Zip... ...zoom!

A clever fellow in Germany, Till Kredner, who co-authors the great website All the Sky, has a a great clip of the Jules Verne transport vehicle and the space station passing over Hohenzollern Castle.

It's greatly sped up, and the smaller, dimmer Jules Verne ATV is in front of the International Space Station (ISS). You can just catch an airplane as it passes 'near' the departing and much brighter ISS.

The ATV is now docked to the ISS, and will remain there for many weeks. It's used to take supplies up, boost the orbit of the ISS, and take garbage away.

Bored? Got a few moments?

Head over to the Galaxy Zoo and do some classifying!

Learn the difference between elliptical and spiral galaxies in a few minutes with an easy tutorial, take a test, and if you qualify you can start classifying galaxies in no time at all.

You will likely be looking at images seen by no other human, and contributing to a massive effort led by English researchers at Oxford University to classify over a million galaxies. There is apparently some evidence from a sample of about 1,600 galaxies that there is a locally preferred direction of rotation, and this effort will try and confirm or refute this with a much better statistical sample using images from the Sloan Digital Sky Survey, which reaches out far beyond the local group.

You will get pretty good at it, and quickly amass several hundred galaxies.

Here are two typical samples:


...obviously a clockwise spiral.

Here's one that's a little more difficult:


...a little less obviously another clockwise spiral.

It can get difficult:



There are some cases, like this one, where the galaxy is so far away that the image is extremely low resolution, and there is really no way to tell.

Sky awareness alert:

Total lunar eclipse viewable from all continents this weekend.

• First penumbral contact 20:18 GMT (not visible in the Americas)
• Interior umbral contact 22:44 GMT (viewable in Eastern South America, Europe Africa & Asia)
• Greatest Eclipse 23:21 GMT (viewable at moonrise in Eastern North America)
• ...
• Last penumbral contact 02:24 GMT (not viewable in Eastern Asia & Australia)

Bonus points:
What is moving - the Earth, its shadow, the Moon, or all three?

Extra bonus points:
How many of the following would you need to know to figure out how far it is to the sun by timing this eclipse?

• Mass of the Earth
• Mass of the Moon
• Mass of the Sun
• Diameter of the Earth
• Diameter of the Moon
• Diameter of the Sun
• Distance to the Moon
• Need more info
  

Sounds of good old Saint Nick:

When something moves really, really fast through the air, we can hear it. Faster than a speeding train. Faster than a speeding bullet. I'm talking hyper-sonic.

Lightning drills a 1 to 2 cm hole in the sky several kilometers long. Thunder is what we hear when the atmosphere is snapped open and then refills the hole. Imagine the sound when a hole about 1 meter in size gets drilled through tens of kilometers in a second or less.

That's what happens when a significant meteor comes down to within 50 km of the surface. The sound produced by this shockwave (particularly the infrasound below 20 Hz) can be detected from several thousand kilometers away. These events are of interest not only because of the spectacular display and their effect on unwary populations (on September 27 an event over the state of Orissa in eastern India caused several people to collapse in shock, and one person died from a possibly connected heart attack), but also because they are detonations in the atmosphere, and could be mistaken for nuclear tests. In fact, the energy of these bolides is often quoted in kilotons of TNT, the standard energy equivalent for nuclear shots. A bolide with total energies over 1 kt is needed for infrasound detection with the current comprehensive test ban treaty infrasound international monitoring system, and estimates of the bolide flux in this range are about 10 events worldwide per year. About 6 to 7% of a nuclear blast's energy goes into sound, and the estimates for bolides range from 0.2 to about 7%.

Here's a great summary of the collision flux with Earth, ranging over 14 orders of magnitude, from an often quoted letter to Nature by Brown, Spalding, ReVelle, Tagliaferri and Worden (10.1038/nature01238 - PDF file):

Other methods that are used to detect these events are satellite optical and IR observations of the fireball, radio reflections, seismic signals (again, just a form of sound), and ground-based video. The proliferation of security cameras has in fact been a good source for fireball data, but often what is seen is a reflection off a car or a window, since the cameras are looking down to catch crime, and not up to catch celestial phenomena.

Things to remember: shooting stars and fireballs are neither stars, fire, nor comets; groundfall (pieces reaching the ground) from an event is extremely rare and very difficult to find, but are often mistakenly reported; eyewitness accounts are almost without exception useless for research (we are poor observers of exciting events).

There is a great article by Alan Hildebrand of the Royal Astronomical Society of Canada here that gives a nice mathematical summary of the chances of seeing a meteorite fall. Summary: of the approximately 7,000 groundfalls in a year, about 5 have a chance of being seen. His comment about a herd of dairy cattle extending a person's awareness cross-section made me laugh...

There is a nice page about the 1947 Sikhote-Alin fireball (and groundfall!) here.

A Colorado website tracks fireballs, here, and seems to have a scientific approach.

Then again, if you are listening on Christmas Eve, and hear a rumble under clear skies, it could be the crack of a reindeer whip you hear.