Tag Archives: Hyades

Can you see the American flag on the moon? Yes!

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Bright Venus (bottom) and Jupiter are joined by the Hyades (right of Jupiter) and Seven Sisters star cluster (top) in the eastern sky at the start of morning twilight today. Photo: Bob King

I got up at 2:30 and casually surveyed the sky while poking around with the telescope till 4. Total meteor count: 0 Delta Aquarids and 2 unrelated meteors. Maybe tomorrow will be better.

Sharing the 50-degree temperatures with the crickets and katydids that inhabit the dewy grass was pleasant enough. Venus and Jupiter along with the Hyades and Seven Sisters star clusters totally jazzed up the eastern sky, and at 4:06 a.m. the space station breezed by. I hunted for the Progress cargo ship along, ahead of and behind the station but never saw it. Did you have better luck?

Apollo 16 astronaut John Young hops while saluting the flag in April 1972. Credit: NASA

The Lunar Reconnaissance Orbiter (LRO) keeps on giving. Flying only 31 miles high above the moon’s surface it snapped a set of newly-released photos of the Apollo landing sites that plainly show the U.S. flags planted by the astronauts.

The flag that John Young saluted is still visible in this picture taken by the LRO. The gray-colored blob is the flag; its contrastier shadow to the left is easier to make out. Also seen are the lunar descent module, astronaut tracks, the Lunar Rover and its tracks. Credit: NASA

One of the most common questions asked by the public when we’re looking at the moon through a telescope is why we can’t we see the American flags or any other sign of Apollo with the Hubble Space Telescope. It IS the most powerful telescope, right? Here’s the rub. The smallest possible thing Hubble can see on the moon is about 328 feet across or the length of a football field. While impressive feat of resolution, no Apollo spacecraft comes anywhere near that size. Every piece of man-made hardware is below the space telescope’s resolution limit.

Because of the lighting angle, the Apollo 17 stands out even better than Apollo 16′s. Credit: NASA

The trick to seeing flags and other details is not necessarily a bigger telescope; it’s getting a camera in orbit close to the moon. That’s what the LRO’s been doing for past few years. Its cameras can record objects 1.6 feet across. Lots of things, including lunar descent modules, experiments placed there by astronauts and even their footpaths come into focus in LRO’s eye. And now, the flags.

Astronaut Harrison Schmitt stands on the surface of the moon next to the U. S. flag at the Taurus- Littrow landing site during the Apollo 17 mission. A “half-moon” Earth is visible at top. Credit: NASA

I swear I can see the contrast difference between the stripes and the dark, starry patch and even a hint of the flagpole in the Apollo 16 photo. Pretty incredible!

The only flag we probably won’t ever see is the first one, planted there by Neil Armstrong and Buzz Aldrin on July 20, 1969. Aldrin reported it was blown over by rocket exhaust as the astronauts left the moon to return to the orbiting command module.

Since the flags are made of nylon they won’t last terribly long under the extreme conditions on the lunar surface. Strong ultraviolet light from the sun has probably already caused the colors to fade. Over a longer time, the flags will turn brittle until one day crumbling into little heaps of dust during a moonquake.

Click HERE for full resolution views of the Apollo landing sites taken by LRO.

 

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!

See the Hyades and taste victory

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The delightful Hyades star cluster is directly below the more familiar Pleiades or Seven Sisters cluster. The stars farther out to the left of the cluster form the tips of the bull's horns (see picture below). This map shows the sky as you face east around 8:30-9 p.m. Maps created with Stellarium

“V” may be for victory, but it’s also the shape of one of the closest star clusters to Earth: the Hyades (HYE-uh-deez). That distinctive shape that makes finding this star cluster easy peasy on a November night. You may already be familiar with the Dipper-shaped Pleiades cluster also known as the Seven Sisters. This pretty bunch has been climbing the eastern sky all fall and is now conveniently placed for viewing around 9 o’clock. Make a fist at the sisters and then look one fist below them. The first star to catch your eye will be a bright orangish spark called Aldebaran (al-DEB-are-on). Spreading to the right of the star are the fainter Hyades. From our perspective on Earth, the cluster appears like the letter “V”, but its true shape is approximately spherical. At first glance, you’ll nail a half-dozen stars with your naked eye, but in total the Hyades contains some 300-400 stars 151 light years from Earth. It’s one of the closest star clusters to our solar system; the Pleiades in contrast is three times farther or about 400 light years away.

The Hyades form the face of Taurus the Bull. Aldebaran represents one of his eyes. Credit: William Jamieson, Urania's Mirror

Beware Aldebaran! It seems to fit the V to a tee, but like someone sneaking into a wedding party who doesn’t belong, Aldebaran has no association with the cluster. It’s in the foreground 65 light years from Earth, and coincidentally happens to be in the same line of sight as the Hyades. Without Aldebaran, the cluster would be a little disappointing; the star adds luster and helps shore up the overall shape.

In this closer view, you can see additional stars in the V-outline including the pretty pair Theta Tauri. I've labeled the 12 stars I can see from my house. The brightest ones are 1,2, 3, 6, 9 and 10. Craving more Hyades? Point your binoculars clusterward.

Once you’ve found the Hyades, try to split the close naked-eye double star Theta Tauri, just to the right of Aldebaran. Astronomers aren’t sure it’s a true double star, but both belong to the cluster. Although separated by slightly less than a 1/10 of a degree, I can split them fairly easily when staring squarely at the pair. Another challenge is to see how many Hyades are visible from where you observe. At my house, on a dark, moonless night, I count a dozen stars within or very close to the V-shaped outline. A few additional members lie scattered about outside the V. How many do you see? The best way to find the faintest ones is to use averted or peripheral vision. Look off to this side or that rather than staring directly at the stars.  After you’re finished with the Hyades, try the same technique with the Pleiades. With a little concentration, I bet you’ll see several more than the usual five most folks see at a casual glance. Little exercises like these sharpen our perception and sometimes surprise us. I never thought I’d see the zodiacal light or its ghostly cousin, the gegenschein, but once I tried and learned to know what to look for, they’re visible many clear nights.

A time exposure of the Hyades cluster with bright Aldebaran. Photo: Bob King

The Hyades has been hanging together a long, long time. Astronomers estimate its age at 625 million years. Many star clusters don’t make it beyond 100 million years, especially those with only a modest number of stars or located closer in to the center of the Milky Way galaxy. Over 1100 star clusters like the Hyades are known in our galaxy (there are likely many more remaining to be discovered), and most “evaporate” or break apart into individual stars over time.

As star clusters revolve around the galaxy’s center, members leave the cluster through gravitational interactions with one another as well as chance encounters with other stars and interstellar gas clouds (and their gravitational meat hooks) met along the way. The Hyades have held together for ages, because they’re out along the edge of the galaxy, opposite the center and thousands of light years away from the heavy stellar traffic of the interior regions. The cluster may also have been blessed at birth with a bigger brood of stars than most. More stars means you’ve got the gravitational wherewithal to keep yourself intact longer. Even if you lose a few, you’ve got more where those came from. Whatever the detailed history of the Hyades, they’ve emerged victorious after 625 million years, and we’re here to celebrate their twinkling place among the stars of November.

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.