Astronomy From Your Back Yard - 1/5 to 1/11 2011
Thursday, January 06 2011 @ 02:16 pm EST
Contributed by: dgrosvold
By Dave Grosvold
Happy New Year! Things are “looking up” in backyard astronomy — at least for the remainder of this week. With the skies relatively clear until the weekend, and the waxing crescent Moon, the resulting sky glow is not bright enough to present much of a problem for evening sky watchers.
One of the most spectacular sights to be had for amateur astronomers on these cold clear winter evenings is the central region of the constellation of Orion. This region is home to large bright nebulae and open clusters easily visible in a small telescope or binoculars. I mentioned M42, the Great Orion Nebula which is the brightest deep sky object in this region last year at this time.
Two objects in this area besides M42 are special treats. The first, NGC 1977, is known as the Running Man Nebula. NGC 1977 is a beautiful blue emission nebula with a dark reflection nebula inside it. Because of the reflected glow from brighter and larger M42, the darker parts of NGC 1977 reflects the colorful hues of M42 and imbue it with a mysterious, ghostly quality. Some have come to refer to NGC 1977 as the Ghost Nebula for this reason.
The second object, NGC 1981, is a large open cluster just above NGC 1977. NGC 1981 is a beautiful sprinkling of 10 or 11 bright stars in the Orion-Cygnus Arm of the Milky Way Galaxy, peppered with a background of the much more distant stars of other regions of the Milky Way. All of the stars in the cluster and the two nebula mentioned above are relatively close neighbors of the Solar System, at a mean distance of only about 700 light years from Earth. This makes it one of the nearest star forming regions we have available for study.
Two other deep sky objects in this region surround the star known as Alnitak, or Zeta Orionis (ζ Ori.) This triple star system, the easternmost star in the Belt of Orion, is surrounded by two well-known faint emission nebula, B33, the Horsehead Nebula, and NGC 2024, the Flame Nebula. These are normally not visible in small telescopes or binoculars, but they are a popular target for astro-imagers.
By 7:30 PM CST Wednesday evening, the Moon has set and the Winter Triangle is well up in the east-southeast, consisting of Betelgeuse in Orion's leftmost corner, bright Sirius in Canis Major below and to the right, and Procyon in Canis Minor to the left of these two. The Winter Triangle is brighter and more colorful than it's well-known summer counterpart. An even larger asterism, the Winter Hexagon, includes Procyon and Sirius, along with four other bright, colorful stars in the eastern evening sky: Rigel in Orion; Aldebaran in Taurus; Capella in Auriga; and Pollux in Gemini.
The brightest "star" in the evening sky this week is NOT a star, but a planet! As the current Evening Star, Jupiter still shines at magnitude -2.3 in Pisces, high in the south above Fomalhaut in Piscis Austrinus. Jupiter is receding from us as Earth begins to round the far side of the Sun from Jupiter, so it appears only 38 arcseconds wide. However, Jupiter is still wide enough to see the South Equatorial Belt re-forming and the transits of the Great Red Spot in a small-to-medium telescope. Uranus is now very close to Jupiter, just 0.6° to the west of the larger planet. Both planets should be close enough so they are both visible in the same field of view in a small telescope when using a medium power eyepiece. A third planet, Neptune, is also still visible in the early evening southwestern sky west of Fomalhaut, on the border between Aquarius and Capricornus. This one is much harder to spot and requires a small telescope or binoculars.
Bright Saturn rises about 30 minutes past midnight this week. By 3:30 AM CST, Saturn is in a perfect position for viewing, high in the southeastern sky in Virgo. That puts it above the thick lower atmosphere long before the sky glow begins in the east as the rising Sun approaches the horizon. The rings are tilted now at about 10°, widening as spring approaches. The rings haven't been this wide since 2007.
Later in the morning this week, very near dawn, Venus shines in the southeastern sky. Though very bright at magnitude -4.3, viewing Venus, in a telescope reveals itself to be only half-lit. Venus is very nearly at it's greatest elongation from the Sun. Venus will begin to grow gibbous in the coming months, while shrinking in diameter as it begins to swing around the far side of the Sun in its faster orbit.
Mercury, too, will be relatively bright at magnitude 0, low in the southeastern sky just before dawn. Notice fainter Antares in Scorpius and the rest of the starry background of the Milky Way, rising in the east before dawn as the winter season marches on.