I can’t believe it. As of today, my two daughters are in college. Like comets leaving the inner solar system, they’re in orbits of their own and destined for faraway places. I love them both and wish them Happy Trails.
Ah, today’s another day when I’m racing about with many tasks ahead. Still, I wanted to update you on Comet Elenin’s progress. It doesn’t look good. The comet remains dim and appears very soft and diffuse with little brightening toward the center – all signs that point to a breakup of the actual comet body that’s buried inside the dusty glow. Its size is estimated at several kilometers. The apparent break-up has caused a release of dust in the past few days that’s been pushed back by the pressure of sunlight into a short dust tail very evident in the photos.
Since Comet Elenin lies nearly in the plane of Earth’s orbit, when it passes near the sun later this month on September 26, the increased amount of dust produced from any breakup will probably cause a nice brightening in the comet due to something called ‘forward scattering’. You’re already familiar with the phenomenon if you’ve ever driven a car with a dirty windshield in the direction of a low sun. Every bit of dirt and bug splatter light up, making it hard to see. A quick hit of the washer switch clears the view. Something quite similar may happen with Comet Elenin.
It’s unknown if the dust will light up soon enough before or long enough after the September 26 date to become visible down here on Earth through a telescope. If the brightening is short-lived, no one will see it on the ground, because the comet will so near the sun in the sky, it’ll be overwhelmed by daylight.
Luckily, we have a “Get Out Of Jail Free” card. The coronagraph on the orbiting SOHO solar telescope will have a great view of Elenin from a few days before until a few days after that date. Its field of view is large enough to include the comet, the inner planets, background stars and the sun’s corona or outer atmosphere. I’ll provide links and daily updates as we get closer to the 26th.
All these changes will not affect us in any way here on Earth. The comet is millions of miles away and won’t get closer than about 22 million miles in mid October. What it might mean however is a dramatic fading around the time of closest approach to the sun (perihelion). That happens this Saturday September 10.
I’ve also been asked whether a crumbling comet might mean trouble for our planet. If Comet Elenin is indeed breaking up, pieces of it streaming down the tail or in a tight cluster at comet-center might eventually show in larger telescopes. The individual fragments – should any survive – will keep tracking along the same general orbit of the comet and will not veer off to threaten Earth, because they’re traveling together in the same direction at very high speed.
I’m crossing my fingers right hoping at least some of the comet carries through perihelion, so we can see it with simple equipment come early October. That’s when it returns to easy viewing in the morning sky. Right now I suspect a telescope will be required.
If Elenin turns into a dud, there will always be other comets. Comet Garradd, currently in the evening sky and visible in small telescopes, will brighten to a dim naked eye object early next year. In the next couple weeks, Comet Honda-Mrkos-Pajusakova will return to the northern hemisphere morning sky. Modest-sized telescopes should show it as a fuzzy round glow perhaps with a tail. Other more distant comets waiting in the wings are also headed toward the inner solar system in the near future and will provide nice shows. And who knows? Someone may discover a new comet next week that might eclipse them all.