Bakersfield Night Sky – September 19, 2009
By Nick Strobel
Super-bright Jupiter is a bit further westward among the stars of Capricornus in the southeast in the evening. Jupiter has been creeping backward (westward) with respect to the stars of Capricornus for the past few months as the Earth has overtaken it in our faster, smaller orbit. The word "planet" comes from the Greek meaning "wanderer" because some of the bright points move among the stars and will even occasionally drift backward ("retrograde") so they seem like they are just wandering around. There is some constraint on their motion, though, as they are always found among the zodiac constellations (plus "Ophiuchus"). The Moon also moves among the zodiac constellations (plus "Ophiuchus"). It will be in waxing gibbous phase as it passes Jupiter on September 29th (see chart B).
The Summer Triangle made of Deneb in Cygnus, Vega in Lyra, and Altair in Aquila is still high in the evening sky in these last few days of the season of summer. Summer ends and the season of autumn (fall) begins on the date of the autumnal equinox that happens when the Sun crosses the celestial equator heading south. The Sun will be directly over the Earth's equator. This happens on September 22nd at 2:19 PM Pacific Daylight Time. Although the weather may still be feeling like summer, the equinox marks the official beginning of autumn according to the calendar. For more details about this, go to www.astronomynotes.com/nakedeye/s5.htm .
The highlight of this time of month, though, is the very close pairing of Venus and the bright star Regulus in the constellation Leo in our early morning sky. On September 20th, they will appear almost on top of each other as Venus passes slightly to the left of Regulus. They appear as one on the scale of chart A below. In binoculars, contrast the colors of the two. Venus will appear yellow-white and Regulus will look blue-white. Venus' color is the result of how its clouds reflect sunlight while Regulus' color is from the light it emits at its high temperature of about twice the Sun's temperature. Venus is sliding toward the Sun so it is now rising only about two-and-a-third hours before sunrise. By the end of the month it will be rising only two hours before sunrise.
Mars is now on the left side of Gemini (in the twin called "Pollux"). At the end of the month, you may be able to see Mercury about 10 degrees below Venus (about a fist held at arm's length) very low in the east. Mercury rises about 50 minutes before sunrise. Just before sunrise see if you can spot Saturn about 5 degrees lower left of Mercury. You will probably need binoculars to pick it out in the pre-dawn twilight.
Want to see more of the
stars at night and save energy? Shield your lights so that the light
only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
last updated: August 30, 2009
Webpage contact: Nick Strobel