I know, I know. This is just weird but I couldn’t resist framing the pig with tonight’s Venus-moon conjunction. Here’s a link to a sumptuous video for you to check out. It’ll take you to the Astronomy Picture of the Day (APOD) site. The video’s creator, Till Credner, crunched 7,000 images into a 4-minute-long movie of the sky. It’s a work of natural art. My younger daughter and I thought the end was the best. Enjoy Credner’s big picture perspective on this final night of ’08.
The sky Wednesday evening (New Year’s Eve) around 5-5:30 p.m. features a double conjunction. Venus and the moon will be a snap to find. Mercury and Jupiter require a wide open horizon and will take a bit more effort. Created with Stellarium
I totally froze my posterior off this morning looking for a new supernova in a bright galaxy called M61 in Virgo. Yes, I found it but the price paid was dear. For the pleasure of seeing the remains of an exploding star, my fingers tingled for a good half hour. On a more summery note, May was in the air with the rising of Scorpius the Scorpion at dawn. This constellation always gives me hope for the coming of warmer weather no matter what the conditions of the moment.
This evening’s crescent moon is shown at left. Small telescope users will see Venus (right) about half lit. Because Venus revolves between the sun and Earth, it shows phases just like the moon. Created with Stellarium
Tonight is a special one. We have two close pairings of the moon and planets at the same time. The showpiece event will be the conjunction of the moon and Venus in the southwestern sky during twilight. You don’t want to miss this one. Much further down in the same direction, try to find the even closer pairing of Jupiter and Mercury. Binoculars will help you spot dimmer Mercury. Have a camera? Venus and the moon will be very easy to photograph in the fading blue. Since both are very bright, you should be able to just point and shoot.
In case you haven’t heard already, we get an extra second of time to party this New Year’s Eve. Official timekeepers around the world will insert a "leap second" into the minute before midnight tonight (Greenwich mean time). For those living in the Central time zone, the second will be added at 5:59 p.m. Time these days is kept by atomic clocks which are accurate to better than 100 trillionth of a second per day, or one second every 1,400,000 years. Unfortunately our rotating planet cannot measure up to those standards.
Because of the gravitational drag of the moon upon the Earth, which causes the daily tides, Earth’s rotation time is slowing down at the rate of 0.002 seconds per day per century. The moon’s gravity raises tidal bulges of water in the oceans, which drag against our planet’s crust, creating the friction that slows our rotation. In order to keep time standards in line with the slowing Earth, we have to insert an extra second into the day every couple years.
The moon’s gravity raises a pair of watery bulges in the Earth’s oceans called tides. Over time, the friction caused by the play between the moving water and the ocean basins slows the Earth’s rotation, lengthening the day. To keep clocks in sync, a leap second has to be added on occasion. Illustration: Bob King
As the Earth’s rotation slows down, that energy has to go somewhere. It’s transferred back to the moon, which responds by moving two inches farther away from Earth every year. Fascinating to think that the time displays on our microwave ovens, stoves and watches are bound up with the grand interplay of the Earth and moon. The closer we look, the more we see how are lives are touched by the cosmos.
Happy New Year! And I hope you enjoy every second of it.
The crescent moon continues to form pleasing alignments with more than just planets. It passed over downtown Duluth and the red beacons of the TV and radio towers in the "antennae farm" Tuesday evening. Details: 150mm lens, f/2.8, 1/15" at ISO 1600. Photo: Bob King
Can you see it? The winter Milky Way is the faint band of light
coursing through the center of the photo. Orion is at right.
Details: 16mm lens, f/2.8, 30-second exposure at ISO 1600.
Photos: Bob King/Duluth News Tribune
I stood on a snowy hill last night, looking up at the winter sky. The wind blew and clouds were just beginning to gather in the south. The stars popped and snapped in the turbulent air, while the Milky Way ran a delicate path from the W of Cassiopeia past Orion and down to the horizon.
The Milky Way in summer. Sagittarius is at right, where the big bulge is.
How many people have seen the winter Milky Way? I would guess not many. The summertime version that cuts through the Summer Triangle and spills southward into Sagittarius the Archer is much more familiar. That may be because we’re outside more in the summer, but it also has much to do with what direction we peer into our galaxy as the seasons change.
This artist illustration of the Milky Way galaxy is modeled on the most recent information. Our galaxy is a spiral with two huge arms and a bulgy bar of stars at its center. During summer, we face toward the center of the galaxy and see a bright Milky Way, while in winter we look out toward the edge in the direction of Auriga. Image credit: NASA/JPL-Caltech / my own annotations
The Milky Way is our home galaxy — a flattened disk with a bulging center containing upwards of 400 billion stars and measuring 100,000 light across. Our sun, with its entourage of planets, is one among the throng. From our perspective inside the disk, we see the stars pile up in the distance to create a narrow band of hazy, unresolved starlight called the Milky Way.
This is a picture of the entire Milky Way taken in infrared light which penetrates our galaxy’s dust to show its true outline. I’ve added the sun to show where we "live" in relation to center and outer edge. Credit: DIRBE
During summer nights, Earth faces in the direction of the galaxy’s center, where the stars are greatly concentrated. Not only that, but the sun is further from the center than the galaxy’s edge — 30,000 light years vs. 20,000. That means there’s more star stuff piled up in the summertime direction. It all adds up to a Milky Way bright enough to see even from suburban skies.
Six months later, we’ve orbited halfway around the sun. When night falls, we now face the winter constellations and the winter version of the Milky Way. If you compare the photos, taken with identical exposure times, the difference in brightness is obvious. On December evenings we look away from the center and into our galaxy’s "rural" townships. Just as streetlights drop away as we leave a bustling city, star numbers drop as you approach the Milky Way edge. As you gaze toward Auriga the Charioter and Perseus the Hero, you eye roams the outer arm of the galaxy until you see beyond into the emptiness of intergalactic space.
A trip to the country on a moonless winter night is the best way to appreciate the delicate curtain of the winter Milky Way. It reminds me of my own breath trailing up to the starry sky.
A Christmas wreath on First Street frames the delicate crescent moon Monday evening around 5 o’clock. Details: 200mm lens at f/3.5, 1/60" at ISO 800. Photos: Bob King Duluth News Tribune
The sky was perfect from downtown Duluth tonight. Even from the window here in the photo studio, we could see the thin crescent in the west along with Jupiter and Venus. I hope you had the opportunity as well. Mercury was difficult at first, but by about 5:20 p.m. even this shy planet showed itself briefly before setting.
If you missed it, there’s another fine conjunction of Venus and moon in the offing for New Year’s Eve. Stay tuned for info on Wednesday.
Another view of the lunar crescent accompanied by
Jupiter and Mercury (J and M) over Interstate 35 in Duluth.
The sky Monday evening (Dec. 29) around 5 o’clock. Find a spot with a wide view to the southwest. Find the moon and then use binoculars to bring in Jupiter and Mercury. Created with Stellarium
It’ll be nice to see the moon again tonight. The 2-day-old crescent returns in the company of three planets. How many you’ll see will depend on how clear your sky is and how low your horizon. If you go out about a half hour after sunset, or around 5 p.m. in our region, finding the moon should be easy. Just look low in the southwestern sky. Venus will be well to its upper left and beaming brightly.
A closer look at the moon and planets alignment tonight. The dimly lit outline of the moon is illuminated by sunlight reflected off the Earth, called Earthshine.
Now it gets a bit harder. The glow of early twilight competes with Jupiter and Mercury, which form a compact grouping lower in the southwest. Reach your arm out to the moon and look three fingers below and to its right to find Jupiter. It will look like a dim spark against the blue sky. The real question is whether you’ll be able to spot Mercury with your naked eye. It’s just a finger below Jupiter.
I always recommend cheating with binoculars in these situations. Focus on the moon and then sweep right to Jupiter and down to Mercury. You should have no problem finding both with optical aid. Then as the sky darkens, try to spot the planets with your eye alone. This has worked for me many times. If you find all three planets, let us know in the comments section below. Good luck!
This is how the Earth will look this evening from the "Earthlit" or dark portion of the moon’s surface. What a sight we’ll be! Our planet will appear in the constellation of Cancer the Crab. The phases of moon and Earth are complementary. When we see a crescent moon, moon dwellers see a nearly full Earth. When the moon’s almost full in our sky, the Earth’s a thin crescent in the lunar sky.
A striking display of cirrus clouds on Christmas Eve morning. Photo: Bob King
Wait until Orion is reasonably high in the southeastern sky before looking at the cluster Collinder 70. This map is drawn for around 9 o’clock. Created with Stellarium
Have you seen Collinder 70 lately? I bet you have. It’s another designation for the Belt of Orion, and a genuine star cluster like the Seven Sisters or the Hyades. Per Collinder was a Swedish astronomy graduate student. For his 1931 doctoral dissertation he wrote a paper about the properties of star clusters. Just to refresh, a star cluster is a bunch of stars all born together from a cloud of gas and dust called a nebula. They "feel" one another’s gravity and hang together for millions of years as a group, as they orbit the center of the Milky Way galaxy.
There are thousands of star clusters in our galaxy, more than enough to satisfy everyone, from the novice to the professional. Some are loose and gangly, while others a packed so tight, you can hardly separate star from star. The best look like jewels spilled from a treasure box.
The border of Collinder 70 (Orion’s Belt) is outlined in the picture above. This is how the cluster appears in a pair of binoculars. I’ve outlined the "Seahorse" figure. Created with Stellarium
Orion’s Belt is the 70th entry in Collinder’s catalog of 471 clusters. Most of these were discovered by other astronomers, but as he examined their photographs of the sky, Collinder discovered a few of his own. Collinder 70 contains about 125 stars, the brightest of which are the Belt stars Alnitak (al-NYE-tak), Alnilam (al-NYE-lam) and Mintaka (min-TAK-kuh). From a dark sky, you’ll begin to see there’s more to the Belt than at first meets the eye. Look carefully and at least a dozen more stars will pop out.
To really appreciate this gem, look at it through binoculars. In my 10x50s, the contrast of the brilliant "three" against a rich background of fainter stars arranged in loops and chains is a most heavenly sight. One particular chain of stars reminds me of a seahorse. Can you see it?
The Belt of Orion is shown in great detail in this time exposure photograph. Just below Alnitak (bright star, lower left), you can see the dark stump of the Horsehead Nebula. Credit: Digitized Sky Survey, ESA/ESO/NASA FITS Liberator
In long time exposure photographs of the Belt, you’ll see that the cluster is swathed in hazy nebulosity. Just below the leftmost Belt star, is a dark patch in the shape of a horse’s head. Called the Horsehead Nebula, it’s almost as well known as its neighbor, the Orion Nebula. The Horsehead is called a dark nebula because it stands out in silhouette against the bright, nebulous background. Although it’s obvious in photos, the Horsehead requires at least an 8-inch telescope and a good map to find. Within the nebula’s dusky borders, new stars are emerging from dense pockets of gas and dust like butterflies from their chrysalises. In the far future, it’s likely that fresh-faced stars within the Horsehead will light it up from within, changing its shape altogether.
This closeup of the Horsehead Nebula shows its chunky texture as well as several stars emerging from inside the nebula. Credit: European Southern Observatory (ESO)
Nothing stays put in the sky. Over several thousands of years, nebulas and clusters look much the same, but in the vastness of time beyond human imagination, stars evolve, clusters break apart and new ones form. A nebula like the Horsehead is worked by forces from within and without, changing its shape like clay in a child’s hands.
This person is silhouetted against the sun and its reflection on the water. Similarly, when the moon gets in line between the sun and Earth during New Moon, it shows in silhouette. Credit: Photos.com
Where the heck’s the moon? Nowhere to be found today. It’s in its New Moon phase, which means Luna is passing directly between the Earth and the sun. We never see a New Moon except under very special circumstances which I’ll describe in a moment. From our perspective, the moon appears in silhouette, the same way the setting sun silhouettes the person in the photo above. Because no sunlight reaches the side of the moon facing Earth, it’s almost completely dark.
The moon is shown for today (Dec. 27) in the left panel, when it passes below the sun in the daytime sky. At right, the New Moon on January 26 will precisely line up between sun and Earth, blocking the sun and creating a solar eclipse. Created with Stellarium
There’s one more reason you can’t see a New Moon — it’s in the daytime sky in the same direction as the sun. Sunlight and blue sky completely overwhelm it. If you could strip away the atmosphere and block the sun with your hand, the moon would be visible just below it today, faintly illuminated by light reflected from Earth’s oceans and clouds. If it weren’t for this Earthlight, the moon would be a black cutout against the starry sky.
If the moon’s orbit was "level" with Earth’s orbit around the sun, every time the moon was New, it would line up exactly between the Earth and sun, and briefly block it from view. This is what happens during a total solar eclipse. But the moon’s orbit is tilted some five degrees (the width of three fingers held against the sky) with respect to the Earth’s. Because of the tip, the moon usually misses the sun at New phase, passing a little above or below it.
The moon’s orbit (in red) is tilted five degrees with respect to the line connecting the Earth and the sun. This causes the moon to usually dip a little above or below the sun at the time of New Moon. The example above shows the moon and Earth positions for today’s New Moon. (Not to scale) Illustration: Bob King
As the moon tracks along its 27-day orbit, its path cuts across Earth’s orbit at two places. If the moon happens to be in New phase and at one of those intersections, the lineup will be exact, and we’ll see a solar eclipse. That’s why eclipses don’t happen every New Moon. Sometimes the lineups are close but not perfect. Then we experience a partial eclipse of the sun. If you think about it, the only time we ever really get to see a New Moon is when it glides across the sun’s face during an eclipse.
In this illustration, the moon lines up directly between sun and Earth. When the moon blocks the sun, it casts a small, dark shadow on the Earth called the umbra. Since the moon keeps moving in its orbit, the umbral shadow moves across the Earth. If it passes over your town, you’ll see a total solar eclipse. If you’re outside the umbra, you see a partial one. For the scoop on upcoming eclipses, click here. Credit: Sagredo
Two to five solar eclipses occur each year and sometimes none are total. There’s one on January 26, but you’ll have to travel to the middle of the South Atlantic Ocean to catch it. The next solar eclipse for our region — a partial one — will occur on May 21, 2012. The next total solar eclipse for the United States is August 21, 2017 when the path of totality will cut straight across the state of Nebraska. I am so hoping to be around for that one!
The star Procyon (lower left), in the little constellation of Canis Minor, rises in the eastern sky, heralding the arrival of Sirius. The left map shows the sky as you look east about 7 p.m. while the map at right is drawn for 8:30-9 p.m. after Sirius has cleared the horizon. Created with Stellarium
Yesterday we looked at Sirius, the sky’s brightest star. Another of its claims to fame is how vividly it twinkles. From northern latitudes, Sirius never climbs very high in the sky, which means it’s affected more by the thicker, denser air in the lower atmosphere than stars higher up. All stars twinkle to some degree from atmospheric turbulence. If you’ve ever flown in a plane before, you know what turbulence means. Sudden changes in the wind caused by jet streams, cold or warm fronts, and changes in atmospheric pressure might make you loose your lunch. Atmospheric turbulence also affects a star’s light, causing it to shift this way and that and even change color.
Stars are at such great distances from us that almost all appear as mere points of light in even the largest telescopes. You can envision their light as the most delicate of threads reaching vast distances across space only to get jounced around by our ever-active atmosphere. The brighter the star, the more obvious the twinkling. Being brightest, Sirius twinkles best of all. Sometimes the twinkling is rapid and dramatic. On those nights, take your binoculars and point them at Sirius. You’ll see it twinkle red, green, blue — every hue of the rainbow. Air pockets of different densities bend and refract its light to create an almost kaleidoscopic effect.
Both Sirius and Procyon are considerably larger than our sun — 3.5x the sun’s diameter for Procyon, and 4x for Sirius. All three stars shine by converting the gas hydrogen into helium in their blazingly hot cores. During the process, a small fraction of gas is transformed into pure energy, the source of starlight. Illustration: Bob King
No great star like Sirius should ever be without an official announcement of it imminent arrival. This job falls to Procyon (PRO-see-on), the brightest star in Canis Minor, the Little Dog. Its name literally means "before the dog", and refers to its appearance in the east shortly before Sirius rises. From Duluth tonight (Dec. 26), Procyon rises at 6:59 p.m., 42 minutes before Sirius. Like an eager puppy, Procyon jumps up in the east with great enthusiasm, running ahead of Sirius as if daring the old dog to get up and play.
Sirius photographed by the Hubble Space Telescope. Sirius’ companion star, Sirius B, is the tiny spot on the lower left next to the spike. It’s a white dwarf, the remaining core of a star after it uses up all its hydrogen fuel. Sirius B packs an entire sun’s worth of matter into a sphere the size of the Earth. It’s so dense, a thimbleful of the material weighs over a ton. Coincidentally, Procyon also has a white dwarf companion orbiting it called Procyon B. Photo: HST, NASA
If you’d like to join in the fun, wait until after 9 o’clock the next clear night. After you’ve found Procyon and Sirius, look above and left of Orion’s Belt to spot Betelgeuse, Orion’s bright ruby. Connect all three to form the Winter Triangle, one of the winter sky’s best known asterisms. We’ll use the Triangle over the next couple months to guide us to many more celestial sights.
(Canis Minor is a small constellation
with one bright star. Stellarium)
A family portrait of Charles and Dotty Duke, and their sons Charles and Tom, face the vacuum of space on the battered surface of the moon in this photo taken by Apollo astronaut Charles Duke. His bootprint is in the foreground. Photo: NASA
Christmas for many of us means a chance to get together with our extended family again. We just returned from a visit with my mom, dad, younger brother and his wife. Our time was rich in fun, food and conversation. Making that family connection gives us a sense of who we are and where we came from. Just ask Apollo 16 astronaut Charlie Duke. When he left for the moon in April 1972, he carried with him a carefully-wrapped portrait of his family.
During the moonwalkers’ busy schedule of setting up scientific instruments and collecting rock samples, Duke somehow found time to lay the portrait on the lunar surface, and take a picture of it. Through bitter cosmic cold, and under the searing radiation of the sun, the photo remains there to this day — a tender statement of family connection on an alien world.
This map shows the sky around 9 p.m. tonight when brilliant Sirius just begins to clear the trees. Shoot an imaginary arrow from Orion’s Belt toward the horizon to find it. Created with Stellarium
Clear skies are forecast for our region tonight. We’ve all heard the Christmas story of the Wise Men following the star in the east. Though no one really knows whether the Bible refers to a natural phenomenon, like a conjunction of planets or a nova, there is a most spectacular star that appears in the southeast every December. It’s Sirius (SEER-ee-us) in the constellation of Canis Major, the Big Dog. For obvious reasons, Sirius is often called by its nickname ‘The Dog Star’. You can easily find it by using the ‘three stars in a row’ that compose Orion’s Belt.
Sirius is the brightest star in the sky. It doesn’t hurt that it’s twice as massive as the sun and 25 times brighter, but one of the main reasons it’s so bright is its nearness to Earth — a mere 8.6 light years. That’s ‘in the neighborhood’ by stellar standards. Most of the stars we see are dozens to hundreds of light years away. Just to give you a feel for distances in the sky, it takes light, traveling at 186,000 miles per second, about 8 minutes to get here from the sun. Light from Sirius takes 8.6 years, while Deneb, in the Northern Cross, requires over 1000 years! Yes, Sirius is close. On a clear night you can almost hear it howling. Check it out later tonight.