Watch for the Zodiacal Light!

This time of year is a great time to look out for an optical phenomenon known as the zodiacal light.

The zodiacal light is an optical phenomenon that is caused by the sun's light reflecting off of cosmic dust in the inner solar system. It can be seen as a faint triangular wedge of light on the horizon, and along the ecliptic.

The best conditions for viewing the zodiacal light are just after sunset in the spring, and just before sunrise in the autumn. Lighting conditions must be extremely dark, however, in order to see the zodiacal light. Any light pollution or moon light will ruin your chances at seeing this phenomenon. Also make sure not to mistake a local town or city's light dome for the zodiacal light.

Many people have been looking for the zodiacal light for years and have not seen it, so if you don't see it, don't be disappointed! Its worth having a look, though!

Clear skies!

Image courtesy of Dominic Cantin.

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Moon to Occult Pleiades Cluster

On the night of April 8, 2008, at approximately 9:45 PM EDT, the moon will occult some of the stars of the open cluster, M45 (otherwise known as the Pleiades). This should be a great event to see in a wide-field eyepiece or binoculars. Watch the stars as they pass behind the moon, they may wink on and off several times as they pass behind ridges and craters!

Clear skies!

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Carnival of Space #45

Carnival of Space #45 is up at Missy Frye's blog. Enjoy!

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What a Birthday Gift!

Tonight's (Mar. 12) viewing conditions so far have made for a great birthday gift! Seeing is very steady, with patchy high clouds. The seeing is the best I've seen yet, as a matter of fact! (Seeing is a rating of how steady the air is) Views of Saturn and the Moon are incredible! I first set my telescope up outside to cool down. Its been pretty cold at night here, so I wanted to give it plenty of time to cool. Once I went back out to observe, I first thought that the night would be a wash because of scattered high clouds. A view through the eyepiece quickly changed this assumption, however.

My first target was Luna. I started off with my 6 mm eyepiece, yielding 208x magnification. On an average night, this would be bordering on unusable, due to typically poor seeing in my area. After viewing through this eyepiece for a while, I realized that the views were much sharper than normal. So I decided to throw in my 4 mm eyepiece, which almost never gets used due to its 312x magnification. This is almost always too much for my local atmosphere to support. To my surprise, however, the image was tack-sharp at 312x! Detail at the terminator was amazing. The craters appeared to pop out in 3-D! I was so astonished at the views at this magnification, that I didn't realize the moon was about to go behind a cloud until it fuzzed out completely!

After the moon went behind a cloud, I saw that Saturn had popped out from behind another cloud. Instantly, I turned my scope around and targeted the planet with my finderscope. My first views of Saturn at over 300x were astounding. There is so much to see there, including the cloud bands, the Cassini Division, Saturn's moons, and the shadow of the rings on the planet. All of these features were obvious in the eyepiece. There was no straining to see the Cassini Division, it was just there. The planet didn't wiggle or waver, just tack-sharp! It almost looked like a text-book image of Saturn!

Eventually, clouds moved in over the entire sky. As I'm writing this, I'm waiting for the clouds to move out again, hoping the seeing will be just as steady. Conditions like these are ones to remember.

Sorry for the sparse writing this week, its spring break time!

Clear skies!

Images courtesy of NASA.

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Carnival of Space #44

Carnival of Space #44 is up at Phil Plait's Bad Astronomy Blog. This week's carnival has a Mars theme!

Clear skies!

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Earth from Mars

Most amateur astronomers have seen Mars. A moderately sized telescope can show a bit of detail. Have you ever wondered, however, what Earth would look like from Mars? Kind of like this..


This image was taken by NASA's Mars Reconnaissance Orbiter on October 3, 2007.

Image Courtesy of NASA/JPL-Caltech/University of Arizona.

Clear skies!

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Spacecraft Experience Orbital Anomalies

As early as Pioneer 10 and Pioneer 11, NASA and other spaceflight agencies have noticed a small discrepancy in the expected and actual trajectories of space probes. The twin probes from the mid-70's flew by Jupiter and then Saturn. The spacecraft was then flung on its way out of the solar system using Saturn's gravity assist. The spacecraft, for the most part, has followed its expected path out of the solar system. There has been, however, a tiny discrepancy in the orbital trajectory of the spacecraft. This discrepancy has become known as the "Pioneer Anomaly". The Pioneer probes are not the only spacecraft to exhibit this strange effect, which has been observed numerous times more recently.

This effect has been observed by tracking the spacecraft's radio doppler shift. Using this data, scientists can obtain very accurate readings of its position and velocity. Standard gravitational models are used to predict its exact location and trajectory. These models, however, have been shown to be off by the most minute amount, and show a tiny acceleration towards the sun, not accounted for by gravity. What could this mean? There are many explanations, ranging from the mundane to the exotic. Some such explanations are given below, as partially quoted from this article on wikipedia:

• Observational error - The problem with this explanation is that 7 separate and independent analyses have confirmed the Pioneer Anomaly.
• An unaccounted for deceleration - This is a distinct possibility. It could be that gas or fuel leaks are actually changing the orbits of the spacecraft. This is unlikely, also, because of the numerous spacecraft that have reported very similar problems.
• Electromagnetic repulsion or attraction, due to charges accumulated on spacecraft.
• Friction with the interplanetary media - An unlikely explanation, as the interplanetary media is much too sparse to adversely affect an orbit.
• Statistical variation in the measurement of the spacecraft's orbits - Again, many satellites and probes have reported similar measurements.
  
• The effects of dark matter and dark energy on our current understanding of astrophysics.
• The effects of distribution of matter in the Milky Way.
  

Several modern spacecraft are also reporting Pioneer anomalies. Six recent flybys of the Earth were considered: two by Galileo, the NEAR mission to Eros, Rosetta, Cassini, and the recent Messenger. In five of these six flybys, the anomaly was detected. The anomaly measured in these craft are very much real. The NEAR mission's anomaly was measured to be off by 13 mm/s with an accuracy of 0.1 mm/s. The spacecraft's velocity error was less than 0.0000001 %, which may seem tiny, but it is very much real, and previously unaccounted for. If this seems tiny, think about it on astronomical scales. Data shows that Pioneer 10 and Pioneer 11 are both about 240,000 miles (400,000 kilometers) closer to the sun than they should be. Now that's cause for concern. The question is, how will we account for this anomaly? What could really be causing it?

Recent theories propose that Pioneer's anomalous acceleration towards the sun [(8.74 ± 1.33) x 10⁻¹⁰ m/s²] is actually quite close to the product of the Hubble constant, which pertains to galaxies' redshifts [70.4^+1.5_−1.6 (km/s)/Mpc] and the speed of light [c = 2.99 x 10⁸]. This is an interesting proposal. We will have to wait, however, to see what its implications are, and whether it is correct. Scientists will be closely watching the trajectory of Rosetta's second flyby and New Horizon's trajectory as it speeds towards Pluto. We'll see if these two craft exhibit similar anomalies. If they do, it could mean a rethinking of our current physical models.

Clear skies!

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Avalanche!

NASA's Mars Reconnaissance Orbiter has caught Mars in the act of geological change! Recent images recieved from the orbiting camera station show a large avalanche on February 19, 2008. The dust cloud seen in the image below is about 590 feet (180 meters) across and 625 feet (190 meters) long.


This is actually one of four such landslide seen in one larger photo, available here. The 2,300 foot (700 meters) cliff seen in this image is part of the raised section that comprises Mars' northern polar region. The ice on the west side of the image is part of Mars' polar ice cap, a frozen deposit of carbon dioxide and water ice. Many of the images obtained by the Mars Reconnaissance Orbiter show seasonal and small-scale changes, such as dust devils. This, however, is the first image of large-scale change in progress, a rare sight indeed.

While the mechanism responsible for the collapse are as of yet unknown, several causes have been proposed. It could have been a "Mars-quake", or a small meteorite impact. It also appears that sections of the upper cliff face have been cracked and eroded by the timely expansion and contraction of the polar ice cap. These weakened sections of the cliff face could be dislodged by gravity or Martian winds. Information gathered from these images could help planetary geologists piece together one more aspect of Mars' mysterious geological history.

Clear skies!

Image courtesy of: NASA / JPL-Caltech / University of Arizona

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