Tuesday, December 11, 2007

Jumpin' Geminids

What you’ll see: You might see a meteor per minute. (Maybe more, maybe less. And the darker the sky conditions, the better!)

When to look: Here in North America, the best time for viewing will be the evening of Thursday, December 13 (with the meteor rate increasing as the night goes on) and somewhat also the evening of Friday, December 14 (declining as the night goes on).

Where to look: Looking toward the constellation Gemini (near Orion and Taurus) will increase your chances of seeing meteors, but it’s possible to see them anywhere in the sky. (See below for more about this.)

**Be sure to allow about 20 minutes in the dark in order for your eyes to adapt! And don’t forget to dress warmly to ensure a comfortable observing session.

(Click on the above Stellarium freeze-frame for an enlarged view.)


All About Meteor Showers:

◦ A meteor is a brief, one to two second streak of light across the sky. Although sometimes referred to as a “shooting star” or “falling star”, a meteor is not a star at all but actually a small rock being heated and vaporized as it descends through the Earth’s atmosphere. (Note that meteors are sometimes also confused with comets. Unlike meteors, comets are chunks of rock and ice in orbit around the Sun, usually with a “tail” and, when visible from Earth, seen in approximately the same position in the sky over the course of several days or weeks.)

◦ In recent years, scientists have discovered that most meteors are surprisingly small—the average bright meteor streak is caused by a rock no bigger than a pencil eraser in diameter!

◦ On any given night of stargazing, you can expect to see a meteor or two. (The rate on an average night is about 2 meteors per hour.) This is because, at any given time, there are always a few small rocks that happen to wander too close to the Earth, and are pulled in by our planet’s gravity.

◦ A meteor shower, or large increase in the hourly meteor rate, occurs when the Earth makes an annual pass through a stream of small rocky debris left by various small rocky objects in our solar system (e.g. comets and asteroids). Typically the best meteor showers are the Perseids (mid-August, when we pass through the debris stream left by Comet Swift-Tuttle) and the Geminids (mid-December, when we pass through the debris stream left by an asteroid called Phaethon), though there are eight other major annual meteor showers. (Usually these latter are somewhat less impressive).

◦ During the Geminid meteor shower, it may be possible to see meteors at any place in the sky, however it’s best to look in the general vicinity of the constellation Gemini. (See the attached star chart; Gemini is to “upper left” of Orion; located 30 to 40° above the eastern horizon by 9:00 pm.)

◦ The “debris streams” mentioned above tend to intersect the Earth at a single point. As a result, during a meteor shower we see a perspective effect, whereby all of the meteors of a given shower appear to radiate, like spokes on a wheel, from one place in the sky. This explains our naming system for meteor showers: the Geminid meteor shower appears to radiate from the constellation Gemini; the Perseids from the constellation Perseus, etc.

(Hat tip for the title "Jumpin' Geminids": Gus Van Horn.)

Saturday, November 10, 2007

Lunar Eclipse 2008

(Image of the Lunar Eclipse of August 27, 2007, taken by Martin Pugh.)

You can find advance information about February's lunar eclipse here.

Check back at Revolving Rock closer to the time of the eclipse for updates and observing advice.

IMAGE CREDIT: Please note that the above photograph is of the August 27, 2007 lunar eclipse, and was taken by astrophotgrapher Martin Pugh. That coloring was stunningly red during that eclipse, and Mr. Pugh's image captures it beautifully. It was showcased on the August 30th edition of Astronomy Picture of the Day.

Wednesday, September 19, 2007

Peru Meteorite Crash Causes 'Mystery Illness'


If you didn't catch this on today's news, check out this article. I'll be curious to hear what the cause of the illnesses is, if it can be determined.

Saturday, September 8, 2007

"In The Shadow of the Moon" Coming Soon to Nearby Theatres

Back in July I mentioned why I think this movie should be seen (and I recommended a related TV series).
It's now making its U.S. premier (in Hollywood and NYC)--which I'm going to attend tonight--and in the weeks ahead, it will appear in major cities nationwide.

Don't miss it!



Wednesday, August 29, 2007

Meteor "Storm" This Saturday?

You're going to start to think I'm crying astronomical wolf. But I swear to you, brother, it's purely coincidence that there's lately been so many celestial events worthy of your attention.

So here we go again...

There's a "skywatching wildcard" early on the morning of September 1st (this Saturday). I'm not going to get your hopes up, but neither can I fail to inform you that it is possible that observers in the Western states may be treated to one of the greatest meteor shower in their lives, with rates of meteors of up to 1,000 an hour. (Compare that with the annual Perseids, which on average deliver 60-80 meteors per hour.)

Possible.

Read the article here, "Earth to Hit Aurigid Meteors?" in Sky & Telescope.

UPDATE: More info here at NASA's dedicated Aurigid Meteor site. The meteor shower will look best from the places marked below:


Amazing Weather Phenomenon Discovered!


Undoubtedly there are earthly phenomena you know about, but just haven't witnessed firsthand. Hurricanes, volcanoes, and earthquakes are a few candidates that personally come to mind. (Despite having lived the majority of my life in Illinois, happily I've even yet to see a tornado!)

Conversely, there are phenomena you may have experienced, but never knew what it was, or even that it had a name, for example: Sun dogs, crepuscular rays, green flash, or Belt of Venus. (I know; cool right? Now you know.)

But how rare is it that you come across a phenomenon which you had neither heard of nor experienced in your entire life? Well, probably as rare as GJs--"Gigantic jets".

Believe it or not, "Gigantic jets" are newly discovered, and were inadvertantly captured on film for the first time in the continental U.S. just nine days ago by one Mr. Richard Smedley of Broken Arrow, Oklahoma. Watch these powerful discharges in the video linked above, and read more about them here, on today's APOD.

Missed the Lunar Eclipse? Despair Not...

There will be another total lunar eclipse, visible across all North America, on February 20, 2008.
This one will occur in the evening hours.

My sincere apologies to you if you missed sleep on Tuesday but wouldn't have bothered doing so had you known this in advance!

But... I hope you did see Tuesday's eclipse. I did, and I'm glad, because not all eclipses are the same! The exact coloration of the Moon depends upon the amount of dust and smoke present in the Earth's atmosphere at the time of the eclipse, as well as how far the Moon penetrates the inner part of Earth's shadow. Tuesday's eclipse was, in my opinion, especially beautiful--a uniform, pale red when the eclipse reached totality--so presumably these factors were at play in just the right way.

Within the next day, I'll update this entry with a link to some photos when I get the chance to look for some good ones.

UPDATE: From APOD, image credit & copyright Martin Pugh.

Saturday, August 25, 2007

Lunar Eclipse on Tuesday (Early Though!)

Here's a heads up that the Moon will pass through the shadow of the Earth on Tuesday, August 28.

There are always two lunar eclipses per year, some of them total, some of them only partial, and not all of them visible from your location.

If you appreciate experiences of cosmic proportions, you'll find total lunar eclipses especially very beautiful. Not only are they a rare opportunity to directly observe the sphericity of that big rock you call home, but they're also the only way you can experience the sum of all sunrises and sunsets happening on Earth at one moment. (That's why the Moon turns that eerie shade of red-orange! Think about it...)

So, you may find it worth your while to set your alarm and crawl out of bed to have a peek. (Did I mention it was early on Tuesday, Aug. 28? Heh. For example, here in southern California, the eclipse doesn't begin until 1:51am, and the Moon won't enter totality until 2:52am.) You can find eclipse information for your locality here at NASA's Eclipse Page.

Advice: Tuesday's Lunar Eclipse

If you're not too familiar with lunar eclipses, here's some good advice to keep in mind if you're planning to observe next week's event. Number one: staring at a lunar eclipse for too long will cause you to go blind. Just kidding. (But can you believe that that's apparently enough of a misconception that NASA feels it's worth speaking to, on their eclipse website?)

Here's the real advice, with elaboration below each point:

1. You want to see the Moon when it's in the umbra, not the penumbra.

There are two parts to any shadow, and this includes the one cast by the Earth: there's the lighter, outer shadow (called the penumbra) and the darker, inner shadow (called the umbra). The effect of Earth's penumbral shadow being cast on the Moon is extremely subtle. So subtle, in fact, that I guarantee you won't notice it. So if you're checking a time table for the lunar eclipse, you'll want to make sure you find out when the Moon first comes into contact with the umbra, not the penumbra. Otherwise you'll find yourself sitting there for over an hour waiting for anything appreciable to occur. I say this out of personal experience (I once went to some length to pack my telescope and drive far out into the country for a "total" lunar eclipse, only to learn that some "total" lunar eclipses are entirely penumbral, i.e. hardly noticeable. Absurdly, this means that there are some partial lunar eclipses more worthwhile than total ones!)


2. To observe this eclipse, you're gonna need an alarm clock, a pot of coffee, and, if you're east of the Pacific Time Zone, a tolerance for slight unfulfillment.

For locations in North America this Tuesday's lunar eclipse occurs in the early morning hours. In fact, for everywhere except the Pacific Coast, the umbral eclipse is beginning in the pre-dawn hours, as the Moon is approaching moonset. Now I don't mean to discourage anyone from trying to go out to see it (quite the contrary!)... it's just that I want to issue this disclaimer, lest I get anyone's hopes up:

Unless you live far out in the Pacific Ocean, you're going to have to get out of bed real early. Additionally, the further east of the Pacific that you live, the lower in the sky (and closer to the time of sunrise) the eclipse event is going to occur, and the Moon will actually set while the eclipse is still in progress.


3. If you own a pair of binoculars, or a small telescope, use it.

But, that said, if you don't, don't fret. Your naked eyes will do just fine.


4. For your convenience:

Here's the time schedule, culled from NASA's Total Lunar Eclipse of Aug. 28, 2007 webpage for when the Moon approximately begins to enter the umbral shadow, and when it completely leaves it:

Eastern Daylight Time: Begins to enter at 5:52 am; completely leaves by 7:22 am
Central Daylight Time: Begins to enter at 4:52 am, completely leaves by 6:22 am.
Mountain Daylight Time: Begins to enter at 3:52 am; completely leaves by 5:22 am.
Pacific Daylight Time: Begins to enter at 2:52 am; completely leaves by 4:22 am.

As I said, for most observers the moon will set while the eclipse is in progress. But if you're curious, you can find Moon- (and Sun-) rise and set data by entering your location and the date (Aug 28) in the following form available at the U.S. Naval Observatory's Complete Sun and Moon Data for One Day.

5. You're not crazy if you do in fact get out of bed to go watch this.

Who cares what your boss thinks about the bags under your eyes? You directly observed the sphericity of the Earth, man! You saw the light of the sum of all sunrises and sunsets! You're one of those rare lovers of the world and all its splendid phenomena!


6. But you are kind of crazy...

You lunatic! I mean did you notice the time tables above--that's insanely early! And it's a worknight, no less! Lunar eclipses are not so rare that it's not like you won't have another chance in your life to see some more, blah blah blah...

(I leave it to your speculation to decide where I'll be early Tuesday morning.)