Orion’s Nebula, view Vesta, Maximum Morning Mercury, Moon meets Jupiter, and Venus Charges Mars!
The Moon and Planets
For the first half of this week, the moon will flood our evening skies with light from on high, while it wanes and rises later each night. In the wee hours of Thursday morning, the moon will rise with Jupiter — sitting only two finger widths to the left (north) of the bright planet. They’ll make a nice binocular sight until the sky lightens around 7 am, when they’ll be due south. On Thursday afternoon the moon reaches Last Quarter, when it’s half illuminated (on the left). Last Quarter moons always rise about midnight and linger into the daytime morning sky. Finally, on Sunday, January 22, the old crescent moon will make a pretty sight in the eastern pre-dawn sky.
Venus continues as the brilliantly bright object visible every evening in the western sky, until it sets around 9:15 pm local time. In a telescope, Venus is showing a “half-moon” shape (phase) this week. Because the evening Ecliptic continues to tilt higher as we slide towards spring, Venus will be carried a bit higher in the evening sky before starting to sink into the sunset next month. Believe it or not, it has not yet reached peak brightness!
Meanwhile, reddish Mars makes a steady march towards Venus this week, the two planets closing to within 6° (about a palm’s width) by next Sunday. Mars sets about 9:50 pm local time. Rounding out the evening planets, blue-green Uranus is halfway up the southwestern sky at dusk — just inside the western (right) arm of the “V” of Pisces the Fishes. The planet sets about 12:30 am local time. Recently it has formed a nice little triangle with two of Pisces’ stars, the double star Zeta and 88 Piscium. Uranus (the blue-green object) sits about a pinky finger width (40 arc-minutes) to the upper left of the two stars. Tiny Neptune is in Aquarius the Water-bearer, a few degrees to the lower right of Venus, and it sets about 9 pm local time.
This is the last week when bright, white Jupiter will be rising in the east after midnight local time. Next week, it officially transitions to an evening object! This winter, it’s been sitting just a few finger widths above the bright white star Spica in Virgo the Maiden. By daybreak, it’s moved above the southern horizon. Saturn is rising this week about 5:15 am local time. You should easily see its yellowish dot low in the east for half an hour before sunrise, while the sky is still dark.
On Thursday, January 19, before dawn, Mercury will reach its greatest angle west of the sun, and reach maximum visibility for this apparition. Mercury is now sitting about 10° to the lower left of Saturn. If you can find a low eastern horizon, look for the planet between about 6:30 and 6:50 am local time. With Mercury just a bit higher than a shallow ecliptic, this apparition is less than ideal for northern hemisphere observers (the next excellent one happens on April 1), but quite good, seen from the southern hemisphere.
Dwarf Planet Vesta, anyone?
On Tuesday, January 17, the large asteroid Vesta reaches opposition, the date when it is closest to earth and brightest for the year. It is sitting high in the evening sky, just below the twin stars of Castor and Pollux in Gemini. Its proper designation is (4) Vesta because it was the fourth asteroid discovered, by German astronomer Heinrich Wilhelm Olbers on March 29, 1807. It is named after the Roman goddess of home and hearth, Vesta. At apparent magnitude 6.1, the asteroid is observable with unaided eyes (under really dark skies), binoculars, and small telescopes. Its motion through the background stars can be noted by observing it on separate evenings.
Last week, we toured most of Orion the Hunter’s major stars (read it here). This time, we’ll focus on his majestic sword, one of winter’s true astronomical treats. The sword hangs well below Orion’s distinctive three-starred belt. Unaided eyes can generally detect three patches of light in Orion’s sword, but binoculars or a telescope quickly 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). For best seeing, pick an evening when the moon rises late or is out of the sky — as it will be next week!
The Orion Nebula is one of the brightest nebulae in the entire night sky and, at 1,400 light-years distant, it is one of the closest star-forming nurseries to us. 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 occupy the corners of 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 faint 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 they are embedded in 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).
While you’re touring the sword, look just below the nebula for a loose group of stars, 1300 light-years away, called Nair al Saif “the Bright One of the Sword”. This main star is a hot, bright star expected to explode in a supernova one day. It is surrounded by faint nebulosity, too. Astronomers believe that this star was gravitationally kicked out of the Trapezium cluster about 2.5 million years ago.
Sweeping down the sword and to the left (east) brings us to the star d Orionis at the tip of the sword. This magnitude 4.7 star is near the limit for visibility in moonless suburban skies. About two finger widths to its right is another star of similar brightness, named Thabit, “the endurer”.
Moving upwards towards Orion’s belt, half a finger width (30 arc-minutes, or the moon’s diameter) above the Orion Nebula, you’ll find another clump of stars dominated by c Orionis and 45 Orionis. A larger telescope, or a long-exposure photograph, reveals a bluish patch of nebulosity around them that contains darker lanes forming the shape of a figure, called the Running Man Nebula. This is another case of gas reflecting light from the two stars mentioned.
Just above the Running Man sits a loose cluster of a few dozen stars best seen in binoculars. Then we jump higher — most of the way towards Alnitak (the eastern-most belt star), to check out a beautiful little grouping of stars collectively called Sigma Orionis. What makes this a special treat is that, in a small telescope, we find four or five stars crammed together. Check it out with your telescope — trust me, it’s pretty! It’s a bit more than a finger width to the lower right of Alnitak. I’ll post some photos here. Let me know what you see!
Stargazing News for this week (from January 15th) by Chris Vaughan.