Southern Colorado Skies / December 25 – 31, 2016

Consider a planetarium program to help you plan your observations. There are many commercial products available, and an excellent program (STELLARIUM) is available free at http://www.stellarium.org/.

JUPITER’S ELUSIVE MOONS

Now that Jupiter is relatively high in the eastern sky before daybreak, this is a good time to observe the giant planet’s four Galilean moons. YOU DO NOT NEED A TELESCOPE for this interesting activity as binoculars will do nicely – even a garden-variety pair is many times more powerful and clearer than the telescope that Galileo used to discover these moons in the early 1600s. What makes observing the satellites interesting is that their positions change from night to night, and they may at times be occulted (go behind Jupiter’s disk) or eclipse (cast their shadow on) the planet’s surface.

The four main “Galilean” moons (many more moons have been discovered over the years) are Io, Europa, Ganymede, and Callisto. I was going to try and describe each of them but so much has been written that I instead refer you to the library or the internet. A good description of these moons may be found at http://solarsystem.nasa.gov/planets/jupiter/moons.

O.k. – so which one is which? Sky and Telescope magazine offers a free interactive tool that allows you to see the relative locations of visible moons at any time. This handy tool also shows other data about the moons, like upcoming eclipses and occultations. Give it a try at http://www.skyandtelescope.com/wp-content/observing-tools/jupiter_moons/jupiter.html.

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THIS WEEK

After it becomes dark, look to the east for the Pleiades cluster high in the sky, with orangish Aldebaran just below it. Orion is now clearing the horizon about that time and by about 9:00 you get a good view of Sirius as well.

Look for the Great Square of Pegasus high in the west after dark.

Neptune moves very close to Mars. See it through your telescope just above Mars.

Tuesday (December 27)

Saturn becomes visible this week after a long absence. Look for it in the southeast about 45 to 35 minutes before sunrise (binoculars will help but watch out for the Sun!). Saturn is below the thin crescent Moon, and Antares is off to their right (west).

Wednesday (December 28)

New Moon at 11:53 p.m. MST.

Friday (December 30)

The two-day-old crescent Moon is visible in the southwest about 30 to 50 minutes after the Sun sets. Look about 30 degrees (three fist-widths at arm’s length) to the lower right (west) of bright Venus.

Saturday (December 31)

Just as it gets starts to get dark, look in the southwest for the crescent Moon, Venus, and Mars forming a diagonal, curving line.

PLANETS

Mercury (in Sagittarius)

Not visible in the Sun’s glare.

Venus (in Capricornus)

Shining brightly n the southwest in the early evening.

Mars (in Aquarius)

Look in the south-southwest at nightfall, to the upper left (west) of Venus.

Jupiter (in Virgo)

Jupiter rises about 1:00 a.m. and is bright in the south-southeast by dawn. That bright star under it is Spica (in Virgo).

Saturn (in Ophiuchus)

Hiding within the Sun’s glare but may be visible starting onj the morning of December 27th (see above).

NASA’s Cassini mission is finishing up its final year of exploration (see NASA’s press release at the following link: http://www.jpl.nasa.gov/news/news.php?release=2016-242.

Uranus (in Pisces)

High in the south by nightfall.

Neptune (in Aquarius)

High in the south by nightfall.

BRIGHTER IRIDIUM FLARES

The following data are based on my location in Pueblo West, Colorado. If you live well outside this area, you should consider checking this information for your site in order to be assured of accurate times, elevations, etc.

Tuesday (December 27): 6:21 a.m. / Magnitude -3.3 / ENE / Elevation 22 degrees

Wednesday (December 28): 5:11 a.m. / Magnitude -3.3 / S / Elevation 17 degrees

Thursday (December 29): 5:05 a.m. / Magnitude -2.2 / S / Elevation 15 degrees

Thursday (December 29): 5:59 p.m. / Magnitude -6.0 / ENE / Elevation 18 degrees

Friday (December 30): 5:44 a.m. / Magnitude -5.8 / ENE / Elevation 14 degrees

Friday (December 30): 6:17 a.m. / Magnitude -3.2 / SE / Elevation 9 degrees

Saturday (December 31): 5:28 a.m. / Magnitude -5.6 / NE / Elevation 10 degrees

INTERNATIONAL SPACE STATION (ISS)

These are too numerous to list here! If you’re serious, load the ISS DETECTOR app on your smart phone or tablet.

Carpe noctem

Dave Furry

Pueblo West, Colorado

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