Here is the transcript for my podcast about how to see the Head of Hydra, open cluster NGC 1981, and reflection nebula NGC 1999 this week.
Check out the Astronomy.com's interactive star chart — StarDome — 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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Head of the class
This week’s naked-eye object is the Head of Hydra (pictured at right). This asterism marks the westernmost part of the sky’s largest constellation.
The Head of Hydra lies 2° due south of the midpoint of a line that joins Procyon (Alpha [α] Canis Minoris) and Regulus (Alpha Leonis). Unless you live under the worst light pollution, you’ll see the Head with your naked eyes.
Six stars form the asterism. The brightest is magnitude 3.1 Zeta (ζ) Hydrae. From there, move west to Epsilon (ε) and Delta (δ) Hydrae. Then swing back east to Rho (ρ) Hydrae. Drop 3.5° southwest to Sigma (σ) Hydrae. At magnitude 4.4, this is the faintest star in the asterism. Finally, head east again to the sixth and final star, Eta (η) Hydrae.
Avert your gaze
This week’s small telescope target is open cluster NGC 1981 in Orion. To locate this easy-to-see object, first find the Orion Nebula (M42). After you’ve soaked up the view from that celestial wonder, look 1° due north.
NGC 1981 is a bright open cluster. Its magnitude, 4.2, ties it for 11th place among open star clusters. It’s large, too. NGC 1891’s diameter is nearly that of the Full Moon.
When you observe NGC 1891 through a small telescope, use a magnification near 100x. Be sure to segregate the stars of the cluster from the surrounding star field. Note that the curved line of three magnitude 6.5 stars just to the east do not belong to the cluster.
Through a mirror, dimly
This week’s deep-sky object is reflection nebula NGC 1999 in Orion. You also can easily find this object by starting at the Orion Nebula. Move your telescope just a bit more than 1° south-southeast of M42, and your field of view will sweep up NGC 1999.
This reflection nebula has a triangular shape, but there’s more. A dark, irregular bar obscures much of the bluish light near NGC 1999’s center. This dark cloud is a Bok globule, a region of dust and cold gas — possibly a star-forming region — that obscures the light from objects behind it. Astronomers named such globules for Dutch-born American astronomer Bart Jan Bok (1906–1983), who pioneered their study.
NGC 1999’s illumination comes from the star V380 Orionis. It sits just outside and to the east-southeast of the dark central region. The star is so young that the reflection nebula NGC 1999 is material left over from the star’s formation.
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Previous episode: Constellation Columba, globular cluster NGC 1851, and spiral galaxy NGC 1808
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