Celestial Lights

Venus, Saturn and Jupiter adorn our spring evenings, March 30, 2007

Venus continues to dominate the evening sky as the very brightest object, after the Sun and Moon. On a moonless night you can see shadows cast by its bright light and you can see a pathway of light shining from Venus upon the still surface of a lake. Through a telescope you can see Venus gradually change shape in the weeks ahead as it gets closer and bigger but becomes a skinny crescent by late summer.

This image, taken by NASA’s Hubble Space Telescope, shows the hot material surrounding a super-massive black hole in the center of the galaxy M87 and one of the jets emanating from it (both characteristic of black holes in galactic centers).

Saturn is already up in the eastern sky as darkness descends. This planet is a treat even in small telescopes because of its beautiful icy rings that encircle it. Look for some of its bright moons orbiting it, as well.

Jupiter is the giant of the planets. In April, it rises close to midnight as a very brilliant point of light. Through a telescope (or even binoculars) you can see four of its largest moons change position over an evening as they orbit Jupiter.

Out to the Virgo cluster of Galaxies

On clear moonless April nights around midnight look overhead out toward our nearest galaxy cluster 50 million light-years away—home to hundreds of galaxies. We live in our Milky Way Galaxy of trillions of stars—the Sun is our star. The Milky Way Galaxy is one of the largest galaxies in a gravitationally bound group of more than two dozen other galaxies, called “The Local Group”—(who came up with that creative name?). The Local Group is weakly bound to the outer limits of the Virgo Cluster.

The centerpiece of the Virgo Cluster is an elliptical galaxy called M87, from its catalogue number. At the center of M87 is a super-massive black hole—with more star stuff than a billion suns crushed of all space into a singularity. The immense gravity of this black hole is drawing in the surrounding stars into a hot glowing disk. This hot star stuff is continuously drawn into the black hole. At the same time a jet of hot gas escapes from both poles of this hot disk. With a mid-sized telescope you can view M87 and its jets. 


Sky calendar, April 2007

By following the Moon as the biggest and brightest “pointer” in the sky, during the month you can identify different planets and bright stars. On subsequent nights you can relocate them without the Moon’s help. Moving about 25 times its own diameter from one night to the next, the Moon is much closer to Earth than the planets of our Solar System and the stars are even farther away. So, even though the Moon appears close to a celestial light they are truly separated by millions, billions or trillions of miles.



Apr 2, Monday: The Full Moon rises at its farthest distance in its elliptical orbit and thus is the smallest Full Moon for 2007.



Apr 5, Thursday: Jupiter will begin to drift westward in front of and toward the stars of Scorpious, most noticeably toward the bright red star Antares until early August because Earth is passing by Jupiter making it appear to “backup.”



Apr 10, Tuesday: Last Quarter Moon rises at about 1am.



Apr 11, Wednesday: Venus passes below the Pleiades Cluster of young stars.



Apr 13, Friday: The Waning Crescent Moon passes just above the planet Mars.



Apr 17, Tuesday: The New Moon rises at its closest distance to Earth and thus will produce large ocean tides. The New Moon is not visible because it has no sunlight shining upon the side that always faces the Earth.



Apr 19, Thursday: The slender Waxing Crescent Moon passes above the Pleiades Star Cluster.



Apr 20, Friday: The Waxing Crescent Moon passes above Venus.



Apr 21, Saturday: Venus passes above the red star Aldebaran, the eye of Taurus-the-Bull.



Apr. 22, Sunday: The radiant for the Lyrid meteor shower rises at about 11pm in the northeast and continues to rise higher in the sky for the rest of the night. If the sky is clear, you should see about 20 “shooting stars” an hour.



Apr. 24, Tuesday: At sunset, the First Quarter Moon is half way across the sky from west to east and will continue orbiting eastward each evening. The Moon is passing above the beehive Cluster of young stars tonight.



Apr. 25, Wednesday: Waxing Gibbous Moon passes above Saturn.



Apr. 29, Thursday: Moon passes above the star Regulus—notice the relative motion of Saturn to Regulus in the coming months.