WHERE: AT EXPLORIT Science Center, 3141 5th Street, Davis.

EXPLORIT SCIENCE CENTER and the ASTRONOMY CLUB present:

Planets in our Solar System!
Saturday, May 1, 2004
at 7:00 p.m. at Explorit

Join us Saturday evening, May 1st, at 7:00 p.m. for our first Dennis Smith Family Astronomy Program of the year. This free event is organized by Explorit Science Center. There will be many exciting hands-on activities for all ages. The theme of the evening will be the nine planets in our solar system. The Astronomy Club will set up telescopes to view (weather permitting) the planets visible in the evening sky.

Our solar system consists of all bodies that revolve around the Sun. The planets, their moons, asteroids, and comets are believed to have accreted out of the same cloud of gas and dust that formed the Sun. Astronomers believe that the Solar System is about 4.6 billion years old.

Planets are known as wanderers as they move about the celestial sky. In fact they only move about a narrow band in the sky known as the ecliptic. This line also connects the Sun and Moon, and the zodiac constellations. Planets do not twinkle like stars, but shine with a steady light reflected from the Sun. They move more rapidly in the sky than the stars and thus are not plotted on star charts.

There are nine planets orbiting our Sun: (in order) Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto. Mercury and Venus are inferior planets (as their orbits lie within Earth's) and Mars etc. are superior planets (as their orbits lie outside Earth's). As Mercury and Venus are inferior planets, they exhibit phases (like our Moon) to Earth-based observers. Superior planets exhibit retrograde (or backward) motions to observers on Earth as the planets and Earth are traveling around the sun in the same direction, but Earth is faster. Thus, Earth periodically overtakes the superior planets, and they appear to move in backward directions for some time and then move forward again

Mercury, Venus, Earth, and Mars are terrestrial planets (they have rocky Earth-like cores), and Jupiter, Saturn, Uranus, and Neptune are gaseous Jovian planets (they have icy Jupiter-like cores). Terrestrial planets are in the inner reaches of the solar system and are bunched up, whereas the gaseous planets are in the outer regions and are widely spread out. Small icy, rocky Pluto (sometimes referred to as a planetoid) does not fall into either category and is more like a jovian moon than a planet.
Most of the planets in the solar system rotate on their axis in the same direction as they orbit the sun - counterclockwise. Venus, Uranus, and Pluto are the exceptions - they have clockwise or retrograde rotations. Most of the planets (except Pluto) orbit the sun in elliptical paths that are nearly circular. Pluto has a highly eccentric orbit that brings it inside Neptune's orbit for part of its revolution.

Terrestrial planets have 0, 1, or 2 moons revolving around them. The gaseous planets have many moons. Some of these moons are volcanic and some have measurable atmospheres. These jovian planets also have rings composed of ice crystals and rocks fragments around them

On May 1 evening, we will look at the rising Moon, bright dazzling Venus, dim reddish Mars, and bright Saturn and Jupiter. There will also be lots of fun activities for the young astronomers. Please bring your telescope or binoculars if you own one.

MAY SKY
Mercury is hard to spot, as it sets close to the sun. Venus (in Taurus) is the brightest in the western sky. Mars (also in Taurus) is at its upper left. Saturn (in Gemini) is above Orion. Jupiter (in Leo) rises at sunset. Moon's phases are as follows: First Quarter: Apr. 27/May 27, Full Moon: May. 4/June 2, Last Quarter: May. 11, and New Moon: May. 18.
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The Astronomy Club is for everyone - adults, children, knowledgeable or ignorant. Come to listen, look and learn, or to share your expertise or experience.