Southern Colorado Skies / December 17-23, 2017

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

Did you see the celestial arc last week? Looking to the southeast before dawn last Wednesday (first photo, below) there are (bottom to top) Jupiter, Mars and Spica, with the crescent Moon just to the left of the arc. In the second (Friday) photo, the Moon drops to form the bottom of the same arc.

THIS WEEK

Have you ever seen the Andromeda Galaxy, also known as M31? If not, you have a wonderful opportunity early in the evening as the “Great Square of Pegasus” is shining high in the southwest sky. Under reasonably dark skies you can catch a glimpse of it with your unaided eyes, although the magnificence of M31 comes through better if you use binoculars or a telescope.

M31 is a close galaxy neighbor, located “only” about 2.5 million light-years away – at that distance it’s the farthest object we can see with the naked eye. M31 is on a collision course with the Milky Way, but don’t start worrying quite yet – it is estimated this event won’t take place for another 4.5 billion years. The Andromeda Galaxy contains about 1 trillion stars, more than twice as many as the Milky Way, Check out more information about M31 at https://en.wikipedia.org/wiki/Andromeda_Galaxy or search other web sites.

(Not sure what that “M” object is? Check it out at http://scaspueblo.com/blog/2017/03/16/what-is-a-messier-object/.)

This is what you can expect to see of the Andromeda Galaxy through binoculars or a small telescope.

 

Sunday (December 17)

New Moon at 11:30 p.m. MST.

Thursday (December 21)

Today is solstice and the shortest day of the year for us in the Northern Hemisphere. The solstice officially occurs at 9:28 a.m. MST as the Sun reaches its southernmost declination for 2017. The good news is that days will now get longer for the next six months.

A weak meteor shower (the Ursids) is predicted to be at its peak tonight and/or tomorrow night. Its radiant (its apparent point of origin) is near the bowl of the Little Dipper. This shower is expected to be active to some degree from dusk to dawn, but you’re likely to see only a few Ursids per hour if you take the time to watch.

DAYLIGHT

 

PLANETS

Mercury (in Ophiuchus)

Mercury finally makes an appearance,at dawn early this week. Look to the southeast about 45 minutes before sunrise.

 Venus (in Ophiuchus) and Saturn (in Sagittarius)

Both planets are deep in the glare of the Sun this week.

Mars (in Virgo), and Jupiter (in Libra)

Both planets rise between 3 and 4 a.m., with Mars being the earlier riser. By dawn they are both well up in the southeast (see above photos).

Uranus (in Pisces) and Neptune (in Aquarius):

Both planets are high in the south by nightfall.

BRIGHT 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 location in order to be assured of accurate times, elevations, etc. If you’re unfamiliar with Iridium flares, check out my article at: http://scaspueblo.com/blog/2017/02/25/iridium-flares/.

Sunday (December 17) 6:00:25 p.m. / Magnitude -4.7 / S / Elevation 29 degrees

Monday (December 18) 4:42:59 p.m. / Magnitude -6.0 / W / Elevation 24 degrees

Wednesday (December 20) 6:13:55 a.m. / Magnitude -2.0 / NNW / Elevation 59 degrees

Thursday (December 21) 6:08:06 a.m. / Magnitude -1.8 / NNW / Elevation 55 degrees

Thursday (December 21) 5:45:21 p.m. / Magnitude -5.7 / S / Elevation 28 degrees

Friday (December 22) 6:02:06 a.m. / Magnitude -3.6 / NNW / Elevation 54 degrees

Friday (December 22) 6:39:17 p.m. / Magnitude -1.8 / S / Elevation 28 degrees

INTERNATIONAL SPACE STATION (ISS)

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

Carpe noctem

Dave Furry

Pueblo West, Colorado

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