Goodmorning moon / Tomorrow’s Titan flyby

Look east Monday morning around 6 a.m. to spot the goodmorning moon. Only 2.5% of the moon will be illuminated by the sun; the remainder by ghostly earthshine. Venus will be about a fist held at arm’s length to the moon’s lower left. Stellarium

Like a lot of parents, we read Goodnight Moon by Margaret Wise Brown to our kids to get them ready for bed at night. The calming words and repetition soothed child and adult alike at the end of the day.

Maybe a sequel titled “Goodmorning Moon” will be written someday about waking up to the smiling crescent in the east and getting ready for the day. Tomorrow morning we’ll see exactly that, a very thin moon, low in the eastern sky at dawn. Its delicate arc will surely make you stop and realize how much beauty nature puts on the plate for enjoyment and study every day.

Venus seekers can use the moon to make one last attempt to find the planet, now nestled very low in the east just a degree or two above the horizon 40 minutes before sunrise.

Animation showing clouds of methane moving over Ligeia Mare, a large sea of liquid methane near Titan’s north pole, between July 20 and 22, 2014 as Cassini departed the moon during the last flyby. Credit: NASA/JPL-Caltech/SSI

While we’re on the topic of planets, NASA’s Cassini spacecraft will make a close flyby of Saturn’s moon Titan tomorrow September 22nd. At 3,201 miles (5,150 km) across, Titan is the solar system’s second largest moon, only 79 miles smaller than Jupiter’s Ganymede. It’s also unique in having a very thick atmosphere – 1.5 times thicker than Earth’s – a feature usually found only on planets.

It’s still not known how Titan managed to hold onto all its air, which consists of primarily nitrogen mingled with methane and various other hydrocarbons that react in sunlight to create an orange smog that gives the moon its distinctive color. Several other moons such as Ganymede, Rhea and even our own moon have atmospheres, but they’re exceedingly thin compared to Titan’s.

In this photo taken by Cassini, Saturn’s airless, cratered moon Dione is juxtaposed with Titan. Titan appears smaller because it’s 600,000 miles farther away from the spacecraft’s perspective. To see beneath the clouds and map the surface, Cassini observes the moon in infrared light and with radar. Credit: NASA/JPL-Caltech

It’s thought that Titan maintains and replenishes its atmosphere through outgassing from its interior. The bitter cold temperatures at Saturn’s nearly billion mile distance from the sun along with Titan’s considerable gravitational pull undoubtedly help preserve and hang on to its air. Comet impacts may also contribute to the moon’s stockpile of ices and organic compounds.

Along with an atmosphere come clouds, though of methane rather than the water vapor variety found on Earth. Temperatures at the surface hover just 90 degrees above absolute zero (-290º F, -179º C), chill enough for methane clouds to form and supply at least some of the precipitation to lakes of liquid ethane, methane and propane below.

This will be Cassini’s 9th flyby of Titan this year. During a flyby, the craft zips by the moon at high speed while keeping its instruments precisely pointed at the target using either its reaction wheels or thrusters, which spin the spacecraft to track the moon as it passes by. Thrusters are also used to keep Cassini from tumbling when it experiences drag while passing through Titan’s upper atmosphere during close flybys.

Descent through Titan’s atmosphere made by the Huygens probe on January 14, 2005

On Monday, Cassini will be traveling at 13,000 mph (21,000 km/hr) and come within 870 miles of Titan’s surface as it photographs seas and lakes – including Ligeia Mars shown above – around the north pole. Another instrument will observe Titan’s southern hemisphere atmosphere in ultraviolet light by observing the dimming of Alkaid, the star at the end of the Big Dipper’s handle as its light passes through the moon’s varied atmospheric layers.

To twinkle or not to twinkle, that is the question

Venus passes Regulus on the morning of September 5. Look low in the eastern sky 30-45 minutes before sunrise to see the pair. Bring binoculars in case twilight overwhelms Regulus. Stellarium

Early Friday morning September 5, skywatchers will see Venus and Leo’s brightest star Regulus in a close conjunction. The two will be separated by just 1° and look very nice in binoculars. Find a place with a view down to the eastern horizon and start looking about 40 minutes before sunrise. Jupiter, higher up in a darker sky, can help guide you to Venus.

This will be Venus’ last encounter with a bright star at dawn before it’s lost in the glare of the sun. It’s often said that one way you can tell a planet from a star is that a planet’s light appears steady, while stars twinkle. Not always. Stars only appear as points of light even through the largest telescopes and are easily shoved this way and that by air turbulence. These tiny shifts in position are what cause twinkling.

When we look at stars low in the sky we look across hundreds of miles of air in the lower, densest part of the atmosphere. Air currents across that great distance push a star’s light around causing it to twinkle. It can have the same effect on bright, naked eye planets when they’re far away and show a smaller than usual disk. Credit: Bob King

Planets have measurable disks and are less affected by the flutter of air, so we rarely catch them shimmering. But when the planet is far from Earth and very low in the sky, the rules change. Both Venus and Mars range in size from tiny blips to substantial disks (or in the case of Venus, a substantial half-moon or crescent). When viewed at low altitude, I’ve seen both twinkle lively.

Illustration showing how a planet, with a measurable disk, defeats air turbulence compared to a star which appears as a tiny point of light through a telescope. Credit: Bob King with Jupiter pic by Damian Peach

I witnessed it last Thursday morning with Venus. Jupiter, larger and higher in the sky, was a steady beacon. Venus, now nearly on the opposite side of the sun from Earth and about as small as it ever gets, trembled like a flame in the wind. What will you see Friday morning?

Venus remains visible for another two weeks before it’s lost in the solar glare. We won’t see the planet at all for more than a month until it returns to the evening sky around Thanksgiving in November. Watch for it to shake and shimmy its way up the western sky until fattening up around Christmas.

Miss the conjunction? Here’s your consolation prize

Clear skies prevailed over Königswinter, Germany for a great view of Venus and Jupiter just 0.2° apart at dawn this morning August 18. Credit: Daniel Fischer

Those killers of all things astronomical – clouds – were back again this morning, so no Venus-Jupiter conjunction here. Looks like I’ll pin my hopes on the one scheduled for next June 30 in Leo at dusk. I’m grateful for the flatness of the solar system, which guarantees that every few years we get repeat planet pairings.

Look east this coming Saturday morning for a sweet pairing of the bright planets and wiry crescent moon. This view shows the sky about 45 minutes before sunrise. Stellarium

I hope some of you got to see the conjunction from your home or on the way to work this morning. While Venus and Jupiter will now part ways, they’ll be one more blast of celestial awesomeness involving the duo and the crescent moon this weekend. Consider it a consolation prize. Who knows, this event might be even prettier than what passed this morning.

On Saturday morning, August 23rd about 30-45 minutes before sunrise, the thin, waning lunar crescent joins Jupiter and Venus in a stunning triangle of loveliness in the eastern sky.The threesome will all fit inside an 8° circle.

Now that I know this is coming I don’t feel so bad about missing the conjunction.

Moon nestles in Hyades then departs for Venus

The crescent moon slips in front of the Hyades star cluster only a degree from Aldebaran tomorrow morning. Don’t miss the other bright star cluster, the Pleiades, just above. Look low in the northeastern sky about an hour before sunrise to catch the scene. Stellarium

That old devil moon’s up to its old tricks again. Tomorrow morning, early risers will see it tucked inside the V-shaped face of Taurus the Bull. Better known as the Hyades star cluster, look for the crescent to pass just 1° north of the bright star Aldebaran. A pair of binoculars will enhance the view by pulling in more stars and revealing details in the spooky, earth-lit moon. Sunlight illuminates the lunar crescent, but the remainder is light reflecting off Earth out to the moon and back again.

The crescent is lit by the sun while the remainder glows dimly from twice-reflected light called earthshine. Credit: Bob King

To the eye, ‘earthlight’ looks smoky gray and nearly featureless though binoculars will show the lunar seas and larger craters. The quality of the light mimics a lunar eclipse but instead of red we see the pale blue glow of sunlight reflecting back from our planet’s oceans.

At 153 light years, the Hyades is the nearest star cluster to our solar system, one of the reasons you can see it without a telescope. Aldebaran appears to be a full-fledged cluster member, but it’s a ruse. The bright, ruddy star lies much closer to us along the same line of sight.

Venus and a very thin crescent moon on July 24 about 45 minutes before sunrise low in the northeast. Stellarium

The Hyades were born in a dense cloud of interstellar dust and gas 625 million years ago around the time underwater life flourished in the late Precambrian era. When you gaze at the cluster tomorrow, the light that touches your retinas left the Hyades the same time Abraham Lincoln took office.

The moon moves on toward Venus after vacationing in the Hyades, passing south of the planet on Thursday morning. It will be extremely thin that morning and should make a pretty sight for anyone looking low in the northeastern sky 45 minutes before sunrise.

Catch Comet Jacques near Venus at dawn

Venus will help us find Comet Jacques in Taurus an hour and a half before sunrise tomorrow morning July 16, 2014. The comet will be near the naked eye star Beta Tauri during the next week. Source: Stellarium

I don’t take getting up at dawn in summer lightly. After all, it means you’ve got to set the alarm for the ungodly hour of 4 a.m. (even earlier if you live in the northern U.S. or southern Canada.) But I wanted to alert you to the return of Comet C/2014 E2 Jacques.

Comet Jacques was taken on July 7, 2014 displays a small, condensed head or coma and two tails – a dust tail to the left and ion or gas tail to the right. Credit: Gerald Rhemann

Jacques disappeared in evening twilight a month ago, passed closest to the sun on July 2 and has recently returned to view low in the northeastern sky at dawn. Still stoked from its solar encounter, the comet shines at magnitude +6, the naked eye limit.

Don’t expect to see it yet without optical aid however. Jacques flirts with morning twilight and only climbs to around 10° (one fist held at arm’s length) the next couple mornings. Low haze and dust will make it look fainter, but not so much that a pair of 50mm binoculars might catch it.

Detailed map with stars shown to magnitude 7. Comet Jacques will be near a great ‘skymark’ this coming week, the star Beta Tauri. Use it and Venus to guide you there. Comet positions are marked every five days; Venus shown for July 16.  Click to enlarge and then print out a copy for outdoor use. Source: Chris Marriott’s SkyMap

We’re fortunate to have Venus and the star Beta Tauri to help guide us to the comet. The critical requirement for seeing Jacques, whether it be in binoculars or more likely in a small telescope, is an open view of the northeastern sky.

Timing is also important. In the northern U.S., the comet will be a little higher in the sky but observers will have to compete with earlier and longer twilights. The southern U.S. has the edge for the moment with the comet a little better placed in a darker sky.

Views will improve for everyone over the next few weeks as Jacques pulls away from the sun, buoyed along by the seasonal drift of the stars and its own westward motion.

Indications are that the comet will remain near the naked eye limit through early August, so we may really get a chance to see it without optical aid from rural skies. In any case, binoculars should reveal it as a small fuzzball rolling across Auriga and Perseus.

The thin crescent moon drops by the neighborhood on July 23, a great morning to seek out the comet. Source: Stellarium

By mid-August, Jacques will fade but remain visible in the evening sky through the remainder of the year. I hope you become fast friends with this blurry blob soon!

* UPDATE July 16, 2014 – Checked the comet this morning and although there were a few clouds, I wasn’t able to see it in 10×50 binoculars. Too much twilight here in the northern U.S. ! But the view in the telescope was excellent. Jacques was an obvious fuzzy glow with a bright center a couple degrees below Beta Tauri even in dawn light. I estimated magnitude 6.

Supermoon fun / Mars-Spica conjunction tonight / Venus visits Mercury at dawn

Passing clouds create a colorful corona around last night’s full moon. Credit: Bob King

The moon coaxed many of us out for a look last night. We had clear if hazy skies in my town which made for a striking display of lunar crepuscular rays. Lunar what? If you’ve ever seen sunbeams poking through clouds in the afternoon or evening, you’re looking at crepuscular rays. Crepuscular comes from the Latin word for ‘twilight’ as the beams are often noticed during early evening hours around sunset.

A delicate display of crepuscular rays radiates across the sky above a cloud-shrouded moon. Credit: Bob King

Bright rays shining through gaps in the clouds alternate with shadows cast by other clouds to form a spreading fan of light and dark columns. The dustier or smokier the air, the more vivid the crepuscular display. Notice how they appear to converge on the moon. This is an optical illusion. The rays are perfectly parallel just like endless rows of beans on a farm that appear to merge together in the distance.

Last night’s supermoon shines back from a mobile phone. I took the picture by holding the phone’s camera lens directly over the eyepiece. Credit: Bob King

Many of us like to take pictures of the moon through a telescope using nothing more than a mobile phone. If you’ve tried this, you know how tricky it is to hold the phone camera in the right spot over the telescope eyepiece. It takes a few tries, but the results can be remarkable. Phones do well on bright celestial object like the planets, moon and sun (with a safe filter). Despite what some ads might tout, phones can’t yet record fainter things like galaxies, nebulae and the like.

Orion Telescopes makes an adaptor to hold a phone securely over the telescope. While it gets mixed reviews, you might want to consider it if you don’t want to invest in a separate camera but would still like to create an album of your own astrophotos.

Mars (top) and Spica last night July 12. The difference in color between the rusty planet and blue-white star was very easy to see. Mars will remain near the star the next few nights but change its position like the hour hand on a clock. Credit: Bob King

I know we’ve all been moonstruck the past few nights, but did you happen to notice how close Mars and Virgo’s brightest star Spica have become? Last night they were separated by only 1.5 degrees; tonight they’ll be in conjunction a squinch closer at 1.3 degrees. Watch for the duo in the southwestern sky near the end of evening twilight.

Mars moves eastward and soon departs Spica en route to its next notable appointment, a conjunction with Saturn on August 25. Have you been up at 5 a.m. lately? Me neither. But my crystal ball a.k.a. Stellarium program tells me that Venus and Mercury are playing tag an hour before sunrise in the eastern sky.

Venus and Mercury shine together low in the northeastern sky during morning twilight the next couple weeks. This map shows the view tomorrow morning 45 minutes before sunrise. Venus will be about 10 degrees (one ‘fist’) high, Mercury half as much. Source: Stellarium

Mercury reached greatest elongation (distance) west of the sun yesterday and now appears about five degrees high in the northeast some 45 minutes before sunrise. Look for it about the same distance below brilliant Venus. This is a good apparition of Mercury, and having Venus nearby makes it easy to spot.

The swiftest-moving planet will hang near the goddess planet for the next two weeks, all the while growing in brightness as its phase fills out from crescent to full.

Farewell Jupiter, hello moon!

The 2-day-old lunar crescent will shine low in the west-northwest tonight June 29, 2014. This view shows the moon about 30 minutes after sunset. Not far away – hidden by the tree – Jupiter makes its last stand. See below. Source: Stellarium

Tonight’s returning crescent moon will help us bid adieu to a planet that brought us through winter and spring to the doorstep of summer.

Jupiter’s put on a great show in Gemini this year. We’ve watched the nightly ballet of its four bright moons, pondered the shrinking of the Great Red Spot (how small it will get nobody knows) and witnessed the planet in many fine conjunctions with the crescent, quarter, gibbous and full moons.

That’s a lot of visual delight, but being one of the brightest planets, Jupiter rarely fails to please. Tonight you might see it for the last time this season using the moon as your guide. Face west-northwest about a half-hour after sunset. With binoculars, sweep the sky about 12 degrees to the right and below the crescent moon. Can you see it with your naked eye?

With a clear view to the west-northwest tonight, the moon will help you find Jupiter one last time. The map shows the sky 30 minutes after sunset from the central U.S. Jupiter lies about 12 degrees – a little more than a horizontally-held fist at arm’s length – to the right and below the moon. Use binoculars first and then see if you can spot it without optical aid. Source: Stellarium

No planet escapes the glare of the sun. The apparent movement of the sun across the sky caused by Earth’s revolution around it means that sooner or later our driven star catches up with the slower-orbiting planets that lie beyond the Earth. Indeed, the sun’s been gaining ground on Jupiter ever since January 5. On that date, the planet was at opposition, rising at sunset and remaining visible until the next morning’s sunrise. The very next day the sun gained 4 minutes on it and hasn’t stopped since.

Jupiter’s now (almost) hopelessly lost in bright evening twilight. It will still roast in the BBQ glow of the sunset until July 24 when it passes just a fraction of a degree north of the sun in conjunction. For several days before and after that date we’ll get to see it in SOHO’s coronagraph, an instrument that blocks out the sun to reveal the solar corona, background stars and occasional comet and planet crossings.

Wow! On Aug. 18, days after Jupiter returns to view in the morning sky, it will pass only 0.2 degrees (1/3 the diameter of the full moon) from Venus in the constellation Cancer. Source: Stellarium

As the sun passes and leaves Jupiter behind, the planet re-emerges in the east in morning twilight in early August. And what a grand entry it will be! On August 18 Jupiter passes just 0.2 degrees from Venus in one of the year’s most spectacular conjunctions.

If you recall, Jupiter spent most of this year in the constellation Gemini beneath the bright ‘twin stars’ Castor and Pollux. On its return in August you’ll be struck by how far the planet has moved east along the zodiac. Ceaselessly orbiting the sun, Jupiter will have abandoned Gemini for the faint constellation Cancer the Crab. And so it goes, round and round and round.

Crescent moon visits a ‘wintering’ Venus / Mercury-moon conjunction for y’all

The slender crescent moon brushes Venus Tuesday morning at dawn low in the northeastern sky. The Pleiades star cluster, better known as the Seven Sisters, floats just above the pair. This map shows the sky facing northeast around 4 a.m. June 24. Stellarium

Wonder where the moon’s been hiding lately? Unless you’re up around 3 a.m. it’s been scarce this past week. All that time our favorite cratered world has been slimming down in the morning sky.

Now it’s a waning crescent fingernail, what many consider the moon’s most eye-catching phase.

Tuesday morning June 24 at dawn the thin crescent will join Venus in the constellation Taurus just below the pretty Pleiades star cluster. About 1 1/2 degrees or three moon diameters will separate Venus and the moon. To see this beautiful conjunction, look low in the northeastern sky at the start of dawn.

For the best view of the Seven Sisters, I recommend binoculars. Whenever I’ve had a reason to be up before sunrise in early summer I make a point of looking at the cluster. Taurus, neighboring Auriga and the Pleiades all belong to the winter sky, but we get a preview of that inevitable season as early as the first mornings of summer. There’s something delicious about seeing the first stars of winter as the robins sing in the dewy woods.

An extremely thin moon will pass very close to Mercury on Thursday morning June 26 as seen from the southern U.S. This view shows the sky facing northeast right around sunrise for New Orleans, LA. The moon will only be about 5 degrees high at the time. Use binoculars to find it. Seeing Mercury will require a small telescope. Stellarium

Live in the far southern U.S.? You’ve got one more lunar visitation. This one will be challenging. On Thursday morning, the moon, just 21 hours before new, will glide a fraction of a degree south of the planet Mercury in a bright sky only minutes before sunrise. The moon will hover very low (5 degrees) in the northeast in a bright sky. Whatever you do, bring binoculars. You might need them to find the moon at all.

Like the moon, Mercury’s an extremely thin crescent and very faint, shining at just magnitude 3.5. Skywatchers might spot it in binoculars, but I’m not betting on it. With very clear skies, there’s a chance of seeing the planet directly above the northern cusp of the moon with a small telescope. Should you succeed, you’ll be rewarded with the rare sight of two delicate crescents one atop the other. Find a location with a wide open view to the northeast and start looking about 15 minutes before sunrise.

The moon will cover up or occult the planet for observers in northern South America, but again, this will happen in a bright sky and prove tricky to see.

Just a reminder. Although no auroras showed last night at mid-latitudes, there’s still a chance for a minor storm tonight. I’ll send out a notice if that happens.


Venus hides a star for 7 minutes

Venus occults or covers the star Lambda Aquarii April 17, 2014 

A planet covering a naked eye star is rarer by far than a total eclipse of the moon, and yet Venus did just that yesterday afternoon (U.S. time) from Australia, New Zealand and Micronesia. No one in the northern hemisphere witnessed the event; Venus passed south of the star from our perspective.

Jonathan Bradshaw of Australia captured this exceptional alignment well in his video despite the shaky atmosphere. Lambda Aquarii, a 4th magnitude star in Aquarius, was wiped from the sky for all of seven minutes.

It’s believed that the last bright star Venus or any major planet covered up was 2nd magnitude Nunki in Sagittarius for observers in eastern Africa in November 1981. Venus next occults Pi Sagittarii in 2035 and bright Regulus on Oct. 1, 2044. Mercury will cover up Theta Ophiuchi on Dec. 4, 2015.

Mars will pass in front of Jupiter in an extremely rare planet-over-planet occultation on Dec. 2, 2223. Stellarium

Very rarely, planets pass in front of each other. Over the 300 year span from 1800 to 2100 only 7 “mutual occultations” of this sort have or will occur. Venus crossed in front of Jupiter in 1818 – that was the last observable one. The next will happen when Mars passes in front of Jupiter on Dec. 2, 2223. Clearly, you and I and even our kids won’t be around for that event, but maybe some of our kids’ kids will.

Nature shows that once again even the most unlikely things can happen as long as one key ingredient is available – oodles of time.

Astronomers find evidence of erupting volcanoes on Venus

Venus and the crescent moon an hour before sunrise on Thursday March 27, 2014. A new study shows that volcanoes may still be active on the planet. Stellarium

Go outside this Thursday at dawn and you’ll see Venus and the crescent moon together in the southeastern sky. A peaceful scene yes, but appearances can deceive.

Beneath Venus’ blanket of acid clouds, astronomers have detected what they believe are active volcanoes.

5-mile-high Maat Mons, the tallest volcano on the planet Venus is seen in this image made by radar with NASA’s Magellan spacecraft. The probe discovered relatively recent (10-20 million years) ash flows near the summit. Click to enlarge. Credit: NASA

Scientists have identified over 1,600 volcanoes or volcanic features on Venus and clear signs of recent lava flows on its surface. Clearly, our sister planet has been volcanically active in the past. Something must be smoothing out Venus’ surface because it has only about 1,000 craters, a very small number compared to other planets. Are volcanoes still active today?

Planetary scientist Alexander Bazilevskiy, with the Max-Planck Institute for Solar System Research in Germany, and colleagues examined pictures taken by the orbiting Venus Express probe and looked for changes in the relative brightness of surface features.

Object “A” shows as a temporary hot spot on June 24, 2008 (middle frame) in the rift feature Ganiki Chasma on Venus. Credit: ESA / Alexander Bazilevskiy

They found four brief flashes of light in a relatively young rift zone known as Ganiki Chasma which was imaged 36 times by the orbiter.

Artist’s impression of an active volcano on Venus. Credit: ESA/AOES

“Venus might have ongoing volcanism,” said Bazilevskiy. The flashes, estimated to be between 980 degrees and 1,520 degrees Fahrenheit (526-826 C) are well above the planet’s normal broiling surface temperature of 800 F (426 C). The team believes the four hot spots, all located near the giant shield volcano Maat Mons, could indicate hot material at or just below the surface. They allow it may also be gas or a combination of both.

Photos of the barren, rocky, hot surface of Venus taken by the Russian landers Venera 14 (left) and Venera 13 and reprocessed by Don Mitchell.

Venus Express has also measured dramatic changes in the content of sulfur dioxide – a gas commonly spewed by active volcanoes – in the atmosphere since it began orbiting the planet in 2006. Since the chemical is normally disassembled by sunlight in a matter of days, something must be happening on the Venus’ surface to replenish it. This new study may prove to be the smoking caldera … er, gun to clinch the case.

Venus photographed by Mariner 10 through UV and orange filters. The planet is covered in perpetual clouds. Credit: NASA

The team continues to look for more evidence of volcanism on this most beautiful of planets. Click HERE to read more about their work.