Here is the transcript for my podcast about how to see the Broken Engagement Ring, globular cluster M68, and the Helix Galaxy 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 unhappy ending
This week’s binocular object is the Broken Engagement Ring, which lies in Ursa Major the Great Bear. It lies 1.5° west of one of the Big Dipper’s Pointer stars: Merak (Beta [β] Ursae Majoris).
The Ring’s brightest star also is its northernmost, magnitude 7.5 SAO 27788. I guess this star supposedly represents the ring’s diamond. From it, the brightnesses drop off quite a bit. The next brightest star glows at magnitude 9.1, and the faintest is magnitude 9.9.
Generally, the Ring’s stars lie south and west of SAO 27788. The Broken Engagement Ring spans 16', which is half the diameter of the Full Moon. The best binocular views will be through units that give magnifications above 10x. Mount your binoculars on a camera tripod for a steadier view.
Globular in the south
This week’s small telescope target is the fine globular cluster M68 in Hydra. You’ll spot it 3.5° south-southeast of magnitude 2.7 Beta (β) Corvi. Although you can see M68 as a fuzzy glow through binoculars, you’ll get a whole new perspective by pointing a small telescope at this object.
At low powers, look at the wide central region. It spans half of M68’s diameter. Also, if your eyepiece gives a wide field of view, check out the star field M68 lies in. The individual stars around the cluster all seem to be about the same brightness, which adds to the easy visibility of the globular.
At a dark site, crank up the magnification to 200x and beyond through your 4-inch scope to resolve a dozen or so of M68’s stars. Notice that the core doesn’t appear round or evenly illuminated. If you use a 6-inch or larger scope, you can see “through” the cluster’s brighter stars to a haze of fainter background points of light.
Ring around the galaxy
This week’s deep-sky object is the Helix Galaxy (NGC 2685) in Ursa Major. Astronomers classify this unusual lenticular galaxy as a polar ring galaxy. Several filamentary strands, made up of knots of luminous star-forming regions, form a helical band perpendicular to the galaxy’s main disk and centered on its nucleus.
These structures suggest that NGC 2685 once had a companion, perhaps like one of the Milky Way’s neighboring Magellanic Clouds. The main galaxy captured the satellite into a polar orbit, and its stars eventually merged with those of the larger system. What was left? Only the gas and dust of the smaller galaxy. New stars formed from this material to produce the luminous ring. It is possible that if the Magellanic Clouds had been closer to the Milky Way, they too would have created a polar ring around our galaxy.
To find NGC 2685, look 3.8° east-southeast of magnitude 3.4 Muscida (Omicron [ο] Ursae Majoris. The galaxy isn’t bright. It glows at magnitude 12.1. At low magnifications, you’ll see a disk-shaped, evenly illuminated glow three times as long as it is wide.
Point a 14-inch or larger telescope at this object, and go after the ephemeral ring that gives the Helix Galaxy its common name. Use a magnification around 200x to start, and increase the power if sky conditions are good enough. I’ve had some luck viewing the ring by moving NGC 2685’s main mass just out of the eyepiece’s field of view.
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Previous episode: Coma Berenices Star Cluster, the Stargate, and spiral galaxy M99