What is the nature of the mysterious dark energy which is accelerating expansion of the Universe? In a recent study published in the Physical Review Letters, physicists are proposing two scenarios: thawing and freezing. In thawing, the expansion of the Universe should eventually come to a stop, and maybe even reverse. In "freezing", the acceleration should continue indefinitely. A new mission: the Joint Dark Energy Mission (JDEM) has been proposed by NASA and the US Department of Energy, and should be able to determine which of these two scenarios is correct.

Here's a picture of Saturn's moon Enceladus side by side with the United Kingdom, to show its actual size. Enceladus is only 505 km (314 miles) across, and it could comfortably fit within the states of Arizona or Colorado.

Dust from asteroids entering our atmosphere could affect the weather more than scientists previously believed, according to a new study published this week in the journal Nature. An international team of researchers have studied the dust trail of an asteroid that burned up as it descended through the atmosphere above Antarctica. The 1,000 tonne asteroid formed a cloud of micron-sized particles large enough to influence the local weather in Antarctica.

The ozone hole above the South Pole has returned, and it's on track to be one of the biggest on record. At this time, the hole is the size of Europe, but it will probably continue growing during September - bigger holes appeared in 1996 and 2000. The size of the ozone hole and the time of its appearance depends on the weather conditions in the southern hemisphere.

Greetings, fellow SkyWatchers! This is going to be an exciting week as we start off watching two planets get farther apart and two planets getting closer. Deep sky studies aren't always the property of telescopes, and I encourage you to turn binoculars toward the "Swan Nebula". The next seven days mean dark skies and New Moon, so hitch your wagon to a star as we fly with the "Eagle", take part in a meteor shower, learn we are not "Dumbbells", reach for the "Ring", and quest for the holy "Veil". If all this leaves you "Blinking", then best get your binoculars and telescopes ready, because...

Here's what's up!

Dream up an hypothesis and envelop it with supporting evidence and you're well on the way to contributing to the scientific process. Given that nature surrounds us with a veritable nirvana of wonders, this reasoning process serves us well. A case in point - many years ago, bright flashes in the sky, followed by powerful explosions, teased our imaginations and brain power then and today. Surendra Verma in his book The Tunguska Fireball plays part detective, part historian and part scientist in presenting some highly speculative yet nevertheless plausible reasons for this natural wonder. Scientific processes by their nature are based on fact, but read this and you can judge for yourself how close imagination is its parody.

If you look closely, you can just see Saturn's moon Pan, making its way in between a gap in the planet's majestic rings. Pan is only 26 km (16 miles) across, and it lives inside the Encke Gap. It's also possible to see the subtle F ring in the upper right-hand corner of the photo. Cassini took this image on August 13, 2005 when it was approximately 2.3 million km (1.5 million miles) above Saturn.

Once again, the sky is getting ready to put on a beautiful show - one that doesn't require particularly dark skies, a telescope, or lots of time to enjoy. Three of the brightest objects in the sky: Venus, Jupiter, and the Moon will gather close together over the next two weeks. Jupiter and Venus will reach their closest point on September 1, but on September 6, all three will be relatively clustered together. All you have to do to enjoy this spectacle is look to the West after sunset.

According to new research from geologists, the Earth's core rotates just a little bit faster - about 1 degree per year - than the crust of the planet. The scientists took advantage of historical records for "earthquake twins" near the South Sandwich Islands. These are quakes that occurred in virtually the same spot with the same magnitude, but were years apart. As the seismic waves passed through the Earth, they were bent as they passed through the Earth's iron core. The shape of this bending has changed over time, indicating the core's faster rotation.

Larry took this close picture of comet Hale-Bopp from Germantown Hills, Illinois. This image was taken with a Nikon 35mm camera and a 200mm lense riding piggyback on the guided telescope.

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.

Joseph Caruana took this picture of M104. Joseph used a Meade DSI PRO to take this image.

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.

Shevill Mathers took this beautiful picture of an aurora beam on the 24th, August from Tasmania, Australia.

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.

Michael Good took this picture of M57 Ring Nebula with Galaxy IC1296 from Roanoke, Virginia. Michael used a Meade 10" LX200 classic.

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.

Wait, don't throw that garbage bag away. It might come in handy if you wanted to build a spaceship. At least, that's what NASA scientists working on new spacecraft materials are proposing. They've invented a new polyethylene-based material called RXF1 that's even stronger and lighter than aluminum. A plastic material like this is actually surprisingly protective against solar flares and cosmic rays since it doesn't produce "secondary radiation", like aluminum.

Amateur astronomers are helping unravel mysteries about about a strange binary star system. Even though space and ground-based observatories will be observing the cataclysmic variable star AE Aqr, astronomers are calling on amateurs to make additional observations as well. AE Aqr consists of a red dwarf feeding material to a white dwarf companion star. Instead of striking the white dwarf, this material is flung out of the system by the star's intense magnetic field. Amateurs are being asked to observe this object every night until September 3.

In the constellation of Pisces, 100 million light-years from Earth, two galaxies are smashing together in a dramatic demonstration of our far future: when the Milky Way collides with the Andromeda Galaxy. This image of NGC 520 was taken with the Gemini North Telescope on the evening of July 13-14, 2005. It's possible to see dark dust lanes and a long trail of stars thrown out by the cosmic collision.

Cassini captured this image of Titan's bright side during its recent flyby on August 21, 2005. The photograph was taken when Cassini was 213,000 kilometers (132,000 miles) from Titan. This picture is a natural image, which shows the thick smoggy atmosphere that normally blocks views of the moon's surface.

Scientists always function on the cutting edge of their field. New discoveries, new processes, and new events highlight a challenging and sometimes rewarding career. However, scientists share this edge with others. For example, authors of science fiction novels regularly create new worlds, new physics and new societies that allow us to contemplate our own existence and guide our scientific studies. Robert Markley in his book Dying Planet captures nuances of both these fields in reviewing how research and literature about the planet Mars have been busily advancing our wonder, questioning and knowledge.

Rick Stankiewicz took this picture of the Moon and Mercury on the 22th, March 2004 from his backyard near Keene, Ontario, Canada. This image was taken with a Nikon Coolpix 995.

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.

NASA scientists think they've developed a strong case that liquid water created the strange gullies discovered on Mars a few years ago. These gullies might indicate underground sites of water, and could be a good place to search for life. Although Mars' environment is too cold, dry and low pressure to support liquid water, it could last a little while as it escaped from an underground reservoir. The lack of debris fields at the ends of these gullies suggests the water froze or evaporated before it reached the bottom.