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And the mystery is that these galaxies--nine of them, each only 5,000 light years in diameter and with as many stars as normal, much larger galaxies--have been measured to be 11 billion light years away. That means we're supposedly seeing them as they appeared 11 billion years ago. Now, according to big bang cosmology, the universe is about 14 billion years old. The compact galaxies we see today should appear to be only 3 billions years old. So what's the problem?

The problem is that galaxies so young shouldn't be so compact. The apparent engine of galaxy formation is gravity, and the longer gravity can work on a system, the more compact the system should get. But most of the "old" galaxies we observe today are not as compact, comparatively speaking. If galaxies do indeed change from one type into another, what phenomenon caused these young compact galaxies to become less compact with age?

In a Hubble news release today, astronomers pondered the issue: 

 "Seeing the compact sizes of these galaxies is a puzzle," said Pieter G. van Dokkum of Yale University in New Haven, Conn., who led the study. "No massive galaxy at this distance has ever been observed to be so compact. It is not yet clear how they would build themselves up to become the large galaxies we see today. They would have to change a lot over 11 billion years, growing five times bigger. They
could get larger by colliding with other galaxies, but such collisions may not be the complete answer."

. . . .

How did these small, crowded galaxies form? One way, suggested van Dokkum, involves the interaction of dark matter and hydrogen gas in the nascent universe. Dark matter is an invisible form of matter that accounts for most of the universe's mass. Shortly after the Big Bang, the universe contained an uneven landscape of dark matter. Hydrogen gas became trapped in puddles of the invisible material and began spinning rapidly in dark matter's gravitational whirlpool, forming stars at a furious rate.

*Tirade warning*
I hate it when scientists have to invoke dark matter to explain conundrums. No one knows what dark matter is. Using dark matter to explain a mystery seems to be like labeling a major engine part a "thingamajig" in hopes that other mechanics will have no qualms installing them, although none of them know what the "thingamajig" actually is. I'll look forward to the day when we have more information to work with than the simple label, "dark matter." Then maybe we'll know with more certainty whether dark matter and hydrogen gas ever had such a furious relationship.
*Tirade warning ended* 

 In the meantime, we can enjoy the discovery of compact galaxies, and puzzle along with astronomers as they observe and study these "small" exhibits of creation.

Image courtesy NASA, ESA, A. Feild (STScI), and P. van Dokkum (Yale University)

Tell me if this isn't a good idea: designing ion engines for space. The European Space Agency (ESA) is integrating ion engines into at least one of their spacecraft. While ion engines have miniscule thrust power, they can operate on solar power for years, unlike conventional fuel boosters, which are powerful but burn up quickly. Theoretically, a spacecraft running on an ion engine would start out slowly but accelerate indefinitely, reaching the edge of our solar system yet still increasing in speed.

The ESA, for now at least, seems to be interested in using ion engines for another purpose, which is to keep their Goce spacecraft in low-earth orbit. In this case the ion boosters would function as a "cruise control," in the words of one ion propulsion developer.

Go here to read the labels for the image. 

Image courtesy ESA 

Astronomers have discovered some odd goings-on at a neutron star:

Like something out of a Robert Louis Stevenson novel, researchers at NASA and McGill University discovered an otherwise normal pulsar which violently transformed itself temporarily into a magnetar, a stellar metamorphosis never observed before.

NASA covers this story in more depth here. 

 A little blurry, but I'm happy with these photos considering I was trying to time the shutter to open during occasional gaps in the clouds. Besides, it was about five degrees out.

The shot above was taken using a digital Canon Rebel XT with a three-and-a-half second shutter speed and f-stop of 5.6. The one below had an eight-second shutter. Both were zoomed to 300mm. 

Images copyright Daniel James Devine

If you live east of the Rocky Mountains, forget about the winter weather and take a few minutes to step outside before you go to bed this Wednesday night. Provided the sky is clear, you'll be treated to a total lunar eclipse about 9 pm Central. Lunar eclipses occur when the Earth blocks sunlight from reaching the Moon. Although you'd think the Moon would disappear during an eclipse--just like the dark portion of a crescent Moon--the disk actually turns a shade of red or bronze instead. Even though the Moon is in the shadow of Earth, some sunlight can bend through the Earth's atmosphere and reach the Moon's highly reflective surface. And since our atmosphere tends to scatter blue light (that's why the sky looks blue during the day), the light reaching the Moon will cast it an eerie red.

Supposedly one of these lunar eclipses got Christopher Columbus out of trouble once. 

The "totality" of Wednesday's eclipse will begin at 9:00 pm Central Standard Time (about 10 pm EST) and last for 50 minutes. A partial eclipse will begin around 7:45, but will not be very noticeable until totality approaches. The total eclipse will be visible to most people in the western hemisphere, but not west of the continental divide. (Sorry Californians)

Mr. Eclipse, who has a splendid page about lunar eclipses here, will no doubt be outside on Wednesday taking more of his remarkable photos. If you plan to take pictures yourself, read his photography tips.

The British Astronomical Association also has an excellent page of lunar eclipse photography. 

 See here for more.

Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

A stellar explosion w/out dust? Astronomers had thought novas created dust. And that stars were formed from it.

What might this mean for the nebular hypothesis of star and solar system formation? 

This image of Mercury was taken just a few days ago by the Messenger spacecraft, as it passed within 124 miles of the planet's surface in a trajectory that will allow it to orbit Mercury in 2011. Messenger will be the first spacecraft to do so.

Image: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington