A Deliciously Dark Sky brings Binocular Treats while Planets Parade at Dawn!
The Moon and Planets
This is the favorite week of the lunar month for astronomers because the moon is completely absent from the evening sky — leaving it deliciously dark for observing dim deep sky objects, or comets. It’s also a terrific week to try for the Orion Nebula and the Andromeda Galaxy in binoculars. Before reaching its New Moon phase on Tuesday, when it’s completely hidden beside the sun, the old moon’s lovely slim crescent will appear over the pre-dawn eastern horizon. On Monday morning, it’s a few finger widths to the left of Mercury and a palm’s width to the lower left of Saturn.
Staying with the pre-dawn sky, Jupiter is the very bright object shining in the east until dawn, when it’s well above the southeastern horizon. Reddish Mars is now sitting to Jupiter’s lower left, and increases the distance by a little bit every morning. It’s much dimmer than Jupiter now, but Mars will steadily brighten over the next six months. Mars and Jupiter are above the horizon by about 3 am local time this week.
Yellowish Saturn rises about 6 am local time, but it will rise earlier and climb higher every morning during the next few months. On Monday morning, the ringed planet will be sitting about three finger widths to the upper right of Mercury, which will be brighter. As the week continues, Mercury will sink out of sight.
Until Jupiter and Saturn begin rising before midnight on March 4 and May 13 respectively, Uranus and Neptune are the only evening planets for the next two months. They’re both in the southwestern sky, but they are challenging to find and observe.
Some Binocular Treats
In early evenings in January, you can follow the Milky Way upwards from the southeastern horizon just east (to the left) of the very bright star Sirius, arcing nearly overhead, and then descending to meet the north-western horizon where Cygnus (the Swan) is about to set. The Milky Way passes between the feet of Gemini (the Twins) and the club of Orion (the Hunter), then climbs higher through Auriga (the Charioteer), and into Perseus (the Hero). At this point, the Milky Way appears dimmest because we are looking along the plane of our galaxy, but in a direction directly opposite the core, so there are far fewer stars there.
Facing the northwest and looking way up, we pick up the Milky Way in Cassiopeia (the Queen) and follow it downwards past Cepheus (the King) and through Cygnus. As we go, the Milky Way thickens and brightens as we look towards the central bulge of our home galaxy. It doesn’t brighten as much as you might expect because a great deal of opaque dust hides the stars there.
The Milky Way hosts a multitude of gorgeous knots of stars and concentrations of gas. These star clusters and nebulae are favourites of astronomers, and you can see many of them using simple binoculars. I’ll highlight a few below, but you can also simply scan along the Milky Way and discover others for yourself.
One of my favorite binocular objects is the large beautiful star cluster known as The Pleiades, or the Seven Sisters. It is located above the triangular face of Taurus, almost overhead in the southern evening sky. It’s also designated Messier 45 (or M45), part of Charles Messier’s famous list of comet-like objects. The Pleiades is made up of the young, hot blue stars Asterope (“A-STER-oh-pee”), Merope, Electra, Maia, Taygeta, Celaeno, and Alcyone that are indeed related — born of the same primordial gas cloud. In Greek mythology, they were the daughters of Atlas, and half sisters of the Hyades. To the naked eye, only six of the sister stars are usually seen, with their parent stars Atlas and Plione huddled together at the east end of the grouping. Under magnification, hundreds of stars appear.
The cluster is about 450 light years away, and makes a wonderful target in binoculars or a telescope, where many more siblings are revealed! A large telescope under dark skies will also reveal blue nebulosity around the stars — this is reflected light from unrelated gas that the stars are passing through. Galileo was among the first to observe the object in a telescope. In 1610, he published a sketch made at the eyepiece. Not surprisingly, many cultures, including Aztec, Maori, Sioux, Hindu, and more, have noted this object and developed stories around it. In Japan, it is called Suburu, and forms the logo of the eponymous car maker. Due to its similar shape, some people mistake the Pleiades for the Little Dipper.
The distinctive winter constellation of Orion (the Hunter) sits in the southern evening sky this time of year. The sword that hangs below Orion’s distinctive three-starred belt contains another favourite sight. Unaided eyes can generally detect three patches of light in the sword, but binoculars or a telescope reveal that the middle object is not a star at all, but a bright knot of glowing gas and stars known as The Orion Nebula (or the Great Nebula in Orion or Messier 42, aka M42).
The Orion Nebula is one of the brightest nebulae in the entire night sky and, at 1,400 light-years from us, it is one of the closest star-forming nurseries. It’s enormous! Under a very dark sky, the nebula can be traced over an area equivalent to four Full Moons!
Buried in the core of the nebula is a tight clump of stars collectively designated Theta Orionis (Orionis is Latin for “of Orion”), but better known as The Trapezium because the brightest four stars form a trapezoid shape. Even a small telescope should be able to pick out this four-star asterism, but good seeing conditions and a larger aperture scope will show another two fainter stars. The trapezium stars are hot young O- and B-type stars that are emitting intense amounts of ultraviolet radiation. The radiation causes the gas around them to shine brightly, by both reflecting off gas and dust as blue light and also by energizing Hydrogen gas, which is re-emitted as red light. That is why there is so much purple in colour images of the nebula.
Within the nebula, astronomers have also detected many young (about 100,000 years old) concentrations of collapsing gas called proplyds that should one day form future solar systems. These objects give us a glimpse into how our sun and planets formed.
Stargazers have long known about the stars in the nebula’s core, but detection of the nebulosity around them required the invention of telescopes in the early 1600’s. In the 1700’s, Charles Messier and Edmund Halley (both famous comet observers) noted the object in their growing catalogues of “fuzzy” objects. In 1880, Henry Draper imaged it through an 11-inch refractor telescope, making it the first deep sky object to be photographed.
In your own small telescope, you should see the bright clump of Trapezium stars surrounded by a ghostly grey shroud, complete with bright veils and dark gaps. More photons would need to be delivered to your eye before colour would be observed, so try photographing it through your telescope or a camera/telephoto lens on a tripod. Visually, start with low magnification and enjoy the extent of the cloud before zooming in on the tight asterism. Can you see four stars, or more? Just to the upper left of M42, you’ll find M43, a separate lobe of the nebula. It surrounds the unaided-eye star nu Orionis (ν Ori).
The “W”-shaped constellation of Cassiopeia is very high in the northern sky — although it will look more like a distorted “M” this time of year. The bright star Ruchbah occupies the right-hand peak of the “M”. Scan with your binoculars about a palm’s width to the upper right of Ruchbah for two close-together clumps of stars. This is the Double Cluster (also designated as NGC869 & NGC884). The pair spans about two moon diameters. Each cluster contains up to 200 young, blue-white stars positioned about 7,000 light-years away from us. It is breathtaking in binoculars or a low power telescope eyepiece. The clusters were described by Hipparchus in 130 BCE, but somehow omitted from Messier’s list, despite their obvious appearance.
Continue your scan beyond the Double Cluster. A fist diameter farther away is prominent Mirfak, the brightest star in Perseus. Mirfak sits near the left edge of a huge concentration of stars called Melotte 20, or the Alpha Persei Cluster. This ideal binocular target is ten moon diameters across! It’s not a true open cluster of stars that formed together, but an enormous sparse grouping of hot young stars located 600 light-years away. Look for a prominent reddish tinted star towards the right side of the group. The background of Melotte 20 is littered with fainter stars of the Milky Way.
Head back to Ruchbah and move two finger widths to its upper left to find the whimsical Owl Cluster, also designated Caldwell 13, NGC457, and the Dragonfly or ET Cluster. It’s only one moon diameter across. It’s one of the most popular clusters for star parties, because it looks like a creature with two bright yellow stars for eyes above an elongated group of stars forming a body, and upswept chains of stellar “wings” on each side. Binoculars will show the cluster, but a small telescope is needed to see him clearly.
Our last object is not part of our galaxy, but it sits beside the Milky Way. It’s the majestic and distant Andromeda Galaxy, or Messier 31. To find it, use the left-hand peak of Cassiopeia’s “M” as an arrow. Look about 15° (or 1.5 fist diameters) from the tip of the arrow for a grey fuzzy patch. At 2.5 million light years away, its faint smudge is among the farthest objects visible to unaided human eyes. Under dark skies, see if you can tell it’s an elongated glowing patch that’s actually about six moon diameters tip to tip!
Astronomy Skylights for this week (from January 14th, 2018) by Chris Vaughan.
This is just a small sample of what you can see. Good hunting!