Saturn best and brightest of the year; Mars stands still

Saturn and Earth line up at opposition on the same side of the sun today when they're closest for the year. In October, when Earth is on the opposite side of the sun, the two planets will be 190 million miles farther apart. Illustration: Bob King

Once a year Saturn and Earth line up on the same side of the sun. The event is called opposition, when the two planets are the closest together. From our perspective on Earth, Saturn will be opposite the sun in the sky. If you face south this evening with the setting sun on your right, Saturn will rise directly opposite in the east at sunset and remain visible all night.

As Saturn revolves around the sun in its 29.5-year-long orbit, we see the rings fan open, shut and fan open again. They're currently tipped almost 14 degrees or halfway to maximum. Credit: Tom Ruen

Last year’s opposition date was April 3; this year it’s April 15. Saturn oppositions occur about two weeks later each year because in the time it takes the Earth to return to another lineup, Saturn has also along traveled further along its orbit. We need about two weeks to “catch up” with the ringed planet and re-align for another opposition.

Since Saturn is the brightest and biggest it will be this year, the coming weeks are an ideal time to train your telescope on the planet for a satisfying look at its rings and satellites. At low power in a small scope you’ll see one ring and Saturn’s brightest moon Titan, the only satellite in the solar system with a significant atmosphere. Observers with larger telescopes will spy Titan’s orange-red color caused by hydrocarbon smog. I’ve easily seen the moon’s hue through my 10-inch reflector when it’s off to one side of Saturn.

Saturn and its brightest moons visible in small and medium-sized telescopes. Iapetus will be bright through early May. The view shows south up - typical orientation in most scopes. Illustration created with Chris Marriott's SkyMap

Larger scopes and calm air also reveal that the single ring is split in two by a narrow dark gap called Cassin’s Division. And if you’re patient, you’ll also see a third, semi-transparent inner ring called Ring C or the Crepe Ring. A thick, gray band – the North Equatorial Belt – crosses the planet between the ring plane and its north pole.

As for Saturn’s family of moons, I mentioned that Titan was visible in a small scope. The moon Iapetus (eye-AP-it-tuss) is almost as easy to spot when it’s far to the west of the planet (western elongation) and showing off its icy hemisphere.

When the moon swings east of Saturn, we see its much less reflective darker hemisphere, causing the moon to dim by nearly two magnitudes from 10.2 to 11.9. As fortune would have it, Iapetus is at western elongation and bright right now. The smaller, fainter moons Dione (dye-OH-nee), Rhea (REE-uh), Tethys (TEE-thiss) and Enceladus (En-SELL-uh-duss) are also visible in larger scopes.

Mars does a loop-de-loop in Leo. It's now about 4 1/2 degrees from Regulus at the stationary point. Beginning tomorrow, it will depart from the star's vicinity and loop back east. Created with Chris Marriott's SkyMap

The Mars event is far less dramatic than Saturn’s opposition. For some months now, the Red Planet has been moving west in retrograde motion, closing in on Leo’s brightest star Regulus. Today it stands still – briefly – and then resumes its normal eastward motion.

Astronomers say that Mars reaches its “stationary” point before resuming “direct” motion. What it means for us is that the planet will now slowly depart from its bright companion Regulus.

The Earth passing Mars causes the planet to appear to move backward in retrograde motion for a time in the sky before resuming its normal eastward path. Credit: NASA

Mars, like all the planets outside Earth’s orbit, appears to travel backwards for a time as the faster-orbiting Earth catches up and passes the planet around the time of opposition. It’s similar to passing a car on the freeway. As you approach the car you plan to pass, it appears to slow down and go “backwards” as you drive by and watch it disappear in your rear view mirror.

Since planets orbit in ellipses and not straightaways like freeways, they soon resume their normal motion a month or so after Earth passes them.

Keep an eye on Mars over the next month and you’ll see it pick up speed as it cruises through Leo and into Virgo where it meets Saturn for a nice conjunction in mid-August.

Just in case you’re still now familiar with where to look for Mars and Saturn, use the map below, which is drawn for 9:30 p.m. local time. Wishing you all clear skies and great Saturn viewing!

Face south to see Mars in Leo and Saturn in Virgo around 9:30 p.m. local time (and later) this week. Created with Stellarium

10 thoughts on “Saturn best and brightest of the year; Mars stands still

  1. Hi Bob
    Sorry it’s me again, but when I ask a question you always have the manners to reply, which you don’t find any many people. I was reading an article that was written by Professor Jocelyn Bell Burnell, I don’t know if you have heard of her or not, but in the article she was saying that we are due for the next large impact from an asteroid, and this is a serious problem, but she says by now, we would have seen an asteroid lethal enough to wipe out Earth approaching, and the next big one if expected in March 2880, what I wanted to know is are we due just now for a large impact, or if there was one would we have seen it by now if it would be such a large asteroid that was approaching, or does she mean that we are due for the next large one anytime soon, I just don’t really understand what she means, and I’m hoping you can help with this once again, I never gave you any URL’s as I have just wrote it the way she has, thanks Bob.

    • Hi Lynn,
      Not having read the article, I imagine Jocelyn Bell Burnell was referring to the fact that statistically we’re due for a big one, but neither she nor anyone else can predict when that might happen. Statistics don’t predict a particular date but a likelihood. Might happen tomorrow, might be another million years. By the way, Bell Burnell was the discoverer of the first pulsating neutron star or pulsar back in 1967.

  2. Thanks Bob again, just watched Jocelyn Bell’s video on her lecture and what I read was different to what she actually said, so sorry about that one Bob, I don’t usually believe what is written on the internet, but I thought that was her own script, but it has taught me a valuable lesson to not to believe all that you read on the internet, people only write what they want you to believe, except yourself of course, your’s is all true :)

      • Hi. I noticed an inordinately large body located due west (viewing from Washington State, Monday, April 16 2012, 10pm).

        I first spotted this bright body a couple of nights ago around 2am, located slightly south of where I spot it tonight. It is larger than any celestial body I have seen (except the moon, of course, and perhaps Haley’s comet in 1997).

        I ruled out Venus, which is supposed to be due south. Obviously not the ISS, which is not geo orbit. Could it be Saturn??

        Please advise.

        Regards,

        AC, Washington State

        • Curious,
          Venus is very, very bright in the western sky until around 11:30 p.m. That’s what you must have seen at 10 p.m. this evening. As for your other sighting at 2 a.m. in the south, that’s almost certainly Arcturus. It’s the brightest object in that part of the sky at that hour. It’s red-orange in color.

          • Thank you for your honest and helpful response. . I rechecked again (tonight) a couple hours later, and it was still as big and the same color…quite literally the largest object I have ever seen…so large, in fact, that if it turned out to be an inner-atmospheric object (ie a high altitude weather balloon or some such), that would be a far more reasonable explanation. This was literally 4 to 6 times larger than the 2nd largest body in the night sky, and its position was far to high to be magnified by the atmosphere.

            If what I saw last night was Arcturos, then this is one and the same (this is the same object tonight as last night, only that it was very slightly south from its location tonight).

            I am assuming it will be there again tonight, and will see what sort of imaging I can manage.
            Thanks again for your honest and helpful response.

            -AC

          • You’re welcome AC. Since you saw it in the same spot in the west two nights in a row, it’s no doubt Venus. Venus does look larger than any other star because of its brightness.
            If you get a photo of it or Arcturus and need verification, send me a copy at rking@duluthnews.com

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