Archive for July, 2009


Saturday, July 25th, 2009

Cruising silently through space, a comet is headed straight toward the planet. Nothing can stop the inevitable impact. It sounds like the setup for yet another disaster movie. But about a week ago, it really happened. However there was never any need to call Bruce Willis. The planet in peril was Jupiter. And far from being a disaster, the impact (probably by a comet, although scientists don’t know for sure) has been a boon for astronomers observing the dark mark left in Jupiter’s atmosphere. Even the testing and calibration of the upgraded Hubble telescope was put on hold to get pictures of the rare event. More information about the impact and Hubble’s picture taking can be found in this article.

To the backyard astronomer, the most important question about the mark left by the impact is “Can I see it?”  The answer is a clear and definite maybe. The good news is that Jupiter is currently in prime viewing position for us in North America, shining brightly in the southern sky. But whether the impact mark (estimated to be the size of the Pacific Ocean) can be seen depends on the quality of your telescope and the viewing conditions. My advice is to go with the highest magnification the seeing allows, put in a dark blue filter (to heighten contrast) if you have one, and give it a try. Of course, with Jupiter rotating on it’s axis, there’s always the risk that even if everything else is good, the mark will be on the “wrong” side of the planet. But at worst, you can still spend some time looking at Jupiter’s cloud bands and large moons, always interesting telescopic targets in their own right.

… in Peace For All Mankind

Monday, July 20th, 2009

40 years ago today, humans, for the first time, set foot on a world other than their own. It was the fulfillment of a goal set in 1961 by President Kennedy when he said “I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth.” The place Apollo 11 landed is the southern Sea of Tranquility (Mare Tranquillitatis). Although the backyard astronomer has no chance of seeing the landing site itself (it can just barely be seen by the Lunar Reconnaissance Orbiter) , the Mare Tranquillitatis can be easily seen, and is highlighted on the picture below. So take a look at the Mare Tranquillitatis tonight, and think of the bravery it took to land there.



Sunday, July 19th, 2009

With all the nebulae, galaxies, globular clusters, and other exotic deep space objects available to the amateur astronomer, sometimes the simple things get overlooked. Sometimes even a single star, easilyAntares in Scorpius visible to the naked eye, can have an interesting story to tell. Such is the case with Antares (aka Alpha Scorpii), a red giant star at the heart of the constellation Scorpius. In fact it’s old Arabic name, Ķalb al Άķrab, translates as the “Scorpion’s heart.” However it’s name Antares translates as “rival of Ares”, Ares being the Greek name for Mars. The reason for the name is obvious, seeing it’s similarity in color and brightness to the red planet. But unlike Mars, Antares is roughly 600 light-years away. And that distance is a good thing. If Antares were at the center of our solar system, it’s outer edge would extend beyond the orbit of Mars. But despite it’s immense size, it’s mass is estimated at only 15 to 18 solar masses. And so it has the very low average density typical to red giants.

There are a couple other interesting notes about Antares. For one, it is a variable star whose apparent magnitude varies from 0.9 to 1.8. Also it has a companion star, Antares B, with a magnitude of 5.5. The difference in brightness makes Antares B difficult to observe. But with a good backyard telescope, both stars may be visible. So the next time you’re looking at the night sky, take note of the Scorpion’s heart that has fascinated so many cultures throughout history.

The Summer Dumbbell

Sunday, July 12th, 2009
The Dumbbell Nebula

As summer continues, let’s turn our attention back to the “summer triangle.” There aren’t all that many planetary nebulae visible to the backyard astronomer, but one of the better ones can be found in the constellation Vulpecula. The Dumbbell Nebula (M27), discovered by Charles Messier in 1764, was the first planetary nebula discovered. It’s magnitude is a bright (by nebula standards) 7.5, and shows the interesting dumbbell shape that led to it’s name.

M27 in Vulpecula

Although M27 is in  Vulpecula, the easiest way to find it is to start with the constellation Sagitta. Using your finderscope, scan up from the end of Sagitta and look for an upside down bowl shape (outlined in yellow) with a star in the middle. Point your telecope at that star, and M27 will be right next to it. It’s easy and worth finding.

Lunar Reconnaissance Orbiter

Sunday, July 5th, 2009
Mare Nubium

NASA’s hoped for return to the moon took another step as the new Lunar Reconnaissance Orbiter has begun sending back images of the moon’s surface. The pictures of the Mare Nubium represent NASA’s first clear, close look at the moon in a decade. Besides allowing more detailed maps of the lunar surface, the orbiter will seek out potential landing sites for future astronauts. More information about the Lunar Reconnaissance Orbiter can be found at this SPACE.COM article.