Struggled to find Uranus? Let the moon take you there tonight

Once you’re done chuckling, we’ll move on. Ahem!

The waning gibbous moon will near the planet Uranus tonight September 10, 2014. From northeastern U.S. it will be covered by the moon. These views show moon and planet from Syracuse (eastern U.S.) and the Midwest at the times shown. Source: Stellarium

If you’ve ever had trouble finding the remote planet Uranus, Luna can help you tonight. The waning gibbous moon will occult or cover up the planet for observers in northeastern North America, Greenland, Iceland and northern Scandinavia around 8 p.m. Eastern Daylight Time this evening.

If you have a small telescope, you’ll be able to watch the bright eastern (left) edge of the moon slowly approach and then hide the planet. Unlike a point-like star, which winks out in a split second when covered by the moon’s edge, Uranus shows a small disk and will fade more gradually over several seconds.

Observers in the wedge-shaped zone that spans the Northeastern U.S., Canada and other northern countries will see the moon cover Uranus. Those living in the U.S. and Canada will spy the planet very close to the moon’s west rim. Credit: USNO

But let’s say like me you live outside the occultation zone. What will we see? From the Midwest, Uranus will be just less than 1° to the west (right) of the moon as it comes up in the eastern sky in late twilight. Over the hours, it will appear to move gradually drift to the west away from the moon as the moon moves eastward in its orbit.

The farther west you live, the farther Uranus will be from the moon’s western edge. But not too far. Even from the California Coast, Uranus strays only about 2° (four moon diameters) to the right of the moon.

The planet may even be easier to see in binoculars from points west because it will be further from the lunar glare. No matter what, it’ll be easy to find the planet, which shines around 6th magnitude.

The view from the U.S. West Coast around 10 o’clock local time tonight. Source: Stellarium

Remember, you’ll need 50 mm binoculars, or better, a small telescope, to view the planet near the moon. Telescope users are encouraged to crank up the magnification and see Uranus’ diminutive disk next the moon, which appears gigantic in comparison. In reality, the 7th planet is nearly 15 times as large.

Uranus only a degree east of the totally eclipsed moon seen from the Midwest on October 8, 2014. Stellarium

Get ready for an even better shot at seeing Uranus. On the morning of October 8th, the full moon will be in total eclipse and the planet will lie very close due east. With no glary moonlight and everyone focused on the eclipse, more people will probably see Uranus at one time than perhaps any time in history.

Moon, Mars, Saturn and Antares gather at dusk tonight

The crescent moon, Saturn and Mars will form a compact triangle in the southwestern sky in this evening August 31st. 3.5º separate the moon and Saturn; Mars and Saturn will be 5º apart. Antares is about two ‘fists’ to the east or left. Stellarium

Don’t miss tonight’s sweet gathering of crescent moon and evening planets. Just look to the southwest in late twilight to spot the trio.

Both Saturn and Mars happen to be exactly the same brightness, shining equally at magnitude 0.8, but each with a distinctly different hue. Can you see the contrast between rusty red Mars and vanilla-white Saturn?

Antares is a red supergiant that’s blowing a powerful stellar wind into space at the rate of several solar masses every million years. One day it’s likely to explode as a supernova. Credit: Wikimedia

All this happens in Libra, a dim zodiac constellation preceding the brighter and better know Scorpius. Scorpius brightest star, Antares, is similar to Mars in color and just a tad fainter.

Visually, this red supergiant star doesn’t even hint of its true proportions because it’s 620 light years away, too far to appear as anything more than a shifting point of light. Measuring in at three times the diameter of Earth’s orbit, if Antares were put in place of the sun, its bubbly surface extending beyond the orbit of Mars.

How Antares would appear if we could get close enough to see it based on simulations by A. Chiavassa and team. Huge convective cells of rising and sinking gas crinkle its surface. Click to read the group’s 2010 research paper on the star. Credit: A. Chiavassa et. all

Recent research shows the star dominated by enormous bubbles of incandescent hydrogen gas called convective cells. Although it has a mass some 18 times that of the sun, the star’s powerful winds – from convection and sheer radiant energy – blast away something like 3 solar masses of material into space every million years. Unless Antares slims down through mass loss, it’s destined to grow a core of iron, collapse and explode as a supernova in the future.

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.

Sunday’s Supermoon sweetens August skies

Tomorrow night August 10 we’ll witness the closest full moon of the year. Credit: Bob King

OK, it’s not the Super Bowl exactly. No, this is better. Tickets are free, there’s plenty of parking and you can watch all night commercial-free. Yes, it’s time for the supermoon!

Tomorrow night, the Full Sturgeon Moon occurs at the same time the moon is closest to the Earth or as astronomers like to say, at perigee. The moon passes through perigee and its distant counterpart, apogee, once every 27.3 days, the time it takes the moon to orbit once around the Earth.

Sometimes perigee happens at first quarter moon or crescent phases and no one pays any attention. But when it occurs at full moon, we sit up and notice.

A sexy new term has even been coined in the past 30 years to describe the perigean full moon. Supermoon.

The moon’s orbit around Earth is an ellipse with one end closer to the planet (perigee) and the other farther (apogee). The year’s most distant lunar apogee happened two weeks ago; its closest perigee takes place during tomorrow night’s supermoon. Credit: Bob King

It’s hard not to be seduced by a big bright ball of pure bling. What’s more, the full moon rises at sunset and remains out all night unlike those skittish crescent moons that quickly hide behind trees and set. Its brilliance lights the otherwise dark road at night and adds an ethereal dimension to drabbest of landscapes.

July’s full moon as well as September’s will occur around the time of perigee, but tomorrow night’s will nearly coincide, making it the closest full moon of 2014.

Tom Ruen created this wonderful illustration showing the three supermoons of July, August and September compared to the ‘submoons’ or distant full moons coming up in 2015. You can easily see the difference in moon size comparing the top row to the bottom. The numbers give the moon’s diameter in arc minutes. 30 ‘minutes’ equals 1/2 degree. Credit: Tom Ruen

How close?  221,764 miles (356,896 km). That’s compared to an average distance of 238,855 miles, so the moon will be a smidge more than 17,000 miles closer to your doorstep than normal. Not only will it appear slightly brighter but 7% larger. Unfortunately, the difference, though real, will be nearly impossible to discern because we have no way to compare simultaneous side-by-side near and far full moons. Only after the fact, say by taking a picture of a distant full moon and placing it alongside a photo of a close one, could you tell.

Lots of us connect the dark spots or lunar ‘seas’ to make the face of the ‘man in the moon’ but how many have seen the rabbit? The ears form the strip over the top, the bright crater Aristarchus is the rabbit’s eye, there are two sets of legs and even a tail. Credit: Luc Viatour

2014′s most distant or apogean moon occurred just two weeks ago on July 27. No surprise given that the closest moon should naturally happen on the opposite end of the moon’s orbit or about two weeks later. The super thin crescent on that date was 252,629 miles (406,568 km) from Earth or nearly 31,000 miles farther than tomorrow night’s full moon – a difference of 13%.

Enough with numbers. They’re only a backdrop for the real show. Go out and enjoy a moonrise tonight and tomorrow night.  Not sure when the moon comes up? Head over to timeanddate.com and type in or search for your city. Since the moment of full moon happens early Sunday afternoon for U.S. and Canadian locations, tonight’s moon will be nearly as full.

I walked a mile in the moonlight last night and hope to do it again tonight. Is there a better month for moonwalking than August?

Crescent moon joins a planet parade / Opportunity ready for marathon run

The moon scoots by two bright stars and two bright evening planets in the next few nights. This map shows the sky facing southwest in late evening twilight. Stellarium

The moon joins a lineup of planets and bright stars hung like tiki lamps across the southwestern sky at dusk. Watch for it to pass near fading Mars Saturday evening and Saturn on Monday.

The Martian landscape photographed by on July 30, 2014. The rover is exploring south along the west rim of Endeavour Crater heading toward a notch called ‘Marathon Valley’ about 1.2 miles (2 kilometers) away. Credit: NASA/JPL

While you’re gazing at the Red Planet, know that the Opportunity rover made news this week when it set a record for the most miles ever driven off-planet, tallying a satisfying 25 miles (40 km) of Martian travels. The previous record was held by the Soviet Union’s Lunokhod 2 rover when it ambled across 24.2 miles of the moon’s surface in 1973.

Out of this world distance records compared. Credit: NASA

Opportunity surpassed that record on Monday July 28 when it registered 25.01 miles en route to a notch called Marathon Valley along the west rim of Endeavour Crater. Mission controllers would like to get a look at clay minerals there that have been spotted from orbit.

Lunokhod 2 crater photographed by Opportunity last spring. The crater’s 20 feet (6 meters) in diameter. Credit: NASA/JPL

When it reaches the Valley it will have completed 26.2 miles (42 km), the official distance of a marathon. When you consider that Opportunity and its sister probe Spirit were only intended to function for 90 days, the current record-breaking feat and upcoming marathon completion are that more remarkable.

101 geysers erupt from Enceladus’ salty deeps

At least 20 geysers blast icy particles and water vapor from cracks in the icy crust of Saturn’s moon Enceladus. Scientists recently confirmed the geyser material derives from a salty ocean beneath the moon’s surface. Credit: NASA/JPL

Future astronauts better watch where their step when exploring the south polar terrain of Saturn’s icy moon Enceladus. A geyser could pop up anywhere.

This graphic shows a 3-D model of 98 geysers whose source locations and tilts were found in a Cassini imaging survey of Enceladus’ south polar terrain by the method of triangulation. Credit: NASA/JPL-Caltech/Space Science Institute

NASA’s Cassini spacecraft have identified 101 distinct geysers erupting on Saturn’s icy moon Enceladus. Cassini has studied and photographed the moon’s intriguing ‘tiger stripe’ fractures for over 7 years and discovered that each of them coincides with a particular hot spot within a fracture.

Three competing hypotheses were put forward to explain how geysers might happen on an ice-covered moon nearly a billion miles from the warmth of the sun.

#1 – Tidal flexing: As Enceladus revolves around Saturn, the planet’s enormous gravity flexes the little moon, heating up its interior and melting ice into water which escapes as vapor through openings in the icy crust.
#2 – Frictional heating: Back-and-forth rubbing of opposing walls of the fractures generate frictional heat that turns ice into geyser-forming vapor and liquid. Same principle as rubbing your hands together to create heat.
#3 – Jaws of ice: The opening and closing of the fractures caused by Saturn’s gravitational might exposes water from below when then quickly vaporizes in the moon’s vacuum.

This artist’s rendering shows a cross-section of the ice shell immediately beneath one of Enceladus’ geyser-active fractures, illustrating how water works its way to the moon’s surface. Credit: NASA/JPL-Caltech/Space Science Institute

But a detailed study by Cassini in 2010 appears finally to have netted the correct explanation. The probe’s heat-sensing instruments matched the geysers’ locations with small-scale hot spots only a few dozen feet across - too small to be produced by frictional heating, but the right size to be the result of condensation of vapor on the near-surface walls of the fractures.

“Once we had these results in hand, we knew right away heat was not causing the geysers, but vice versa,” said Carolyn Porco, leader of the Cassini imaging team and lead author of the first scientific paper on the discovery. “It also told us the geysers are not a near-surface phenomenon, but have much deeper roots.”

Researchers concluded the only logical source of the material forming the geysers is the sea now known to exist beneath the ice shell. They also found that narrow pathways through the ice shell can remain open from the sea all the way to the surface, if filled with liquid water. This implies, at least in my mind, that liquid water might exist as pools in hot spots encircled by thick rims of ice (condensed water vapor) on the moon’s chill -330° F (-201° C) surface.

Imagine standing nearby watching fountains of vapor turn to ice crystals before your eyes and sparkling like diamond dust against the black starry sky.

Source: JPL

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.

Can a boot print on the moon last a million years?

Buzz Aldrin first photographed a pristine patch of the lunar soil (left) before stepping onto it with his boot (right). The fine-grained consistency of the soil crisply records details in the tread. It’s estimated the impression will last 1 to 2 million years. Click to enlarge. Credit: NASA

One of my favorite pictures taken during the Apollo 11 mission to the moon 45 years ago was Buzz Aldrin’s famous boot print in the lunar soil. While it looks like he might have been doing it just for fun, pressing his boot into the fine, powdery soil had a purpose.

Aldrin and Neil Armstrong were asked to carefully observe and assess the properties of the regolith. Notice things like how deep their boots sank in the gritty stuff as well as how it affected their ability to walk about on the surface. Close up photos were taken, including 3D stereo images. Mission control didn’t leave a pebble unturned. It was all part of the mission’s Soil Mechanics Investigation.

After taking the first boot print photo, Aldrin moved closer to the little rock and took this second shot. The dusty, sandy pebbly soil is also known as the lunar ‘regolith’. Click to enlarge. Credit: NASA

The soil on the Moon is very fine-grained, with more than half of all grains being dust particles less than 0.1 millimeters across. It not only adhered to their boots in fine layers but provided good traction. Typically the astronauts boots sunk down only one-half to one inch (1.5-2.5 cm) into the lunar regolith.

In this view taken with a camera mounted on the Lunar Module (LEM), Buzz Aldrin takes the picture of his boot next to the rock seen in the earlier photo. The first boot print is just behind his foot. Credit: NASA

Even though the moon is airless, windless and essentially waterless, erosion happens. Bombardment by protons from the solar wind and micrometeorites (bits of interplanetary dust shed by comets and spalled from asteroids) never stops.

Earth’s atmosphere slows micrometeorites, allowing them to drift down gently to the surface. No so on the airless moon, where space grit grinds away mercilessly on the lunar rocks. Before the unmanned Surveyors landed, some astronomers thought that moon dust might be so deep it would swallow a spacecraft. Before Neil Armstrong made his historic ‘first step’, he first tested the ground to make sure it was firm.

More than 3.5 billion years of bombardment by micrometeorites have rounded the outlines of the lunar Apennine Mountains. The lunar module Apollo 15 ‘Falcon’ in the foreground. Click to visit NASA’s Apollo 11 image archive.  Credit: NASA

Their surfaces are riddled with countless ‘zap pits’ from micrometeorites that strike the surface at thousands of miles an hour. Slowly, inexorably the mountains are ground into more rounded forms. It’s estimated that micrometeorites churn the lunar soil once every 10 million years. Aldrin’s boot prints and for that matter, all the impressions in the dust left by the astronauts and their equipment, will remain in place for 1 to 2 million years. Incredibly long by human standards.

Extreme temperature differences between daytime highs and nighttime lows also must play a part in breaking apart rocks and furthering erosion. At the lunar equator, mean surface temperatures reach almost 260 ºF at noon and then drop to -279 ºF during the night. The moon also gets whacked by larger meteorites that send up plumes of dust that fill in crevices and soften sharp edges.

Sunday marks the 45th anniversary of the Apollo 11 lunar landing, when our toes touched a world other than Earth. While astronauts left countless impressions in the lunar dust, Aldrin’s single boot print has come to symbolize humanity’s first steps from the cradle of Earth into that big thing we call the universe. I hope we can return soon.

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.

Supermoon feast begins – it’s three in a row, baby!

Overnight tonight we’ll see the first of three supermoons in July, August and September. Credit: Gary Hershorn / Reuters

If the moon’s orbit were circular there’d be no such thing as ‘supermoons’, the occasional, extra-large full moons we see about once every 13 months. But circular orbits are exceedingly rare. Most celestial bodies dance about each other in ellipses. At one end of the ellipse, the two bodies are closest; at the other end, farthest.

The moon revolves around Earth in an elliptical orbit, passing through perigee (closest point to Earth) and apogee about once each month. When perigee occurs at full moon, we see a supermoon. Credit: Bob King

When the full moon coincides with its time of closest approach to Earth – called perigee – its disk can be up to 14% bigger and 30% brighter than typical full moons. In 2014 we get three consecutive perigee or supermoons in a row. The first occurs tomorrow morning July 12 at 3:28 a.m. CDT about 3 hours before the moment of full moon. Not a perfect match but close.

The next supermoons happen on August 10 (1 p.m. CDT) and September 8 (10:30 p.m.)

“Generally speaking, full moons occur near perigee every 13 months and 18 days, so it’s not all that unusual,” said Geoff Chester of the US Naval Observatory. “In fact, just last year there were three perigee Moons in a row, but only one was widely reported.”

The size difference between an apogee (foreground) and perigee or supermoon. Would that we could see them simultaneously to truly appreciate their different sizes. Credit: Tom Ruen

Supermoons get a lot of press because the word ‘super’ attached to anything these days naturally attracts attention.

While the phenomenon is very real, it’s also really hard to see because there are no rulers you can hold up to the sky to compare the size of one full moon to another. They ALL look big especially when the full moon’s near the horizon. That’s when the infamous ‘moon illusion’ kicks in and psychologically inflates the lunar disk up another notch.

Still, there’s every reason to go out and enjoy a full moon, super or not. The striking beauty of a moonrise, the curious mix of light and dark areas representing ancient crust (light) and titanic impact craters (dark) and the soft, yet stark illumination of the landscape where mystery abounds in every shadow. I could go on and on.