Moon Closes In On Saturn Tonight, Beckons Us Back To The Sky

The moon, one day past full, rises over the ice on Lake Superior last night. Its squished shape is caused by atmospheric refraction. Near the horizon, light rays from the bottom half of the moon are bent more strongly upward than those from the top, causing the bottom half to “push up into” the top and creating an oval shape. Credit: Bob King

No way is the moon done serving up delights. Tireless as ever even after a long slog through Earth’s shadow Monday night, it lifts our gaze to the planet Saturn tonight.

Lovely shot of the moon reflecting off both ice and water in Lake Superior last night. Credit: Jan Karon

Look moon-ward after 11 o’clock tonight and bang – Saturn will be right in front of your nose. The two worlds are in conjunction this evening and paired up very close to one another in the southern sky.

Moonrise happens around 10 p.m. but I’d suggest you wait until after 11 to see them best. From most locations, the two will be only about a degree apart.

Glare made seeing Spica before last night’s eclipse challenging unless you covered the moon with your thumb. Saturn and the moon will be just as close tonight, but the moon’s slimmed and dimmed since full and Saturn’s brighter than Spica, so you should have no problem seeing them side by side.

Looking southeast around 11:30 p.m. this evening you’ll see the moon rise right alongside the planet Saturn. Stellarium

Use the opportunity to point your telescope at the planet famous for its hula hoop act. Saturn will be brightest and closest for the year on May 10 when it reaches opposition. Just as with Mars and the other outer planets, opposition is the time when a planet lines up with Earth on the same side of the sun. This cozy familiarity brings the planet into bright view. 10x binoculars will reveal the planet’s oval shape (thanks to the extra added width of the rings), and a small telescope magnifying 40x will bring at least one ring into clear view.

Saturn with its rings wide open to view on April 6, 2014. The three most prominent are visible: the innermost, translucent C Ring, the wide bright B Ring and the outer A ring. Cassini’s Division, a 3,000-mile-wide gap, separates the A and B rings. The rings shine brightly because they’re made of chunks of water ice. Credit: Anthony Wesley

Most skywatchers would agree that Saturn is most attractive when the rings are tilted near their maximum. During planet’s 29.5 year orbit around the sun, their inclination to Earth varies from 0 degrees (edge-on) to 27 degrees. This month we see the north face of the rings tilted near maximum at 21.7 degrees.

Open rings means you can spot Saturn’s biggest ring gap called Cassini’s Division more easily now than anytime in the past few years. Named after Giovanni Cassini, a Italian/French astronomer who discovered the division and four of Saturn’s moons back in 1675, this “clear zone” spans some 3,000 miles (4,800 km) and separates the bright, wide B Ring from the narrower A Ring.

Although it looks like a black, empty gap, spacecraft have discovered that Cassini’s Division is filled with material similar to that in the less massive and translucent C Ring. It shows up well in this photo taken by the Cassini spacecraft under the planet’s ring plane with the rings and division backlit by the sun. The moon Mimas is at top. Credit: NASA

Spacecraft like NASA’s Cassini probe, which has been orbiting and studying the planet since 2004, have revealed that the gap isn’t as vacant as it appears. As far back as 1980, the Voyager 1 probe showed that that Cassini’s Division contains material similar to that found in the less massive C Ring. It’s even organized into multiple concentric rings divided by yet finer gaps.

Wishing you a happy night.

9 Responses

  1. Edward M. Boll

    Blizzard here at home. I can recall seeing a reflection of the Full Moon on Lake Superior during a penumbral eclipse on our honeymoon on October 6, 1987 at Gooseberry.

    1. astrobob

      That’s a nice memory I bet. If the moon had been in the eastern sky, I might have recorded it reflecting in the lake but all the good eclipse was in the west.

  2. Edward M. Boll

    By April 25, 3 comets should be within large binocular range, Jacques probably the brightest, then Panstarrs K1 and Linear X1 still might be.

    1. astrobob

      Yes, LARGE binoculars. I couldn’t see Jacques two weeks ago with my 15-inch. It was in light pollution but not that bad. It’s a rather diffuse object. PANSTARRS K1 is quite small though expert observers with large binoculars should see it. The easiest will be LINEAR X1 though it’s low at the start of morning twilight.

  3. Cale101

    We, in Central Florida, had a 22 degree halo around the sun today. In all of the pictures a bright object could be seen. Could this have been Saturn?

    1. astrobob

      Hi Cale,
      Saturn isn’t visible during the daytime. Did you mean the moon last night? If so, then yes! A halo would have included Saturn.

  4. caralex

    Bob, now that the LADEE mission has finished, and the craft impacted on the moon’s surface, can you do a blog on the mission results?

Comments are closed.