Tag Archives: Pleiades

Waning moon stalks Jupiter as Halloween approaches

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The waning gibbous moon heads toward Jupiter in the next few nights. The two will be closest – only 2 degrees apart – the day after Halloween. The map shows the sky facing east around 9:30 p.m. local time. Created with Stellarium

Jupiter doesn’t know it, but the stealthy moon is on track to make a close approach to the planet this Thursday night. Tonight you’ll find the waning gibbous moon in edging into the constellation Taurus about one outstretched fist to the right of the Seven Sisters or Pleiades. Since it’s only one day past full, you’ll probably need binoculars to see the cluster. On Thursday, Jupiter and the slimming moon combine forces to shine with a mesmerizing radiance in the northeast around 9:30 p.m. and later.

Jupiter’s innermost bright moon Io moves into the planet’s shadow starting at 11:10 p.m. CDT this evening. Even a small telescope will show the eclipse. Create with Meridian software

If you have a telescope, you’ll see Jupiter’s moon Io to disappear as it’s eclipsed by Jove’s giant shadow. Eclipse occurs at 11:10 p.m. (CDT) tonight Oct. 30. Start watching a few minutes before that time. By 11:15 the moon will be gone.

Jupiter Wednesday night Oct. 31 at 9:30 p.m. (CDT) with Io’s shadow transit already in progress. South is up in both Jupiter panels. Created with Meridian software

Halloween night offers up yet another telescopic treat. As soon as Jupiter’s up in the east, you can follow the progress of Io’s inky shadow as it tracks across the clouds of the planet’s southern hemisphere. The event is called a shadow transit.

It begins at 8:18 and wraps up at 10:28 p.m. If you return at around 11:15 p.m. you’re in for another surprise – Io itself will exit the west side of the planet and appear like a bright pearl pinned to Jupiter’s limb.

Jupiter on Oct. 14 with the shadow of Io visible as a dark dot inside the planet’s limb. The two prominent stripes are the north and south equatorial cloud belts. Click image to see the video of Jupiter rotating. Credit: Damian Peach

Amateur astronomer and astrophotographer Damian Peach, who takes some of the finest, most detailed pictures of the planets and moon, recently compiled a sequence of photos of Jupiter made between Oct. 10 and 13 into a very cool animation. Click the link to watch an entire 9.8 hour rotation of the planet condensed into less than a minute. Peach hails from the UK and uses an 11.8 inch (30cm) Meade Schmidt-Cassegrain for his photography.

What’s lovelier than the Pleiades in September?

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The Pleiades star cluster rises between the trees in the northeastern sky on a recent night. The attractive group comes up around 10 p.m. local time and is high in the east around midnight. Photo: Bob King

What’s lovelier on a September night than watching the Pleiades rise in the east? Whether you’re alone or in a group, when the “seven sisters” appear, everyone stops what they’re doing for a minute to admire this most beautiful star cluster. When I’m at a star party, someone inevitably calls out their first appearance like a courier announcing Caesar’s return to Rome. Yes, they’re that big of a deal.

The Pleiades represent the seven daughters of Atlas and Pleione, which are also members of the dipper-shaped cluster. Asterope and Calaeno usually require binoculars to see. Credit: John Lanoue

The name Pleiades (PLEE-uh-deez)  comes from ancient Greek myth. Also called the Seven Sisters Cluster, the stars represent the seven daughters of the titan Atlas and sea-nymph Pleione. The origin of the name is uncertain but may be related to the word plein ( ‘to sail’), since the stars’ conjunction with the sun in spring and rising at sunset in fall marked the beginning and end of the sailing season in ancient Greece. Other possible origins include peleiades (‘flock of doves’) which is consistent with the story of Zeus turning the sisters into doves as they were pursued by Orion.

An interpretation of the Pleiades from a 10th century Anglo-Saxon manuscript called a codex (Codex Vossianus 79).

Being a compact group of bright stars quite unlike any other in the sky, the Pleiades have figured prominently in the sky lore of many cultures. Most people I know refer to the cluster as a “little dipper” or miniature version of the Big Dipper. My eye sees a shopping cart or baby stroller. Here’s just a small sampling of how others have interpreted their appearance:

* Japan – a strainer or dabs of paint on the sky
*  Celtic mythology – associated with a fall festival of the dead since the cluster rose in the east as the sun disappeared in the west in that season
* Maya Indians – a rattlesnake’s tail
* Mono people (Native Americans) of California – Six wives who loved onions more than their husbands and who now live happily in the sky.
*  Babylonians – Mul Mul or “star of stars”
* Maori of New Zealand – “Matariki” or little eyes
* Czech Republic – “Kuratka” or many small, young chickens

It’s their sheer compactness that delights the eye. They’re gathered so close together they seem enveloped in a fuzzy cocoon that further adds to their appeal. Poet Alfred Lord Tennyson said it best in his poem Locksley Hall:

“Many a night from yonder ivied casement, ere I went to rest,
Did I look on great Orion sloping slowly to the West.

Many a night I saw the Pleiads, rising thro’ the mellow shade,
Glitter like a swarm of fire-flies tangled in a silver braid.”

The Pleiades cluster contains about 1000 stars. Its core – what we see with the naked eye – is about 8 light years across or twice the distance to Alpha Centauri. Most of its stars are young, hot and blue. The cloudiness around the stars is starlight reflecting off a dust cloud through which the cluster is currently passing. Credit: NASA

My old friend Roy would recite those famous lines on winter nights observing together from my old suburban Chicago neighborhood. I have many memories of good times with the Pleiades and many associations, too. They’re always a reminder of the coming winter when they sail high across the southern sky. In mid-September the sisters make  their first appearance in the east around 10 o’clock.; by mid-October they’re up at 8.

The Pleiades are exactly what they appear to be – a real, physically connected cluster of stars. They coalesced from a cloud of dust and gas about 100 million years ago smack in the middle between the appearance of the first flowering plants and disappearance of the dinosaurs. Located about 440 light years from the Earth, the light you see tonight left the cluster in the late 1500s, some 30 years before Galileo first pointed his telescope at them. His sketch shows many more stars that you can see with the naked eye alone.

Sketches of the Pleiades by Galileo. Notice the line of stars stretching to the left of the “dipper”.

At a casual glance, you’ll probably see just five or six stars, but if you peer closely, the seventh, Pleione, will materialize. The real fun starts when you avert your vision and look around rather than directly at the cluster. A smattering of faint stars will suddenly pop into view boosting your total to 8, 10, 14??

Give it a try, then beam in on them with binoculars. Whoa! Instead of seven, you’ll see many dozens, including a most attractive stream of stars  shown so well in Galileo’s drawing.

I wish you smooth sailing with the daughters of the night.

Venus and her sisters; Tell time at night with the Big Dipper sky clock

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Venus and the Seven Sisters star cluster last night - what a sight! Details: 200mm at f/5.6, ISO 800 and 20-second guided exposure. Photo: Bob King

It was great to stand in the front yard last night under a clear sky and see Venus and the Pleiades. A casual glance showed a sprinkling of little stars around the brilliant planet. Binoculars gave the best view of the “8 sisters” with Venus the dominant by far. I tried to see how many Pleiads I could count with the naked eye. The five brightest were easy enough but the sixth – Taygeta – was tricky. Pleione was beyond me. It was also fun to recall that 8 years ago to the day I stood in the yard and watched Venus in almost the same position inside the cluster. Apparently I was on time for my next appointment.

A wider view of Venus and the Pleiades along with Jupiter (at bottom). 35mm at f/5.6, ISO 800 and 20 seconds. Photo: Bob King

Tonight Venus glides up and to the left of the star cluster, so if it was cloudy by you last night, you have another shot at seeing them together.

After a good swig of the western sky show, I checked out a new paperless way to tell time using the Big Dipper and North Star. In yesterday’s blog we looked at a simple star clock you can make with paper and scissors. Today we’ll pretend we’re out at night with neither watch nor guide.

The map below shows the North Star as the center of a clock face with the two Pointer Stars in the Bowl of the Big Dipper as the hour hand.  Our example shows the sky at 9 p.m. local time.

To start, face north and look high in the northeastern sky to find the Big Dipper. Draw a line through the two Pointer Stars until you arrive at the first easy-to-see star. That’s the North Star or Polaris. It’s about 5 “Pointer lengths” away. The line connecting the North Star and Pointer Stars now becomes the hour hand on our celestial clock.

To find the time using the Big Dipper and North Star we imagine the northern sky as the face of a clock. Key hours are marked. Illustrations created with Chris Marriott's SkyMap

1. Estimate the time the Pointer hour hand indicates to the nearest quarter hour (15 minutes). In our example, it’s 1 o’clock.

2. This next step is key. We now adjust the clock for the time of year. On March 7, the Pointer Stars stand directly above the North Star at midnight standard time. All you have to do is figure to the nearest quarter month how much time has elapsed since March 7. Since tonight’s April 4th, that rounds off to one (1) month. If it was April 15 instead, the number would be 1 1/4 or 1.25.

3. Add the two figures from above and then multiply by 2 as in: 1 (from 1 o’clock) and 1 (one month) = 2. Then 2 x 2 = 4. Now subtract that sum from 24, so 24-4 = 20. The result will be the time in 24-hour or military style. 20 hours military is the 20th hour of the day or 8 p.m. Add an hour for daylight-saving time and we arrive at 9 p.m. By gosh, that’s correct! Note: If your final number is greater than 24, subtract from 48 instead.

Facing north about 5:15 this morning, the Pointers were now off the left of the North Star in the 9 o'clock position. I figured the time as: 9+1=10. Multiply by 2 = 20. Subtract 24 - 20 = 4 and added one hour for DST to arrive at 5 or 5 a.m. Close enough.

It’s important to remember to add that hour for daylight time when it’s in use and to face north. With practice – and checking against a watch for accuracy – you’ll soon become a master of time at night. Be aware that where you are within your time zone will affect your time estimate. If you try this a few times, you’ll soon be able to factor that in and fine tune your time. I tried this simple method both last night and this morning before dawn and was frankly surprised how well it worked. If you’ve got some time on your hands, let us know how you fare.

Venusian delights; Orion preps for leave of absence

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The moon drops by Mars and Regulus in Leo Monday and Tuesday nights. Maps created with Stellarium

Watch tonight as the gibbous moon nears Regulus and Mars in Leo high in the southeast. The trio will form a line about 10 degrees long or a fist held at arm’s length against the sky. In the western sky, don’t forget Venus and the Pleiades or Seven Sisters star cluster. The brilliant planet enters into the cluster’s domain this evening. A pair of binoculars will give a wonderful view. Tomorrow night Venus will join the sisters for a sleepover.

Binocular view of Venus and the Pleiades tonight. Try to catch the two if weather allows. It won't happen again for 8 years.

When you’re out at nightfall this week, give a look toward Orion, now tipping over in the western sky by 9-10 p.m. In another few weeks, the hunter will disappear from view when he’s swallowed up by evening twilight.

You’ll notice that Orion’s Belt is now nearly horizontal. The left end points to twinkling Sirius, the brilliant white star in the south-southwest; the right end toward the orange star Aldebaran and the V-shaped Hyades star cluster and beyond to the Pleiades.

Orion tips to the west by 9 o'clock in the evening during early April. Use his Belt to navigate a nearly straight line to Sirius, the Hyades and Pleiades. Photo: Bob King

This laying-down” of Orion is a sure sign of winter’s passing. Time to bury the sword and embrace the season’s rain, warmth, ticks, flowers, mud and greenery.

Venus and Pleiades on a beautiful collision course

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Night by night Venus and the Pleiades approach each other until the planet's smack inside the cluster next Wednesday evening April 3. Positions shown for around 9 p.m. CDT. Created with Stellarium

If you enjoyed the dazzle of Jupiter and Venus at dusk recently, get ready for Act II, when Venus passes through the most famous star cluster of all, the Pleiades. Also known as the Seven Sisters cluster, the Pleiades is that little bunch of stars in the shape of a miniature dipper. It’s located in the zodiac constellation Taurus the Bull and sparkles in the western sky at nightfall.

The stars in the Pleiades are named after the seven daughters of Atlas. Dad and mom (Pleione) are also included. Most people can see six with ease. Pleione is more difficult; Celaeno and Asterope are generally not visible. Credit: John Lanoue

Although not as showy as Jupiter and Venus together, rarely does a bright planet passes directly through the sky’s brightest star cluster. The Pleiades represent the seven daughters of Atlas, the Greek god who carried the heavens on his shoulders. Located 425 light years from Earth, the cluster is rich in hot, blue-white stars. Astronomers estimate its age at 100 million years.

Venus inches closer to the sisters night by night until joining them on April 3. That evening the planet will blaze just to the left of cluster’s brightest star Alcyone (al-SYE-oh-nee). Don’t expect Venus to quietly blend in. At magnitude -4.4, it shines more than a thousand times brighter than 3rd magnitude Alcyone.

Brilliant Venus in the Seven Sisters cluster back on April 3, 2004. Photo: Bob King

Over millions of years, the regular and repeating gravitational attraction between Venus and Earth have caused their orbits to reach what astronomers call “near-resonance”. The two planets are now in a comfortable relationship such that for every 8 orbits Earth makes around the sun, Venus completes 13. Seen from Earth, Venus returns to nearly the exact same part of the sky every 8 years.

No matter when you look up at Venus, you’ll see it there again in 8 years. And if you guessed that the last Venus-Pleiades visit occurred in April 2004, you’re right!

I’m curious how many cluster stars will be visible with the naked eye with Venus tucked inside on April 3. The best views will be with binoculars and small, low power telescopes. If you’ve never looked at the Pleiades before with optical aid, you’ll love the view. So many more stars are visible, and with the brightest planet in their midst, get ready for a spectacle.

Auroras way up north plus the moon visits a famous star cluster

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Andy Keen, who lives in Northern Lapland in Finland, had a great view of the northern lights last night. "The colours were fabulous - green, red, pink, turquoise, neon blue - the full works," he said. Details: 14mm lens at f/2.8, ISO 800 and 4-second exposure. Click image to see more photos and a video on Keen's website.

Bright auroras have dressed up the Arctic sky the past two nights after the sun’s wind of charged particles – electrons and protons – pried an opening in Earth’s magnetic field and spiraled down into the upper atmosphere. There’s still a possibility for aurora tonight primarily for those living in the far north. Take a look if clear skies are in your forecast. We’ve had clouds in my town and a now a blizzard on its way, so my eyes will be blinkered for a while.

The moon will be near the Seven Sisters star cluster tonight (Feb. 28) and the Hyades cluster tomorrow night. Created with Stellarium

Tonight the quarter moon is tucked under everyone’s favorite naked eye star cluster called the Pleiades (PLEE-uh-deez) or Seven Sisters. The cluster is shaped like a tiny dipper, and when the moon’s not quite so close to it, most of us see six or seven stars with ease. Binoculars show dozens more. The Pleiades, located about 400 light years from Earth, is a relatively young group of stars compared to our sun; their birth from a massive cloud of dust and gas happened during the age of the dinosaurs a mere 100 million years ago. It’s also the brightest star cluster in the sky.

The Hyades form a distinctive V-shape that represents the face of Taurus the Bull. The bright star at left, called Aldebaran, is a foreground star and not a member of the cluster. It's often referred to as the bull's eye. Photo: Bob King

One outstretched fist to the left or east of the Seven Sisters is a larger, looser star cluster called the Hyades (HY-uh-deez). It’s the closest star cluster to our solar system at a distance of 151 light years. That’s one of the reasons it appears larger and more spread out than the neighboring Pleiades. The Hyades occupy a volume of space some 30 light years across and are moving through space together like a school of fish.

Despite its closeness, the Hyades are fainter than the Pleiades because its stars are more than six times older with ages around 625 million years.

Clusters are born with stars of all different masses. Mass or the amount of stuff a star has determines its temperature, color and how fast it devours the nuclear fuel in its core. The biggest, brightest ones burn up their fuel fastest, either ending their lives as supernovas or evolving into dim white dwarfs. Because of the Hyades rather advanced age, its brightest stars have either blown up or faded away, leaving the smaller, fainter but more frugal fuel users – basically stars with masses similar to or less than the sun – dominating the herd.

Astronomers uses the "eyes" of the Earth on a particular date and then again six months later to measure a nearby star’s parallax or shift against the more distant background stars. Illustration: Bob King

The Hyades are probably the most famous star cluster in the world of astronomy, even eclipsing the Pleiades in importance. Why? Because they were a key steppingstone into deep space as astronomers looked for ways to determine distances to remote stars.

Astronomers use parallax, the apparent shift of nearby stars against the distant background stars when seen from two widely-separated points of view, to measure the distance to the closer stars. You can see a parallax shift when you hold a finger at the end of your nose while opening and closing your right and left eyes in a blinking pattern. Your finger will appear to shift back and forth against the distant background. Measure the distance between your eyes and the angle your finger makes, and you can find the distance to your finger with simple trigonometry.

In this illustration, you can see how a star shifts against the background ones when photographed through a high powered, professional telescope on opposite sides of Earth’s orbit. Illustration: Bob King

To measure the distance to  a star using parallax, astronomers need a super-wide set of eyes, because even the closest ones are so incredibly far away, they show only minute shifts.

That’s where Earth’s orbit comes in (see above). We measure the star’s position against the background stars on one side of our orbit and then again six months later when we’re on the other side. Since we know the baseline length – 180 million miles – and can measure the parallax shift, we can easily calculate the star’s distance. It works beautifully -  at least out to about 300 light years. After that, the shifts are too small to measure directly.

That’s where the Hyades come in. The cluster contain lots of stars of many different types, and since it’s so close, we can use parallax to measure its distance. Next we find a cluster with similar stars but too far away to show a shift and measure the brightnesses of those stars. Since we’ve determined that its stars are the same types as those in the Hyades but say, 100 times fainter, we know they must be 10 times farther away or approximately 1,500 light years from Earth. Bingo! We’ve taken another step deeper into the cosmos.

(Just an FYI – The intensity of light falls off as the square of the distance. It’s known as the inverse square law. 100 times fainter = 10 times farther. 10,000 times fainter = 100 times farther.)

Using the Hyades stars this way, astronomers have hopscotched into the depths of the galaxy. A most clever way to “expand” our universe, don’t you think? To learn more about parallax, please click HERE, and don’t forget to send the Hyades a “thank you” this week.

Dark light of the moon and shifting sunset shadows

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The moon just a day past first quarter phase. Though brilliant to the eye, it's nearly 10 times fainter than the full moon. Photo: Bob King

I skied in the woods under last night’s first quarter moon and learned something about trust. In the mix of shadow and low light, I could see the trail clearly only half the time. Along the stretches where darkness or shadow obscured the track, I kept the faith while gravity and momentum did their thing. After an hour of skiing, I’m happy to report there were no falls and only a few moments of trepidation. I learned to really open up my eyes as well as to trust what lay ahead.

A first quarter moon is only 1/10 as bright as a full moon. That doesn’t sound like much, but it’s a surprising amount of light really.

Part of the trail was lit by artificial light. After leaving this cocoon of easy navigation, the woods looks dark indeed, but within five minutes, my eyes were dark-adapted all over again. The trail grew more distinct, peeling birch bark showed shiny highlights under the moonlight, and occasional snow crystals sparkled off to sides.

Tonight the moon will have swelled a bit beyond half and shine a few percent brighter than last night. It’s high up in the south at nightfall just 2 degrees below the Seven Sisters (Pleiades) star cluster. If you block the moon with your thumb and look above and to its right, you might be able to see the cluster with your naked eye. City dwellers, for whom the Pleiades are never visible with the naked eye even under moonless skies, can use the moon as a guide to find them with binoculars.

Tonight the moon will be between the Pleiades and Hyades star clusters. Created with Stellarium

The moon’s high position in the sky reminds us of where the sun once was … and will be again. On and around May 20, the sun will occupy the moon’s spot and remain up for hours just as the moon will tonight. Moonrise this morning was around 10:30 and it won’t set until tomorrow around 2:30 a.m.

Five images taken over 8 minutes of sunset over the Sierra Nevada Mountains. Credit: Andrew Kirk

Yesterday, Andrew Kirk of Bishop, Calif. sent me a fascinating series of photos taken near sunset showing the shadows of mountain peaks cast on dust in the air. Look at each frame closely and you’ll notice at least two things: the shadows lengthen with time, just as your shadow does near sunset, and they rotate about the sun pivoting from right to left. That’s because the sun is not only going down but also moving to the right or north at the same time.

If you watch your own shadow at sunset, it will pivot in the same way as the ones in the photo do. Most amazing is that only 8 minutes elapsed between the top and bottom images. Thanks Andrew for sharing your unique and beautiful perspective on our planet’s daily motion!

Moon and Pleiades a sweet sight in binoculars tonight

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The waning gibbous moon lines up closely with the Seven Sisters star cluster tonight. The bright star Capella in the constellation of Auriga the Charioteer is about four outstretched fists to the left of the moon. Using Capella and the moon, try to find the stars Mirfak and Algol in Perseus. Later this week we'll revisit them. Created with Stellarium

Tonight’s moon comes up in the northeastern sky in Taurus the Bull. Since it’s five days past full phase, its light has diminished enough so that sky watchers in rural areas can again see the Milky Way slicing across the southern sky. We’re in for a treat because the moon will be very close to the Pleiades or Seven Sisters star cluster. It rises relatively early around 8:45 p.m., but the best time to see this fine pairing is at 10 p.m. or later, when they’ve cleared trees and buildings. While not a great naked eye event, due to the lunar glare, the view in binoculars will be outstanding. Both will fit easily in the same field of view and stand in striking contrast to one another.

As the moon revolves around the Earth, the angle it makes between us and the sun widens. This exposes more of the moon to sunlight and its phase fills out. After full, the angle narrows and the phases play out in reverse. Credit: NASA

This past Saturday night my older daughter had to determine the moon’s phase for a homework assignment. She hesitated but then got the correct answer: waning gibbous.

The moon fills out from the time we first see it as a thin crescent in evening twilight up until full moon, when the side facing us is 100% illuminated by the sun. The line separating the daylight from the nighttime portion of the moon is called the terminator. Night after night, the terminator moves to the left or east exposing more of the moon. Picture the terminator as the line of advancing sunrise. Features that were previously in darkness rotate into the sunshine as the angle between the moon, Earth and sun widens with each passing night. Unlike Earth, where the nights last a matter of hours, a typical lunar night lasts almost two weeks. That’s because it takes the moon almost a month (27.3 days) to rotate once on its axis. A night on the moon is a very chilly experience. With no atmosphere to speak of and plenty of darkness to go around, temperatures plummet to an average of 250 below Fahrenheit.

When waxing toward full moon, the terminator or sunrise line advances to the left and exposes fresh moonscapes. After full moon, the terminator becomes the advancing line of sunset. It once again moves to the left (east) night after night until nothing's left but a thin crescent at dawn. Photos: Bob King

When the moon is full, it’s directly opposite the sun and all lit up the same way someone might shine a big, bright light directly into your face. The terminator disappears briefly at full but soon reappears along the moon’s western edge the day after.

Have you noticed the moon looks a little out of round the past couple nights? The western edge is missing because the sun is now setting there after the long lunar day. Slice by slice, the terminator, which is now the advancing line of lunar sunset, gobbles up the moon, converting it from full to waning gibbous and then to a half. The half or 3rd quarter moon refers to the moon having completed 3/4 of its orbit around the Earth since new moon.

The moon's phase depends on its position in relation to the sun and Earth. This diagram looks down on Earth from north. Sunlight is coming in from the right, as indicated by the yellow arrows. Over a month, we see the moon cycle from new moon to full and back to new again. Times shown are when the moon is due south and highest in the sky. Credit: Minesweeper

Several nights later, the moon’s phase will have narrowed to a thin crescent, and by October 7 – new moon – we’ll see no moon at all. It will lie almost directly between us and the sun in the daylight sky. The side facing the sun will be fully illuminated, but the side facing Earth will be in complete shadow. A day later the cycle begins anew with a fresh and thin crescent low in the west at dusk.

More satellites than you can shake a laser pointer at

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The Seven Sisters cluster clears the trees around 11 p.m. earlier this week. The brightest members form a small dipper shape. The other stars you see crowded around the dipper also belong to the cluster and are easily visible in binoculars. Details: 200mm lens, f/2.8, 15-second exposure at ISO 6400. Photo: Bob King

I’ve been enjoying watching the Pleiades star cluster come up in the east these evenings. As far as I’m concerned, it’s first in the roll call of winter stars. You can see the cluster yourself low above the horizon starting around 10 o’clock. By 11, it’s up high enough for easy viewing.

Venus and the moon this evening in twilight about 20-30 minutes after sunset. Created with Stellarium

Earlier tonight, just after sunset, find a location with a clear view toward the southwestern horizon. You’ll find Venus there accompanied by a thin crescent moon. Through a small telescope, Venus now has a distinct crescent shape similar to but thicker than tonight’s moon. It’s an interesting juxtaposition of two very different worlds – one blisteringly hot with a dense carbon dioxide atmosphere and perpetual cloud cover, the other airless and subject to the extremes of both heat and cold. They do share several features in common. Both have craters and volcanic features like lava channels and domes of extruded magma. Volcanism is likely still going on on Venus, but the moon appears to have quieted down volcanically at least 100 million years ago.

The X-37B is a reusable, robotic spacecraft launched into orbit last April. Credit: NASA/Boeing Phantom Works

In an earlier blog, we visited the U.S. Air Force’s new military surveillance satellite the X-37B, which resembles a miniature space shuttle. The reusable, unmanned craft orbits some 250 miles above the Earth and is visible as a faint star crossing the southern sky. The craft is making evening passes during the next week and a half. Like the space station, it will look like a steady, moving “star” traveling from west to east. Unlike the station, it’s much fainter at only 4th magnitude, similar to the stars in the Little Dipper or those in the Pleiades Cluster. Its nightly path cuts through or just above (north) of the constellation Sagittarius the Archer, better known as the Teapot. You can use yesterday’s map of the Teapot to help you look in the right direction. For Duluth, Minn. and region, X-37B will first appear in the southwest, cross the southern sky near Sagittarius and then move toward the southeast and fade. For times for you city as well as very helpful maps, login to Heavens Above, select your city and then click on the X-37B link.

* Tonight starting at 8:39 p.m. Passes typically take about 3-4 minutes
* Monday Sept. 13 at 8:51 p.m.
* Tuesday Sept. 14 at 8:08 p.m.
* Weds. Sept. 15 at 9:02 p.m. Briefer pass in southwest only
* Thurs. Sept. 16 at 8:19 p.m.

Heavens Above is a wonderful tool for finding additional bright satellites, including quite a few brighter than X-37B. Once you’re logged in, go under the Satellites heading and click on Daily predictions for all satellites brighter than magnitude: 3.5. This will call up a list that for my town contains almost 40 satellites easily visible from my home during morning and evening hours. Brighter ones include the Titan 4B rocket booster, the Lacrosse 2 surveillance satellite and UARS, the Upper Atmosphere Research Satellite. Each is comparable in brightness to a star in the Big Dipper. Clicking on the name of each satellite will take you to an information page where you can click the Passes (visible) link to get a list of times for viewing. Such an embarrassment of riches. Have at it!

The sisters of fall meet the waning moon

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The moon, Aries, the Pleiades and the Hyades are splayed across the eastern sky around 1 a.m. tomorrow morning. Created with Stellarium

Tomorrow morning the last quarter moon will be near the Seven Sisters star cluster also known as the Pleiades (PLEE-uh-deez). This true star cluster has a shape like a small dipper and is sometimes confused for the real Little Dipper constellation. The Pleiades are 440 light years from Earth and comprise a gravitationally-bound cluster of some 500 stars. With the naked eye you’ll see six or seven stars huddled closely together like friends around a fire, binoculars show dozens and telescopes far more. The nearness of the moon will help you find the cluster, but its light will compromise the view. Try binoculars to see them best.

The Pleiades is a young star cluster with many hot, blue-white stars. Its compact form makes it the most obvious cluster visible with the naked eye. The blue mist is a cloud of fine interstellar dust the cluster passing through. Starlight illuminates the dust by reflection. Credit: NASA, ESA, AURA/Caltech, Palomar Observatory

Above the moon, you’ll easily spot one of the smaller constellations, Aries the Ram, comprised of three stars arranged like a bent index finger. Below the Seven Sisters is yet another star cluster, the Hyades (HYE-uh-deez). It’s takes up a bigger piece of the sky in part because at 150 light years distant, it’s considerably closer than its sister cluster. The bright star Aldebaran is closer yet but happens to be in the same line of the sight as the Hyades; it’s not a true cluster member.

The Hyades were sisters to Hyas, the son of the Greek god Atlas. When Hyas was killed by a wild boar, the sisters were so saddened they died of grief. Zeus took pity upon them and placed them in the heavens in the constellation of Taurus the Bull. The Hyades were half-sisters to the Pleiades, who were also daughters of Atlas.  Atlas was the dude who was forced to carry the heavens on his shoulders. One version of the Pleiades  story recounts that Orion pursued the young ladies because Atlas was too preoccupied with his celestial weightlifting. To ease Atlas’ concerns about Orion’s intentions, Zeus turned the daughters into stars and floated them up to the sky.

Statue of Atlas carrying the heavens on his back. Credit: Luis Miguel Bugallo Sánchez

In late August, both star clusters only begin to nudge into the night sky – you have to stay up late to catch them. By fall, they rise during the evening hours and presage the arrival of the winter constellations Taurus, Orion and Gemini.

If you’re more of an early evening sky watcher and would rather wait for fall for the Pleiades to come to you, no problem. We’ve got some sleep-saving viewing times for the International Space Station (ISS) through the remainder of the week.

All passes listed below will happen in the northern sky with the space station moving from northwest to northeast. The times are Central Daylight and good for the Duluth region. For times for your town, please click HERE and key in your zip code.

* Tonight starting at 9:11 p.m.
* Tues. Aug. 31 at 8:02 p.m. and again at 9:38 p.m. The second pass will be short. Watch for the ISS to turn red through binoculars as it enters Earth’s shadow.
* Weds. Sept. 1 at 8:30 p.m.
* Thurs. Sept. 2 at 8:58 p.m.
* Fri. Sept. 3 at 9:25 p.m.
* Sat. Sept. 4 at 8:17 p.m. and 9:52 p.m. Another opportunity to watch the sun set on the station as it enters Earth’s shadow.

Tomorrow we’ll look at how a new impact crater – with meteorites – was discovered in southern Egypt by someone scanning Google Earth photos.