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July 20: Moon landing throwback
Saturn's largest and brightest moon is Titan - a world that is, in fact, larger than the planet Mercury! Shining at mid-8th magnitude, Titan is easy to view through a telescope this morning, once the ringed planet rises high enough to easily catch in your optics.
By about 2 A.M. local daylight time, Saturn has reached roughly 25° above the eastern horizon. It's the brightest point of light here, hanging above the large figure of Cetus the Whale. Zoom in on Saturn with a telescope and you'll easily pick up Titan, which lies just northwest of the planet this morning. It's moving westward as the hours pass, pulling farther away from its parent world over time, but still in the same telescopic field of view.
You'll likely see other moons as well, such as 10th-magnitude Dione, Rhea, and Tethys. The former two lie east of Saturn, but the latter is just to the west, and depending on when you look, closing in on Saturn's southwestern limb. It won't quite make it, though - shortly before 4:30 A.M. CDT (as the Sun is nearly rising along the East Coast), Tethys disappears into Saturn's shadow, which also stretches southwest of the planet.
Sunrise: 5:49 A.M.
Sunset: 8:23 P.M.
Moonrise: 1:57 P.M.
Moonset: -
Moon Phase: Waxing gibbous (57%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon's illumination is given at 10 P.M. local time from the same location.
We’ll return to Saturn tomorrow morning, the 22nd, to catch the 10th-magnitude moon Dione skimming north of the planet's pole from about 3 A.M. to 4 A.M. EDT. Point your telescope toward the ringed planet as soon as it's readily visible above your horizon to see how the view has changed since yesterday: Titan is now far (nearly 2') to the planet's northwest, while Rhea is quite far to the east. Around 2 A.M. EDT, Tethys is just north of the rings also to the east of the planet, and Dione is closing in from the northeast.
Over the next few hours, Dione will pass north of Saturn but won't transit, leaving a sliver of dark space between the world's limb and the moon. However, its tiny shadow will transit - if you're an experienced planetary imager, particularly with video capture, this is for you. (If not, you're not likely to see the shadow by eye.) The shadow leads the moon, appearing at the northeastern limb just after 1:30 A.M. EDT and taking two hours to complete its transit. It disappears from the northwestern limb just as Dione is roughly due north of Saturn's pole.
Imagers, stay alert - next up is Tethys' shadow, which appears at the eastern limb just above the rings around 4 A.M. EDT. Tethys itself then begins a transit around 4 A.M. CDT (note the time zone change). Again, only imagers will likely see this event, as the small moon will be hard to make out against the bright cloud tops. Tethys' shadow transit ends around 4:30 A.M. MDT (again, note the time zone change), while Tethys slips away from the disk about 30 minutes later.
Alison Klesman is senior editor of Astronomy magazine. She holds a Ph.D. in astronomy and has studied a variety of topics, from minor planets to supermassive black holes.
The post The Sky Today on Tuesday, July 21: Catch Titan near Saturn appeared first on Astronomy Magazine.
