approach occurring about 19:26 UTC when it will achieve a magnitude of less than seven, which is somewhat fainter than naked eye visibility.

Here’s a JPL video animation showing just how close that “closest asteroid ‘fly by’ in recorded history” will be.

[Was Jupiter sleeping?! - Ed]  Just be thankful Ogdy was too.  He hasn’t always…

However, the other highly predictable astronomical event for 2013 has the potential to be highly spectacular.

Comet C/2012 S1 (ISON) is a sungrazing comet discovered on 21 September 2012. 

Here’s an image of the comet on 4 October, 2012, with “a well developed and elongated coma” visible - from the Remanzacco Observatory blog.

It’s still some distance out but, estimated to be almost 2 miles wide, it’s getting a lot of people very excited.

“Comet ISON appears on course to achieve sungrazer status as it passes within a solar diameter of Sun’s surface in late 2013 November. Whatever survives will then pass nearest the Earth in late 2013 December,” NASA astronomers explained in a posting. “Astronomers around the world will be tracking this large dirty snowball closely to better understand its nature and how it might evolve during the next 15 months.”

The comet, which is estimated to be nearly two miles wide, will likely be one of the largest comets to ever pass Earth. While there is a chance that ISON will disintegrate when it approaches the sun, some astronomers say heat from the sun will vaporize ices in its body, creating what could be a spectacular tail.

That depends on a number of known unknowns… as astonomer Bill Gray told the Planetary Blog

It looks potentially very interesting indeed. The orbit is very well-determined. We can say, with complete confidence, that it’ll come very close to the sun (about 0.012 AU, almost but not quite “sun-grazing”) on 29 November 2013, plus or minus a day. At that point, it might get very bright, as some sungrazing comets have in the past (such as Ikeya-Seki in 1965, and C/2006 P1 McNaught in 2007).

So we’re quite sure where it’s going. The uncertain part (as always with comets) is how bright it’ll be.

I expect that it’ll at least be of considerable interest to comet observers, much as C/2006 P1 was. But estimating comet brightnesses a year ahead of time is about like asking who’s going to win the World Series next year. It could be astonishingly bright, or it could fizzle. I think it was David Levy who said that comets are like cats: they have tails, and do whatever they want to do.

But it could be even more spectacular than Comet Lovejoy – Space Weather has earth-bound observations of that event. [Video courtesy of the Image Science & Analysis Laboratory, NASA Johnson Space Center]

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  • David Crookes

    Many thanks for a mosr opulent posting, Pete, and happy new year. An asteroid in the wrong place at the wrong time could give this terrestrial ball a quare dig in the bake.

  • Pete Baker

    It has in the past.

    And it’s why we still rely on Jupiter paying attention…

  • Greenflag

    ‘It has in the past’

    Just as well for if that asteroid had not hit the Yucatan peninsula and adjoining Gulf of Mexico -65 million years ago -we (humanity ) or mammals would not be here either . Perhaps Great Jove reckoned those dinosaurs had been around for 150 million years too long?

    But then the dinosaurs in their time would not have had the consciousness to know that even their existence and long reign on Earth was fortuitously enabled by the 100,000 year long volcanic eruptions in the Siberian Traps 250 million years ago -which gave rise to the greatest ever extinction of life forms known as the Permian extinction.

    We are all (7 billions of humanity ) extremely lucky to be here at all -at all .Mammals may have won the ‘Universal Lottery ‘ 65 million years ago and the primates and eventually homo sapiens lucked out due to tectonic events resulting in the closing of the Panamanian Isthmus 7 million years ago and the knife edge survival of a small number of humans following the Supervolcanic Toba eruptions 75,000 years ago .

    Thank Jupiter

  • Pete Baker

    “Thank Jupiter”

    Even when he’s asleep on the job…

  • carl marks

    Pet thanks
    The relevant dates have been noted, a place called Port in Donegall has low light pollution, and if possible I intend to be there with a few friends and a scope or two depending on cloud cover we might get lucky. If anyone fancies joining us all you will need is a tent (plus sleeping bag of course) bring alcohol and food, even if we don’t see any asteroids it should be great craic.

  • carl marks

    Meant Pete thanks, not thanks pet