Watch Io snuff out Ganymede at Jupiter tonight

The moon kisses up to Aldebaran last night (Feb. 25) during evening twilight seen from Duluth, Minn. Credit: Clint Austin

The moon kisses up to Aldebaran last night (Feb. 25) during evening twilight seen from Duluth, Minn. Credit: Clint Austin

First, my apologies. I so wanted to alert you to the half moon’s pass of the bright star Aldebaran last night. But there were network problems with the blog, and I wasn’t able to post.

No doubt many of you noticed it all the same. A quick look up at the moon and you couldn’t help but see the star a little more than one lunar diameter to the southwest. The farther north you lived, the closer they drew together. In far northeastern Canada the moon occulted Aldebaran. Checking the moon several times overnight, it was amazing to see how quickly it departed Aldebaran, forced by its perpetual orbital motion to “go east, young moon, go east”.

Tonight our satellite moves a fist further east in Taurus the Bull and beams atop Orion the mighty hunter at nightfall. It’s 8 days past new phase and absolutely resplendent with craters. Sic your telescope on it and marvel at the ruggedness of all that ancient terrain bludgeoned by forgotten meteorites and asteroids.

The view through the telescope this evening just before Ganymede is eclipsed by Io's shadow. Created with Stellarium

The view through the telescope this evening just before Ganymede is eclipsed by Io’s shadow. The deepest part of the eclipse will occur around 9:35 p.m. Created with Stellarium

East of Orion you’ll find the blazingly bright planet Jupiter right along the border of Leo and Cancer. I’ve written before about this being a special season for Jupiter’s moons. Because Earth’s equator is aligned with Jupiter’s, and the brightest moons orbit above the planet’s equator, we can see them eclipse and occult one another in what astronomers call “mutual events”.

Tonight, little Io will cast its shadow on the largest Jovian moon, Ganymede. While not a total eclipse, it’s close, with a good deal of Ganymede in shadow at maximum (although not 97% as I wrote earlier). This should be easily visible in a small telescope at low to medium magnification. The eclipse begins at 9:31 p.m. CST (3:31 UT) and ends at 9:40 p.m. (3:40 UT). Jupiter will be very well placed for viewing across all of the Americas at the time.

Now here's something cool - a double mutual event. Europa eclipses then occults Io on January 28 captured by Theo Ramakers of Oxford, Georgia.

In this double mutual event, Europa eclipses then occults Io on January 28 captured by Theo Ramakers of Oxford, Georgia. The eclipse is quick in the time lapse, occurring about 1/2 second in. Look for the shadow passing across the top of Io.

Get that scope out at least a half hour beforehand and let it cool down if you’re in a cold climate otherwise Jupiter will look all mushy. Then start watching about five minutes before the eclipse begins, so you can get familiar with Ganymede’s normal brightness.

During the eclipse you won’t be able to see Io’s shadow with your eye, but Ganymede will fade by one magnitude and then re-brighten as the shadow first covers and then departs its 3,275-mile-wide globe.

Wishing you clear or at least partly cloudy skies tonight!

Jupiter doesn’t get any better than NOW

Jupiter shows off its north and south equatorial belts – the two thick stripes – and Great Red Spot in this picture taken on Feb. 6. Credit: Christopher Go

Brash Jupiter finally has its day. Big and bright, the planet’s been easing up in the east earlier and earlier each night this winter. I’ve been watching it through my car window while driving home from work at dusk.

Jupiter reached opposition yesterday, when it beamed directly opposite the Sun in the sky. Like the full moon, the planet rose at sunset and remained visible all night, setting at sunrise. Opposition occurs when Earth and Jupiter line up on the same side of the Sun putting them closer together than at any other time of the year.

Jupiter and Earth are lined up on the same side of the Sun at opposition and closest for the year. Now is the best time to observer the solar system’s largest planet in a telescope or pair of binoculars. Credit: Bob King

Skywatchers seize the time of opposition to regularly observe a planet; closeness equals greater brightness and also larger apparent size. And size is what we need to see the fascinating details that make these quivering disks come alive as real places.

This weekend, Jupiter’s chubby face will be 1.5 times larger than when viewed around solar conjunction on August 26th when the planet drops into the Sun’s glare in the western sky.

Jupiter straddles the border of Leo and Cancer not far from Leo’s brightest star Regulus. The inset shows how the planet and its four brightest moons will look in a small telescope this evening around 9 p.m. CST. North is at upper left in inset. Created with Stellarium

So what’s there to see? Lots! Jupiter is a meteorologist’s paradise, but you don’t have to be one to appreciate the planet’s changeable weather and balletic moons. Even binoculars will show a tiny disk, and if you look very closely, you’ll see up to four star-like points flanking either side of the planet. These are the four brightest moons – Io, Europa, Ganymede and Callisto in order of increasing distance from Jupiter.

Jupiter’s about 11 times larger than the Earth and has no solid surface. Its globe is covered in clouds of ammonia ice.

As they revolve about the planet, they create new arrangements every night. I’ve seen lots of eye-catching groupings with some of the most surprising symmetries over the years. And while I enjoy The Tonight Show, Jupiter’s moons are usually more entertaining. To find out where they are and what they’re up to any given night, check out Sky and Telescope’s Jupiter Moons Observing Tool.

Sometimes a moon will “disappear” when it passes in front of or behind the great planet. Other times, Jupiter’s shadow will eclipse a moon. This season, because Earth’s equator is aligned with Jupiter’s, we can even see the moons eclipse and occult one another in what astronomers call “mutual events”. For your observing pleasure, I’ve included a list of the best mutual events at the end of this article.

One of the most amazing discoveries I made some year back was that I could see Jupiter’s moons as actual disks, not just points. When the air is especially steady, power up to 150x or higher and look closely at each of the moons in a 6-inch or larger scope. In good seeing, each will show a minute disk with Ganymede clearly the largest of the four. One of them, Io, is colored orange from sulfur-laden lavas erupted from its interior that now coat the surface. Can you see the color?

With a small telescope and low magnification (40- 50x) two gray “tire tracks” rut the planet’s disk. These are the north and south equatorial belts, so called because they flank Jupiter’s equator. Higher power, steady air and a bit of stick-to-itiveness and you’ll also pick out the thinner stripes like the north and south temperate belts and the polar regions which look like gray beanie caps.

I’ve labeled the most prominent belts in this photo taken by Anthony Wesley on Feb. 6, 2015. Strong winds whip Jupiter’s clouds into alternating dark belts and bright zones. Sulfur and possibly phosphorus compounds may be responsible for the dark tone of the belts as well as the Great Red Spot. Credit: Anthony Wesley

Dark belts are separated by lighter zones and the whole works is streamed into stripes by narrow, high-speed winds called jets that border the zones and belts. Winds rip along at up to 400 mph (640 km/hr). Because Jupiter makes a complete spin on its axis at the amazing rate of just 9.9 hours, you can watch new features rotate into view by revisiting the planet in your telescope several times during the night.

Jupiter’s weather is as changeable as Earth’s. Belts narrow, widen, split in two or even disappear altogether for a couple years before reforming. The familiar Great Red Spot (GRS), a hurricane-like storm more than twice Earth’s diameter that’s raged for centuries, changes color from pale tan to brick red. This year it’s pink-colored and nestled in a pale “hollow”. You’ll need good seeing, a 4.5-inch or larger telescope and magnification of around 100x to spot it.

To know when to look for the GRS, click HERE and you’ll get dates and times when it’s front up and center on Jupiter. The times shown are Universal or Greenwich Time. Subtract 5 hours for Eastern, 6 for Central, 7 for Mountain and 8 for Pacific.

I can’t say enough about this planet. Mars shows lots of detail too, but it’s typically so small you have to work hard and consistently to appreciate its vague markings. Saturn of course is fantastic but features in its atmosphere are subtle and change slowly. Venus and Mercury show phases but precious little else. Only Jupiter happily gives away its secrets even to the beginning observer with a small telescope.

Now here’s something cool – a double mutual event. Europa eclipses then occults Io on January 28 captured by Theo Ramakers of Oxford, Georgia.

Below are times when the planet’s moons pass either fully or partially in front of one another (called an occultation) and eclipse each other.

During an occultation, you can watch the moons get closer and closer until they merge into a single object. Minutes later they separate and go their own way. To watch one, be sure to start observing at least 10 minutes before the times shown. Moons will fade in brightness when occulted but I’ve found this difficult in practice to see because they’re sitting atop one another and appear as one.

In an eclipse, the shadow of a moon will cause the other to fade for a few minutes and then re-brighten. If the fade is 50% or more, you can see the change in brightness through the scope. Really fun to watch. Bolded events are the best eclipses of the bunch.

Mutual events for Jupiter’s satellites in February – Times are CST:

Feb. 8 11:26-29 p.m. Io occults Europa (pair very close to Jupiter)
Feb. 8 11:32-34 p.m. Io eclipses Europa 2% shadowed (pair very close to Jupiter)
Feb. 14  6:20-28 p.m. Europa eclipses Io 85% (comfortable separation from planet; should be very easy to see fading)
Feb. 16 1:23-26 a.m. Io occults Europa
Feb. 16 1:44-47 a.m. Io eclipses Europa
Feb. 17 11:48-57 p.m Europa eclipses Callisto 44%
Feb. 19 6:34-43 p.m. Io eclipses Ganymede 84% (deep eclipse, very nice!)
Feb. 21 8:04-11 p.m. Europa occults Io
Feb. 23 7:42-47 p.m. Ganymede occults Io
Feb. 23 8:38-45 p.m. Ganymede eclipses Io 57% (pair very close to Jupiter)
Feb. 26 8:17-24 p.m. Io occults Ganymede 36%
Feb. 26 9:31-40 p.m. Io eclipses Ganymede 97% (Deepest and best eclipse event of the month)
Feb. 26 10:27-39 p.m. Callisto eclipses Ganymede 58%
Feb. 27 11:33-36 p.m. Europa eclipses Ganymede .2%
Feb. 28 10:09-16 p.m. Europa occults Io 59%
Feb. 28 11:01-11:08 p.m. Europa eclipses Io 90% (another excellent eclipse)

Hubble snaps spectacular views of Jupiter triple transit

These new NASA/ESA Hubble Space Telescope images capture a rare occurrence as three of Jupiter’s largest moons parade across the giant gas planet’s banded face on January 23-24 this year. Credit: NASA/ESA/Hubble Heritage Team

Some of us saw the triple shadow transit last week and some battled clouds. The Hubble Space Telescope had a ringside seat 347 miles above the cloud deck. Wow, what a view!

At left, you can see all three shadows and two of the moons. The photo at right on the right shows the end of the event about 42 minutes later. Icy white Europa has entered Jupiter’s disk while Io’s shadow has moved off. Credit: NASA/ESA/Hubble Heritage Team

The photos are so sharp and detailed they hardly look real. Gorgeous stuff. Notice how sharply outlined each moon appears yet the shadows look fuzzy. Why? For the same reason your own shadow has a soft outline. The light source is the Sun, which even at Jupiter’s distance of over 400 million miles, still shows as a small disk and not a point.


Really cool time lapse of the triple shadow transit at Jupiter

Light from an extended disk creates shadows with blurred outlines because light from one side the disk or other “wraps around” around the edges of your body and partially tempers the darkness. Only a point source like Venus can create a shadow with a sharp border.

Io partially covers Callisto’s shadow, while at top is the shadow cast by Io. Credit: NASA/ESA/Hubble Heritage Team

Here’s one final image, a crop of the original. The colors and appearance look so unearthly.

 

 

 

 

 

Jupiter and the Full Moon make a lovely pair tonight

First, my apologies. Due to a system upgrade all the images from the blogs have been taken down temporarily, nor can I post any new ones. This hurts my soul but at least I can use these things called words.

In a nutshell,  there’s a really nice conjunction of Jupiter and the Full Snow Moon tonight. Just take a look out east when the sky gets dark and there they’ll be shining in tandem in Cancer the Crab. If you’d like to read a more complete explanation of the event and why it’s special beyond just looking plain beautiful, head over to Universe Today where you’ll find more information and some of the photos I’d hoped to use here. Thanks for hanging in there.

Triple shadow transit makes for triple the fun

Will Gator shot this excellent series of Jupiter portraits during different phases of the triple shadow transit last night and this morning with an 8-inch telescope. North is up and east to the left. In “D”, the top “dot” on the left side is the moon Callisto. The others are the shadows of (l-r) Europa, Callisto and Io. Credit: Will Gator

I had to dog last night’s triple shadow transit to see it but I’m glad I did. We had clouds nearly the entire time. But even with a crummy sky, Jupiter was bright enough to push through the ceiling at key times during the event.

Through the scope the planet drew a sharp profile with nice cloud belt detail. It was really fun to watch Io’s shadow catch up with and merge with Callisto’s shadow and then separate (panel C above). For a while the two looked like an headless ant or “negative double star”. Even more amazing was seeing the moon Io overlap Callisto’s shadow at 12:20 a.m.

For just a few minutes, Callisto’s black shadow turned a pale orange-gray, obviously lighter in tone than the neighboring shadow of Io. It simply looked wrong! Three minutes later Callisto returned as the biggest and most dominant shadow. Never seen anything like it.

When Europa squeezed onto the Jupiter’s disk at around 12:30 a.m. the show moved into high gear. It took a bit of concentration to see Europa as it casts the smallest shadow of the four Galilean moons. Just to its south, along the southern edge of the South Equatorial Belt, I could easily make out the moon Callisto. I managed about seven minutes of triple shadow viewing before the clouds became impenetrable.

After packing all the equipment away, I happily sat down and shared a glass of wine with my wife. Hope we’re all still around for 2032 when the next trifecta takes place.

Guide to Friday’s rare triple moon shadow-blast on Jupiter

Shadow transit of Jupiter’s moon Io captured on January 8th this year. Late this Friday night, Io, Europa and Callisto will cast their shadows simultaneously on the planet in a rare triple shadow transit event. Credit: John Chumack

We’re down for a very rare event this weekend that won’t happen again until December 30, 2032 – at least across the Americas. Between 12:28 – 12:52 a.m. (CST) Saturday morning, Jupiter’s moons Io, Europa and Callisto will simultaneously cast shadows on the planet’s cloud tops. Naturally, you’ll need a telescope to see this but only a modest one. You can follow the entire show in a 4 1/2 inch or larger instrument magnifying around 75x.

As Galileo was the first to note, Jupiter’s four brightest moons – Europa, Io, Callisto and Ganymede – revolve about the planet like a solar system in miniature. Each has its own period of revolution ranging from 1.7 days for innermost Io to 16.7 days for more distant Callisto. The moons periodically pass behind the planet (and temporarily get hidden from view), off to one side where they pass through Jupiter’s shadow in eclipse and in front of the planet.

Simulation of Jupiter around 12:40 a.m. (CST) Saturday, January 24th. Two moons and all three shadows will appear projected against the planet’s pale white equatorial zone.
Created with WinJUPOS

When in front of Jupiter, the moons cast their own shadows on its cloud tops. Through a telescope they look like jet black pinpoints for the smaller satellites (Io, Europa) and small dots for Callisto and Ganymede. Amateur astronomers look forward to watching these black dots move across the Jupiter’s cloud belt in part because we’re watching an eclipse happening on another planet. Imagine if you were there within the shadow looking back toward the Sun. From that perspective the moon would cover the Sun in partial or total eclipse. Cool thought.

So here’s the deal. One shadow transit every so often isn’t unusual, two at the same time is more so and a triple happens on average only once or twice every decade. In a word, don’t miss this opportunity.

If you want to catch all three shadows, you’ve got 24 minutes between 12:28 and 12:52 a.m. (CST) Saturday morning January 24th. Before and after that slot, you’ll see the shadows of one or two of the moons but not all three. Below is a list of the CST times, with Universal or UT times in parentheses) when each shadow enters and exits the planet’s face. To convert to your time zone, add an hour for Eastern time, subtract an hour for Mountain and 2 hours for Pacific.

Friday night Jan. 23 – Saturday morning Jan. 24:

* Callisto’s shadow enters disk – 9:11 p.m. (3:11 UT)
* Io’s shadow enters disk – 10:35 p.m. (4:35 UT)
* Europa’s shadow enters the disk – 12:28 a.m. (6:28 UT)
** TRIPLE TRANSIT from 12:28 – 12:52 a.m. (6:28 – 6:52 UT)
* Io’s shadow leaves disk – 12:52 a.m. (6:52 UT)
* Callisto’s shadow leaves disk – 2:00 a.m. (8:00 UT)
* Europa’s shadow leaves disk – 3:22 a.m. (9:22 UT)

Jupiter at 11:52 p.m. (CST) Friday night when Io and Callisto’s shadows will appear to merge. Meanwhile, Io undergoes a partial eclipse in the shadow “beam” cast by Callisto. Source: WinJUPOS

This triple event is unique enough, but there’s even more happening in what I like to call the “pre-game show”. As each moon enters the planet’s face like actors in a play, their shadows will cross over and bump into one another. I’ve included diagrams showing what to expect. For more details on the triple play and special events leading up to it I hope you won’t mind clicking over to this article I wrote for Sky and Telescope online.

The pre-game show wraps up with the moon Io transiting over Callisto’s shadow around 12:20 a.m. CST. The change in the shadow’s appearance should be obvious to the eye. Source: WinJUPOS

Since it was overcast here for the last triple shadow transit in October 11-12, 2013 you can imagine how much I’d like to see clear skies this time around. 2032’s a long, long ways out.

Once-in-6-year-alignment makes Jupiter’s moons dance in shadows

Jupiter and his Great Red Spot photographed on January 3rd through a 14-inch telescope. Credit: Paul Maxson

Now that Jupiter’s up in the east by 9 o’clock local time, we have lots of opportunities to observe it before bedtime. That’s good because the Jupiter system is currently edge-on to the Earth and Sun, allowing us to see the planet’s brightest moons eclipse and occult one another now through August.

Io, Europa, Ganymede and Callisto all orbit very close to the plane of Jupiter’s equator. From our perspective on Earth, the moons usually pass a little above or below one another and escape each other’s shadows. But every six years or so, Earth and Sun cross the plane of the satellites’ orbits putting us “level” with Jupiter’s equator.

Instead of missing one another, the moons appear to merge into one during occultations and cast their shadows on one another during eclipses. This cyclic but relatively rare planetary alignment last happened in 2009 and won’t again until 2020.

The six varieties of eclipses and occultations possible among Jupiter’s four brightest moons now through August. Credit: Dave Dickinson

While you may not be able to resolve the four brightest moons in your telescope, you’ll have no difficulty watching them approach one another and meld into either an extremely close “double moon” or a single object during an occultation. Minutes later, the pair breaks apart as each moon follows its own track around the mothership.

Io eclipses Ganymede back on August 16, 2009. Credit: Christopher Go

During an eclipse, one moons will cast a shadow on another, causing it to fade the same way our moon dims when entering Earth’s shadow during a lunar eclipse. Assuming a fairly deep eclipse, you’ll be able to watch a Jovian moon fade and then re-brighten in a matter of minutes.

Again, you won’t see the shadow itself because the moons are so tiny, but the drop in brightness is clearly visible especially during deep eclipses.

With Jupiter coming to opposition on February 6th you’ll have lots of opportunities to catch at least one of each type of phenomenon. Not to mention, that all the moons cross over the Jupiter’s bright equatorial zone as they orbit the planet, making shadows they cast on the cloudtops easier than ever to see. Those are called shadow transits, and we’ll feature those soon, too.

Io eclipses Ganymede on Christmas night 2014. Credit: Paul Maxson

Below is a list of the best upcoming mutual events of the four brightest satellites for locations across North America. To view them, you’ll need at 3-inch or larger telescope.

A drop of 0.5 magnitude or larger during an eclipse or occultation should be apparent to the eye by carefully comparing before and after views. For occultations, you can also have the pleasure of seeing the moons in close embrace

Two for the price of one. Io occults and then eclipses Europa in this animation of still photographs taken on September 28, 2009. Credit: Brian Combs

For a customized table of events when Jupiter’s easily visible in a dark sky from your location, click over to this list of observatories, do a Control-F (Command-F on Mac) and type in the name of a larger city within a few hundred miles of your location. Next, copy the 3-digit code number and then paste it into the window on the IMCCE table creation page. Click enter and you’ll get a handy list of every event visible from your location through August.

To help you pick which eclipse events are worth your time, make sure the “Δm” (change in magnitude) is 0.5 or greater. Times listed in the table are Universal Time. Subtract 5 hours for EST, 6 for CDT, 7 for MST and 8 for PST. Also, each moon is listed by number rather than name. Io=1, Europa=2, Ganymede=3 and Callisto=4, so “2e4″ means Europa eclipses Callisto.

More event information and some great animations are available at SAF Planetary Observation Commission’s page.

Events – Times are CST:

Jan. 15 – Io eclipses Callisto starting 6:13 a.m., ending 6:39 a.m. Magnitude drop: 0.5
Jan. 18 – Ganymede occults Europa starting 8:31 p.m., ending 8:37 p.m. Mag. drop: 0.5
Jan. 23 – Callisto eclipses Ganymede starting 3:06 a.m., ending 3:20 a.m. Mag. drop 1.4!
Jan. 25 – Ganymede occults Europa starting 11:13 p.m., ending 11:19 p.m. Mag. drop 0.5
Jan. 28 – Europa eclipses Io starting starting 12:18 a.m., ending 12:27 a.m. Mag. drop 0.5
Jan. 29 – Io occults Europa starting  8:31 a.m., ending 8:35 a.m. Mag. drop 0.6

Nice sequence showing Io occulting Ganymede on December 21, 2014. The moons meet and part over 22 minutes. Credit: Paulo Casquinha

Bear in mind, these are the most easily observed events. There are many more! I’ll post a new list at the beginning of every month through the summer. Let us know if you get to see one of these. Good luck!

Tie down the furniture honey, tomorrow’s Zero G Day!

Will you float into the air tomorrow morning January 4th? Read on to find out your chances of success. Credit: Rob Wink (flickr.com/photos/rlw-photos/)

If you wake up levitating over your bed tomorrow morning at 9:47 a.m. (PST) you have a very active imagination. According to a recent article published the Daily Buzz Live, that’s when Pluto and Jupiter will align. Their combined gravity will temporarily counteract Earth’s gravitational pull and make us all virtually weightless for several minutes.

The story goes on. If you jump in the air “it should take you about 3 seconds to land back on your feet instead of the usual 0.2 seconds.”

Accompanying the story is an authentic-looking tweet that appears to come from NASA.

Who wouldn’t like to float in the air? In one of my favorite recurring dreams I jump in the air and float like an astronaut for many minutes, turning and navigating with just a twist of my body.

Well, unless you’re on board the International Space Station or an astronaut training in NASA’s “vomit comet”, a special designed KC-135 airplane that flies deep parabolic loops to briefly simulate zero-g, don’t worry about nailing down the furniture tomorrow morning.

Fake tweet from purportedly from NASA that accompanied the story in Daily Buzz Live. Gotta love that end-of-the-world-as-we-know-it hashtag #beready!

Of course this is all a hoax. While the tweet is fake and serves to legitimize the claim, the story does have a factual origin. The prediction was first made by none other than Sir Patrick Moore, a well-known and beloved British astronomy popularizer.

On April 1, 1976 during a BBC radio show, Moore announced a once-in-a-lifetime opportunity that would occur when Pluto passed temporarily behind Jupiter. Listeners were advised that if they jumped at exactly 9:47 a.m. that day they’d experience a temporary sensation of weightlessness. The show was an April Fool’s Day spoof, the prediction a joke. Yet people actually called in claiming to have been lifted off the ground.

We are suggestible lot. We see a dark shape down the road in moonlight and imagine a hulking animal when it’s only the neighbor’s garbage can. It’s a wonderful ability because it prepares us for the unexpected, but we need to leaven this skill with logic.

Levitation on the home planet is unlikely for the moment except in the hands of creative photographers. Credit: Rachel Marie Smith

Let’s put on our critical thinking caps and start poking some holes. Assuming you weren’t familiar with the April Fool’s story, how would you proceed in debunking the claim?

You might first check whether Pluto and Jupiter are lined up on January 4th. That’s easy. Open up one of many star-charting programs like Stellarium and you’ll quickly discover that Jupiter shines in the evening sky in Leo. Pluto is in the opposite part of the sky in Sagittarius and invisible in the glare of the Sun.

Your suspicions should also be aroused by googling a bio of Patrick Moore. There you’ll discover he died two years ago. The Buzz story is written in the present tense as if Moore were still alive. Another red flag.

Jupiter and Venus in conjunction at dawn over Lake Superior on June 30, 2012. Planetary alignments can’t be physically sensed by us on Earth. Even their combined gravity is too weak to detect at the human scale. Credit: Bob King

Finally, contrary to urban myth and a zillion Youtube doomsday-scenario videos, planetary alignments do not affect life on Earth in any significant way. While massive Jupiter has a powerful gravitational pull, it decreases rapidly with distance. The amount of tugging you feel from the planet here on Earth is the same gravitational force exerted by a compact car three feet (1 meter) away. Pluto is really tiny with a far weaker pull. Putting them together does not magically magnify their gravitational reach.

You can line up all the planets, the Sun and moon in row and still go about your day with absolutely no sensation from their combined gravities. The moon and Sun are by far the strongest gravitational entities in the solar system in terms of their effects on Earth. Though only 2,160 miles in diameter, the moon is close enough to produce the tides, while the Sun is distant but far more massive than all the planets combined.

A few times a year the Sun and moon perfectly align in a total solar eclipse. Ever heard of someone hovering above the ground during totality? Me neither. Except in a spiritual sense of course!

The next time you hear of crazy claims being made about alignments and such, be skeptical. If the Internet has taught us anything, it’s to exercise critical thinking whenever we sit down in front of the flickering screen.

Stargazing on Christmas night

Merry Christmas and a happy holiday! I hope you’re enjoying time with family and friends and a clear night is in the forecast. Should you poke your head out tonight, here’s what’s up.

Look for the crescent moon and Mars in the southwestern sky at the end of twilight tonight December 25th. Comet Finlay and Mars will still be tight the next few nights.  The alignment is line-of-sight only — the two are actually about 45 million miles apart. Stellarium

At nightfall, a pretty crescent moon ornaments the dim constellation of Capricornus not far from Mars. Barely half a degree to the planet’s east a 6-inch or larger telescope will net you Comet 15P/Finlay, now fading from its recent outburst. It’s currently magnitude 9.6 with a little tail pointing to the east.

Comet 15P/Finlay passed only 1/6th of a degree from Mars on December 23-24. This photo was taken on the 24th and shows the glaring planet and comet almost touching. Click for a map to help you find Finlay in your telescope. Credit: Damian Peach

In a remarkable coincidence, comets have passed very close to the planet Mars twice this year. Comet Siding Spring drew physically close on and around October 19th, while Comet Finlay only appears next to the planet thanks to a lucky line-of-sight alignment.

A grand entry of stars dances across the southeastern sky around 10 o’clock local time. Comet C/2014 Q2 Lovejoy will be 10° high at that hour in the constellation Columba the Dove as seen from the northern U.S. and even higher from the central and southern states. Stellarium

Later tonight, around 10 o’clock, look to the south. Orion has now climbed boldly into view along with sparkling Sirius and the “Winter Triangle” figure. Tucked below Lepus the Hare you’ll find our Christmas comet, Lovejoy, now glowing at magnitude 5.5 and faintly visible to the naked eye from a dark sky location. Binoculars show it as a big ball of fuzz. For more information and a map showing its travels in the coming nights, click HERE.

Comet Lovejoy on December 23 looks like a Roman candle with a blue coma and long, faint tail. Credit: Michael Jaeger

Photos of Lovejoy show a huge coma or comet atmosphere more than half the size of the full moon tinted green from fluorescing carbon and cyanogen molecules; its super-skinny tail glows blue from light given off by carbon monoxide excited by ultraviolet light from the Sun.

Jupiter is easy to see now in the eastern sky in Leo around 10 o’clock local time. Stellarium

If you now direct your gaze to the east around 10 p.m., Jupiter jumps right out. After Sirius and the moon, it’s the brightest nighttime object the sky this winter. Use the planet to help you find the Sickle or head of Leo the Lion and its brightest star, Regulus.

Jupiter in binoculars tonight around 10 p.m. (CST). All four of its bright moons will be strung out in a nearly straight line very close to the planet (big glow at center). Stellarium

Sharply-focused and steadily held 10x binoculars will show all four of its bright moons, assuming one or more aren’t passing either behind or front of the planet or in eclipse. Lucky for us, Io, Europa and Ganymede will line up in a neat row east of Jupiter with Callisto well off to its west tonight. How many will you see?

Wow! What a blast. This fireball lit up Japanese skies early this morning. The Belt of Orion is at upper right. Credit: SonotaCo

Finally, reports are coming in about a powerfully bright fireball that streaked across Japan’s skies around 2 a.m. local time this Christmas morning. I’ve not been able to track down a brightness estimate, but the pictures show an object at least as brilliant as the full moon.

Moon and Jupiter with a side of JUICE, please

The waning gibbous moon lingers near Jupiter tonight and tomorrow night (Dec. 11) in the constellation Leo. This map shows the sky facing east around 11 p.m. local time. Source: Stellarium

Find the moon tonight and you’ll be led straight to Jupiter. Tomorrow night, too. Earth’s only satellite will spend the next two evenings wooing the largest planet which shines brightly to the west of Leo’s Sickle.

As Jupiter rises earlier and earlier, pushing higher into the evening sky, the European Space Agency’s JUpiter ICy moons Explorer Mission or JUICE recently got the green light to proceed to the next stage of development – working out the details of payload equipment and mission support among the many partners involved in the project.

JUICE will launch in 2022 and arrive at Jupiter in 2030 to begin a three-year-plus study of the giant planet and three of its largest moons – Ganymede, Callisto and Europa. The spacecraft will bristle with cameras, spectrometers, a radar, an altimeter, radio science experiments and sensors used to monitor the flow of charged particles (electrons, protons and others) in the Jovian system.

Artist impression of JUICE at Jupiter in the year 2030. JUICE will spend part of its mission in orbit around Ganymede, the moon at upper left. Credit: ESA/AOES

Scientists will explore Jupiter’s atmosphere, tenuous dust ring and its magnetosphere, a bubble of magnetism that enshrouds the planet similar to the one that funnels the solar wind into Earth’s upper atmosphere to spark auroras. No surpries – Jupiter has auroras, too.

JUICE will also investigate each of the three moons up close and their interactions with Jupiter, especially Ganymede. Detailed investigations Ganymede, the planet’s largest moon, will be performed when the probe enters into orbit around it – the first time any moon other than our own has been orbited by a spacecraft.

Europa, Ganymede and Callisto are all believed to hold oceans of liquid water beneath their frigid crusts. The mission will study the moons as potential habitats for life as it seeks to determine what conditions are required for planet and moon formation and the emergence of life.

This artist’s concept of Jupiter’s moon Ganymede, the largest moon in the solar system, illustrates the “club sandwich” model of its interior oceans. Credit: NASA/JPL-Caltech

JUICE will first visit Callisto, the most cratered object in the solar system, then fly by Europa twice, making measurements of the thickness of its icy crust. In 2032 the spacecraft will enter into orbit around Ganymede and study both its surface and internal structure including that possible hidden ocean.

“JUICE will give us better insight into how gas giants and their orbiting worlds form, and their potential for hosting life,” said Prof. Alvaro Gimenez Canete, ESA’s Director of Science and Robotic Exploration.