Mars returns to glory

This month provides a great opportunity to see all five naked-eye planets in the evening sky. But the title for “planet of the month” has to go to Mars. The Red Planet reaches opposition and peak visibility December 8, 26 months since its previous opposition. Because Mars lies opposite the Sun in our sky, it remains visible all night. The ruddy planet also comes closest to Earth in December (on the 1st), so it looms largest when viewed through a telescope.

You can find Mars in the northeast as evening twilight fades. It lies among the background stars of Taurus, directly below the Bull’s V-shaped head. The planet far outshines the neighboring stars, however, peaking at magnitude –1.9.

For the best views of Mars through a telescope, wait until late evening when it appears higher in the sky. The planet’s disk spans 17" in early December. That’s plenty big enough to reveal several dark markings during moments of good seeing. The most conspicuous of these is Syrtis Major. The feature resides near the center of Mars’ disk in the late evening hours during December’s second week.

Jupiter shines at magnitude –2.5 in mid-December, nearly a magnitude brighter than Mars. The giant planet stands high in the northwest as darkness falls and dominates the dim background stars of southwestern Pisces.

Jupiter remains a splendid sight through any telescope. The planet’s 42"-diameter disk displays an alternating series of bright zones and darker belts that run parallel to the equator. Smaller atmospheric features pop into view under good seeing conditions. Also keep an eye out for Jupiter’s four bright Galilean moons, which stand out clearly when they aren’t hidden in front of or behind the planet’s disk.

Look lower in the west to spot Saturn. The planet lies in eastern Capricornus, whose faint stars are no match for the magnitude 0.7 ringed world.

The best time to turn your telescope toward Saturn is in early evening when it lies farther above the horizon. Any instrument reveals the planet’s stunning ring system, which spans 37" and tilts 14° to our line of sight in mid-December. The 8th-magnitude moon

Titan also shows up easily. A 4-inch scope brings in a trio of 10th-magnitude moons: Tethys, Dione, and Rhea.

The two inner planets make brief appearances during evening twilight. Mercury rises first. The best time to see it comes around its greatest elongation December 21, when it lies 20° east of the Sun and stands 8° high in the westsouthwest 45 minutes after sunset. Glowing at magnitude –0.5, it should appear obvious if you have a clear and unobstructed horizon. A telescope reveals Mercury’s 7"-diameter disk, which appears slightly more than half-lit at greatest elongation.

Although Venus continues to draw slowly away from the Sun in December, it doesn’t gain much altitude. On the

31st, it appears 7° high a halfhour after sundown. It likely wouldn’t show up at all if it weren’t so bright, but its magnitude –3.9 brilliance helps it pierce the bright twilight. A telescope shows a fully lit disk that measures just 10" across.

The starry sky

Brilliant Orion stands out in the northeastern sky after darkness falls in December. But I’d like to focus on two lesserknown though still impressive constellations just above and to the right of the Hunter: Lepus the Hare and Eridanus the River. The north-south border between these two figures lies a few degrees west of Mu (μ) and Epsilon (ε) Leporis.

A few centuries ago, however, another constellation existed between the Hare and the River. A relic of its former presence can be found in the formal name of 4th-magnitude 53 Eridani, a star that lies about halfway between Mu

Lep and Gamma (γ) Eri. The International Astronomical Union officially approved the name Sceptrum for this star.

The name came about because it was the brightest star in that former constellation: Sceptrum Brandenburgicum, or the Brandenburg Scepter. A scepter is a staff sovereigns use as a sign of authority.

German astronomer Gottfried Kirch (1639–1710) invented this constellation in 1688. It later appeared in Johann Bode’s 1801 star atlas, Uranographia. The constellation depicted the scepter of Frederick III (1657–1713), Elector of Brandenburg and Duke of Prussia.

It’s hard to make out a scepter’s shape in these stars, though a hint of it appears in the form of a line of three faint stars north of Sceptrum that includes 46 and 47 Eri. The upper, decorative top of the specter ran south from 53 and incorporated 54, 58, 59, and 60 Eri.

If you have ever visited Berlin, the name Brandenburg probably rings a bell. One of the most prominent structures in the city is the 18th-century Brandenburg Gate at the western end of Unter den Linden. Historically, the structure marked the start of the road to the town of Brandenburg an der Havel that lies west of Berlin, after which Brandenburg, the German state that surrounds Berlin, is named.

Kirch was an important German astronomer. He made several discoveries, some with his wife and fellow astronomer Maria, including the Wild

Duck Cluster (M11) and the globular cluster M5. He became Astronomer Royal at Frederick III’s court and was the first director of the original Berlin Observatory.