A Spoonful of Saturn to Sweeten the Evening

July 13, 2019 - Comment

Transfer over Jupiter, it is time for Saturn to shine! At opposition this week, the ringed planet is at its brightest and closest for the 12 months. Discovering Saturn is straightforward this season. The zero-magnitude planet is positioned in asterism-rich Sagittarius about three outstretched fists (30°) decrease left of good Jupiter close to a little

Transfer over Jupiter, it is time for Saturn to shine! At opposition this week, the ringed planet is at its brightest and closest for the 12 months.

Jupiter's mate

Discovering Saturn is straightforward this season. The zero-magnitude planet is positioned in asterism-rich Sagittarius about three outstretched fists (30°) decrease left of good Jupiter close to a little bit asterism known as the Spoon.

Saturn’s again! It joins Jupiter within the southern sky on the finish of nightfall for a one-two punch of planetary pulchritude. Jupiter leads the best way, shining brilliantly in Scorpius within the southern sky close to the top of nightfall. Saturn hangs its mild three outstretched fists to Jupiter’s decrease left within the constellation Sagittarius. You may instantly discover a number of little stars close to the planet dubbed the Spoon. It is one among three asterisms — simply recognizable patterns of stars — in that constellation. The others embody the primary define of Sagittarius, higher often called the Teapot, and its deal with, the Milk Dipper, appropriate for dipping within the close by Milky Means.

Saturn reached opposition on July ninth at 1.four billion km from Earth. For Saturn, that is shut, so we see it at its greatest and brightest for the subsequent couple months. The lean of its rings makes a giant distinction, too. They’re well-presented with a cant of 24°, solely three° shy of most. Saturn struts round at magnitude +zero.1 with a diameter of 18.four″ (arcseconds), just like the obvious dimension of Mars at a modest opposition. The planet’s diameter broadens to 42.9″ for those who embody the rings.

Stellar company

Saturn is in wealthy firm this season, sharing the sky with shiny Milky Means star clouds and quite a few deep-sky objects. This photograph was taken on July eighth.
Bob King

We view Saturn’s northern hemisphere this 12 months together with the north face of the rings. Like Jupiter, Saturn sits close to the “backside of the bowl” on the south finish of the ecliptic, so it by no means climbs very excessive within the sky as seen from mid-northern latitudes — solely about 25° excessive from the central U.S. Due to atmospheric turbulence prevalent at low altitudes, the planet typically appears tender and blurry, so it helps to watch it repeatedly in hopes of catching sharper views on nights of calm air.

Nested planet

Saturn in its full glory on July 11. Across the time of opposition, discover how the shadow of the globe falls immediately behind the planet onto the ring airplane; after opposition it would more and more pivot to the west. The shadow is at the moment tangent to the outer fringe of the A hoop, so the globe simply suits throughout the confines of the rings. North is up.
Christopher Go

In a unusual coordinate coincidence, each Jupiter and Saturn share the identical declination of –22° 08′ on July 18, so observers with equatorially-mounted scopes can middle Jupiter within the discipline of view and swing the scope throughout 30° of sky to seek out Saturn at almost the identical spot. Talking of enjoyable visuals, the complete Moon will likely be in shut conjunction with the planet in a single day Tuesday, July 15th. The 2 will rise collectively shortly after sundown and attain a closest separation of simply ¾° round three a.m. Central Daylight Time (8h UT) on the 16th.

This diagram identifies Saturn’s most outstanding options seen in novice telescopes. South is up.
Damian Peach / E. Kraaikamp / F. Colas / M. Delcroix / R. Hueso / G. Therin / S. Sprinau / S2P / IMCCE / OMP

So far this season I’ve succeeded in observing the planet on three nights of fantastic seeing. Apart from the uncooked great thing about Saturn’s exceptionalism I’ve seen some good particulars together with the three main rings, a pale grey north equatorial belt and the dusky grey north polar area. All have been plainly seen in my 10-inch Dob at 180×.

Every ring varies in width and depth from the slim, outer A hoop, to the huge and shiny B ring, to the filmy, dusky character of the innermost C ring. I additionally discerned Cassini’s Division, the slim, black hole between the A and B rings, nearly all the best way across the planet. Composed of 99.9% water ice with sprinklings of impurities, the rings differ in thickness from as little as 10 meters to a kilometer! Get pleasure from them whilst you can. The latest Cassini discovery of ring rain coupled with the equatorial movement of ring materials into the planet’s ambiance may imply they’re going to be gone in 100 million years.

The rings disguise many of the planet’s southern hemisphere, however the northern is in plain view. Verify it routinely for uncommon exercise because it’s well-known for infrequent outbreaks of “white spots,” large storms that effectively up from beneath the higher cloud deck. That final actually huge one occurred in late 2010–2011 and was plainly seen in novice telescopes.

Ice grains glitter

What a distinction opposition makes! Evaluate Saturn’s rings at opposition in 2017 with the view a number of months prior in March. The Seeliger Impact is clear.
Christopher Go

Being composed of water ice, the rings replicate mild effectively and seem noticeably brighter than the planet’s golden globe. The distinction between rings and disk could be stark across the time of opposition because of the Seeliger Impact. At opposition, the Solar strikes the ring particles face-on from our perspective, so the shadows they solid are tucked out of view behind. With out shadows to partially cancel the sunshine, the rings surge in brilliance. It is fairly apparent in the mean time. Once you observe the planet, make a psychological observe of the rings’ look after which examine the view to their look in a number of weeks.

Whereas Jupiter’s main moons are all simply seen within the smallest of telescopes, Saturn’s are extra numerous in phrases in brightness and distance from the planet. And since Saturn’s axis is tilted 26.7°, the moons describe orbits in looping ovals across the planet quite than the extra acquainted refrain line at Jupiter.

Saturn and family

That is simulated view of Saturn at 150× in a telescope on July 10th at 11 p.m. CDT (midnight EDT; 10 p.m. MDT; 9 p.m. PDT.) North is up. Further stars are proven as Saturn lies in a wealthy discipline.

The simplest and brightest is Titan, which at ninth magnitude is seen in telescopes as small as 60 mm (2.four inches). It swings round Saturn each 16 days like a canine on a tether. A 6-inch scope will present 4 extra of Saturn’s satellites so as of brightness: Rhea (magnitude 9.9), Tethys (10.four), Dione (10.6) and Iapetus, which ranges from 10.2 to 11.9. An Eight-inch will pull in Enceladus (11.9) when it is farthest from the planet’s glare at best elongation, and a 10-inch and darkish skies ought to internet Hyperion (14.four). A magnification of 50–75× is ample for Titan and Iapetus, however to obviously see Rhea, Dione, and Tethys in Saturn’s glare, attempt 150–200×.

I’ve heard that Mimas (13.1) is seen in a 12.5-inch scope, however I’ve by no means seen it in both the 10- or 15-inch. Mimas orbits very near the planet with a interval of simply 23 hours and is extraordinarily tough to coax from the glare of the rings. Would-be Mimas watchers would do effectively to to mark their observing calendars for Might 2025 when the rings are subsequent edgewise and disappear from sight for a time. Some stuff you simply gotta watch for.

Iapetus orbits Saturn as soon as each 79.three. days. We see its shiny, ice-covered hemisphere at western elongation, the sooty darkish aspect at japanese elongation, and a mixture of each when this moon is in conjunction on the nearside of Saturn (inferior) or far aspect (superior). To not scale.
Bob King

Let’s return for a second to Iapetus, arguably Saturn’s most entertaining moon. When at western elongation in its 79-day orbit, it shines at magnitude 10, second solely to Titan in brightness, however fades to 12th magnitude at japanese elongation. The variation is attributable to which aspect of the moon we see. When east of the planet, we view the darkish, rocky aspect; when west of Saturn, we see the ice-coated hemisphere.

This month we’re in luck! Iapetus reaches western elongation on July 15th and will likely be shiny and straightforward to identify west of Saturn by means of month’s finish. You’ll be able to hold observe of the Saturn’s 5 brightest moons at Sky & Telescope’s interactive Saturn’s Moons web site. To search out these moons and the remainder, obtain Stellarium, decide a date and time, zoom in on the planet, and put together to be enthralled.

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