Get to know our local sky
—Darin Templet, RRAS
On Saturday, April 17, in conjunction with Coronado State Monument’s Earth Day Celebration, the Rio Rancho Astronomical Society will provide solar telescopes to allow safe viewing of the Sun from 9:00 a.m. to 3:00 p.m.
That evening, starting at 8:00, the Rio Rancho Astronomical Society will host its monthly meeting and stargaze at Coronado State Monument. Special guest speaker will be Dr. Mark Boslough of Sandia Labs who will give a presentation of his analysis of meteoric glass that was found in the southwestern Egyptian desert, a piece of which is in a pectoral necklace in the Tutankhamen collection. A stargaze will follow the meeting, weather permitting, and telescopes provided by members of the Rio Rancho Astronomical Society will show views of Mars and Saturn, as well as various nebula, star clusters, and galaxies. The public is invited to attend both events.
For more information, log on to www.rrastro.org or call 220-5492.
April 2010 Night Sky
Moons of our solar system—Part I
It seems that everywhere we look in our solar system, multiple moons orbit planets, with some exceptions. Mercury and Venus are moonless.
Venus was once thought to have a moon named Neith, after the chief Egyptian goddess of Sais. Astronomer Giovanni Cassini first reported observing the moon in the late 1600s. Periodic sightings by astronomers continued until 1892. Today we know there is no moon, so the early reports are attributed to background stars mistaken for a moon.
Luna, Earth’s moon, may have been formed early in the history of the solar system when a Mars-sized object slammed into the Earth spewing molten material into orbit. This gelled into what we now know as our moon. Our Moon is more than one quarter the size of Earth itself (2,159 miles diameter). Many astronomers favor making the Earth-Moon system a double-planet system.
Mars has two moons which are more likely captured asteroids: Deimos and Phobos. Deimos is the outer moon orbiting Mars every 1.26 days. This small, irregular rock is only 3.1 x 7.6 x 6.5 miles across. This moon circles only 14,600 miles above Mars and, from the surface, would appear 1,000 times larger and four hundred times brighter than the full Moon on Earth. For an observer on the surface of Mars, 2.7 days elapse between Deimos’ rising and setting because the planet’s rotation is nearly the same as the moon’s orbital period.
Phobos, the closest moon, orbits Mars very fast, completing its orbit in only seven hours and 39 minutes. You will see this moon rise in the west and set in the east, just opposite of what is expected, because of its quick orbit. The most prominent surface feature is Stickney Crater, where a large impact nearly shattered this tiny body and left a large gaping hole on one end. The diameter of this moon is less than 14 miles.
Now, on to one of the two big dogs when it comes to moons. Jupiter sports 63 known moons—don’t worry, I’m not going to list them all here. The four big ones were discovered by Galileo. These are worth getting out your small telescope to watch as they visibly move around Jupiter each night. Unfortunately, this month, Jupiter is up during daylight hours.
Io is the most volcanic body known, with lava flows, lava lakes, and giant calderas. It has volcanic geysers spewing plumes of sulfurous gas over three hundred miles high. Orbiting just more than 150,000 mile above Jupiter’s cloud tops, Io acts as an electrical generator as it moves through Jupiter’s magnetic field, developing 400,000 volts across its diameter and generating an electric current of three million amperes that flow back to the planet.
Europa is named after the beautiful Phoenician princess who, according to Greek mythology, Zeus saw gathering flowers and immediately fell in love with. This moon is unique among the moons of Jupiter. Its icy surface is one of the brightest in the solar system. Europa may be internally active, such that under the ice, there may be liquid water which can harbor life.
Ganymede is the largest moon of Jupiter and is the largest in our solar system with a diameter of 3,280 miles. If Ganymede orbited the Sun instead of Jupiter it could be classified as a planet in its own right. This moon has no known atmosphere, but does have a complex geological history. It has mountains, valleys, craters and lava flows and its surface is mottled by both light and dark regions.
Callisto is the second largest moon of Jupiter, the third largest in the solar system, and is about the same size as Mercury. It lacks any large mountains, probably due to the icy nature of its surface. Impact craters and associated concentric rings are about the only features to be found on Callisto.
Next month, we’ll venture out to more moons in our solar backyard.
The Planets and the Moon
• Mercury will be following the sun early in the month, allowing you to glimpse it just after sunset in the west. On the morning of the 15th, find the trio of Mercury, Venus, and the third-quarter Moon 45 minutes after sunset on the west-northwest horizon.
• Venus will set a bit later than Mercury in the west. Look for it to be bright and low after sunset. On the morning of the 4th, Easter Sunday, find Mercury and Venus in a conjunction just above the western horizon 45 minutes after sunset. Mercury will be three degrees to the right of Venus. On the 16th, look for the Moon to be eight degrees below Venus at nightfall.
• Mars still shines almost directly overhead about 8:30 in the evening. On the 21st, look for Mars in the constellation Cancer, just five degrees above the first-quarter Moon.
• Jupiter is mostly up this month during the sunlit hours placing it on the far side of the sun from us. The Moon joins Jupiter before sunrise on the 11th. You’ll need binoculars to see Jupiter five degrees below the moon, 25 minutes before sunrise on the eastern horizon.
• Saturn will be up in the east after sunset. There will be a Moon-Saturn conjunction on the 25th. Saturn will be 10 degrees above the waxing gibbous Moon. Look with good binoculars or a small telescope. This will be a great time to look for the rings.
• The Moon is new on the 14th at 6:29 a.m. MDT and full on the 28th at 6:18 a.m. MDT.
Easter falls on the 4th as this is the first Sunday after the first Full Moon of Spring.