A Dread Doomsday ... Faint Comet. Or Two

We were graced with a comet last month! Okay, Comet C/2009 P1 Garradd wasn’t history’s most impressive comet. But it was fun watching it fly past the Coathanger asterism, an eighth-magnitude splotch that was easy to find even from the light pollution of San Jose.

We don’t get comets that often that are easily visible from the backyard, so it’s nice to see one at all.

I didn’t manage Garradd in binoculars – did you?

Well, usually we don’t get to see comets that often. But after September’s comet, October brings us not one but two more.

Comet C/2010 X1 Elenin makes its closest approach to Earth on October 16, though that’s still about 35 million kilometers (22 million miles) away. And no, that’s still not all that close – it’s like Venus at opposition. Elenin’s perihelion, its closest approach to the sun, is about a week earlier on October 10; the comet should be brightest between those two dates.

Elenin is a relatively small comet, but some initially hoped it would brighten enough to be visible with the naked eye. That doesn’t look likely now. Back around the end of August Elenin was hit by a coronal mass ejection from the sun, and as I write this it looks like it’s started to break up. The most optimistic estimates now for its brightness at closest approach are down around 9th magnitude, dimmer than Garradd. At worst, it may break up completely and not be visible at all, at least not in amateur telescopes.

Modest little Comet Elenin has another claim to fame, though.

Apparently there was speculation earlier this year that unknown forces would alter Elenin’s orbit and pull the comet much closer to Earth, causing much destruction and mayhem. Apparently there are even those who say little Elenin is the dread object Nibiru, prophesied by doomsayers to have a disastrous encounter with the Earth in 2012 (or 2003, or various other years that change as the years pass and nothing happens).

Though strangely, when I went to look up the details of these predictions, I didn’t have much luck in finding doomsayer websites warning us about Elenin. All I could find is astronomers debunking the theory, without finding the bunk itself. (Must be a conspiracy.)

Of course Elenin is too small to cause any problems unless it hits us directly, which it certainly isn’t going to do.

JPL’s Donald Yeomans calculated the gravitational force we’ll see from Elenin at its closest:

“So you’ve got a modest-sized icy dirtball that is getting no closer than 35 million kilometers,” said Yeomans. “It will have an immeasurably minuscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”

By the way, Leonid Elenin was working from Lyubertsy, Russia when he discovered the comet last December ... but he was using the International Scientific Optical Network’s observatory near Mayhill, New Mexico. It’s pretty cool that you can discover a comet from that far away. Technology is wonderful – even to an old-fashioned dob-driving girl like me.

But remember I said there were two comets, not one. On October 8, a few days before Elenin’s closest approach to the sun, it will appear very near short-period comet 45P/Honda–Mrkos–Pajdušáková (and you thought Hyakutake had a tough name!) This comet will be just past its September 30 perihelion, when it’s expected to reach magnitude 7.3 – so with luck, it may be brighter than either Elenin or Garradd.

Incidentally, Honda–Mrkos–Pajdušáková passed 9 million kilometers (under 6 million miles) from us this past August, far closer than Elenin will ever get. And it’s been making regular close passes for years (it was discovered in 1948). It’s strange that doomsday soothsayers would focus on Elenin when Honda–Mrkos–Pajdušáková is so nearby.

Go figure.

What if you want to look at something besides comets? Well, Jupiter is at opposition on Oct 29, and also fairly high in the sky, transiting at 65 degrees. Not only that – it’s was also at perihelion this year (back in March), so this will be an unusually close opposition, with Jupiter’s disk spanning almost 50”. We should get fantastic views of this beautiful and complex planet over the next few months.

Uranus and Neptune are well placed and visible all night, in Pisces and Aquarius (off the left horn of Capricornus), respectively.

You can also catch Pluto, but start as soon as it gets dark – on the edge of M24 in Sagittarius, Plutu sets around 11 p.m.

Venus is low in the dusk sky, joined by Mercury late in the month.

Mars is in the morning sky; by month’s end Saturn emerges from behind the sun to join it.