Polaris, or the North Star, is one of the most famous stars in the sky. But did you know it's actually a triple star system? In a small telescope it's easy to see two stars, but it took the massive resolving power of the Hubble Space Telescope to spot the third. By resolving this third star, astronomers hope to be able to accurately measure Polaris. This is very important because Polaris is a member of a special class of stars called Cepheid variables which are used by astronomers to measure distances.

This beautiful photograph taken by the Spitzer Space Telescope shows a region of space containing one of the largest clusters of stars ever seen. It appears to weigh in at 20,000 times the mass of our Sun, and contains at least 14 red supergiant stars. These supergiant stars are about as large as stars can get, and will die a violent supernova death within only a few million years. Spitzer used its infrared instrument to peer through the thick gas and dust that shrouds the centre of the Milky Way, obscuring them from view.

Astronomers have discovered that nearby satellite galaxies, the Large and Small Magellanic Clouds, are interacting with local dark matter to warp the disk of the Milky Way. It was originally believed that the Magellanic Clouds had too little mass to affect the shape of the Milky Way. Researchers from UC Berkeley have created a simulation that includes data about the Milky Way's dark matter. As the Magellanic clouds orbit our galaxy, they introduce a warp to our galactic disk that matches observations.

Greetings, fellow SkyWatchers! If you're not "seeing double" yet, you will by the end of the week as we explore the wonderful world of multiple stars systems. There will be plenty of lunar features to keep you busy and some history to study as well, so be sure to put on a coat if it's cold and head out tonight, because...

Here's what's up!

Astronomers have found evidence of monstrous black holes at the heart of galaxies with the mass of millions of stars, or ones with just the mass of a single star. But not much in between (100 to 10,000 stellar masses). One of the newest pieces of evidence for a medium-sized black hole was captured by NASA's Chandra X-Ray Observatory. It measured the orbit of a star trapped in a death spiral around one of these medium-mass black holes.

This moody image of Saturn was taken by Cassini on December 5, 2005. It was taken using a special combination of the spacecraft's spectral filters to reveal delicate haze in its upper atmosphere. A methane-sensitive filter makes the high altitude features stand out, while a polarizing filter makes the small haze particles bright. The small white dot at the right side of the rings is Saturn's moon Dione.

NASA's Stardust spacecraft performed its 18th and second-to-last flight maneuver on January 5th, perfecting its aim for Earth. On January 15, 2006, the spacecraft will release its sample return capsule, which will re-enter the Earth's atmosphere. The capsule is carrying particles collected by Stardust as it passed through the tail of Comet Wild 2. NASA will then fly the capsule back to the Stardust Lab at the Johnson Space Center in Houston.

Astronomers from MIT and Williams College were fortunate enough to be watching Pluto's moon Charon at the moment that it passed in front of a very dim star. By measuring how the light from this star dimmed as it passed behind the tiny, distant moon, they were able to come up with a very accurate measurement of Charon's size (606 km or 377 miles). They also determined that the moon doesn't have any appreciable atmosphere, lending evidence that it was formed when something smashed into a proto-Pluto millions of years ago.

This image, taken by ESA's Mars Express spacecraft, shows an unusually shaped impact crater Hesperia Planum region of Mars. The crater is approximately 11 x 24 km (7 x 15 miles) across and has ejecta surrounding it where molten rock splashed around when a meteor carved it out. While most impact craters are circular, this elongated shape means that the space rock hit Mars at an extremely low angle (less than 10 degrees). Similar craters have been seen on the Moon.

The powerful Gemini telescope produced this amazing photograph of the N44 superbubble complex (also known to astronomers as NGC 1929). A cluster of hot, young stars have pushed out a cavernous bubble in this nebula 325 by 250 light-years across. Additional smaller bubbles can be seen inside the nebula, which could have been formed by collapsing gas and dust.

A team of European astronomers has calculated the rate that supernovas are exploding in the Milky Way: approximately one goes off every 50 years. They came to this calculation by measuring the amount of gamma rays coming from radioactive aluminum at the centre of the Milky Way. They were able to estimate that there's a total of approximately three solar masses of radioactive aluminum in the galaxy - produced by supernova exploding every 50 years or so.

I'm sure some of you noticed we missed this week's What's Up, and I apologize, my whole family was a little sick this week, so I wasn't able to put much work into the website. However, I have a big surprise for all of you. Tammy has been hard at work for the last 4 months writing a book... for you.

What's Up 2006 - 365 Days of Skywatching

This is a FREE 407-page downloadable book containing What's Up material for every day in 2006. You can download the book to your local computer, go to the day you like and print off the page to take outside with you nicely formatted. It's also got tons of other material including general skywatching advice, equipment selection, and hundreds of beautiful photographs. We've been working pretty hard on this. :-)

And yes, this book is absolutely free. Download it, send it to your friends, print it off. Oh, and if you could tell everyone you know, we'd really appreciate it. :-) We'll still be having the same old web content as well, and some additional material to support the book. I'm still getting that all together, but I didn't want to delay the release any longer.

Also, this is an experiment, so give me any feedback you have, suggestions for improvements, etc.

Fraser Cain
Publisher
Universe Today

The centerpiece of NASA's Vision for Space Exploration is the new spacecraft that will carry astronauts to the moon, Mars and beyond. Jeff Hanley, appointed as Constellation Program manager in October, discusses the development of the new Crew Exploration Vehicle, the role of the International Space Station, and the path of the 'Vision.'

When the Apollo astronauts stepped out onto the lunar surface, they were the first human eyes to see this alien landscape. And one of the strangest things that they saw were the shadows. On Earth, our shadows aren't black, but blue, thanks to the scatter light passing through our atmosphere. But on the Moon, which has no atmosphere, the shadows are utterly black. The darkness of the shadows was one of the first things that Neil Armstrong noticed as he stepped off the lunar module and onto the surface of the Moon.

This natural colour photograph shows Saturn's moon Tethys going past the planet's huge globe with the thin line of rings curving at the horizon. The craters Odysseus (top) and Melanthius (bottom) are also visible on Tethys surface. This image was captured at a distance of approximately 2.5 million kilometers (1.6 million miles) from Saturn by the Cassini spacecraft narrow-angle camera on Dec. 3, 2005.

Pluto is far away from the Sun, so you'd think it should be cold - but it's actually colder than astronomers were expecting. Its temperature was taken using the Submillimeter Array (SMA) on Mauna Kea in Hawaii, which was able to distinguish between Pluto and its moon Charon. Pluto is about 43 K (-382 degrees F), while Charon is 10 degrees warmer. Scientists think that heat from the Sun is converting nitrogen ice on Pluto to gas, which cools it down, similar to evaporation effect when something wet feels colder.

Gregory Cranwell took this picture of Great Orion Nebula on November 24, 2005 from Tucson, Arizona. Gregory used a LXD 75 Schmidt Newtonian 8" with a Canon Rebel XT 8.0 megapixel digital SLR.

Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.

Jamie Johnstone took this picture of the Moon. Jamie used a Canon EOS 300D fitted with an old Elicar 200mm lens with a 5X converter on.

Do you have photos you'd like to share? Post them to the Universe Today astrophotography forum or email them to me directly, and I might feature one in Universe Today.