Here is the transcript for my podcast about how to see Coma Berenices Star Cluster, the Stargate, and spiral galaxy M99 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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An easy-to-see cluster
This week’s naked-eye object is the Coma Berenices Star Cluster, which also carries the designation Melotte 111. Its name gives away its location in the constellation Coma Berenices the Hair of Berenice.
This open cluster spans a whopping 4°. Finding it is easy — well, from a dark site, that is. Just look for magnitude 4.3 Gamma (γ) Comae Berenices. This star isn’t part of the cluster, but it sits on Melotte 111’s northern end.
The brightest stars in the Coma Berenices Star Cluster are 12, 13, 14, 16, and 17 Comae Berenices. (15 Comae is Gamma.) These five stars shine with magnitudes 4.8, 5.2, 4.9, 5.0, and 5.2, respectively. Through binoculars, you’ll count an additional 50 stars brighter than magnitude 10.
Ready for hyperspace
This week’s small telescope object has many names, but the one amateur astronomers use most is the Stargate. It lies in the constellation Corvus the Crow. You’ll find the asterism of the Stargate midway between magnitude 3.0 Delta (δ) Corvi and magnitude 4.7 Chi (χ) Virginis.
The Stargate is a triangle of stars within a larger stellar triangle. Neither triangle is huge. The large triangle measures roughly 5' on a side. The small triangle spans less than 1' on a side. Some observers have reported seeing the Stargate through binoculars. I’ve seen it through 16x70 binoculars. You’ll need a unit with a magnification of at least 10x and with front lenses 50 millimeters across or larger.
If you have trouble resolving the smaller triangle through your binoculars, point a small telescope at this group. Use an eyepiece that gives a magnification of about 50x. That power will show both triangles well.
The brightest of the Stargate’s outer three luminaries shines at magnitude 6.6. Stars of magnitudes 6.7 and 9.9 complete the big triangle. The small triangle’s stars glow more subtly, at magnitudes 8.0, 9.7, and 10.6.
Wheels within wheels
This week’s deep-sky object is known as St. Catherine’s Wheel and the Pinwheel Nebula. And, although it is a galaxy, it’s not the more famous Pinwheel Galaxy, which is M33 in Triangulum. The Pinwheel Nebula is spiral galaxy M99, and it lies at the southwestern edge of the constellation Coma Berenices the Hair of Berenice. The nearest bright star is Denebola (Beta [β] Leonis). Once you find that magnitude 2.1 luminary, M99 lies 7.2° due east.
When you first observe M99, you might think the galaxy looks a bit “off.” In fact, even through a 10-inch telescope, M99 appears to have only one spiral arm, which winds under the galaxy’s southern edge. This arm appears brighter because it’s full of large star-forming regions. Through the telescope, you’ll recognize them as the bright “clumpy” areas.
You’ll need at least a 14-inch telescope and magnifications above 250x to see M99’s two other spiral arms. They’re thinner than the southern arm, but the one that extends northward is the easier of the two to see. The core these arms attach to is large and evenly illuminated, and it takes up about a quarter of M99’s overall diameter.
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Previous episode: constellation Canes Venatici, the Whirlpool Galaxy, and the Whale Galaxy