April's Celestial Lights
By Phyllis Burton Pitluga (Apr 7, 2006)
Last month we began to explore the three-dimensional aspect of our nighttime sky, from the moon and farther out to the planets and to the realm of the farther stars. But this is just beginning our outward journey.
When we look out into our Milky Way Galaxy at night, the individual stars we see are in the foreground. That's why the stars are all around us. These stars are the ones we connect into constellation patterns, even though the stars of any one constellation may be quite far apart and would make a completely different pattern from a different point of view. Mingled among these stars of different ages are clouds of gas and dust and clusters of fairly young stars.
When we look at the milky band of light crossing our western evening sky this time of year, we are looking at the merged light of distant stars toward the outer edge of our galaxy. (You need clear, dark, moonless skies to really follow this band of light.)
Since we live inside our island galaxy of stars, we can never photograph how it looks. But, by analyzing star distances and distributions, we have a fairly good idea of how our Milky Way Galaxy must look: a flattened pinwheel of stars, similar to the Whirlpool Galaxy, thirty-six million light years away and overhead in our spring evening sky.
Look at the Hubble Space Telescope image of the Whirlpool Galaxy and imagine it as a mirror reflection of our own Milky Way Galaxy. Our solar system is imbedded in this disk about two-thirds from the center.
In the center of our galaxy the stars are older yellow stars. But out in the spiral arms where we live, the stars are young. The dark lanes are where new stars are brewing; hot new stars are lighting the bright pink hydrogen clouds, and the blue stars have blown away their cocoons of gas and dust with the strong stellar winds they produce.
It is out here where we live that many of the most beautiful telescopic views can be located. For example, the Beehive Cluster of young stars is a delight even with binoculars. This cluster is to the left or east of Saturn (to identify Saturn see the Sky Calendar for April 6th).
Saturday, April 1:
Crescent moon just above the Pleiades star cluster
Monday, April 3:
Moon passes above Mars
Wednesday, April 5:
First quarter moon
Thursday, April 6:
Moon passes above Saturn
Saturday, April 8:
Moon passes above the bright star Regulus, a fast-spinning star 77 light
years away and the brightest star in the constellation of Leo
Thursday, April 13:
Full moon passing just above the bright star Spica, a hot star 262 light years away and the brightest star in the constellation of Virgo
Saturday, April 15:
Waning gibbous moon passes below Jupiter
Monday, April 17:
Moon passes below the bright star Antares, a red giant star 604 light years away in the constellation of Scorpious
Thursday, April 20:
Last quarter moon
Saturday, April 22:
Lyrid meteor shower, not a spectacular display of "shooting stars," could have about 20 meteors per hour visible low in the northeast about 11pm before the moon rises
Monday, April 24:
Moon passes below Venus
Wednesday, April 26:
Moon passes above Mercury
Thursday, April 27:
New moon
Saturday, April 29:
Crescent moon passes just above the Pleiades star cluster
Phyllis Burton Pitluga is Astronomer Emerita of the Adler Planetarium and Astronomy Museum, Chicago, and is now a San Miguel resident.