Saturday: You
know Metis and Thebe and Adrastea and Amalthea. Io and Ganymede and Callisto
and Europa. But do you recall? There are 79 Jovian moons in all. Just 60
years ago, Jupiter was thought to have only 12 moons. But, astronomers are
red-nosed with delight that the advent of supersensitive electronic cameras has
caused the number of discovered moons to rapidly increase. Jupiter’s 79 moons
range in size from Ganymede, with a diameter of 5,262 kilometers, to numerous
moons with diameters of only one kilometer. Our moon has a diameter of 3,475
kilometers. (One kilometer is 0.62 miles.) Saturn is second place in the moon
race with 62. Uranus is next with 27. Then comes Neptune with 14, Mars with 2,
and Earth with 1. Even dwarf planets have moons. Pluto has 5, Eris has 1,
Haumea has 2, and Makemake has 1. Eris is an outer solar system object that was
discovered in 2005 and named in September of 2006. Because astronomers thought
it was larger than Pluto, people called it the tenth planet for a while. (More
recent measurements show Eris to be a little smaller in diameter than Pluto.)
Haumea, the newest dwarf planet with a moon, was discovered in 2004 and
officially named a dwarf planet on September 17, 2008. Go to
http://goo.gl/Xkoeq for more information about Solar System moons.
Sunday: So you
think your mother has problems on Mother’s Day because she had you as you as a
child? Her mother issues can’t be as bad as Cassiopeia’s issues. First, she was
chained to a chair for boasting about her beauty. Second, she has to revolve
around the North Star night after night. Third, her daughter Andromeda was
nearly killed by a sea monster. Look for poor Cassiopeia about one and a half
fists held upright and at arm’s length above the north horizon at 10 p.m.
Cassiopeia looks like a stretched out “W”.
Monday: Give me an
“M”. Give me a “3”. What does that spell? “M3.” “Big deal,” you say. It was a
big deal to French comet hunter Charles Messier (pronounced Messy A). M3 was
the 3rd comet look-alike that Messier catalogued in the late 1700s. M3 is
a globular cluster, a cluster of over 100,000 stars that is 32,000 light years
away. It is too dim to be seen with the naked eye but is fairly easy find with
binoculars. First find Arcturus six fists above the southeast horizon at 11
p.m. Move your binoculars up one binocular field of view so two stars of nearly
identical brightness are in your field of view. When the top star is in the
lower left part of your field of view, there should be a fuzzy patch near the
center of your field of view. This is M3.
Tuesday: Jupiter is
a half a fist above the southeast horizon at 11:30 p.m.
Wednesday: Spica is
less than one fist below the Moon, about three fists above the south horizon at
11 p.m.
Thursday: Mars’ two
small moons, Phobos and Deimos, are not visible in typical backyard telescopes.
But they are an interesting study. The prevailing view among most astronomers
is that they are captured asteroids. That makes sense given Mars’ proximity to
the asteroid belt. But recent findings by European astronomers indicate that
Phobos is very porous and made of material similar to the surface of Mars. This
implies that Phobos may consist of chunks of Martian debris that was blasted
off by numerous impacts and gravitationally bound together. Unfortunately, the
Russian Phobos-Grunt probe launched late 2011 to collect material from Phobos
crashed to Earth after malfunctioning. For more information about this recent
model of Phobos’ formation, go to http://goo.gl/8sw3rM. For more
information about Mars, look about two fists above the west horizon at 9:30 p.m.
Friday: At 5 a.m.,
Jupiter is a fist and a half above the south-southwest horizon, Saturn is two
fists above due south, and Venus is just peeking up above the east horizon,
nearly lost in the glare of the rising Sun.
The positional information in this column about stars and planets is typically accurate for the entire week. For up to date information about the night sky, go to https://nightsky.jpl.nasa.gov/planner.cfm.
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