The 3-day-old crescent moon made a brief appearance Halloween night in this scene taken from downtown Duluth. The moon’s bumpy, distorted edge is caused by turbulent air. Photo: Bob King / Duluth News Tribune

The slender crescent moon showed for only a little while before setting tonight. Did you see it? It was well below Venus in bright twilight. Over the next few nights, watch for the moon to move up from the west and pass Venus tomorrow night, Nov. 1. The night before the election, it’s parked right beneath Jupiter in a scene that begs for your attention. Take a break from the campaign commercials around 6:30 on Monday the 3rd to enjoy these two luminaries. 

A very thin moon will hang just below Venus, low in the southwestern twilight sky this Halloween evening. The darker, outline of the moon is lit by sunlight reflected off the Earth, called Earthshine. — created with Stellarium

Plan to do a little trick or treating tonight? If you start early, I guarantee you’re in for a celestial treat. Look low in the southwest between 6 and 7 o’clock to find the "evening star" Venus, then drop your gaze just below the planet to spy the crescent moon. Thinner than a thin-lipped smile, the moon hovers just a few fingers above the horizon. If the sky is clear enough, you may even see the moon’s complete outline. The crescent itself is lit directly by the sun but the darker, spooky part is illuminated by sunlight reflecting off our planet. Since reflected light is much fainter than direct sunlight, that part of the moon is much dimmer than the crescent.

The Seven Sisters star cluster is framed by one of the jack o’lantern’s eyes in this map which shows the eastern sky around 8:30 p.m. tonight. The cluster is about three outstretched fists above the horizon. The ancient civilizations of the Maya, Aztecs and Celts used the group to mark the start of a special night celebrating the dead and supernatural. — created with Stellarium

Once darkness creeps in, look to the northeast for the Seven Sisters star cluster, otherwise known as the Pleiades (PLEE-uh-deez). This close-knit group of stars has long been associated with Halloween. Historians trace Halloween’s roots back to the ancient Celtic civilization in Britain. The Celts called it the day Samhain (SOW-in), which marked the end of the Celtic year and the beginning of the winter season. They believed that during Samhain the border between the living and the dead dissolved away, allowing deceased souls and other ne’er-do-wells to share the world with the living. In ancient times, the Pleiades reached culmination — their highest point in the sky — at midnight on Halloween night. Because of this coincidence, the cluster came to be associated with the dead and the dark side, a celestial signal to be on guard for evil as well as a reminder to honor the dead.

Because of the wobbling of Earth’s axis over a period of many thousands of years (called precession), the Seven Sisters no longer culminate at midnight on Halloween. That date is now delayed until November 21. No matter. The Pleiades are still nearly as high at midnight as in the olden days. If you look up at them tonight and feel a little chill, it might be more than just the temperature dropping.

This is one small piece of a large panorama in approximately true color of the area around the Phoenix lander. It shows the polygonal patterning of ground, similar to patterns in permafrost areas on Earth. Solar panels fill the foreground, while the spacecraft’s meteorology mast, topped by the telltale wind gauge, extends into the sky at left. Photo: NASA/JPL-Caltech/University Arizona/Texas A&M University

Remember the Phoenix Mars Lander, the one that found ice and has spent the past five months analyzing Mars dirt? It’s located on a lumpy plain in Mars’ arctic, where the temperature has been dropping steadily with the coming of autumn. The average high temperature there over the past week has been 50 below zero, while at night the mercury plunges to 141 below. Coupled with fewer hours of crucial sunlight to feed its solar panels, the ship hasn’t been able to fully charge the batteries that keep its electronics and heaters running.

Yesterday and today, Phoenix didn’t respond to attempts to communicate with it. NASA is fairly certain that lower power levels have triggered a program that keeps the craft "awake" for only two hours a day. Scientists will keep trying to talk to Phoenix and access its condition.

Everyone involved in the program has good reason to give themselves a big pat on the back. The lander’s primary mission was expected to last three months, but it’s still alive after more than five. Early on, the sun was up for 24 hours and 37 minutes a day (day length on Mars). Now it’s below the horizon for seven hours a night.

"It could be a matter of days, or weeks, before the daily power generated by Phoenix is less than needed to operate the spacecraft," said JPL mission manager Chris Lewicki. "We have only a few options left to reduce the energy usage."

If you’d like to explore the full 360-degree, panoramic photo of the Marscape around Phoenix, click on this link and take a break while the 11MB loads. When you return, rove on.

The goddess of beauty and love is poised above a red light in downtown Duluth across from the Civic Center two nights ago. The planet is easy to spot after 6 p.m. low in the southwestern sky. Photo: Bob King / Duluth News Tribune

Venus is the downtown planet — one of the few bright enough to register an impression with the casual skywatcher. Two nights ago, anyone who happened to approach the intersection of 5th Avenue West and 1st St. in Duluth, might have seen Venus perched atop the traffic light there around 6:15. Despite the great difference in brightness, Venus held her own.

If you live in Duluth, one of the easiest ways to spot Venus — if you’re traveling east at the end of the workday — is to pull off 21st Avenue East and the freeway and look back toward the city. You can’t miss its beacon-light appearance over the city skyline to the right of the Aerial Lift Bridge.
 

Mercury is still visible in the dawn sky around 7 a.m. for the next few mornings. Look two fists to the right of due east and one fist up from the horizon. There are no other stars in the area. The only one you’ll see is the planet. Photo: Bob King / Duluth News Tribune

Morning observers can still see Mercury for a few more days before it drops back down toward the sun. It popped up above my treeline just before 7 this morning (Oct. 30). You know you’re looking at Mercury because it’ll be the only bright "star" in the southeastern sky about 45-55 minutes before sunrise. Try to find a clearing where you can see down near the horizon. For the Upper Midwest, tomorrow morning’s clear sky forecast will give us Mercury-seekers another shot at the planet.

Two airplane vapor trails appear to twist together above
the Depot in downtown Duluth Wednesday afternoon. The
brilliant spot is a sundog, formed by sunlight’s interaction with
ice crystals in the clouds. Photo: Bob King / Duluth News Tribune

I’ve been seeing airplane vapor trails all day. I can’t help it. Ever since this morning’s spectacle, I’ve had my eyes skyward. On the way to a photo assignment, I happened to look up and see these two sinuous ones from downtown around 1:30 this afternoon (Oct. 29). You’ll notice that they’ve fattened up into broad bands of clouds as a result of higher than usual moisture in the upper atmosphere (see previous blog). At the same time, a brilliant sundog appeared nearby in the clouds to the left. Sundogs form in plate crystals in cirrus clouds. These are flat, hexagonal ice crystals that look very much like bathroom tiles. When the crystals are oriented with their broadsides horizontal, they bend or refract sunlight into two intensely bright spots 22 degrees on either side of the sun. In this case, the clouds were on just one side of the sun, so only one sundog formed. Notice that the sundog’s right edge is colored orangey-red while the left is pale blue. Red light gets bent less than blue, so the two colors separate from each other after they’re refracted by the ice.

The lower section of a vapor trail from an airplane (at top), casts a shadow onto the
sunrise-tinted air just after 7 this morning, October 29. Photo:
Bob King / Duluth News Tribune

I don’t normally run down the road at 7:15 in the morning but today was different. I found myself chasing a bright, elusive butterfly of an airplane contrail just before sunrise.

Maybe some of you were out and saw this too. I was walking the dog when I noticed a dark blue "ray" against the pink glow of the eastern sky just before sunrise. I figured it was a crepuscular ray from a distant cloud beyond the beyond the horizon. Sometimes clouds you can’t even see, shadow the rising sun and fillet its light into long shafts of light and shadow against the sky. This time however, a vapor trail from a commercial airplane played the role of a cloud. It cast a single, long shadow against the glowing pink air. The shadow towered almost to the top of the sky. I quickly ran home and dug out my camera before the scene faded away.

Because the air was relatively humid at the elevation of the plane, part of
its vapor trail expanded into a striking display of cirrus clouds just minutes before sunrise. Photo: Bob King / Duluth News Tribune

Vapor trails or contrails, as they’re called, form behind high-flying aircraft. As the planes burn fuel, they give off a swirling mix of water vapor and carbon dioxide. Just as you can "see your breath" in cold air, warm water vapor from the plane’s exhaust condenses in the cold, upper atmosphere into clouds of frozen droplets. Many contrails evaporate and disappear quickly in the dry air above 25,000 feet, but the atmosphere must have been more humid this morning. I watched in amazement as part of the contrail expanded into a spectacular display of cirrus clouds. Particles released from the burning jet fuel served as seeds for additional water in the air to condense and grow into this small, but very colorful display.

This satellite photo shows multiple contrails over heavily-trafficked, airplane corridors in the southeastern U.S. Under the right conditions, contrails can develop into extensive clouds. Photo: NASA

Water vapor released from the exhaust of a typical, high-flying passenger jet quickly crystallizes into streams of tiny, expanding clouds just the way your breath does on a cold winter day. The air temperature at 35,000 feet, the typical crusing altitude of a cross-country flight, is around 60 below zero. Photo: Adrian Pingstone

This is a sequence of 12 pictures taken over 45 minutes on March 12 this year as the Cassini spacecraft approached Saturn’s moon Enceladus. Cassini flew only 32 miles from the moon’s surface shortly after this sequence. Photos: NASA

NASA’s Cassini spacecraft continues to amaze with its closeup photos of Saturn’s moons. Once again, we feature icy Enceladus (en-CELL-uh-duss), famous for its icy geysers. Scientists are still analyzing the data from the very close flyby of the moon on October 9 as they gear up for another close pass on Halloween. As children count their candy, Cassini will be shooting detailed photos of the tiger stripe fractures that band the moon’s south polar region.

During a close flyby in August this year, Cassini snapped this photo of Enceladus’ fractured surface. See all those bumps? Those are blocks of water ice littered across the rugged landscape. The low sun angle really brings out their texture. Photo: NASA

Enceladus is the tiny dot at the center of the wispy arc. The moon is situated in one of Saturn’s many rings — this one called the E ring. Geysers spewing from fractures in its surface release water ice and other particles into the ring  The curvy jets of vapor near the moon extend many thousands of miles into space. Photo: NASA

Here you can see the blue-colored fractures across Enceladus’ south polar region. The moon’s surface is mostly water ice. Although small, Enceladus is geologically active. Water, ethane, propane and other chemicals have been found in the geysers shooting out of the stripes.

Use the bigger and brighter constellations Pegasus (the Great Square) and Cassiopeia to direct you to our two featured groups — Triangulum and Aries. Each is small enough to be covered by one outstretched fist. The map shows the sky around 8 p.m. over the coming week. — created with Stellarium

With the Square of Pegasus and Andromeda now dominating the eastern sky during the early evening hours, we can use these star groups to find a pair of small but distinctive constellations. Face east around 8 o’clock this coming week, and look a little more than halfway up in the sky to locate the Great Square. Andromeda peels off to the left of the Square, and if you keep moving in that direction, you’ll bump right into Cassiopeia. She’s represented by five stars in the shape of the letter W.

Now look just below Andromeda. See that little triangle tucked under there? That’s Triangulum the Triangle, known to the ancient Greeks as Deltoton, because its shape resembled their letter "delta". Three stars is all it takes to make this group, and none are particularly bright. But what it lacks in brightness, it more than makes up in an easy-to-recognize shape. Later this week, we’ll use Triangulum to find a galaxy you can see in binoculars.

Dip down below the Triangle, and you’ll see Aries the Ram, a constellation nearly as small as its neighbor. Aries is a member of the elite group of zodiac constellations, the ones that the sun, moon and planets travel through as they move across the sky in their orbits. Aries is planetless this year but come 2011, Jupiter will scootch up for a visit, and enliven this otherwise small group. Aries is another "3-star wonder" like Triangulum, and reminds me of a crooked index finger. A small telescope splits the westernmost star (furthest right), called Gamma Arietis, into a beautiful pair of two equally bright, white stars.

Each of the 88 constellations has its own size ranking based upon area. Aries is the 39th largest while Triangulum is well down the totem pole at 78th. That’s still 10 spots above the Southern Cross (Crux), smallest of the 88. The biggest? That would be Hydra the Water Snake.

Big or little, each constellation holds a place in mythology as well as special treats for visual and telescopic observers.

I spoke to a group of very young kids and their parents earlier today about the planets and stars. The kids were energized and eager to participate. When we watched the crashing asteroids video, they happily provided the sound of things blowing up. Then we discussed how you can’t hear anything in space because there’s no air. Their parents asked insightful questions. One question seemed simple on the surface: what’s the difference between a star like the sun, and a planet. The questioner posed it because he knew the Earth was hot inside like the sun.

A cutaway diagram shows the different layers of the Earth. The crust is the thinnest layer while the inner core and outer core combine to make up more than half the planet. Photo: Lawrence Livermore National Labs

This got me thinking. Yes, Earth is hot inside, and you don’t have to go all the way to the core to find that out. The Earth is divided into four main layers: crust, mantle, outer core and inner core. The rocky crust is about 18 miles thick, followed by the mantle, which starts below the crust and goes down some 1800 miles. Heat from the decay of radioactive elements like uranium makes the mantle rock soft and pliable. The lighter rocks that compose the continents float on top of the mantle, and get shoved around this way and that by the mantle’s plastic movement. That is the essence of plate tectonics.

Continuing our journey to the center of the Earth, we reach the outer core, which starts 1800 miles beneath our feet and extends 3,200 miles down. It’s composed of hot liquid iron and sulfur. Currents within the iron, coupled with Earth’s spin, create an invisible magnetic bubble around our planet called a magnetic field. Your compass points north because of the spinning iron in the outer core. The inner core is nearly pure iron and under such high pressure, it’s actually solid. Picture an 800 mile diameter ball of glowing, 11,000 degree metal. The tremendous pressure of all the matter above it keeps the inner core firm.

What we know about the Earth’s structure comes to us from studying how seismic waves from earthquakes are reflected from its interior. These waves travel where no human can.

Earth’s inner heat goes back to the beginning of its formation. As chunks of rock stuck together to form the growing planet 4 1/2 billion years ago, the energy of all the pieces falling together released an enormous amount of heat. Radioactive decay of uranium added even more, until the planet completely melted. Heavy stuff like iron sank to the core while the lighter rocks floated to the top. Long ago, the crust cooled enough for rocks to solidify and life to thrive, but the Earth’s interior still retains much of that early heat of gravitational collapse. The Earth radiates some of its heat energy into space but not enough to be felt by anything — not even the moon.

Temperatures of 40 million degrees in the sun’s core "cook" hydrogen into helium and release energy in the process. This energy slowly leaves the core and travels more than 400,000 miles before it reaches the surface as heat and light. The surface of the sun is called the photosphere; the corona is the sun’s atmosphere.

The sun is more than 100 times larger than the Earth and composed mostly of hot, flammable hydrogen gas. Checking its core temperature, we find the sun’s interior sizzles at 40 million degrees. At those temperatures and pressures, hydrogen atoms fuse together they way they do in manmade thermonuclear bombs. Every second, the sun fuses or converts 600 million tons of hydrogen atoms into 596 million tons of helium. The remaining four million tons is released as pure energy. The energy leaves the core and heads to the sun’s surface in a journey that lasts at least 10,000 years. From there it radiates out into space as light and heat. The sun has enough hydrogen to burn this way for billions of years. The next time the sun touches your cheek, think how much time it took that bit of warmth to travel from its origin in the sun’s center to the pleasant sensation on your face.

The sun and all the stars are literally burning spheres of gas that radiate prodigious amounts of heat and light across space. Lucky for us, we’re at the right distance from the sun for life to go wild. Stars are much too hot to provide a habitat for life — or anything solid for that matter. The cooler planets provide ideal nurseries for life the thrive. Photo: Halfdan

It’s interesting that the blazing solar surface, which we dare not stare at, is almost the same temperature as the center of the Earth. Our planet’s heat is modest and well-contained. We don’t share it with the rest of the planets. The sun and its kindred stars are flaming balls of hydrogen gas, bright enough to see across light years. They can’t help but share their bounty with the chilly, little planets. Remember too, that planets don’t shine by themselves, but only by the light they reflect from the sun. Switch off the sun, and Earth would orbit in eternal night.

Leaves from the aspen trees along my road stick to the clay road this morning. Photo: Bob King

These popple leaves were pasted across a short stretch of road near my home this morning. They held firm to their stems longer than most before finally breaking away overnight. I felt a little sad seeing them all down at once. Part of me wants to hold onto fall as long as I can. My friend Will can’t wait for snow. He told me that if the snowy forecast holds true today, he’ll put on Christmas music. I tend to fall in love with every season so I’m not worried about winter really. Every leaf that falls lets a little more starlight shine through. Soon Orion’s legs will twitch between bare twigs.