April night sky offers eclipse view

The sky guy

Posted: Sunday, April 03, 2005


  Graphic courtesy of Andy Veh

Graphic courtesy of Andy Veh

Find Orion in the southwest with Sirius, the brightest star, to its lower left, Procyon and Castor and Pollux (the twin stars in Gemini) to its upper left, Taurus with orange-tinged Aldebaran and the star cluster Pleiades above it, as well as Capella in its pentagon of Auriga very high in the west.

Watch for Saturn forming a small oblique triangle with Castor and Pollux, now high in the southwest, as well. You'll see its rings in a small telescope.

The Milky Way runs south to north this month. On the northern horizon, find the bright stars Vega and Deneb. Notice also the "W" of Cassiopeia inside the Milky Way in the northwest. Next to it is the house of Cepheus, then the Little Dipper and, finally, almost in the middle (in the zenith), the Big Dipper.

Actually you may want to start with the Big Dipper overhead anyway because its last two stars point to Polaris, the North Star, at the end of the Little Dipper's handle, while the Big Dipper's own handle arcs toward bright and orange Arcturus fairly high in the east. From there conclude the journey with Jupiter at the left beneath Leo. A small telescope will reveal its four large moons and perhaps its cloud bands.

The diagram shows the low southern sky during the night of April 23 when Earth eclipses our moon during a penumbral partial lunar eclipse, lasting from 11 p.m. through 3 a.m. This is the least desirable kind of eclipse. During an umbral lunar eclipse, parts or all of our moon fall completely in Earth's shadow, but during a penumbral eclipse our moon still gets sunlight.

In other words, an observer on our moon would see our sun only partially eclipsed by Earth, so that quite a bit of sunlight illuminates our moon.

Fred Espenak, NASA's most eminent eclipse expert, writes on his Web site: "Penumbral eclipses are difficult to observe. Nevertheless, a subtle yet distinct shading should be visible across the northern half of the Moon, especially during the one hour period centered on maximum (around 1 a.m.)." I take it as a challenge and figure it'll be worth observing this lunar eclipse — if for once somebody pushes those clouds off the Kenai.

For more information from Espenak, just type "espenak" on Google and you get great predictions, charts and information on all upcoming eclipses around the world.

Eclipses come in at least pairs every half year. If you happen to travel to the Southern United States or the Pacific side of South America, you can see a partial solar eclipse Friday. Unfortunately Alaska is too far north for this one as our moon's shadow misses us.

Toward the end of the month Venus starts to emerge from our sun's glare. Try finding it very low in the northwest during dusk. Venus will be an evening planet for the rest of the year.

Last but not least, find Mars very low in the southeast before dawn. With binoculars you may be able to find Neptune nearby, which is right above Mars around April 12. Uranus is also visible with binoculars.

Andy Veh is the physics and astronomy instructor at Kenai Peninsula College. This column appears on the first Sunday of each month. He can be reached at aveh@uaa.alaska.edu.

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