May 1999

by Steve Stefanik

The planet to watch this month will be Mars, having reached its closest point to Earth (53.8 million miles) on May 1, making it appear its biggest (16 arc seconds) since 1990. Look for the bright -1.6 magnitude red-orange orb rising in the east just as the sun is setting in the west. It is continuing to close in on the bright blue first magnitude star Spica in the constellation Virgo. Through a telescope with an aperature of 6 inches or larger you can see some of its surface features including moutainous regions and its northern polar ice cap. By the end of the month however, it will have shrunk to 14 arc seconds and dimmed to -1.1 magnitude. It will be gone by the end of summer not to be seen again until the year 2001, so get out there!

Venus is still the brilliant -4.1 magnitude "evening star" that you see high in the western sky as Mars is rising. Its still continuing to rise in altitude and increasing in size. Currently its positioned between "the horns of the bull" in the constellation Taurus but by May 9 it will enter Gemini "the twins". By the end of the month it will be within 4 degrees of Pollux one of Genini’s two twin first magnitude stars (the other being Castor). Through binoculars or even a small telescope you will see that its in a gibbous phase (more than half illuminated) but will diminish as the month progresses. However, as its illumination decreases, its size is increasing as it speeds towards Earth in its shorter faster orbit with a net increase in brightness as we head into next month.

The only other planets you might catch a glimpse of are Uranus and Neptune if you have a telescope or binoculars. Both rise around mid-night among the stars of Capricorn. Uranus is the brighter of the pair at magnitude +5.8 while Neptune is a much dimmer +7.9. They won’t reach opposition until late July and early August.

The planet Pluto is in a great position to be observed this month in the constellation Ophiuchus but requires a telescope with at least an 8 inch aperature and several successive clear nights to confirm its movement against the background stars.

The only other planet that will be difficult to see this month is Saturn. It has been in conjunction with the sun since April 27 and won’t emerge from the glare of the sun until the end of the month when it will rise more than an hour before sunrise.