Here is the transcript for my podcast about how to see the Spring Triangle, the Mini Coathanger, and irregular galaxy NGC 4449 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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Three’s not a crowd
This week’s naked-eye object is the Spring Triangle. This giant geometrical figure is visible in the spring all night long from any location in the Northern Hemisphere.
Three dazzling stars mark this asterism. The brightest is Arcturus (Alpha [α] Boötis), which shines at magnitude –0.04 near the bottom of the constellation Boötes the Herdsman. Orange Arcturus is the fourth-brightest nighttime star overall and the brightest north of the celestial equator.
Next in brightness is Spica (Alpha Virginis), the luminary of the constellation Virgo the Maiden. Spica is the very definition of a 1st-magnitude star, but its brightness isn’t constant. Its apparent magnitude varies between 0.92 and 1.04 over a period of just more than 4 days. Unlike Arcturus, Spica shines with a blue-white intensity that betrays its hot surface temperature of more than 20,000° Fahrenheit (11,400 K). Arcturus’ orange surface is cooler, on the order of 7,300° F (4,300 K).
The third Spring Triangle star is Denebola (Beta [β] Leonis), the star that marks the tail of the constellation Leo the Lion. And although Denebola, at magnitude 2.1, is the sky’s 59th-brightest star, it’s only 36 percent as bright as Spica, and it emits just 14 percent the light output of Arcturus.
May I take your coat?
This week’s small telescope target is the Mini Coathanger asterism way up north in the constellation Ursa Minor the Bear Cub. Amateur astronomer Phil Harrington named this asterism because of its resemblance to the more famous Coathanger, also known as Collinder 399, which lies in Vulpecula.
To find the Mini Coathanger, look 1.9° south-southwest of magnitude 4.2 Epsilon (ε) Ursae Minoris in the Little Dipper’s handle. The Mini Coathanger is made up of 10 stars. They range in brightness from magnitude 9.2 SAO 2721 to magnitude 10.8 GSC 4574:802. From its hook to its base, the Mini Coathanger measures 9'. The base, at 17', is nearly twice that length.
A rectangular galaxy
This week’s deep-sky object is irregular galaxy NGC 4449 in the constellation Canes Venatici the Hunting Dogs. You’ll find this object 2.9° north-northwest of magnitude 4.2 Chara (Beta [β] Canum Venaticorum). The galaxy’s high surface brightness makes it easy to observe.
Astronomers classify NGC 4449 as a magellanic type galaxy because it appears similar to the Large Magellanic Cloud, a satellite galaxy of the Milky Way visible from the Southern Hemisphere. Both galaxies have large stellar bars running through them.
Through an 8-inch telescope, you’ll see NGC 4449’s unusual rectangular shape. It has a bright, concentrated nucleus that also looks rectangular. Crank the magnification past 250x, and examine the irregular halo outside this galaxy’s core.
If your seeing is good, an 11-inch scope will help you spot several concentrations of star-forming activity. The main one lies to the north, but a smaller one is just south of NGC 4449’s core. Larger telescopes will bring out more detail in the galaxy’s central region.
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Previous episode: The Y of Virgo, globular cluster M3, and spiral galaxy NGC 4731