StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JUNE 2001

JUNE STAR MAP | INDEX | MOON PHASES

249 JUNE 3, 2001: Watching Mars: I had a friend named Ernie Andrews, whose passion it was to observe Mars. He would stay up all night watching the Red Planet dance in his telescope, waiting for those several moments of unexpected calm, when the atmosphere between his eye and the edge of space steadied, and Mars was revealed in its most intricate detail. I had such an epiphany back in the ‘80s when teaching at Kutztown University. I was observing Mars with my students, and Ernie had tagged along to glimpse Mars through the University’s 18-inch reflector. Everybody had their turn at the eyepiece focusing on a jittery red blob with a whitish polar cap. Mars was boiling and bubbling similar to the way a distant scene wavers in the heat. That same turbulence causes stars to scintillate or twinkle. Since planets present discernible disks in telescopes, the changing differences in the density of the atmosphere, caused by winds aloft, makes this twinkling effect less apparent. We often say that planets shine with a steady light or they appear to twinkle more slowly than the stars. That night at Kutztown was one of the most memorable for me. When I gave Mars one last look before proceeding to the next object, the air stilled and I could see the Martian polar cap with such clarity that an uneven jaggedness around its edges could be discerned. Vaporizing ice was probably causing the roughness of texture. By the time that Ernie made it over, Mars was bubbling again and my five second epiphany had concluded. The morale of this story is that if you’re going to observe bright Mars in the next month or so, be prepared to spend a little bit of quality time with your telescope. You won’t regret it, I promise.

250 JUNE 10, 2001: Big Week for Mars: Mars fans, this is your BIG week for the Red Planet. Look low in the SE at 11 p.m. Mars is brightest this week as it moves westward among the stars towards its rival, Antares, in the constellation of Scorpius, the Scorpion. The two will make a striking pair throughout the June, but Mars will outshine Antares by over 23 times. The Red Planet will be at opposition on Wednesday evening, meaning that it will be opposite to the sun, and therefore visible all night. The faster moving Earth has caught up to Mars and is currently passing Mars at a distance of slightly less than 42 million miles, making this the finest opposition since 1988. Because Mars’ orbit is the third most oval-shaped path of the nine planets, the Red Planet’s distance from the sun varies by almost 10 percent from its average distance. Oppositions can be favorable like this one, when Earth passes Mars near the position where Mars is closest to the sun, and unfavorable when Earth passes Mars, when Mars is farthest from the sun. Once Mars reaches opposition the race begins all over again, with the faster moving Earth pulling ahead and having to circle around the sun and catch up to Mars for the next opposition to occur. Since Mars takes 687 days to circle the sun, after one year, Earth and Mars are nearly opposite to each other in the sky. After another year, Earth is once again approaching Mars and getting ready to pass it. The actual period is almost 780 days or 2.13 years between successive oppositions. Mars will return to opposition on August 28, 2003, but this time we will be nearly as close as we can get to the Red Planet, 34 million miles. In 2003, Mars will shine over 1.5 times brighter than this Wednesday.

251 JUNE 17, 2001: It's Summertime: This Thursday marks the first moment of summer, but it will happen before most of us rise for work. The sun reaches it farthest position north of the Equator at 3:35 a.m., EDT before beginning its long relentless descent which culminates with the winter solstice in late December. Have no fear, Thursday is still the longest day of the year and the sun will reach its highest noontime position in the sky for Allentown. So enjoy the moments. While it is summertime in the Northern Hemisphere, winter begins at the same moment for folks south of the Equator. If you are in southern Africa on the 21st, there is something very special about this winter solstice. The solstice marks the first total solar eclipse of the new millennium. In a narrow swath of territory stretching through Angola, Zambia, northern Zimbabwe, Mozambique, and Madagascar, the moon’s shadow will race across the Earth’s surface causing the first day of winter to have two sunrises and two sunsets, and be just a little shorter than usual. Six members of the Lehigh Valley Amateur Astronomical Society hope to have ringside seats for this event. Three of the five planets visible to the unaided eye should be in the sky to greet these viewers when totality occurs. Jupiter and Mercury will be only five and eight degrees west of the sun while Saturn will be nearer to the horizon, but hopefully visible. Venus, and Mars, will be positioned below the horizon at their location. From the Lehigh Valley, see Mars low in the south right after darkness during late June and July. Venus, the brightest of the nine planets, should be plainly visible by 4:30 a.m. low in the east if buildings or trees are not obscuring your view. Happy summer!

252 JUNE 24, 2001: Chacoan Darkness