June 2001

By Steve Stefanik

This June Mercury, Saturn, and Jupiter, which put on a spectacular display last month, will have set by the time it gets dark. Uranus and Neptune don’t rise until after 11:00 p.m. in the constellation Capricornus and are too dim to be seen without the aid of a telescope. The planet Pluto, which is in the constellation Ophiuchus, requires taking a picture with a camera attached to a telescope on successive nights to detect it. Venus rises in the east about 2 hours before sunrise and doesn’t get very high above the horizon before the morning sky brightens. Mars will be the only visible planet in the evening sky this month but don’t despair. It will present us with the best views of this mysterious world since 1988.

Mars rises in the east with the constellation Ophiuchus as the sun sets. It will reach opposition on the 13^th when it will be directly opposite us from the sun. It will grow to 21 arc seconds in size, that’s almost half the apparent size of Jupiter if you recall seeing how big that was this past winter. It will also be the brightest its been in the last 13 years, reaching –2.4 magnitude.

Not every opposition is as good as this year’s. Due to its elliptical orbit it can come as close as 34.6 million miles (at perihelion) or as far as 61 million miles (at aphelion). The largest it can appear is 25 arc seconds, which will occur during its next opposition in 2003. This year, on June 21^st, it will come within 42 million miles, 19 million miles closer than it did in 1999. Mars will only be this size for a short time however, so take this opportunity to get a good look at it. Even through a small telescope you’ll be amazed at what you can see.

During this opposition Mars is at its autumnal equinox (its Fall) and you may spot either of its polar ice caps. You will undoubtedly see some of its dark mountainous regions and some of its light sandy deserts. Mars rotates once in 24 hours and 39 minutes so you will see some of the same features night after night only 40 minutes later. It takes 36 days to see the entire surface rotate once, one earth-night at a time.

On the very day that Mars is at it’s closest to Earth, the Earth reaches the Summer Solstice on June 21^st at 3:38 a.m. EDT, when it is tilted the furthest toward the sun (23.5 degrees). The sun sets at its most northerly point on the western horizon that evening and begins its six month regression southward once again. The good news is that the sun will set earlier and rise later and the nights will begin to get longer providing more time to observe the nightsky.