Here is the transcript for my podcast about how to see Heavenly G, NGC 2112, and the Double Bubble Nebula .
Check out the Astronomy.com's interactive star chart to see an accurate map of your sky. It'll help you locate some of this week's key targets. Astronomy magazine subscribers have access to a slew of cool functions with StarDome PLUS.
Each week, I highlight three different night-sky targets for you to see:
- One object you can find with your naked eyes or through binoculars
- One object to find with a small telescope
- One deep-sky object to find with an 8-inch or larger telescope for you avid astronomers
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A giant asterism
This week’s naked-eye object is an asterism made of eight brilliant winter stars that come from six different constellations. It’s the Heavenly G, sometimes called the Winter Oval or the Winter Octagon.
Recall that an asterism is an unofficially recognized grouping of stars. Sometimes, an asterism comes from the stars of a single constellation, as in the case of the Big Dipper in Ursa Major. In other cases, such as the Heavenly G, asterisms use stars from several constellations.
In order, the stars of the Heavenly G are Capella (Alpha [α] Aurigae), Castor (Alpha Geminorum), Pollux (Beta [β] Geminorum), Procyon (Alpha Canis Minoris), Sirius (Alpha Canis Majoris), Rigel (Beta Orionis), Aldebaran (Alpha Tauri), and Betelgeuse (Alpha Orionis). Whew! That’s a mouthful.
For sheer extent, the G is the second-largest asterism, trumped only by the spring sky’s Diamond of Virgo. I’ll tell you about that one in a few months. But no asterism contains as many brilliant stars — eight of the top 23, and four of the top 10 — as the Heavenly G.
Look away from the Orion Nebula
This week’s small telescope target is open cluster NGC 2112 in Orion. This object, which lies 2,800 light-years away, glows at magnitude 9.0.
To find NGC 2112, move 4° northeast from Zeta (ζ) Orionis, the bottom star in Orion’s belt. A 4-inch telescope at 100x reveals two dozen faint stars strewn across an area 8' in diameter. Although the cluster appears loose, a strong background glow hints at the presence of dozens of unresolved stars. For those, however, you’ll need a larger scope.
A two-for-one treat
This week’s deep-sky object is the Double Bubble Nebula, also known as NGC 2371 and NGC 2372. This twin-lobed planetary nebula resides in Gemini and glows at 11th magnitude.
This object’s common name comes from its unusual appearance: Two rounded puffs of gas lie side by side, with each lobe getting brighter toward the middle.
You’ll find the Double Bubble 1.7° north of magnitude 3.8 Iota (ι) Geminorum. And although you can spot it through an 8-inch telescope, a 12-inch or larger instrument will help you see more of its details.
When you’re first hunting NGC 2371-2, use low power. This object measures 54" by 35", making it nearly as big as the Ring Nebula (M57) in Lyra. An OIII filter definitely helps.
If the seeing is good, crank the magnification past 200x, and look for a brightness difference between the two lobes. Then try to spot the central star. If you can observe it, you’ll see the object whose radiation fuels the glow of the Double Bubble Nebula.
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Previous episode: Constellation Lepus, the Crab Nebula, and the Raspberry Nebula
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