Space Lizard Amateur Astronomy Blog

With Jupiter now returning to prime time for viewing (currently rising around midnight) amateur astronomers will be turning their view to this old favorite and it’s four large moons. But with just one glance you’ll notice something has changed. Normally, Jupiter’s two large cloud belts are easily visible through even a modest telescope. But when you look now, you’ll only see one. The South Equatorial Belt began fading late last year, and since May has all but disappeared. This sort of thing has happened before, most recently in 2007 when the belt faded slightly. And in the past the belt has always come back, often making a rather dramatic return. As scientists don’t completely understand the mechanism that causes this, there’s no sure way to know when the belt will be back. But based on precedent, it could be anytime in the next two years.  Until then, enjoy a slightly different view of our solar system’s largest planet.

Low in the western horizon, just after sunset, is a nice pairing of planets. Easily visible is the always bright Venus. But just to it’s right is the usually more elusive planet Mercury. A bright magnitude -0.2, and being near the even brighter Venus, makes this an excellent opportunity to see our solar system’s innermost planet. At the same time, high in the south in the constellation Cancer, the planet Mars is visible. And in the southeast in the constellation Virgo, you can see Saturn. It’s not often you can see four out of the five naked eye planets at the same time. But if you have a clear view of both the east and west horizons the next few nights, you’ll get your chance.

We are all well familiar with the phases of the moon – sometimes too familiar on the nights when a full moon interferes with our ability to see some deep sky object. But did you know the the planet Venus goes through similar phases? The phases result from the orbit of Venus being inside Earth’s orbit. Of course this means Mercury has phases as well. But as Mercury is so small and difficult to see to begin with, it’s phases are much more difficult to observe. However Venus is currently easy to see, shining brightly as the “morning star.” The best time to observe Venus is shortly before sunrise, after the sky has begun to brighten slightly. Not only is venus higher in the sky, but with the contrast between Venus and the sky reduced, details such as phase are easier to see. At this time the phase should be obvious through any small telescope. Some people with sharper eyesight than I have even claim to be able to see the extreme crecent phase with the naked eye. But don’t expect to see major changes over a few nights, as you can with the phases of the moon. While the moon goes through a complete cycle, from new to full and back to new, in about a month, it takes Venus well over a year to complete a similar cycle.

Why look at just one planet when you can see two? In the coming weeks there will be a pair of close planetary pairings. But  with both showing up in the predawn hours, you’ll have to get up early to see them. The most obvious pairing, easily visible to the naked eye, is Venus and Mars. Just start by finding Venus low in the east, now in the constellation Pisces. At a dazzling magnitude -2.9, it’ll stand out clearly. Slightly lower and to the left will be Mars, shining at magnitude 1.2. As time goes on the pairing will become even better, with the planets appearing higher in the sky, brighter and closer together.   They will reach their closest point on June 21. By then they will be in the constellation Aries and will be shining at magnitudes -3.5 and 1.1 respectively. 

While Venus and Mars are putting on their show, another interesting pairing will be taking place in the constellation Capricorn. But without a telescope, you’ll only see half of this pairing. During the last week of May, Jupiter and Neptune will appear less than a degree apart. With Jupiter at a bright magnitude -2.5, it will stand out clearly in the southeastern sky, along the eastern edge of Capricorn. Look slightly above Jupiter for Neptune. If you’re using a low power eyepiece, they should both be visible in the same field of view. With Neptune at a dim magnitude 7.9, it won’t be the most spectacular pairing. But it’s always interesting when two planets appear so close, and it’s also a good chance to spot a planet that can sometimes be hard to find. The picture at right shows how the pairing would look on the morning of May 20. Star Mu Capricornus, at magnitude 5, will join the pair. The red circle indicates a typical field of view through a low power eyepiece. Although not shown in the picture, Jupiters large moons will add to the show and are always worth a look. So if you’re up early (or very late, as is the case for some of us) don’t miss this pair of planetary pairings.

As last week’s full moon begins to wane, let’s take a look at lunar impact crater Tycho. Named for early Danish astronomer Tycho Brahe, it is often regarded as the finest example of a rayed crater. It’s rays, formed of material ejected by the impact that formed the crater, extend across a significat portion of the lunar surface. Another intereting feature of Tycho crater is it’s central peak, rising roughly 1.6km above the crater floor. As may be guessed from it’s sharply defined appearance, Tycho is a relatively young crater; it’s age estimated at 108 million years. It’s sharp appearance also makes Tycho an easy crater to find. Just look in the moon’s southern highlands, follow the rays back to their center, and it will be obvious which crater is Tycho. Start with low magnification to take in the intricate and beautiful system of rays, then push in with higher magnification for the crater itself. This is one crater worth a second look.