Monthly Archives: November 2010

Blizzard rages on Comet Hartley 2 – You gotta see this

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This Nov. 4 image, taken by the Deep Impact spacecraft during its closest approach, shows part of the nucleus of comet Hartley 2. The sun is off to the right. A distinct cloud of individual ice and snow chunks surrounds the comet. All images credit: NASA/JPL-Caltech/UMD

NASA just released several spectacular new photos of Comet Hartley 2 taken during the November 4 flyby. Living in Duluth, Minn. and having a fondness for snowstorms, I was tickled to see that the photos showed the comet in the process of creating its own blizzard. Hartley 2′s porous and fluffy snow chunks measure between an inch and a foot across. They’re composed of water ice similar to snow on Earth, but their method of delivery is decidedly different. Instead of falling down from the sky, Hartley 2′s snow falls up. It’s shot up from beneath the surface when sunlight causes dry ice (frozen carbon dioxide) to vaporize. The gas rises and breaks through the surface in the form of jets or mini-geysers, carrying pieces of water ice and comet dirt with it. This is the first time scientists have seen individual hunks of snow and ice around a comet.

Tons of fluffy snowballs the size of pennies to basketballs sparkle in the sunlight to the left of Comet Hartley's nucleus. The sun's heat in the vacuum of space will vaporize much of the material and form the fuzzy glow around the nucleus called the coma.

“When we first saw all the specks surrounding the nucleus, our mouths dropped,” said Pete Schultz, EPOXI mission co-investigator at Brown University. “Stereo images reveal there are snowballs in front and behind the nucleus, making it look like a scene in one of those crystal snow globes.”

Sunlight heats the Hartley 2's nucleus and converts solid dry ice beneath the surface into gas. As the gas breaks through the surface in the form of jets, it carries along water and ice and snow picked up along the way.

Remember that smooth middle section of Hartley 2? Well, it appears a different mechanism is at work there. Instead of getting blasted out, water ice turns to vapor and then percolates through the loose surface material.

Got a pair of those red-blue 3D glasses? You'll enjoy seeing the entire nucleus of Hartley 2 with jets and its icy particle cloud. Circles have been added to highlight the location of individual particles.

During the flyby, the Deep Impact probe was struck at least nine times by particles with a mass slightly less than that of a typical snowflake. No damage was done, but the potential was there considering the craft buzzed by at more than 27,000 miles per hour. Hey, it’s bad enough during a storm in Duluth, when you can feel the sting of ice crystals and snow on your face in a “wimpy” 30 mph wind. At least our storms come and go, but you wonder how long Hartley 2′s blizzard has been raging. Has it been snowing there for a matter of months when the comet is near the sun, or do at least a few carbon dioxide jets remain active throughout the comet’s orbit? If that’s the case, Hartley 2 might be a world of endless snow storms. For more information and photos, please see NASA’s Mission News. You can also watch a short movie of Hartley 2′s icy particle sprays in action.

Solar sail sets sail Saturday

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This series of photos of Comet Schwassmann-Wachmann 3 not only show the dust tail, created by pressure from sunlight, but also a portion of the comet breaking up into fragments either from the sun

Sunlight breaks through gray clouds and you feel its sudden warmth on your cheek. Unfelt is the pressure of the sunlight itself. One of nature’s greatest wonders is light’s dual nature: it’s both a wave and a particle. The particles are called photons, each a little bundle of energy that exerts real, physical pressure on an object. And the closer you are to a light source, the greater the pressure. In the everyday world, the pressure of light is negligible, but on very light materials in the near-perfect vacuum of outer space, it’s considerable. The next time you see a photo of a comet with a long dusty tail, consider that it was the pressure of photons streaming from the sun that pushed the dust away from the comet’s head to create the eye-catching plume. To give you an idea of how slight the pressure is, it would take 30 billion red laser pointers to lift a penny off a table.

The Japanese IKAROS solar sail was deployed in June. It measures 66 feet along the diagonal. Credit: JAXA

The same principle applies to the potential of using lightweight solar sails to ferry cameras and other instruments on missions to asteroids, planets and even a star using only the gentle push of sunlight. The Japanese were the first to unfurl a solar sail earlier this year called IKAROS or Interplanetary Kite-craft Accelerated by Radiation Of the Sun.  It was named after the mythological Icarus, who tried to escape imprisonment on the island of Crete by donning a pair of wax-coated wings and flying over the sea to freedom. Like a typical youth, he ignored his father’s advice to avoid flying so high that the sun would melt the wax that held the feathers together. Icarus’ wings fell apart and he plunged into the sea and drowned. The Japanese Aerospace Exploration Agency (JAXA) was more cautious. They stowed a sail, made of aluminized plastic only 0.0003 inches thick and covered in thin-film solar cells, aboard their Venus Climate Orbiter. In June, en route to Venus, the sail was unfurled. The sail will be released,  fly past Venus and continue on, using nothing but light pressure from the sun as “propellant”.

llustration of the 100 square foot NanoSail-D in orbit. Credit: NASA

Solar sails start don’t generate much thrust, but over months and years, the acceleration imparted by all those billions of photons adds up to some impressive numbers. At Earth’s distance, a square kilometer of sail attached to a payload with the total combined weight around 11,000 lbs. can reach a speed of over 7 miles a second after six months time.

Many of us will have a shot at seeing a U.S. solar sail in orbit very soon. The NanoSail-D mission is scheduled to blast off Saturday (Nov. 20) from the Kodiak Launch Complex in Alaska It’s tucked into a small satellite the size of a loaf of bread on board the larger FASTSAT or Fast, Affordable Science and Technology Satellite. The 100 square foot aluminum-coated polymer sail – as thin as a one-ply bathroom tissue – will be unfurled 10 to 12 days later and is expected to remain in orbit between 70 and 120 days. At 400 miles high, the drag caused by Earth’s tenuous upper atmosphere will probably outweigh any pressure from sunlight; the mission is more a test of technology than anything else. The sail and spacecraft are expected to spin, which means that brief flashes of sunlight bouncing from its highly reflective surface will be visible to sky watchers on the ground. Based on its steep orbital inclination of 72 degrees, the sail should pass over nearly every location on the planet.

I can’t wait to see it. When information on when and where to view this shiny experiment becomes available, we’ll post it here. For more information, please stop by THIS SITE or check out the NASA Fact Sheet on the mission.

Avoid eternal disappointment, have a backup plan

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Venus cleared the trees in a dark sky this morning just before the start of morning twilight. To the right of the planet is the star Spica. Up top is Saturn. Details: 35mm lens at f/2.8, ISO 800 and 30-second exposure. Photo: Bob King

Things don’t always work out as you anticipate. Last night, I’d hoped to see the dark clouds of the SEB revival that announce the return of Jupiter’s equatorial stripe, but even in a 10-inch telescope, I couldn’t make them out. Ditto for the northern lights. Despite a cheery forecast earlier in the day, the northern sky was dead. No lights. Clouds early in the evening prevented viewing a newly discovered asteroid that passed only 20,000 miles over my house. By the time the sky cleared, it had already moved on, become too faint to spot in a scope. Then this morning, I dutifully stood out in the 22-degree chill hoping to see a few Leonid meteor flashes, but the miserly lion wouldn’t part with a single one. When your hopes aren’t met, it’s wise to have a backup plan. Mine was seeing the planet Saturn through the telescope and Venus ablaze below it. As Woody Allen once said: “80% of life is just showing up.” By the way, don’t let my experience with the meteor shower dissuade you from getting up for a look tomorrow morning. You might just hit it right.

A beautiful shot of Comet Ikeya-Murakami taken on the morning of November 14. A suitable instrument and time exposure photography reveal a much more striking comet than can currently be seen in amateur telescopes. Credit: Michael Jaeger

I also checked up on the Japanese comet Ikeya-Murakami, still in the constellation Virgo about five degrees below Saturn. To my surprise, it has nearly faded away! In a 15-inch telescope at the very start of morning twilight, the comet took a lot of concentration and coaxing to distinguish from the sky background. On the other hand, our old friend Comet Hartley 2, now in the constellation of the Unicorn (Monoceros), is still faintly visible in ordinary binoculars.

A computer simulation of Earth's dust tail/ring seen from a vantage point outside our solar system. Colors indicate density; purple is lowest, red is highest. Credit: Christopher Stark, GSFC

While we’re on the topic of comets, it looks like our very own Earth has a tail, too. NASA’s Spitzer Space Telescope, which can detect the faint glow given off by sun-warmed dust motes, passed through it a few months ago.

“As Earth orbits the sun, it creates a sort of shell or depression that dust particles fall into, creating a thickening of dust – the tail – that Earth pulls along via gravity,” explained Spitzer Project scientist Mike Werner. “In fact, the tail trails our planet all the way around the sun, forming a large dusty ring.” The dust doesn’t originate from the Earth or those shelves you haven’t touched in a month, but rather from the breakup of asteroids and material strewn by comets along their orbital paths. Astronomers have found dust disks around 20 stars to date. Bumps, tails and warps in those disks have led to the discovery of a number of planets. The planets themselves might be too tiny to be obvious or lost in the glare of their host stars, but the warps are much larger and easier to image.

This diagram shows Fomalhaut, its planet Fomalhaut b and the dust disk. Credit: NASA/ESA/A. Feild

“In some stars’ dust disks, there are bumps, warps, rings, and offsets telling us that planets are interacting with the dust,” explains Mark Clampin of NASA’s Goddard Space Flight Center. “So we can ‘follow the dust’ to the planets.  That’s exactly what happened in 2005, when astronomers inferred the existence of a planet around the bright star Fomalhaut (FOE-ma-low) in Pisces Austrinus by the sharp inner edge of the star’s dust disk. They had a hunch that a hidden planet was herding material. Three years later, the Hubble Space Telescope nabbed Jupiter-sized Fomalhaut b, the star’s planetary companion.

I’m thrilled Earth has a tail. Perhaps alien astronomers will one day find us because we’re so good at making waves. For more on the topic, check out this NASA release.

Do you dig the planet Jupiter? Do you have a telescope, even a small one? Then tonight you’ll have reason to stay glued to the eyepiece for a six-part ‘performance extraordinaire’ of the planet’s moons. Here’s the schedule – all times are Central Standard. If you’re on the East Coast add an hour, mountain states subtract an hour and along the West Coast, subtract two hours.

Act I
5:46 p.m. The shadow of the moon Europa appears over Jupiter’s cloudtops along the planet’s eastern edge. It will take about 2 1/2 hours to move to the western edge.
Act II
6:08 p.m. Europa itself departs Jupiter’s disk and appears like an earring pinned to its western edge.
Act III
6:34 p.m. Io reappears from being eclipsed by Jupiter’s shadow 1/2 of a Jupiter diameter to the planet’s east. Watch it materialize from the darkness.
Act IV
7:15 p.m. Ganymede gets occulted or covered up by Jupiter at the planet’s east edge.
Act V
8:29 p.m. Europa’s shadow exits Jupiter’s disk.
Act VI
9:06 p.m. Ganymede – nearby east of the planet – slowly disappears into Jupiter’s shadow during eclipse. To catch it fading, be watching a little beforehand.

Leonid meteor shower peaks this week

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Leonid meteors are named after Leo the Lion, the constellation from which they appear to radiate. The red dot is the radiant. Meteors seen near the radiant will leave very short trails; those further away, longer trails. Created with Stellarium

The Leonids are back! This annual meteor shower returns every mid-November with a small display of some 15-20 meteors per hour for pre-dawn sky watchers. The best times for viewing will be after moonset tomorrow and Thursday mornings. About every 33 years, the Leonids (LEE-oh-nids) produce a very rich display that can number in the thousands per hour. When that many meteors blaze across the sky, astronomers call it a storm. The storms of 1833 and 1866 are the stuff of legend with the sky raining meteors like the end of days. The last storm period occurred between 1998 and 2002; the next won’t happen until 2033 or 2066. In these ‘tween times, meteor watchers make do with any Leonids they can get their eyes on.

A Leonid meteor from the 2009 shower shoot across the sky. Photo: Bob King

Like nearly all meteor showers, the material that we see burn up in a flash is dust shed from the tail of a comet. In the case of the Leonids, that would be Comet Temple-Tuttle, discovered in 1865-66 by Ernst Tempel and Horace Tuttle. Each November, Earth’s orbit intersects that of the comet’s. Dust left from previous passages of Tempel-Tuttle strikes the upper atmosphere at speeds of around 44 miles per second or more than 158,000 miles per hour. That’s plenty fast enough to vaporize sand or gravel-sized chunks  in a flash of light some 70 miles high in our planet’s ionosphere. Auroras and meteors both occur at approximately the same height, so lucky observers might catch sight of both tomorrow morning.

I have to emphasize that this won’t be a major Leonids year, since we’re not passing through a particularly dusty filament of comet debris, however if you’re game, the best time to watch is after 3 a.m. tomorrow and after 4 a.m. Thursday. Leo will be well up in the eastern sky and the radiant – the point from which the meteors will appear to originate – is squarely within the “backwards question mark” that forms the head of the Lion. With dawn beginning around 5:30 or 6, you’ll have at least two dark, moon-free hours.

Credit: George Varros/NASA

You can face almost any direction to see meteors, but I like to look to the south or southeast toward the constellation. Depending on where you live, these babies require some cold weather fortitude. Dress well and warmly. If you stay up until dawn, look way down in the southeastern sky for a little treat – the planet Venus should be shining brightly.

We were cloudy last night, so I can’t speak to whether the northern lights made an appearance or not. The Kp or auroral index was up slightly but not as much as anticipated. Conditions still look good for tonight and tomorrow night. Solar particles and their entwined magnetic field appear to be pointing in the right direction for a “hookup” to Earth’s field. Forecasting is something of an art, and of course, nature always has last say.

Forecast: Chance of aurora tonight through Weds.

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The moon shines through clouds at dusk yesterday. Photo: Bob King

We got hammered over the weekend by a windy, wet snow storm. Eight inches fell at our place. The heavy stuff stuck to the trees and quickly transformed their spindly outlines into a range of snowy peaks. I never expected to see any stars after the storm passed, but the moon and later Jupiter somehow found a way to get through. This picture was taken during twilight under high clouds with snow falling.

Watch the waxing moon pass to the upper right of Jupiter tonight. Created with Stellarium

Tonight the moon will be in close company with the planet Jupiter. If the clouds part, take a look. Two of Jupiter’s moons will be easy to spot in binoculars: Ganymede will lie immediately to the right of the planet and Callisto farther to the left side. Io and Europa will form a pseudo double moon very close to the right (west of) Jupiter. Telescope users can watch Io, at 8:41 p.m. CST, and then Europa at 8:46 p.m., occulted or covered by Jupiter’s giant globe. The moons slide right up to the edge of the planet and then slowly dim from view as their orbits take them behind the planet from our perspective.

A CME or coronal mass ejection, which has been headed toward Earth since last Thursday, will likely interact with our planet’s magnetic field and shower the ionosphere with high speed electrons and protons. You know what that means. Aurora! Major auroral storms are forecast for high arctic latitudes tonight with a possibility of minor storming along the northern tier of states and Canada according to NOAA’s space weather prediction center. More minor storms are predicted for Tuesday and Wednesday nights. CMEs are enormous bubbles of hot gas that occasionally erupt from the sun’s atmosphere. The subatomic particles they contain are flung into the solar system – sometimes toward Earth – at high speeds where they can stimulate a display of northern lights.

This photo of sunspot group 1124 was taken today by NASA's Solar Dynamics Observatory. The group has been growing rapidly and could be the site of moderate flares. Each of the two main spots is about the size of Earth. Credit: NASA

We have certainly left the solar doldrums behind. A year ago it was day after day of no sunspots and little solar activity. In 2009, 260 of 365 days were spotless; this year to date, there have only been 45 spotless days. The trend looks good. Sunspots are cooler regions on the sun’s surface where magnetic fields (the same kind as in ordinary magnets) are concentrated and intense. And it’s within sunspot groups that those fields sometimes break and reconnect, releasing prodigious amounts of energy in the form of flares. That’s why aurora watchers get excited when we see new and large sunspot groups pop up on the sun. I’ll be on the watch tonight even if it’s cloudy, checking the Kp index and extent of the auroral oval.

Constellation watching from Earth orbit

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The boot of Italy is outlined by artificial lights in this photo taken from the cupola in the space station on October 28. I've labeled some of the prominent stars above our planet. Click on the photos for hi-res versions. Credit: NASA

I never thought to look for familiar stars or constellations in the recent photos of the Earth at night taken by the Expedition 25 crew aboard the International Space Station until today. But there they were. Familiar Vega in Lyra the Harp, part of the Northern Cross and Draco the Dragon and even the Big Dipper. They’re all there hanging over Earth from a vantage point we rarely get to experience. The glare from the “daytime” Earth is so bright from orbit that it’s very difficult for the astronauts to see stars in the black sky above the planet’s orb. Their eyes never become adapted to the dark. During the brief orbital night, stars are naturally easier to see because the sun’s below the horizon and interference from artificial lights peppering the surface below is minor. It’s just so cool to see the Earth and night sky together in context – an illuminating activity for the armchair astronaut.

The Northern Cross, part of Draco and the Big Dipper were caught in this photo taken over Cairo, Egypt last month. The bottom of the cross is cut off by the curvature of the Earth. Credit: NASA

This next few days are the last ones for evening passes of the space station for a while. I’ve listed CST times below for the Duluth, Minn. region. For times for your city, click HERE or login at Heavens Above.

* Tonight starting at 4:41 p.m. Wow, that’s early -  only 4 minutes after sunset for Duluth! You may want to try for it anyway, because the station will rise in the northwest and pass directly overhead where it will be brighter than Jupiter. A second, very low pass starts at 6:18 p.m. in the southwestern sky.
* Monday Nov. 15 at 5:07 p.m. reasonably high pass across the southern sky moving s.west to s.east.
* Tuesday Nov. 16 at 5:34 p.m. Another low pass across the southwestern sky. That’s it for the week. The next round will occur in the morning sky in a couple weeks.

The white spot on Jupiter, first recorded by Christopher Go on November 9, has not only grown but become the site of new, darker clouds welling up from Jupiter's faded southern equatorial belt. The change in its appearance between the nights of Nov. 9-13 is dramatic. Credits (from left): Gary Walker, Rolando Chavez and Brian Combs

That little white spot on Jupiter we’ve been reporting on the past week appears to be the start of the revival or return of the planet’s dark southern equatorial belt (SEB). In recent days it’s expanded, and streamers of dark material are now developing around it. Based on the photos, graciously provided by three talented astrophotographers, the darker clouds should be visible visually in a moderate-sized telescope as a darker patch in the otherwise very faint southern stripe. Look around longitude 290 degrees (CMII) near the middle of the SEB.

To find what longitude on Jupiter is facing you any particular time at night, I recommend the free software tool called Meridian found at this website. After downloading and installing, set it up for your time zone, and then key in the time you’ll be out observing. Don’t expect to see a big, dark blotch quite yet. Look for a subtle dark mark or fleck in the belt using medium and high magnifications. Good luck!

Milky Way galaxy caught blowing bubbles

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Visible light is one small part of the electromagnetic spectrum. Everything from radio waves to gamma rays are forms of light. They differ only in their wavelengths and frequencies. Radio waves are as tall as buildings while the waves of gamma rays are only the size of an atom's nucleus. Credit: NASA

There are so many different kinds of light or electromagnetic radiation out there, and to see them as clearly as we see the visual world, you need a special instrument for each one. Radios decode invisible radio waves sent from a transmitter into music and news. A room filled with people slowly heats up from infrared radiation or heat radiating from our bodies. You’ll need a special infrared detector to actually see that heat, otherwise you’ll have to do with feeling sweaty. Our eyes detect the colors of the rainbow, which occupies a small section of the electromagnetic spectrum. Visual light has a wavelength of about 1/50,000 of an inch. That’s the distance between one crest to the next as light travels from here to there in the shape of a very regular, repeating wave. We see light’s rainbow colors and not radio waves or X-rays, because our eyes evolved on a planet around a star, and stars emit most of their light in the visual portion of the spectrum. We are attuned to the sun.

Diagram of a light wave. Credit:NOAA

UV light waves are two orders of magnitude shorter than the rainbow spectrum, and gamma rays are only 4 billionths of an inch or as long as subatomic particles. Light of short wavelength has a higher frequency, meaning its waves are packed together more tightly. Since we cannot deny the laws of physics, scientists long ago determined that light’s energy is proportional to its frequency. The higher the frequency, the more energy. No one’s ever going to get a sunburn standing in front of a radio antenna bathing in long wavelength-low frequency radio light, but too much exposure to short wavelength-higher frequency ultraviolet light from the sun will literally burn your skin tissues. Thankfully, our atmosphere and ozone layer protects us from much of the sun’s UV light as well as higher frequency (and more damaging) X-ray and gamma ray light.

NASA's Fermi space telescope scouts the sky for energetic activity - everything from black holes to gamma ray flashes shooting out the tops of thunderstorm clouds. Credit: NASA

To see all the universe has to offer in terms of light, scientists, working with engineers, develop and loft space-based telescopes above the atmosphere into Earth orbit, where they’re free to study stars, galaxies and black holes in their wavelength of choice. Things invisible to the eye suddenly stare you in the face when viewed in, literally, a different light. Infrared light penetrates the dusty cocoons surrounding newborn stars, allowing us to catch them right at birth. X-rays and gamma rays are shot into space by highly energetic events like gamma ray bursts or when matter gets sucked down into the maw of a black hole.

From end to end, the newly discovered gamma-ray bubbles extend 50,000 light-years, or roughly half of the Milky Way's diameter, as shown in this illustration. Credit: NASA's Goddard Space Flight Center

Just this week, NASA announced that its Fermi Gamma-ray Space Telescope detected a massive new structure in the Milky Way galaxy that may have created by an eruption from the supermassive black hole in the galactic core. Two gigantic bubbles, each 50,000 light years across, extend north and south of the galaxy’s center. If you could see them with your eyes, they’d span more than half the sky from the constellation Virgo (visible in spring) to Grus the Crane, a fall constellation. The structure’s shape and emissions suggest it was formed as a result of a large and relatively rapid energy release. Astronomers are considering two possibilities: jets of particles from the past powered by matter that fell into the Milky Way’s central black hole or the outflow of gas from a long-ago burst of star formation. Either one is exciting to contemplate. And neither would be known were it not for scientists opening a window on the gamma ray end of light’s grand spectrum.

The moon, Jupiter and Fomalhaut tonight. Created with Stellarium

A final observers’ note – if it’s clear by you this evening, you’ll see the first quarter moon make a nifty triangle with Jupiter and the bright star Fomalhaut (FOME-uh-low) in the southern fish or Piscis Austrinus. Fomalhaut is the brightest star so far discovered that’s orbited by an extrasolar planet.

Goddess of love awakes at dawn

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The left panel shows Venus tomorrow morning an hour before sunrise or about 6-6:15 a.m. for the Duluth region. The right panel shows the same scene a week from tomorrow. Notice that Venus will be higher up and hence easier to see then. Maps created with Stellarium

Venus was a Roman goddess associated with love and beauty – an appropriate name for the most brilliant of the planets. The ancient Greeks knew this “star” by two different names. When visible in the evening sky, it was called Hesperus, but when it rose in the east before sunrise, it was named Phosphorus, a word that means ‘light-bearing’. Nowadays you’ll often hear Venus referred to as either the morning or evening star.

Venus looks like a little crescent moon in binoculars and telescope.

This weekend the planet returns to view for early morning sky watchers. If you’ve got a nice open horizon to the southeast, you should have no trouble spying the goddess about “one fist” held at arm’s length above the horizon an hour before sunrise. Venus will be nearly lined up with Spica, Virgo’s brightest star, and Saturn higher up. A pair of 8x-10x binoculars carefully focused and held with steady hands will reveal Venus as a thin crescent. Train them on Saturn as well. Though you won’t be able to resolve the rings themselves, if you’re sharp-eyed, the planet should appear slightly oblong. That’s because the ring plane extends out on either side of the planet giving it a slightly stretched appearance.

Venus goes through phases like the moon as it orbits the sun. When it's a morning crescent, it lies to the right (west) of the sun as seen from Earth. Illustration: Bob King

In the next week, Venus will climb steadily higher in the eastern sky at dawn as it moves out and away from the sun from our perspective on Earth. You’ll also be able to see its crescent slowly fill out just like the moon’s. Both effects are due to the changing geometry between our planet and Venus as it revolves around the sun.

Most of you already know that Venus’ shiny appearance belies a hellish world, once we drop below the planet’s perpetual cloud cover. It’s nearly pure carbon dioxide atmosphere is so dense, that the pressure a person standing on the surface would experience is nearly the same as 3300 feet under Earth’s oceans. The cloud deck on the dayside is about 12 miles thick and an excellent reflector of light just like Earth’s clouds. That’s why Venus is so bright to the eye.

Photo taken by the Venera-13 lander on Venus in 1981 and reprocessed by Don P. Mitchell. It shows bedrock outcrops and gritty soil on a volcanic plain. The camera cover is in the foreground.

The Russians landed a number of Venera spacecraft on the planet’s surface in the ’70s and ’80s and measured temperatures of 800 degrees. Venus’ greater proximity to the sun than Earth’s led to a catastrophic greenhouse effect, which heated the surface and atmosphere,  boiling away any water it may once have had. Venus now has the hottest surface of any planet in the solar system. Throw in sulfuric acid rainfall, lightning and a barren volcanic landscape, you realize there’s much more to this planet than first meets the eye.

One last observing note for this evening: the Demon Star Algol will undergo one of its periodic fadings, as its larger, fainter companion star eclipses it tonight. It will dim from its normal 2.1 to magnitude 3.4 by 11:52 p.m. Central time. That means if you look anytime before 9, Algol will appear at its normal brightness.  From 10:30 onward, the fading should become obvious. Click HERE for a chart and more information.

The pretender meets the genuine article

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Using binoculars, look above tonight's crescent moon to find two bright stars: Alpha and Beta. Both are double stars that any pair of binoculars can split in two. Maps created with Stellarium

The crescent moon has been thickening all week and bright enough now to put a substantial shadow beneath your feet. Tonight if you look toward the moon around 6-6:30 p.m., you might just notice two stars nearly in line above it. Those are Capricornus the Sea Goat’s brightest stars, Alpha and Beta Capricorni. Chances are you’ll need binoculars to see them clearly because of the lunar glow.

Alpha is the wider of the two pairs of stars, but both are easy prey in most binoculars.

We’ve visited these two luminaries in an earlier blog, but in case you’ve never gotten acquainted, let me first introduce you to Alpha. It’s comprised of Alpha-1 and Alpha-2. Alpha-1 is the fainter and located 1/5 of the moon’s diameter to the northwest of brighter Alpha-2. Despite appearances, this seeming pair is an “optical” double or chance alignment of two stars at very different distances.

Alpha 1,2 Capricorni sure looks like a convincing double star in this photo. In reality, the brighter star is 109 light years away, while Alpha-2 Cap is 690! Credit: Wikipedia

But there’s more than meets the eye here. Each Alpha star is itself a true, physical double star when viewed through a small telescope. Alpha-1 has a 9th magnitude companion nearby (45 arc seconds) to the south-southwest, while Alpha-2′s companion is of similar brightness but farther out (154 arc seconds) to the south-southeast.

Like each of the Alphas, Beta is also a true double, where the two stars revolve about their common center of gravity as they travel through space together. Both of Beta’s components are very easy to see in binoculars, and the sight of two bright pairs of stars so near one another in the sky is unique … even if one is just pretending.

Mystery missile news plus join me for a jaunt on Mimas

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http://www.youtube.com/watch?v=eAZLYn44FeQ/

A spectacular contrail stands straight above the horizon last October at sunrise. The plane had moved on out of the frame as the contrail expanded. Photo: Bob King

You’ve probably heard about the mystery missile seen off the coast of southern California Monday night. Apparently no missile launches were underway at the time, and no hits or damage were reported. It appears more likely the “missile” was an aircraft contrail caught in the last rays of sunlight. Contrails form from water vapor in jet exhaust condenses into a streak of cloud behind the plane. If you watch the video, you’ll agree it’s a dramatic one. I once saw a contrail that looked similar to a rocket launch. It was early morning and a transcontinental jet shot straight up from the eastern sky at sunrise. The trail looked perfectly vertical, but I knew the plane’s great distance, combined with its flight path directly toward me, created the illusion.  In reality, the contrail was horizontal and parallel to the Earth’s surface the whole while. The contrail of the “mystery missile” may have been created in similar fashion by a plane flying toward the observer rather than away, giving the appearance of moving up instead of to the side.

This may not be the end of the story however. One other possibility I’ve heard raised is that it could still be a missile – one fired from a Navy ship or submarine off the coast. What do you think? I think once someone can positively identify which plane flight left the contrail, we’ll finally get a definitive answer.

Gary Walker got a nice photo of the spot last night. The dark spot is the shadow of the moon Io; the pinhead-sized white spot is to its right. Credit: Gary Walker

Excitement is building among amateur astronomers about the possible return of the stripe that disappeared on Jupiter earlier this year. Here’s another photo of the planet taken last night that shows the small, white spot that recently appeared in the faint Southern Equatorial Belt that might presage the belt’s return to its more typical dark appearance. For now, the planet still appears with only one prominent dark belt – the North Equatorial Belt or NEB. It’s easily visible in even the smallest telescopes at 40x and higher. The white spot has been growing since first seen a day ago. I’ll report more as events unfold.

A new image of Saturn's moon Mimas taken by the Cassini probe from a distance of 64,000 miles on October 16. Credit: NASA/JPL/Space Science Institute

I love space photos that fire the imagination, which is why I had to share these two of Saturn’s diminutive moon Mimas (MY-mas). This asteroid-sized moon is 246 miles across and absolutely saturated with craters. The big one the right, named Herschel after William Herschel, discoverer of the planet Uranus, measures 80 miles across and takes up almost 1/3 of the moon’s surface. The wallop inflicted from the impact must have come close to shattering the satellite to bits. Mimas is composed of mostly water ice and just large enough to compress itself through its own self-gravity into a nearly spherical body. Objects much below Mimas’ size tend to be irregular in shape because they lack the mass to crush themselves into a ball.

A portion of Saturn's F-ring is silhouetted against Mimas, which hovers in the background. Credit: NASA/JPL/Space Science Institute

Even though Mimas is big enough to join the ranks of sphericity, its gravity is only .008 times as much as gravity’s pull here on Earth. Put into perspective, if you weigh 130 lbs. here, you’d only weigh 1 lb. on Mimas. That’s a serious weight loss program! Some day astronauts will walk the surface of this little moon and feel so light and free, they’ll set aside the science experiments a moment and jump for joy. I would.