Rocky moon meets the ringed planet tonight

Look to the waxing gibbous moon tonight July 7 and you’ll see the planet Saturn about 1 degree above it. This map shows the sky around 10 o’clock local time. Stellarium

Forgive this ultra-brief appearance, but I’ve been exploring a virtually unknown astronomical paradise the past few days – Las Vegas! Although it seems incongruous, given Vegas’ image, the Las Vegas Astronomical Society has a very active presence here.

A recent photo posted by the Cassini spacecraft photo group shows Saturn’s magnificent rings, polar vortex and the jet stream-created polar hexagon. The hexagon, which is wider than 2 Earths, forms a six-lobed, stationary wave that wraps around the north polar regions at a latitude of roughly 77 degrees North. Credit: NASA/JPL-Caltech

The group planned a public outing for the Mars-moon conjunction on July 5 but were clouded out. Maybe tonight their members will get a clear sky for the Saturn-moon conjunction. I’ll be in a plane at 35,000 feet for the event crossing my fingers I get a window seat on the ‘right’ side.

Celestial fireworks light up the sky on the Fifth of July

The crescent moon shines in the southwestern sky tonight July 2 not far from Leo’s brightest star Regulus. It’s headed for two fine conjunctions later this week. Stellarium

We celebrate Independence Day this Friday the 4th with parades and good food topped off with colorful fireworks. Consider that the opening act. Festivities continue into the weekend with two spectacular conjunctions of the moon and planets.

Saturday evening July 5 allow your gaze to wander up to the first quarter moon. Levitating above it will be a bright red light – the planet Mars! They’ll be close. From most of the central and eastern U.S. and Canada the two are separated by just a half degree or one moon diameter. Look a short distance to the left of moon and you’ll also spot Virgo’s brightest star Spica.

The first quarter moon pays a close visit to Mars on Saturday July 5 and then passes Saturn two nights later. The views show the scene from the central U.S. around the start of nightfall. Stellarium

If you live farther south, the moon will inch closer to Mars. From sizzling Miami, the duo’s only a 1/3 of a moon apart, while the moon will completely cover or occult Mars for up to an hour across a wide swath of South America. Click HERE for a map and times showing where and when the occultation will occur.

Though Mars isn’t quite as bright as it was at opposition in April, it’s still brighter than its color rival Betelgeuse in Orion. With haze-free skies and a pair of binoculars you might be able to see it atop the moon a short time before sunset. Certainly worth a try.

Everybody loves an encore after a great performance, and the moon’s happy to oblige. Two nights later on July 7 it glides about a degree (two diameters) directly below Saturn. Once again, the moon will occult the planet as seen from the southern half of South America. While these sky events aren’t exactly stars exploding before our very eyes, their quiet beauty is worth our admiration.

Cassini at Saturn – 10 years of beauty and discovery

Saturn and its rings photographed with Earth (lower right) in the background on July 19, 2013. Click for a full, hi-res view. Credit: NASA/JPL-Caltech/SSI

Today marks the 10th anniversary of NASA’s Cassini mission to Saturn. Originally slated for four years, the mission was granted two extensions and will continue through September 2017. Now dubbed the ‘Cassini Solstice Mission’, it’s named for the Saturnian solstice which occurs in May that year. All the extra time granted to keep the probe running has allowed astronomers to study seasonal changes during Saturn’s 29.5 year orbit of the sun. Saturn has seasons just like Earth, but they’re leisurely affairs, each lasting about 7.5 years.

This image shows the first flash of sunlight reflected off a hydrocarbon lake on Saturn’s moon Titan on July 8, 2009. The glint off a mirror-like surface is known as a specular reflection. Click to enlarge. Credit: NASA/JPL-Caltech

Cassini has not only made a remarkable number of new discoveries but returned what many of us consider the most beautiful photos every taken of another world. Planetary scientist Carolyn Porco, who leads the Cassini imaging team, has a knack for capturing images of both scientific import and spectacular beauty. How can you help it when your subject’s the most picturesque celestial body in the known universe?

First color image of Titan’s surface taken by the Huygens lander. The two icy rocks below center  measure about 6 inches across (left) and 1.5 inches (right). They’re about a yard from the spacecraft. Click for more details. Credit: NASA/JPL-Caltech

Here’s a short list of Cassini’s most notable discoveries since arriving in 2004:

* Titan revealed as a colder analog of Earth with rivers, lakes, seas filled by rainstorms of liquid hydrocarbons like ethane and methane and an atmosphere composed primarily of nitrogen.

* First landing by the Huygens probe – dispatched by Cassini – on a moon orbiting another planet. Huygens touched down on Titan after parachuting to its surface on Jan. 14, 2005.

* Discovery of active, icy plumes on the Saturnian moon Enceladus that appear to originate from a 6-mile-deep subsurface ocean confirmed just this spring. Enceladus joins Jupiter’s moon Europa and Mars as potential habitats for life.

Vertical structures rise abruptly from the edge of Saturn’s B ring to cast long shadows on the ring in this image taken 2 weeks before the planet’s August 2009 equinox. The structures tower as high as  1.6 miles (2.5 km) above the plane of the rings, much higher than their general thickness of just 30 feet (10-m). Click to enlarge. Credit: NASA/JPL-Caltech

* Spectacular closeup photos revealing the individual characteristics of many of Saturn’s moons as well as active and dynamic structures within the planet’s rings like vertical ‘ice pillars’ and the birth of a new moon.

* First complete view of the north polar hexagon and discovery of giant hurricanes at both of Saturn’s poles.

* Close up study of the planet’s massive thunderstorm from first detection on Dec. 5, 2010 into 2013.

Enceladus shows off its plumes to NASA’s Cassini spacecraft cameras. Click to enlarge. Credit: NASA/JPL-Caltech/SSI

There’s so much more, much of it reported here over the years. If you’d like to go deeper, start at the Cassini Solstice Mission homepage. Be sure you check out some of the favorite Cassini images selected by members of the team.

The spacecraft has been remarkably trouble-free, and from an
engineering standpoint, the main limiting factor for Cassini’s lifetime
now is how much propellant is left in its tanks. Future studies include examining the rings and moons in ever greater detail.

Care to see more photos? Click to view the Cassini Imaging Diary.

Two asteroids approach in the night / See Saturn’s elusive moon Iapetus

Map showing Ceres and Vesta as they approach each other closely this coming week. Both asteroids are near the easy-to-find star Zeta in Virgo not far from bright Mars (see map below). Although the asteroids appear very close together in the sky, they’re really about 51 million miles apart with Vesta in the foreground. Click to enlarge. Source: Chris Marriott’s SkyMap

This coming week there will be something for everyone in the night sky whatever instrument you choose: telescope, binoculars or naked eyeballs.

The biggest asteroid, Ceres, and brightest, Vesta, have been on converging paths since early spring. Right now they’re about a moon diameter (1/2 degree) apart and closing with each passing night. Saturday night July 5 – one week from today –  they’ll be three times closer yet, separated by just 10 arc minutes. To see this double asteroid treat a pair of 35 or 50mm binoculars should do the trick.

Use this wider view to help get oriented. Our two featured asteroids are near the 3rd magnitude star Zeta Virginis just above the bright pair of Mars and Spica. The map shows the sky around 10 p.m. local time tonight June 28, 2014 for the central U.S. Stellarium

Just as moon routinely has conjunctions with bright planets and stars during its monthly round through the zodiac, Vesta and Ceres will be in conjunction one directly atop the other on July 5. Vesta will shine at 7th magnitude and be easy to spot in binoculars; fainter Ceres at magnitude 8.3 will take a little more effort. Since asteroids are too small and far away to show as disks in most telescopes, the pair will look like a temporary ‘double star’ in all instruments.

Double your conjunction fun on Saturday night July 5. The same night Ceres and Vesta are closest, the moon and Mars form a tight duo nearby. From parts of South America, the moon will cover or occult the Red Planet. Stellarium

Another celestial duo debuts on the very same night the asteroids are closest. For observers in the U.S. and Canada, the moon, some 7 degrees south of Vesta-Ceres, passes only a half degree from Mars. Two conjunctions in the same small pocket of sky on the same night!

For U.S. observers, this all happens the night after the July 4 Independence Day fireworks. Could July start with more of a bang?

Another telescopic delight is happening a stone’s throw from Mars around the planet Saturn. Of the 62 known moons of the ringed planet, one of the most peculiar is 907-mile-wide Iapetus, which orbits well beyond the more familiar telescopic moons Titan, Rhea, Tethys and Dione.

Ever seen Saturn’s peculiar moon Iapetus? Right now it’s west of the planet and bright — second only to the moon Titan. Click to enlarge. Source: Starry Night

Iapetus has two faces really. One is shiny white and bright as snow, the other dark as the sky above Gotham City. The moon takes 79 days to complete one orbit around Saturn and like our own moon, keeps one face locked toward the planet. When it orbits east of Saturn, Iapetus shines dimly at magnitude +12 because its dark side faces us. But when it’s off to the west of the planet, the brilliant side turns our way and we see it shine two magnitudes brighter.

Saturn’s moon Iapetus, 907 miles (1,460 km) in diameter, has a dual personality. One hemisphere is covered with bright ice, the other with darker material possibly ejected by impacts on the more distant moon Phoebe. Credit: NASA / JPL / Space Science Institute

Greatest brightness occurs at the time of greatest distance west of the planet which happens on July 3. You can use the map above to help you follow the moon through its cycle of bright to dim. For more information, please see this recent article in Sky and Telescope.

Magnetic collapse makes Saturn’s auroras dance the cha-cha

Images of auroras over Saturn’s north pole in ultraviolet light with the Hubble Space Telescope capture moments when Saturn’s magnetic field is affected by bursts of particles streaming from the Sun. Click to enlarge. Credit: NASA, ESA, Jonathan Nichols (University of Leicester)

Saturn shines brightly in the late May evening sky. You can see it now at nightfall by following an arc starting with fiery Mars and passing through Spica. Continue and you’ll end up at Antares, the alpha luminary in Scorpius. Did you know that it also shimmers with auroras too just like the Earth?

Recent Hubble Space Telescope photos taken in ultraviolet light, where the aurora shines brightly, show bursts of light shooting around Saturn’s polar regions traveling at more than three times faster than the speed of the gas giant’s roughly 10-hour rotation period.

Saturn’s auroras shine brightly in UV but would appear deep red at the bottom and violet at top with the naked eye. That’s because hydrogen gas dominates the planet’s atmosphere and emits light in different colors when bombarded by the energetic electrons in the solar wind. On Earth, excited oxygen and nitrogen molecules produce the more familiar greens, reds and blues of northern lights.

A magnetosphere is that area of space around a planet that’s controlled by the planet’s magnetic field. The shape of the Earth’s magnetosphere is the direct result of being blasted by solar wind, compressed on its sunward side and elongated on the night side forming a magnetotail. Saturn’s is similar. Credit: NASA

University of Leicester researchers recently discovered an amazing connection between Saturn’s and Earth’s auroras. Both planets are surrounded by teardrop-shaped magnetic domains called magnetospheres generated by the churning of materials within their cores. In each case, the side facing the sun is compressed and flattened, while the other side is drawn out into a long tail called a magnetotail.

“Our observations show a burst of auroras that are moving very, very quickly across the polar region of the planet. We can see that the magnetotail is undergoing huge turmoil and reconfiguration, caused by buffering from solar wind,” said Jonathan Nichols, of the University of Leicester’s Department of Physics and Astronomy, who led the Hubble observations.


NASA’s THEMIS Spacecraft See magnetic reconnection / collapse in Earth’s magnetotail

What’s happening – and you can see it clearly in the video above – is that the incoming solar wind connects to and ‘peels back’ a portion of the magnetic field on the dayside of both Earth and Saturn. When the lines pinch together and reconnect on the back or magnetotail-side, a torrent of solar electrons is funneled into the upper atmospheres of both planets. Voila – aurora borealis! Here’s another video showing it from a slightly different perspective.


Dance of Saturn’s auroras

“The particular pattern of auroras that we saw relates to the collapsing of the magnetotail,” Nichols added. “We have always suspected this was what also happens on Saturn. This evidence really strengthens the argument.”

Cool beyond cool. Earth and Saturn are auroral buddies.

Follow the arc from fiery Mars in the south through Spica to find Saturn. Keep going all the way to Antares. All four are magnitude 1 or brighter. The map shows the sky around 10:30 p.m. local time facing south. Stellarium

Saturn disappears, Mercury appears during ‘night of the planets’


Saturn covered and uncovered by the moon earlier today by Dave Herald, Murrumbateman, Australia

Enjoy the video. Dave Herald did a great job recording this morning’s Saturn occultation. The images are very sharp. I always find it remarkable how atmosphere-less the moon is. There’s not a hint of softness in the planet as it’s devoured by the lunar limb. If there were substantial air, the planet would gradually soften and fade.

For a moon or planet to be completely without air is next to impossible. The solar wind knocks atoms from minerals on the lunar surface and sends them reeling into the virtual vacuum above the surface. Studies have found potassium, sodium, helium and argon in the moon’s exosphere, the name given to the lunar atmosphere. Bombardment of the moon’s surface rocks by micrometeorites and the solar wind release potassium and sodium; helium and argon probably bubble up from radioactive decay of those same rocks. Helium may also arrive via the sun’s wind.

Glow from sodium in the lunar atmosphere. The light from the moon has been blocked by the telescope, but the size, position and phase of the Moon are shown by the superimposed image in the center. Rayleighs are a measure of brightness. Credit: NASA

At sea level on Earth, we breathe in an atmosphere where each cubic centimeter contains 10,000,000,000,000,000,000 (10 quintillion) molecules; by comparison, the lunar atmosphere has less than a million molecules in the same volume.

Comets and meteoroids striking the surface temporarily enhance the amounts of other atoms and molecules. But the sum total of all the sputtering and interacting is an atmosphere equal to the amount of air you’ll find 250 miles high where the space station plies it orbit. Not much.

Mercury stands all by itself low in the northwest in this photo taken about 50 minutes after sunset last night. Credit: Bob King

At my house, we saw no occultation of Saturn, but the two did stand together in the southeastern sky at dusk. On the opposite end of the heavens, Mercury made a fine naked eye appearance in the northwestern sky.

Jupiter glows over Amity Creek last night. Both the creek and the sky were lit by the light of the full moon. Credit: Bob King

I first caught it around 9:15 p.m. some 40 minutes after sunset and watched it for at least a half hour. Capella and Jupiter – both higher up in a darker sky – made for great sight lines to the planet.See yesterday’s map for details.

Jupiter in Gemini remains the most brilliant object in the western sky at dusk during early evening hours. I watched it from a nearby creek that rushed with water from snow melt and recent rains.

Mars stood between Jupiter and Saturn. This week the ‘boring’ hemisphere – the one with fewest dark markings – is turned toward western hemisphere observers.

The Moon, Mars (upper right), Saturn (lower left), Spica (immediate right of moon) and Arcturus (top) as seen from Dayton, Ohio on May 12. Credit: John Chumack
Dayton, Ohio

But there’s still much to see – enough to easily stay up past your bedtime. The north polar cap on Mars remains visible despite the seasonal summer ‘heat’, and white clouds topping the planet’s major volcanoes are visible along the planet’s western edge. Check it out.

Full Flower Moon blooms and hides Saturn this week

Saturn and the moon Tuesday and Wednesday nights (May 13-14) just before midnight as viewed from the U.S. Midwest. Stellarium

38 degrees today in Duluth with a chill wind off Lake Superior. Must be May again. Time for the Flower Moon, the traditional name given to May’s full moon. Such a lovely moniker but nearly always lost on this frozen outpost I call home.

Tonight the moon’s in that awkward phase between half and full called gibbous, but tomorrow night it will shine nearly full and round in the southern sky just a few degrees to the right or west of Saturn. When full on the 14th, the moon will move to the opposite side of the planet.


Moon-Saturn occultation from Perth, Australia Feb. 22, 2014 captured by Colin Legg

While a moon-planet conjunction isn’t unusual, an occultation is. This time around, skywatchers in Australia and New Zealand are in the right location to watch the moon hide or ‘occult’ Saturn for about an hour early Weds. evening May 14 Australian time.

U.S. and Canadian observers can watch the waxing moon slowly approach Saturn overnight Tuesday. The best views will be had at the onset of dawn on the West Coast where only a degree (two full moon diameters) will separate the two early Wednesday.

If you could move fast enough to the west to avoid encroaching daylight and south to raise the moon a tad higher against the starry backdrop, you’d find yourself in Australia Wednesday night watching the moon slowly slide over the planet Saturn.

An earlier Saturn disappearance.

Planet occultations are awesome events to watch through a telescope because they give us an inkling of what it’s like to see a planet ‘set’ and ‘rise’ over an alien landscape, a place other than Earth.

What am I talking about? As the moon approaches Saturn, the planet will appear to ‘set’ as the bright edge of the moon encroaches and slowly nibbles away at Saturn until only a ringtip remains. Once the planet disappears, observers must wait about an hour for it to reappear on the moon’s other side, when it ‘rises’ from the limb by degrees until it’s in the clear once more. A wonderful sight!

I’ve seen occultations of Jupiter and Saturn and wouldn’t miss another except for the expense and time of flying to Australia. Closer to home, I’m game anytime.

Happily, we all can be close to home for this event. Astrophysicist Gianluca Masi will broadcast the occultation live online from his Virtual Telescope website beginning at 10:15 a.m. Universal Time May 14 or 6:15 a.m. EDT, 5:15 a.m. CDT, 4:15 MDT and 3:15 PDT. Yes, that’s early, but I know some of you may want to catch it.

Map showing where the Saturn occultation is visible. Some cities, like Darwin, will see Saturn graze the edge of the moon. Click to find times for individual cities. Times will be in Universal Time. Add 9.5 hours for Australian Central Standard Time. Credit: IOTA

Meanwhile, if you live in Australia or New Zealand and are reading this, click the map above for a list of times for individual cities when Saturn disappears and reappears.

The moon and its close companion, double star Zubenelegenubi, as they’ll appear early Tuesday evening. Stellarium

Six more moon-Saturn occultations occur this year but none are visible in North America. Curious about future events? Peruse this list when you have a few free minutes.

Even if northerners have to wait a while for the next planetary occultation, we can still enjoy Saturn flirting with the Flower Moon two nights in a row. Plus there’s a consolation prize! Look at the moon through binoculars tomorrow night (May 13) and less than a moon-diameter south you’ll spot the best-named double star in the whole sky: Zubenelgenubi (zoo-BEN-el-je-NEW-bee). Even binoculars can split this one.

With a tip of its rings, Saturn greets Earth on opposition day

The north face of the rings are tipped nearly wide open toward Earth this year, making for wonderful views of the planet through a small telescope. Notice that Saturn’s south polar region barely pokes out below the ring plane. This is a fun detail to try and see in a telescope. Credit: Anthony Wesley

Saturday is truly Saturn’s day this year. We mark the ringed planet’s opposition today, the time when it’s closest to Earth and brightest for 2014.

Opposition occurs when Earth passes between Saturn and the sun. When both planets lie on the same side of the sun, they’re almost 175 million miles closer than when they’re on opposite sides. That translates to a bigger, brighter Saturn. Because Saturn travels a little ways around its 29.5 year orbit every year, Earth requires about 13 days to catch up to it at each succeeding opposition. We’ll line up again next year on May 23.

Earth and Saturn are lined up with the sun today and 173 million miles closer than they’ll be in about six months when Saturn is in conjunction with the sun. Illustration: Bob King

The word opposition refers to Saturn being opposite the sun in the sky, rising when the sun sets and setting at sunrise. In a word, it’s visible all night long. Just about anytime you feel like pointing your telescope Saturn’s way, it awaits your gaze.

But before we talk telescope views, let’s take a minute to pinpoint the planet’s location in the evening sky. While it rises at sunset, it doesn’t clear the low trees until about an hour and a half later. Skywatchers at mid-northern latitudes will find it low in the southeastern sky around 10 o’clock well to the lower left of Mars, due south at that hour.

This map shows the sky around 10 p.m. local time tonight May 10 facing south-southeast. Saturn is smack in the middle of the dim constellation Libra below and to the left of Mars and Spica. Stellarium

Tonight the gibbous moon won’t be far from Mars, making it exceptionally easy to find the Red Planet. Swing down to the lower lower left of Mars to spot Saturn. You shouldn’t have trouble spotting it – at magnitude +0.1 it’s nearly as bright as Vega and a pale yellow-white. The ring bearer’s out all spring and summer, so there will be many opportunities to see it.

The ring bearer calls the dim zodiac constellation Libra the Scales home in 2014. Because the moon’s waxing toward full, it’s tricky at the moment to see Libra’s dim stars. Wait till after May 16 for a better view. Maybe then you’ll notice the whimsical “Saturn Cross” like I’ve been seeing the past couple weeks.

A whimsical “Saturn Cross” formed from Libra’s brightest stars with Saturn at its center. Libra precedes the gangly Scorpius the Scorpion with its bright star Antares. Viewing time shown is 1 a.m. in mid-May. Stellarium

The “Cross”, which just happens to be oriented north-south like the constellation Crux a.k.a. ‘Southern Cross’, is simply a different way to see Libra’s four most prominent stars. Saturn marks the center of the crossbeam.

If you’ve never seen the real Southern Cross, this might serve as a cheap, no-airplane-travel-required substitute. Mostly I bring it up as an easy way for you to add a new and rather faint constellation to your life list.

As Saturn travels around the sun in its 29.5 year orbit, we see one side of the rings for about 15 years, followed by an edgewise presentation. The rings – made of dirty water ice – are huge at some 155,000 miles wide (250,000 km), but they’re only about 30 feet thick and virtually disappear when seen edge-on.

That last happened in 2009. Since then they’re re-opened with the north face visible for some 15 years.

Saturn on April 6, 2014. Its clouds belt are less contrasty than Jupiter’s and except for the prominent north equatorial belt not easy to see. A small telescope and magnification as low as 30x will show the rings. Higher power will show the wide B-ring and thinner, outer A-ring. Also visible is the dim C-ring, the dusky band in the foreground crossing in front of the planet. Credit: Efrain Morales Rivera

This year the ring plane’s tipped open 21-22 degrees, nearly the maximum of 27 degrees which occurs in 2017. A large tip exposes lots of ring ice particles to sunlight, boosting the planet’s brightness.

Views of Saturn at different ring plane inclinations taken by the Hubble Space telescope. Rings are labeled in the top image. Credit: NASA/ESA

That’s all good news for both visual and telescopic observation. Even a 2.4-inch telescope will show the rings, with a larger instrument providing a brighter, larger picture and sharper resolution of the three brightest rings. I love the planet’s subtle colors through the eyepiece – the globe looks pale brown or butterscotch to my eye and the rings distinctly brighter and whiter.

Saturn and its brightest moons around 10 p.m. CDT tonight. Titan is brightest at magnitude 9 and very easy to see. North is up. Credit: Meridian software

Small scopes will also show the brightest moons including Titan, Rhea, Dione, Tethys and Iapetus. To find where the moons are on a given night and time, check out Sky and Telescope’s handy Saturn javascript utility, free Meridian software (used to make the diagram above) or download the $2.99 app SaturnMoons.

Saturn’s the best. No other sight in the sky elicits the wonder and amazement of guests at the telescope. Look at the ringed planet every night you can, and the more friends and family your share it with, the better.

Mercury returns, planets align, life is good

Mercury is just entering the picture tonight but by May 10 it will be easy to see, along with three other evening planets, 45 minutes after sunset in the northwestern sky. The pink arc is the ecliptic, the apparent path the sun takes during its yearly travels. It’s also followed closely by the planets and moon. Click to enlarge. Created with Stellarium

Planets are popping up everywhere. We’ve touched on Jupiter and Mars many times the past few months, but recently Saturn and now Mercury have entered the scene. Maybe you’ve noticed Saturn now in the southeastern sky at nightfall. From the northern U.S. and southern Canada, it’s bright but low at nightfall. Saturn reaches opposition a week from now when it will be at its closest and brightest for 2014. Each night that passes, the ringed rises higher and becomes better placed for viewing.

Mars, brilliant and fiery orange-red, now dominates the southern sky before midnight, standing above fainter Spica in the constellation Virgo. Only a month past opposition, we’re smack in the middle of the best time to observe the Red Planet through a telescope. I try to catch a look every clear or partly cloudy night but nearly missed the chance last night.

Two different hemispheres of Mars. The left image from May 2 shows a shrinking north polar cap and clouds blanketing the base of several volcanoes (dark dots) along the left edge of the planet. Right view taken on April 14 shows the hemisphere currently facing U.S. observers at nightfall. Credit: Christopher Go (left) and Anthony Wesley

The sky suddenly cleared after almost a week of overcast. I figured I’d walk my dog first and then set up the telescope, but 15 minutes later, clouds reappeared in the west. I turned around and footed it back home as quickly as I could, catching just five minutes of Mars light before a blanket of clouds suffocated the starry sky. Yeah, it was worth it.

Jupiter on May 2 displays its two most prominent belts visible in small telescopes, the North and South Equatorial Belts. Credit: Christopher Go

You might think it’s crazy to look at a planet night after night. Amateur astronomers do this for several reasons. First, most nights the air is too turbulent for a clear, sharp view. Looking often maximizes your chances of seeing the planet crisply in stable air. Almost nothing in observational astronomy beats viewing Mars or Jupiter or Saturn without air currents gooing things up. At these special times the dross falls away and the planet looks absolutely real. No exaggeration, you feel like you’re right there.

Planets also rotate. One hemisphere faces us one night, another on a different night or different time of night. Repeated observation gives you a certain familiarity with the “landscape” and alerts your eye to any changes happening. Remember, on most planets, weather plays a role in their appearance. Unexpected changes like a newly-spawned dust storm on Mars or the disappearance of a cloud belt on Jupiter lend an air of anticipation to the night’s viewing.

The sky from the central U.S. facing west-northwest this evening May 3 about 25 minutes after sunset. Mercury will be very low (about 3-4 degrees) but bright. The crescent moon passes just north of the star Eta in the constellation Gemini. Stellarium

Let’s talk about Mercury a minute. Skywatchers blessed with a clear view down to the west-northwest horizon can find the little planet as soon as this evening. Face the sunset direction about 20 minutes after sunset and sweep a few degrees above the horizon with your eyes or a pair of binoculars. The planet now shines at magnitude -1.4 or nearly as bright as it can, an equal to Sirius, the brightest star.

If you don’t succeed, try again in a week on the 10th. After the late January show, the period from May 10-23 will be the best time this year to see the planet at dusk.

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.