SJAA Ephemeris March 2006 | SJAA Home | Contents | Previous | Next

The Shallow Sky

Which One is the Planet?

Akkana Peck

New Horizons launched aboard an Atlas V rocket from Cape Canaveral Air Force Station, Florida, on January 19, 2006.Photo courtesy of NASA/JPL-Caltech.


Mars is still visible high in the evening sky at sunset. It's very small now (its disk is only about twice the size of Uranus') so it will be difficult to see much detail even in a large telescope. Its magnitude is fading fast throughout the month as we recede from it in our faster orbit around the sun; but it's very similar in brightness to that of the nearby red star Aldebaran. At mid-month their magnitudes match exactly. Take a look — it's a perfect chance to see how well you can tell a star from a planet with the naked eye.

Saturn is high in the sky throughout the prime hours of the evening, and perfectly placed for observing, just a couple of degrees away from the Beehive (M44). The rings are tilted about 20 degrees to us, with the south side showing.

Jupiter rises a few hours before midnight, but it's still quite far south, in Libra, and never gets very high. Of course, there's still plenty to see on the biggest of planets even when it's low in the sky. For instance, moon shadow transits show well even in poor seeing, and there are several double transits worth seeing this month. On March 14th, check out the double satellite/shadow transit (Io and its shadow, plus Ganymede skirting Jupiter's northern edge) starting around 7pm. There's another very similar transit involving the same suspects at 9:30 on the 21st. Then starting around 9:50 on the 28th, Io and Ganymede transit together again, but this time we should see a bit of Ganymede's shadow as well.

Mercury disappears into the sunset glare early in March, so if you want to observe it, the first few days of the month are your best bet. It will reappear in the morning sky around the end of the month.

Late March is a good time to watch for the zodiacal light in the evening just after the sky first gets dark.

Venus is visible in the morning sky through most of the month. On mornings around the 26-27th, it passes within a couple of degrees of Neptune. They aren't very high, and Neptune would ordinarily be difficult to locate this low in the sky, but you might be able to find it by looking for the dim blue orb two degrees south of Venus and very slightly west.

Uranus is invisible -- too close to the sun. Pluto is tricky, hidden in the morning sky in Ophiuchus, but an ambitious observer might have a chance.

Speaking of Pluto, the New Horizons Pluto mission blasted off successfully on January 19th (after some nail-biting delays due to weather) and is on its way to Pluto. It won't get there until 2015. Fortunately, the spacecraft launched in time to take advantage of a gravitational slingshot effect from Jupiter as it passes by; if the probe had been delayed a few more weeks, it might have missed Jupiter's help, and wouldn't have gotten to Pluto until 2018, which might have been too late to investigate Pluto's tenuous atmosphere.

Just before the New Horizons launch, Project Stardust came back to us from its mission to Comet Wild 2, floating to a perfect touchdown the Utah desert. Its aerogel collectors are full of particles from the comet, and should keep mission scientists busy for years to come. And you can help: they've put the call out to volunteers to help analyze the particles. The goal is to find grains of interstellar dust mixed in with the pieces of comet and other solar system debris. You can use a web application (no special software needed) to look at microscope images of the particles, and try to recognize those that came from outside the solar system. There's more information at: here.

We'll just miss the penumbral lunar eclipse on March 14: it ends just before the moon rises here, but if you happen to be visiting more easterly states on that night, check it out. We also miss the companion solar eclipse, on the 29th, but let's hope that the SJAA folks who are traveling to see it have a nice show and bring back pictures and stories for the rest of us.


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