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Here is the transcript for my podcast about how to see the star known as La Superba, globular cluster M80, and Abell 1656 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
--Start transcript--
Superb!
This week’s first target is one of the reddest stars in the sky. It’s official astronomical designation is Y Canum Venaticorum, but observers usually call it La Superba.
It received its common name from Italian astronomer Angelo Secchi. The star’s color so impressed him that he christened it “the superb one,” or La Superba.
Astronomers classify La Superba as a semi-regular variable star. That means most of the time the star’s brightness varies between a peak of magnitude 4.8 and a low of magnitude 6.3. It takes 160 days to go from one peak to the next … usually.
La Superba has a surface temperature near the minimum for stars, about 2,800 kelvins. (That’s about 4,600° Fahrenheit.) Compare that to the temperature at our Sun’s surface, which is 5,800 K (10,000° F).
La Superba also is a carbon star. Carbon compounds like soot accumulate in the star’s upper atmosphere. The particles scatter light near the blue end of the spectrum. What’s left for us to view is the red component of the star’s light.
As the particles build up, the star fades in brightness and also gets redder. Eventually, the carbon absorbs enough radiation to escape the star, and the cycle starts again.
To find La Superba, look a bit more than 7° north-northwest of magnitude 2.9 Cor Caroli (Alpha [α] Canum Venaticorum) in the constellation Canes Venatici. A sky-distance of 7° equals the field of view of many binoculars. And although you can find La Superba through binoculars, its color appears best through small telescopes.
Don’t forget this cluster
This week’s small telescope target is globular cluster M80 in the constellation Scorpius. It’s easy to find. First, locate the 1st-magnitude luminary Antares (Alpha [α] Scorpii). Then, move 4.5° northwest. M80 sits midway between Antares and magnitude 2.6 Graffias (Beta [β] Scorpii).
Charles Messier discovered this object in January 1781. He later added it to his catalog as number 80.
At magnitude 7.3, you’ll easily sweep up this globular through a 3-inch telescope. Its stars appear tightly packed, so a small scope won’t let you resolve the ones near M80’s bright core.
When you observe this cluster, you’ll notice the magnitude 8.5 star SAO 184288. It sits only 4' to the northeast of M80’s center. That star sits much closer to us than M80 and has nothing to do with the cluster.
A crowded field of galaxies
This week’s large telescope target is the Coma Galaxy Cluster, also designated Abell 1656, which lies in the constellation Coma Berenices. For those of you using go-to drives, “Abell 1656” may not be in your database. Instead, target either of this cluster’s brightest galaxies, magnitude 11.9 NGC 4874 or magnitude 11.5 NGC 4889.
Abell 1656 spans a whopping 4°. Within that neighborhood, hundreds of member galaxies lie in range of a large amateur telescope. The Coma Galaxy Cluster’s richest region, however, is the center, which measures 0.5° across and covers the same area as the Full Moon.
Even through a large scope, you won’t pull out much detail from individual members. The exceptions are magnitude 12.8 NGC 4911 and magnitude 12.5 NGC 4921. Both are spirals and respond well to magnification above 300x.
But, perhaps the main point of viewing the Coma Galaxy Cluster is just to see it. After all, this is a group of nearly 1,000 galaxies that lies more than 300 million light-years away.
--End transcript--
Previous podcast: Star V Hydrae, globular cluster NGC 5634, and the Ursa Minor Dwarf