Here is the transcript for my podcast about how to see the Y of constellation Virgo, globular cluster M3, and spiral galaxy NGC 4731 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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Alphabet soup
This week’s naked-eye object is a large asterism in the constellation Virgo called the Y. It’s made up of six stars, the faintest of which still shines brighter than 4th magnitude, so you’ll see it easily even from the suburbs.
Start at Virgo’s brightest star, Spica (Alpha [α] Virginis). This blue-white 1st-magnitude luminary marks the bottom of the Y. From Spica, move 14.5° northwest to magnitude 2.7 Porrima (Gamma [γ] Virginis).
From Porrima, the Y branches in two directions, toward the north-northeast and the west-northwest. And if you’re a fan of strange star names, you’ll enjoy these. The north-northeast leg contains Minelauva (Delta [δ] Virginis) and Vindemiatrix (Epsilon [ε] Virginis). The west-northwest branch contains Zaniah (Eta [η] Virginis) and Zavijava (Beta [β] Virginis).
So many stars
This week’s small telescope target is globular cluster M3 in the constellation Canes Venatici the Hunting Dogs. To find it, start at the brilliant star Arcturus (Alpha [α] Boötis). Draw a line 25° long up to the northwest until you hit Cor Caroli (Alpha Canum Venaticorum). M3 lies near the midpoint of this line.
No other bright deep-sky object lies nearby, so you’ll have no trouble zeroing in on M3. And, here’s a test for you sharp-eyed observers: Try to spot M3 without optical aid from a dark site. At magnitude 6.3, it’s a tough naked-eye catch, but many observers have seen it, so it’s not impossible.
M3 looks great even through a 4-inch telescope. The cluster has a wide, bright center that accounts for about half of this object’s width. Surrounding the center are dozens of stars whose density gradually decreases with their distance from M3’s core.
Start with a magnification around 100x and increase the power if the steadiness of the air warrants it. M3 isn’t small — its overall size is half that of the Full Moon — but it is dense. Through ever-larger scopes, you’ll resolve more and more stars in this amazing cluster.
S marks the spot
This week’s deep-sky object is spiral galaxy NGC 4731 in Virgo. It’s not a bright galaxy — only magnitude 11.3 — but it has several features I think you’ll find worth your observing time. NGC 4731 lies 3.3° east-northeast of magnitude 4.7 Chi (χ) Virginis.
This dim galaxy appears highly distorted into an “S” shape because it doesn’t travel through space alone. You’ll easily spot its brighter companion. Look only 0.8° to the northwest for magnitude 9.2 NGC 4697. Gravitational interaction with this elliptical galaxy has nearly destroyed NGC 4731’s spiral arms.
Through a 10-inch telescope, observe NGC 4731’s long, relatively bright central bar. If your observing site is dark enough, crank up the power past 200x, and look at the wide, irregular spiral arms that originate from each side of the bar. The western arm appears somewhat brighter. Tiny bright patches within both arms signal the existence of hotspots of star formation. Through a 20-inch or larger telescope, use a nebular filter to increase the contrast of those regions and the galaxy’s already formed stars.
At an estimated distance of 65 million light-years, NGC 4731 sits on the far side of the Virgo Cluster of galaxies.
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Previous episode: The Broken Engagement Ring, globular cluster M68, and the Helix Galaxy