It’s double duo week: Moon-Jupiter and Venus-Uranus

The nearly full moon is in conjunction with Jupiter tonight. Their minimum separation of 5 happens around 10 p.m. (CST). Source: Stellarium

The nearly full moon is in conjunction with Jupiter tonight. Their minimum separation of 5° happens around 10 p.m. (CST). Source: Stellarium

I looked until around 11 p.m. last night but moonlight diluted any aurora that may have out. But the predicted storm did hit between about 2 a.m. and dawn this morning. While some readers might think I stay up all night, I really did sleep through this aurora. I know at least a few of you saw it. Tonight, there’s a chance for more minor storming.

There’s also an even better chance you’ll be struck by two very bright objects in the eastern sky at nightfall: a plump gibbous moon and the jolly giant planet Jupiter. They’ll be in conjunction tonight just ahead of Leo’s brightest star Regulus. Pairings like these make for great company and contemplation while walking the dog at night.

Venus and Uranus will be very close together on March 4th, an ideal time to find the fainter planet in binoculars. Source: Stellarium

Venus and Uranus will be very close together on March 4th, an ideal time to find the fainter planet in binoculars. Source: Stellarium

A planet-to-planet pairing occurs on Wednesday evening the 4th when Venus and Uranus will be just 1/3° apart. Like last month’s close graze with the crescent moon, this will provide yet another easy opportunity to see a planet that is too dim for most to see with the naked eye. Just point your binoculars at brilliant Venus in late twilight in the western sky and look for a tiny speck of light immediately below it.

I love how planets can appear so close and yet be so far from one another. Venus is a quick jaunt at 128 million miles from Earth compared to Uranus’ 1.9 billion miles, nearly 15 times farther away.

The stars in the constellation of Orion all look like they are at the same distance. Turn the constellation through 90 degrees and you can see the stars are actually at different distances. Two of the Belt stars plus the two bottom stars in the constellation are far from the sun but relatively near one another in space. Betelgeuse is much closer to us. Credit: ESA

The stars of Orion might be easily dismissed as all being at the same distance from us. That’s how they appear on the 2-D “surface” of the sky. Butturn the constellation through 90 degrees (look at it from the side) and you can see the true distances of each star. Notice that Betelgeuse is much closer to us than the Belt stars. Credit: ESA

When we see conjunctions and appreciate the real distances between objects in the sky, it’s helpful to remember the same applies to the constellations. We see familiar rectangular outline of Orion and the neat arrangement of his three belt stars by lucky chance. Looking back toward Orion’s stars from a different direction in space (a couple hundred light years beyond the solar system) Orion would be unrecognizable.

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!

Planetary traffic jam lookback / Speedy comet update

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

To capture the planet Uranus (at lower right) I had to overexpose the bright, sunlight lunar crescent. Naturally, this made the earth-lit portion stand out very clearly. Credit: Bob King

Wow, we had quite a weekend. The moon visited every evening sky planet while Venus and Mars squeezed together for their closest approach of the year. We’ve already looked at the “triple play” conjunction that occurred Friday. I thought it would be fun to look at the other alignments that have made the past few nights so memorable.

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015. Credit: Guy Sander

The moon (top) along with Venus and Mars Saturday evening Feb. 21, 2015 from near Duluth, Minn. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Here, Guy has enlarged portions of the image to better see all three planets involved. Credit: Guy Sander

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and Mars slides closer to the Sun. Credit: Bob King

Venus and Mars were still close Sunday night Feb. 22, but they will part in the coming days as Venus moves up and away from the Sun while Mars slides closer. Credit: Bob King

As for that fast-moving comet discovered last week and en route to the evening sky, Karl Battams, an astrophysicist and computational scientist based at the Naval Research Laboratory (NRL) in Washington DC, is right now at his computer measuring positions of the comet from photos made with the orbiting Solar and Heliospheric Observatory (SOHO).

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Comet SOHO-2875 survived its close passage of the Sun and may make an appearance in the evening sky soon. This photo montage was made using the coronagraph (Sun-blocking device) on SOHO. Click to watch a movie of the comet. Credit: NASA/ESA

Once enough positions are known, he’ll send the data off to the Minor Planet Center where a preliminary orbit will be determined. With that information I can make a nice map showing us where to look for it. Stay tuned.

Moon meets Uranus next / Oddball comet update

Wow! What a fine photo from last night's conjunction. Venus, Mars and waxing crescent Moon over sculpture "Calling The Power" by Larry Bechtel at Vic Thomas Park. Credit: Terry Aldhizer

Wow! What a fine photo from last night’s conjunction. Venus, Mars and the waxing crescent Moon over the sculpture “Calling The Power” by Larry Bechtel at Vic Thomas Park in Roanoke, Virginia. Credit: Terry Aldhizer

Close-up of the moon, Venus, Mars gathering last night. The earthshine on the moon is amazing! Credit: Terry Aldhizer

Close-up of the moon, Venus, Mars gathering last night. The earthshine on the moon is amazing! Credit: Terry Aldhizer

We were  hopelessly cloudy for last night’s conjunction. You were luckier I hope. Don’t forget, tonight’s thicker crescent passes very close to the planet Uranus, occulting it from the far northeastern U.S. and southeastern Canada. Venus and Mars will also be in conjunction today and a smidge closer that they were yesterday evening.

Wide view of Uranus and the moon on tonight (Feb. 21)  as seen from the Midwest about an hour and a quarter after sunset. Source: Stellarium

For the Central Time Zone, Uranus will lie 0.5° west of the moon in twilight, 1° away the Mountain States and 1.5° for the West Coast. What a great opportunity to spot the 7th planet in binoculars. Not only that, but a simple time exposure with a tripod-mounted camera will easily show it. Wait till late twilight and try a range of exposures starting around 5 seconds at ISO 800 with the lens wide open to f/2.8 or 3.5.

Uranus in early twilight (left) just before its dramatic disappearance behind the earth-lit edge of the moon tonight Feb. 21 as seen from Portland, Maine. 36 minutes later Uranus emerges at the bright crescent’s edge. Both disappearance and reappearance occur in a dark enough sky to see in a small telescope. Source: Stellarium

Map showing where the occultation of Uranus by the moon will be visible. Between the white lines, it’ll be visible in a dark sky. Blue is twilight and the red dotted line is daytime. Uranus is too faint to see in the daytime sky. Click the map to get a list of disappearance and reappearance times for a variety of cities. Credit: IOTA/Occult

Most of the time the moon occults stars along its path since there are a lot more of those than planets. Because they’re so remote, stars are little more than points of light; as the moon moves over them they disappear with surprisingly suddenness. Since Uranus displays a real, measurable disk it will take a second or two to disappear behind the moon’s edge.

SOHO-8275 comet about 7 east of the Sun this morning at 9:06 a.m. (CST) this morning. Credit: NASA/ESA

SOHO-2875 comet about 7 east of the Sun this morning at 9:06 a.m. (CST) this morning. Credit: NASA/ESA

The little comet we discussed yesterday continues trekking away from the Sun after its searing encounter two days ago. SOHO-2875 still shows a short tail and hangs in there around magnitude +3.5. It reached the edge of the field of view of the Solar and Heliospheric Observatory’s C3 wide-field coronagraph this morning headed east-northeast.

Since the field of view of the coronagraph is 15°, the comet’s presently about 7° east of the Sun, too close to spot yet in twilight. Give it 4-5 more days and someone may see it in a telescope in evening twilight. As soon as an orbit becomes available I’ll put together a chart to help you find it.

Spectacular fireball over Pittsburgh / Juvenile moon alert


Pittsburgh fireball February 17

A fireball meteor at least as bright as the full moon flared over the Pittsburgh region around 4:50 a.m. Eastern time Tuesday morning. The object, detected by three NASA meteor cameras, was moving at a speed of 45,000 miles per hour. Based on its brightness, NASA’s Meteoroid Environment Office estimated the object at 2 feet across with a weight of 500 pounds. Something like a very heavy TV falling out of the sky.

“I’ve seen many meteor showers and this wasn’t anything like that. Instead of crossing the upper atmosphere, this feel almost directly down and brighter than any thing I’ve ever seen of this nature,” reported John D. of Elyria, Ohio. “It looked so big that my son and I expected to hear or see an impact.”

Based on data from pictures taken by multiple cameras, an orbit for the Pittsburgh fireball could be made. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA.Copyright David L. Clark, prepared by NASA MEO

Based on pictures taken by multiple cameras, NASA scientists determined an orbit for the Pittsburgh fireball. Originating in the asteroid belt between Mars and Jupiter, it came a long way to get to PA. Copyright David L. Clark, prepared by NASA MEO

“The entire landscape was lit up like daytime. Startling experience. I was very fortunate to be looking out window at the time.” So wrote Robert M. of Clarion, Penn. in his report to the American Meteor Society’s fireball reporting website.

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

Map showing reported sightings of the fireball. To date, 125 reports have been received. Credit: AMS

NASA’s cameras first spotted the meteor at an altitude of 60 miles northwest of Pittsburgh and last saw it 13 miles above Kittanning, northeast of Pittsburgh. Around 13 miles altitude, the meteoroid entered its “dark flight” phase, when the air slowed it down enough to drop in free fall.

When we see a meteor, we don’t actually see the object itself but rather a brilliant “tube” of ionized air caused by the rock’s incredibly speedy passage through the atmosphere. Once a meteoroid loses sufficient speed, it no longer has the energy to ionize or make the air glow around it and falls in dark flight.

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit:

Earth seen from the perspective of the meteoroid moments before it entered our atmosphere to become a fireball. Click to see the movie. Credit: Copyright David L. Clark, prepared by NASA MEO

Some people heard sonic booms during the fall, a good sign that the meteoroid (what you call a meteorite before it hits the ground) fragmented and dropped pieces on the ground east of Kittanning. According to Bill Cooke of the Meteoroid Office, seismographs in the region recorded the pressure wave created by the meteoroid’s flight.

Like most meteors and meteorites, this one’s a visitor from the main asteroid belt located between Mars and Jupiter. If pieces did survive the atmosphere’s ferocity, may I be the first to welcome them to their new home.

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

Watch for a 1-day-old super-thin crescent moon below the duo of Venus and Mars tonight. This map shows the sky about 35 minutes after sundown. Source: Stellarium

On another note, I wanted to remind moon lovers that a very young, very thin 1-day-old moon will be visible during early twilight in the western sky this evening starting about 25 minutes after sundown.

The moon’s about about one fist held at arm’s length below the pair of Mars and Venus. Tonight’s act is a warm-up for tomorrow night’s very close gathering of the moon with the two planets. For more information on that event, click HERE.

Tracking down February’s mystery supermoon – where is it?

This week’s new moon will be unusually close to Earth. Think of it as a ghostly supermoon. As is true for any new moon, it will be too close to the Sun in the daytime sky to see. This illustration shows the moon’s appearance and location if our eyes could somehow make it out through all the daylight. Source: Stellarium

Here comes the supermoon! But wait, doesn’t that only happen around full moon? Well, not always. Every month the moon swings around Earth in its elliptical (oval) orbit. On one side of the ellipse, it’s closest to Earth and on the opposite side, farthest. When it’s at its closest point, called perigee, at the time of full moon, we call it a supermoon.

During the closest supermoons, our satellite can appear up to 30% brighter and 14% larger. Whether anyone can actually see the difference is open to debate simply because there’s no normal-distance moon nearby with which to make a comparison.

No one pays attention to first quarter or crescent supermoons even though the moon can be closest to us at those phases, too. Thanks to incessant media coverage, only full supermoons get coverage. We like full moons for all sorts of reasons. When an extra close one’s in the offing, as happens on Sept. 27 this year, that’s just one more reason to like them.

The moon’s orbit around Earth is an ellipse with the Earth off-center at one the ellipse’s foci. During its 27-day-long orbit, the moon passes through perigee (closest) and apogee (farthest) points. This week’s new moon will be the second closest perigee of the year after the Sept. 27 full moon. Illustration not to scale. Credit: Bob King

Lest crescents and quarters get short shrift I’m here to hawk this month’s supermoon. Full disclosure. Since it occurs during new moon phase on Feb. 18 you won’t see it. No one sees a new moon except when it happens to be eclipsing the Sun. But northern hemisphere skywatchers can spot the moon two days before new and just one day after new this month, and it’ll be nearly as super as on the18th.

Tomorrow morning Feb. 16 the planet Mercury will lie about 9.5° (about one fist held at arm’s length) to the lower left of the thin crescent two days before new moon phase. This map shows the sky facing southeast about 40 minutes before sunrise. Source: Stellarium

What’s more, if you have a good view of the southeast horizon, tomorrow morning’s skinny crescent will lie near the planet Mercury low in the southeastern sky 40 minutes before sunrise. Be sure to carry along a pair of binoculars as Mercury is near “last quarter” phase and not nearly as bright as it can be.

The moon’s average distance is 240,000 miles, but tomorrow morning at 6 a.m. (CST) it will lie just 226,549 miles from Earth. At 1 a.m. Feb. 18 – the time of the invisible supermoon –  it will be 4,723 miles closer. The following day the moon slides out a bit to 222,092 miles en route to a striking double conjunction with Mars and Venus on Friday the 20th.

Even though we won’t see February’s supermoon, our planet will sense the difference. The additional gravitational force exerted by the close moon will make for unusually high tides. High tides occur when the Sun, moon and Earth are all in a line as they during both new moon phase and at full moon.

The moon, still very close to perigee, pops up in the western sky at dusk on Thurs. Feb. 19 well below Venus and Mars, now in close embrace. This map shows the sky about 35-45 minutes after sunset facing west. Source: Stellarium

So tomorrow morning you can catch the moon near Mercury at dawn, and on Thursday the 19th you’ll have the chance to enjoy the delicate grin of a one-day-old crescent in the west at dusk. Finally, on Friday, don’t miss the close conjunction of the moon with Mars and Venus.

Our satellite has a busy schedule this week!

 

A triple-scoop conjunction with a cherry on top!

Venus and Mars (at right) are drawing closer every night. This photo was taken at dusk Thursday Feb. 12 an hour and 15 minutes after sunset. On Feb. 20-21 they’ll be just half a degree apart or 8 times closer. The moon joins the pair on the 20th. Details: 35mm lens, f/3.5, ISO 800, 12 second exposure. Credit: Bob King

Get ready. One week from tonight fate has arranged a celestial spectacle. That night (Feb. 20) a two-day-old crescent moon will “triple up” with the planets Venus and Mars after sundown.

The entire bunch will fit within a circle 1.5° wide or just three times the diameter of the full moon. Like a glittering pendant around your sweetheart’s neck the trio will dangle above the western horizon in the afterglow of sunset. This is a not-to-miss event and one that should be fairly easy to photograph.

Moon, Mars and Venus around 6:45 p.m. (CST) on Feb. 20 in the western sky. Be sure to look for the darkly-lit part of the moon illuminated by sunlight reflecting off Earth called earthshine. It’s a beautiful sight in binoculars. Source: Stellarium

Look toward the west in the direction of the setting Sun; the best viewing time will be 45 to 90 minutes after sunset. With plenty of light to work with, taking a picture of the scene shouldn’t be too difficult. Attach your camera to a tripod and use the information in the photo caption as a place to start. Try to keep your exposure times to 20 seconds or less. Any longer and the planets will stretch into short trails instead of compact dots due to Earth’s rotation.

When you look at the LCD screen on the back of your camera, don’t be surprised if the crescent moon is completely filled out. Time exposures in semi-darkness necessarily overexpose the bright sunlit crescent. The rest of the moon is illuminated by dimmer earthshine, sunlight reflected from the Earth to the moon and back.

From the East Coast, the moon will lie a little farther to the right of Venus and Mars than depicted in the map; from the West Coast, it sits above the pair. Conjunction with Venus occurs around 5 p.m. (CST) and with Mars an hour later.

Venus and Mars will be close conjunction the following night (Feb. 21) only 0.5° or one moon diameter apart. If the weather doesn’t cooperate on the 21st, don’t sweat it – the two planets will be close from the 19th through the 22nd. You’ll easily tell the two apart. Venus is SO much brighter than Mars (about a hundred times) and the lunar crescent brighter yet. This promises to be one of the best moon-planet gatherings of the year.

Uranus in early twilight (left) just before its dramatic disappearance behind the earth-lit edge of the moon on Feb. 21 as seen from Portland, Maine. 36 minutes later Uranus emerges at the bright crescent’s edge. Both disappearance and reappearance occur in a dark enough sky to see in a small telescope. Source: Stellarium

Here’s a wider view of Uranus and the moon on Feb. 21 as seen from the Midwest about an hour and a quarter after sunset. Source: Stellarium

Ah, but the moon won’t be quite finished with its magic. There’s still the cherry on top. The very same night – Feb. 21 – the crescent covers up or occults the planet Uranus for skywatchers in northeastern U.S. and southeastern Canada during twilight. For the Central Time Zone Uranus will lie 0.5° west of the moon, 1° from the Mountain States and 1.5° for the West Coast. Amazing stuff – yet another opportunity to easily spot planet #7 in binoculars.

Map showing where the occultation of Uranus by the moon will be visible. Between the white lines, it’ll be visible in a dark sky. Blue is twilight and the red dotted line is daytime. Uranus is too faint to see in the daytime sky. Click the map to get a list of disappearance and reappearance times for a variety of cities. Credit: IOTA/Occult

Most of the time the moon occults stars along its path since there are a lot more of those than planets. Because they’re so remote, stars are little more than points of light; as the moon moves over them they disappear with surprisingly suddenness. Since Uranus displays a real, measurable disk it takes a second or two to disappear behind the moon’s edge. This should be a very fun occultation for those lucky skywatchers living out East. Maybe it will help take their minds off the unrelenting snow.

Darkside of the moon? What dark side?


Take a walk on the lunar farside

We may never see it from Earth but sure as pants, the moon’s farside basks in sunshine just like the “man in the moon” side. In this new NASA video, compiled using images taken by the Lunar Reconnaissance Orbiter (LRO), we can watch it happen right before our eyes as the moon’s farside waxes from crescent to full and back to crescent phase.

The far side of the moon lacks the many dark patches called lunar seas, which are gigantic, lava-flooded impact-carved basins. The largest lunar basin, named South Pole-Aitken and lacking the lava coverage of the others, might be seen with the naked eye as slightly grayer than the rest of the farside. Click for a map of farside features. Credit: NASA

We also get to see clearly how different the farside looks compared to the near. The near complete lack of “dark spots” or lunar seas would make it impossible to see a face up there. At best we might discern two small dark patches – the Sea of Moscow (Mare Moscoviense) and the floor of the crater Tsiolkovski which is flooded in dark, now frozen lava. The rest of the Full Farside Moon would appear a glaring white to the naked eye.

Since the moon completes a rotation in the same time it takes to revolve about Earth, an observer on Earth always see the same face. All parts of the moon receive sunlight during a lunar orbit. Illustration: Bob King

So how did we get stuck with just one side of the moon? Because the moon orbits around the Earth in the same time it takes to spin on its axis, it always keeps the same hemisphere pointing at us. This is called synchronous rotation and is caused by the gravity of the Earth acting upon the moon to slow its rotation to a rate equal to its orbital period of 27 days. That’s why we’re stuck with seeing the same face for as long as humanity has gazed at the moon. Much farther back in time, the moon rotated faster. If we’d been around to gaze up, we would have been able to see all 360° of the lunar sphere.

Nowadays you’ve got to get out there and orbit the moon in a spaceship to catch a view of the backside. The Apollo astronauts are the only humans who’ve seen it.

Another view from NASA’s Lunar Reconnaissance Orbiter of the moon’s farside with Earth in the background. Credit: NASA

When you look at the moon, the white stuff is ancient, crater-saturated crust that cooled more than 4 billion years ago. The dark “seas” formed later, mostly between 3 and 3.5 billion years ago. The farside is mostly ancient crust and thicker than the nearside crust – 50 miles vs. 37 miles.The extra thickness is likely reason for its dearth of seas; molten rock from below couldn’t reach the surface to fill basins carved by impacts.

This series of photos taken by the LRO show the moon through nearly a full rotation so you can see how the near side transitions to the far. Credit: NASA/Goddard/Univ. of Arizona

How the moon’s crustal thickness came to vary is still open to debate. Tides raised in the still-molten moon by Earth’s gravity may have played a role. Crust ejected and piled on top of the original lunar crust by the impact that excavated the enormous 1,600-mile-wide (2,500 km) South Pole-Aitken Basin may also have been responsible.

Now that you’ve seen both sides, the next time you see a thin crescent moon think about the farside. If you could just get around the back of the crescent for a look, you’d see a nearly full moon on the other side.

And as for the “dark side” of the moon? That’s what you see during a partial or total eclipse of the Sun. A rare sight if there ever was!

 

 

 

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.

What would it look like if Mars, Saturn or Neptune replaced the moon?

The becomes part of the figure of the Winter Hexagon this evening. Most of the brightest stars of the winter sky form the hexagon with the exception of Orion’s Betelgeuse, which gets stuck in the middle of the figure.  The map shows the sky facing southeast around 8 o’clock local time. Created with Stellarium

Tonight the nearly full moon will become part of the Winter Hexagon, one of the biggest and easiest to see asterisms of the winter sky. You’ll find Luna twixt Procyon in Canis Minor and Pollux in Gemini along the eastern side of the figure which is comprised of six bright stars. When connected by imaginary lines, the stars form a hexagon 65° tall by 45° wide that reaches from the zenith to low in the southern sky.

Saturn at the moon’s distance from Earth rises majestically above the skyline. Appearing more than 33 times larger than the moon, its globe is 16.5° across while the rings extend nearly 40° from end to end or more than twice the size of the constellation Orion. Credit: Roscosmos

The moon’s 240,000 miles from Earth and 2,160 miles (3,475 km) in diameter. To get there by foot would take you 9 years. Seen from Earth, the lunar sphere spans just 1/2° of sky – you can more than cover it up with the tip of your pinkie finger.

At 7,500 miles across, Venus is only a few hundred miles smaller than Earth. It would appear very white and bright and just under 1.75° across or just shy of 4 times larger than the moon. Credit: Roscosmos

Yesterday we replaced the Sun with Polaris, Vega, Sirius, Alpha Centauri and Arcturus to get a feel for the real dimensions and appearance of what are otherwise tiny twinkling points of light.

Today we’ll replace the moon with several of the planets to better appreciate their true dimensions. Like the stars, all the planets look like dots of light to the unaided eye.

At 4,212 miles across, Mars is only about twice the size of the moon and would be 1° across. Your pinkie would just cover it. Credit: Roscosmos

Wouldn’t it be nice to just walk outside and see Jupiter’s Great Red Spot and all the wild weather happening within its many cloud belts? At the moon’s distance, all you’d have to do is look up on a clear day. Jupiter’s so big Earth would become another of its moons. We’d also be bathed in its dangerous radiation environment. Credit: Roscosmos

Uranus is four times the size of Earth and would appear a pale blue color in our sky. Credit: Roscosmos

Neptune’s deeper shade of blue is caused by methane gas in its atmosphere which absorbs light of longer wavelengths (yellow, orange and red). Neptune’s about 1,000 miles smaller than Uranus. Credit: Roscosmos

Covered in craters and just 1.5 times the size of the moon, Mercury would appear similar to our own satellite in the sky. Credit: Roscosmos

Now this looks weird. Earth in Earth’s sky? Of course this is how big the Earth would appear from the moon – 1.8° across or just shy of four times the size of the full moon. Credit: Roscosmos

And now for the video: