Skywatcher's Guide: December 2019 and January 2020


Stars and Constellations

In December, the summer constellations are still visible for the first few hours of the night towards the west.  The Summer Triangle is still fairly high, with Vega heading to the west-northwest, Deneb closest to the zenith, and Altair in the west-southwest.  The center of the Milky Way is now below the horizon, but there is still a good portion of our galaxy we can see streaking high across the sky. The fall sky is now very prominent, getting high in the eastern sky.  The "W" of Cassiopeia is very high in the north-northeast. In the absence of the Big Dipper (part of our spring sky) Cassiopeia can be used to locate the north star: The top (open side) of the "W" faces to the north, so in that direction look for a star about the same brightness as the main stars in Casssiopeia, and that will most likely be Polaris.  Next, the Great Square of Pegasus is nearly in the middle of the sky.  Andromeda is nearby in the northeast, with Perseus just below.  There is also a fairly bright star called Fomalhaut in the south, though its constellation Piscis Austrinus is not easy to distinguish.  Finally, the winter sky is beginning to come up along the eastern horizon.  Taurus the bull is now up in the east with the bright star Aldebaran and the Pleiades (aka the seven sisters or Subaru) star cluster.  Auriga the charioteer is also up in the northeast, with the bright star Capella.

In January, the summer constellations are now very low in the west.  Deneb is the highest point of the Summer Triangle in the northwest, with Vega below near the horizon, and Altair more towards the west.  The Milky Way continues to streak across the sky, though the summer portion is now giving way to the winter portion.  The fall constellations are now right in the middle of the sky.  More of the winter constellations are now up, most notably Orion the hunter in the east below Taurus.  Gemini the twins are also up in the east-northeast just below Auriga.

Interesting Stars Visible in December and January (during observatory hours)

Name / Designation Apparent Magnitude
(lower = brighter)
Sirius -1.44 8.6  
Vega 0.03 25  
Capella 0.08 42  
Rigel 0.18 770  
Procyon 0.4 11  
Betelgeuse 0.45 427  
Altair 0.76 17  
Aldeberan 0.87 65  
Pollux 1.16 38  
Markab 1.25 140  
Deneb 1.25 3230  
Regulus 1.36 77 means "Little King"
Castor 1.58 52  
Polaris 1.97 431  
Alpheratz or Sirrah 2.07 97  
Mirach 2.07 199  
Algol 2.09 93 variable star
Enif 2.38 670  
Almak 2.1 / 5.0 & 6.3 355  triple star system w/ 64 yr orbit
Albireo 3.2 / 5.8 & 5.1 390 / 380  possibly a triple star system
Eta Cassiopeiae 3.5 / 7.4 19 480 yr orbit

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Solar System

Mercury will be visible in the morning sky for most of December, but will be lost in the sun's glare by early January.  It may reemerge in the evening sky by the end of the month.

Venus is prominent in the western sky after sunset, getting higher each night.

Mars is visible in the morning sky, moving through Libra and Scorpius.

Jupiter may be visible right after sunset in early December, but will pass behind the Sun before the end of the month.  It then may be visible in the morning sky by the end of January.

Saturn is visible in the evening sky for most of December, but will be passing behind the Sun in January.

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Calendar of Night Sky Events

Date Event
12/03/19 First Quarter Moon.
12/11/19 Appulse of Venus and Saturn. — Separated by 1.8°
12/11/19 Full Moon.
12/11/19 Appulse of Venus and Pluto. — Separated by 1.1°
12/14/19 Peak of Geminids meteor shower.
12/18/19 Last Quarter Moon.
12/21/19 Southern Solstice. — Official beginning of our winter.
12/25/19 New Moon and annular solar eclipse — Not visible from Tucson.
01/01/19 Jupiter at conjunction; occultation. — Hidden directly behind the Sun.
01/02/20 Appulse of Mercury and Jupiter. — Separated by 1.5°.
01/02/20 First Quarter Moon.
01/04/20 Peak of Quadrantids meteor shower.
01/05/20 Earth at perihelion. — Our closest approach to the Sun for the year.
01/05/20 Mercury at superior conjunction. — Passing behind the Sun.
01/10/20 Full Moon and penumbral lunar eclipse. — Not visible from Tucson.
01/12/20 Appulse of Mercury and Saturn. — Separated by 2.0°.
01/12/20 Appulse of Mercury and Pluto. — Separated by 1.3°.
01/12/20 Appulse of Saturn and Pluto. — Separated by 0.7°.
01/13/20 Pluto at conjunction. — Passing behind the Sun.
01/13/20 Saturn at conjunction; occultation. — Hidden directly behind the Sun.
01/17/20 Last Quarter Moon.
01/24/20 New Moon.
01/27/20 Appulse of Venus and Neptune. — Separated by 0.07°.

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Deep Sky

The summer Milky Way is now partially below the horizon at the beginning of the night, but the winter Milky Way is getting more and more prominent.  There are many open star clusters that can be seen with only binoculars scanning this part of the sky.  For example we have the asterism of the Coathanger between Aquila and Cygnus in the fainter constellation of Vulpecula.  The Pleiades (M45) is visible naked-eye in the east just above the face of Taurus which itself is another cluster called the Hyades.  We also have the Double Cluster in Perseus high in the north-northeast.  Finally, the constellation of Auriga in the northeast contains M36, M37, and M38 in close proximity.

There aren't as many globular clusters we can see this time of year, but there are still a few.  M15 is visible near the head of Pegasus in the west-southwest.  The next brightest one is M2 in Aquarius to the southwest.

For nebulae, we have several in the plane of the galaxy, one of which is the North America Nebula (C20) to the west-northwest in Cygnus.  The spectacular Orion Nebula (M42) is now just rising at the beginning of the night in the east. For planetary nebulae we have the Ring Nebula (M57) in Lyra, the Dumbell Nebula (M27) in Vulpecula, and the Blue Snowball (C22) in Andromeda.

And now the galaxies:  Our neighbor the Andromeda Galaxy (M31) is now very high in the middle of the sky and is visible on dark nights with the naked eye.  Also nearby is the Triangulum Galaxy (M33), visible with binoculars.

Interesting Deep Sky Objects to Observe during December and January (during observatory hours)

Designation Name Apparent Magnitude Apparent Size Distance
Messier 45 Pleiades 1.6 110' 440 open cluster
Messier 31 Andromeda Galaxy 3.4 3° x 1° 2,900,000 spiral galaxy
Messier 44 Beehive Cluster 3.7 95' 577 open cluster
Messier 42 Orion Nebula 4 85' x 60' 1400-1600 diffuse nebula
Messier 33 Triangulum Galaxy 5.7 67' x 42' 3,000,000 spiral galaxy
NGC 7293 Helix Nebula 7.3 16' 450 planetary nebula
Messier 27 Dumbbell Nebula 7.4 8' × 6' 1,250 planetary nebula
NGC 7009 Saturn Nebula 8 36" 2,400 planetary nebula
Messier 81 Bode's Galaxy 8.5 21' 1,200,000 spiral galaxy
Messier 57 Ring Nebula 8.8 1' 2,300 planetary nebula
Messier 82 Cigar Galaxy 9.5 14' 1,200,000 galaxy

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Frequently Asked Questions

What's happening in 2020?

There are several exciting things to look forward to as we go into the new year.  First, there are four missions scheduled to be launched to Mars in the summer.  NASA plans to send an as yet unnamed rover that will be a near twin of Curiosity and also includes a small drone helicopter that they will use to scout out potential destinations for the rover.  Russia and ESA are working on a rover called Rosalind Franklin that, along with a stationary lander, will search for evidence of present or past life on Mars.  Then China and the United Arab Emirates both have missions planned to reach Mars for the first time for their respective countries.

There are also a few lunar missions scheduled to be launched in 2020, including a lander from private company Moon Express, a lander/rover from India, a set of four cubesat orbiters from NASA and Japan, and a lander from China.

The University of Arizona's own OSIRIS-REx spacecraft will be taking its sample of the asteroid Bennu in July, which will be returned to Earth in 2023.  Japan's Hayabusa 2 spacecraft will be returning its sample of asteroid Ryugu in December.

Ongoing missions include Juno (at Jupiter), the Parker Solar Probe (passing Venus to bring it closer to the Sun), and BepiColombo (passing Earth and Venus en route to Mercury).

As for what we can see in our sky from Earth, we will have excellent viewing of Venus from February through April, and excellent viewing of Mars from September through November.  There are a couple penumbral lunar eclipses we will see in July and November.  (These are not the most spectacular types of eclipses, but we'll have some better ones in 2021.)

There is always cool stuff happening in space.  I can't list everything, but these are the ones I think are the most exciting.  If you think I left anything out, please send me a message.  But most importantly, keep looking up!

If you have any questions you'd like me to answer in the next issue of SWG, please let me know.  I'm also happy to take suggestions or comments, and also pictures if you'd like to send them.  Happy viewing!

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  • Cornelius, Geoffrey. The Starlore Handbook: an Essential Guide to the Night Sky. San Francisco, CA: Chronicle, 1997. Print.
  • Ottewell, Guy. Astronomical Calendar 2012. Raynham, Mass: Universal Workshop, 2011. Print.
  • Ottewell, Guy. Astronomical Calendar 2013. Raynham, Mass: Universal Workshop, 2012. Print.
  • Ottewell, Guy. The Astronomical Companion. 2nd ed. Raynham, Mass: Universal Workshop, 2010. Print.
  • Astronomy Magazine. February 2013. Volume 41, No 2.
  • Astronomy Magazine. February 2013. Volume 41, No 3.
  • Sky & Telescope. February 2013. Volume 125, No 2.
  • Sky & Telescope. March 2013. Volume 125, No 3.

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