27 Oct 2011
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Perseus holds the head of Medusa, whose eye is marked by Algol, the "Demon star." (Credit: Stellarium.org)

A star perfect for Halloween currently lies in the northeast evening sky within the constellation Perseus. It’s Algol—the “Demon Star”—and it represents the eye of Medusa.

According to myth, if you looked at Medusa you’d turn to stone. Perseus managed to chop off Medusa’s head by looking only at her reflected image in his shield.

Algol looks like a single star to us, but it’s actually a multiple star system. From our point of view on Earth, two of the stars in the Algol system orbit each other such that one star periodically passes in front of (eclipses) the other, blocking its light.

When the light from this “eclipsing binary” dims every few days, you can imagine it as the eye of Medusa, still winking after the head has been cut off.

Head of Medusa

Sorry, but you've just been turned to stone.

If you’d like to hear the full story of Perseus and Medusa along with other tales of madness, murder, and mayhem in the night sky, please join Morehead Planetarium and Science Center for a special edition of our live planetarium program Carolina Skies.  In honor of Halloween, we will have several “Scare-olina Skies” shows:

  • Adult versions: Scare-olina Skies shows on Saturday night, October 29, 2011 (at 7:00 p.m. and 8:30 p.m.) feature themes designed for adults and older teens.
  • Family-friendly version: Scare-olina Skies on Sunday, October 30, 2011 (at 3:30 p.m.) is designed for children ages 5-12 and their families.

Watch out! Medusa will make an appearance on the planetarium dome during Scare-olina Skies.

This photograph of the International Space Station was taken from the space shuttle Discovery after the two spacecraft undocked on March 7, 2011. (Credit: NASA)

Pretty much everyone in the Eastern part of the U.S. who has clear skies can get a view of the International Space Station (ISS) tonight (Monday, October 17, 2011). To see it, be outside by 7:16 p.m.

Over the following six minutes the ISS’s orbit around Earth takes it over the East Coast. For our area, the space station is predicted to first appear between 7:16 and 7:17 p.m. low in the southwest. It will pass almost directly overhead at 7:19 p.m., and finally disappear low in the northeast at 7:22 p.m.

Look for a very bright white “star” that is noticeably moving. And wave hello to the three people currently onboard.

If you don’t notice the ISS in the first couple of minutes, don’t give up. You can increase your chances of spotting it by inviting friends to help scan the sky with you. You might also practice “ambush astronomy” and introduce nearby friendly pedestrians to one of the coolest things to see in the sky.

Although the space station orbits our planet about every 90 minutes, you won’t see every pass. According to predictions on Heavens-Above and NASA’s satellite sightings page, tonight’s ISS pass should be the easiest one to see from this area for the rest of October.

If you miss the real thing, you can see a simulated ISS pass by attending Morehead's Carolina Skies planetarium program. Just ask your presenter before the show.

This is the bad news. (Image credit: Luc Viatour)

Many people’s favorite annual meteor shower, the Perseids, will peak the night of August 12/13, 2011.

The good news: That’s a Friday night/Saturday morning. For many people, this is a convenient time of the week to be outside looking for meteors—those streaks of light (also known as “shooting stars”) created when cosmic debris interacts with the Earth’s atmosphere.

The bad news: The Moon will not be cooperating this year. On August 13 it’s full, meaning the Moon will be up all night, its bright light hiding the dimmer meteors from view.

Tips if you decide to view the Perseids this year:

  • To see most meteors, go out during the last dark hour before dawn.
  • Get the Moon out of your field of view, and look toward the northern half of the sky. You’ll want a view unobstructed by trees or buildings.
  • Take a chair to sit in, and look about halfway up the sky.

For more tips, see the American Meteor Society site.

If it’s too cloudy that night or you just don’t want to make the effort, you can still see some meteors (the simulated kind) by coming to Carolina Skies at Morehead this Sunday, August 14, at 3:30 p.m. At your request, the presenter can send a few meteors shooting across the planetarium sky.

Moonlight won't interfere with the peak of the Perseids in 2012.

Harry Potter would have needed magic to pass his astronomy exam in book 5.

J.K. Rowling, the author of the Harry Potter books, must be a bit of an astronomy buff. She named a number of her characters after stars or constellations, such as Bellatrix, Draco, Regulus, and Sirius. And in her book about Harry’s fifth school year at Hogwarts School of Witchcraft and Wizardry, Rowling even gave Harry an astronomy exam.

What an exam, though! Harry appeared to have an impossible task that night—to note the location of the constellation Orion in the June sky.

Rowling had Harry successfully complete Orion on his star chart, but Orion wasn’t visible in the night sky from anywhere on the planet that month. In June, when viewed from Earth, the stars of Orion lie roughly in the same line of sight as the Sun. So Orion is above the horizon only in the daytime.

To see Orion in the middle of the night in June, Harry must have used some serious magic, possibly whipping the Earth to another place in its orbit around the Sun. Let’s hope he received extra credit.

This week, we’ll use Morehead magic to re-create the night sky on the planetarium dome for two programs about what you can see this summer:

Both programs are aimed at Muggles (non-magic people, in Harry Potter’s world) who want to learn to identify what’s overhead on North Carolina summer nights. Please register online in advance.

During the Summer Skies programs, we'll see Orion's enemy, Scorpius (another Harry Potter character, known to fans who have read to the very end of the series).

February 2008 lunar eclipse (credit: Jayme Hanzak)

The next time the Moon is full, it will pass into the Earth’s shadow, causing a total lunar eclipse. The action happens early Tuesday morning, December 21, 2010, between 1:33 and 5:01 a.m. Totality is from 2:41 to 3:53 a.m. (All times Eastern.)

So seeing it probably means inconveniencing yourself unless you work the night shift or will be in another time zone. (Lucky folks on the West Coast, for example, get to subtract three hours from all the times above.) If the skies are clear enough, here’s why it is worth losing sleep to see the eclipse:

1) You will see the Moon turn a weird color.

When the Moon passes into the Earth’s shadow, rather than disappearing altogether, it will probably turn red. Or maybe orange, or gray, or brown. The Earth’s atmosphere bends sunlight and sends it into the Earth’s shadow, so in effect you see light from all the sunrises and sunsets on Earth. The exact color of the Moon depends on what’s in our atmosphere as well as how deeply into the darkest part of the shadow the Moon passes.

2) You can prove to yourself the Earth is round.

When the eclipse is in a partial phase, you can see that the Earth’s shadow is curved.

3) You can imagine a ferocious dog taking a bite out of the Moon.

According to a Korean myth, a lunar eclipse happens when a king’s “fire dog” attempts to steal the Moon and bring its light to the Land of Darkness. When this huge, fierce dog bites into the Moon he finds it painfully cold. His mouth freezing and his teeth singing with pain, the dog then spits out the Moon.

4) You haven’t gotten to see a total lunar eclipse in nearly 3 years.

The night of February 20-21, 2008, was the most recent total eclipse of the Moon visible from anywhere on Earth.

5) …and you may have missed that eclipse anyway.

That week I was presenting a stargazing seminar for public school teachers at the Ocracoke campus of the North Carolina Center for the Advancement of Teaching, where I remember good views of the eclipse. But members of the Chapel Hill Astronomical and Observational Society (CHAOS) reported cloud cover during the early stages.

6) …and your NEXT chance to see a total lunar eclipse from here won’t be until April 2014.

And its timing during the night isn’t any more convenient for the East coast than this Dec. 21 eclipse, so don’t wait for that reason.

To witness a simulation of the eclipse with no loss of sleep, and to learn more Moon-related stuff, please join me at the Moon Myths planetarium program:

  • A 90-minute version designed for adults and teens happens this Wednesday, Dec. 15, from 7:30-9:00 p.m. In addition to spending time under the planetarium sky, we’ll do a hands-on “moon dance” (no actual dancing required) to explore how the Moon’s orbit is related to phases and eclipses. And if the weather permits, we’ll spend a few minutes outside looking at the real thing through a telescope.

Register for either program at the Morehead Web site.

Amy Sayle is setting an alarm to catch the lunar eclipse.

Geminid meteors appear to radiate from the constellation Gemini the Twins. (Credit: International Astronomical Union, Sky & Telescope)

The Geminid meteor shower peaks the night of December 13-14, providing its annual cosmic light show. Alas, our current forecast predicts temperatures dropping toward the teens that night. Here’s why it’s worth freezing yourself* to view the meteors (assuming you have reasonably clear skies):

1) The Geminid meteor shower is strong and reliable.

It’s actually already happening. The shower is active from December 4-16, with the peak on Tuesday morning, December 14.

2) You can watch the sky act out a mythological story.

The streaks of light you’ll see (also called, confusingly, “shooting stars”) result from debris from a rocky object called 3200 Phaethon. In Greek mythology, Phaethon’s disastrous attempt to drive the Sun chariot across the sky resulted in Zeus (Jupiter) hurling a lightning bolt that caused Phaethon to tumble out of the chariot “like a shooting star.” In addition to seeing meteors streaking through the sky and imagining Phaethon’s last ride, you will also see Jupiter—the planet, that is—if you are out before midnight. But let’s hope for no lightning bolts.

3) You don’t have to wake up insanely early.

Unlike most meteor showers, which require going outside at what most of us consider a ridiculous hour, the Geminids are worth looking for anytime after about 9 p.m. (Monday, Dec. 13). At that time you will also see Jupiter and the waxing gibbous Moon appearing close together—a lovely sight, though that moonlight may prevent you from seeing fainter meteors.

4) If you’re willing to go out to a dark site after midnight (early morning Tuesday, Dec. 14), you may see roughly a meteor or more per minute.

The single best hour is likely to be centered around 2 a.m. The Moon will have set, and high in the sky will be the radiant—the point in the constellation Gemini from which Geminid meteors appear to originate. Around that time, meteors will appear to fall down in all directions. To see the most meteors, you need a sky free from light pollution. Seek an open view as far away from city lights as you can.

5) All you need are your eyes. And warm clothes.

Do give your eyes at least ten minutes to adjust to the dark. You do not need to know how to identify the constellation Gemini. The American Meteor Society suggests that if it’s before midnight, try facing toward the east, keeping the Moon out of your field of view. Closer to 2 a.m., try looking about halfway up the sky, in whatever is the darkest direction for your location.

*So that you don’t actually freeze yourself, remember to dress really, really warmly, and wrap yourself in a blanket or sleeping bag.

Amy Sayle is looking forward to presenting "Moon Myths" this week in the climate-controlled planetarium theater.

When you look at the space station flying over, someone might be looking down at you. (Credit: Expedition 24 crew, NASA)

Are you a morning person? If so, this Thanksgiving holiday provides good opportunities for you and other early birds along the East Coast to see the International Space Station (ISS).

If the sky isn’t too cloudy, the two best ISS passes will be the mornings of Thursday, November 25 (Thanksgiving Day), and Saturday, November 27. Both times the ISS will first appear low in the southwest. Over the next few minutes, you can watch it pass to nearly the zenith (top of the sky) before it disappears low in the northeast.

For our location, Heavens-Above currently predicts that the Thursday pass will happen from 6:32 to 6:37 a.m.  Saturday’s will be from 5:49 to 5:53 a.m. Black Friday shoppers who like to get out insanely early will also be treated to an ISS pass from 5:23 to 5:27 a.m. that morning, but it will be much lower to the horizon.

To find the space station, look for a very, very bright “star” that is noticeably moving. The ISS is so bright that it won’t matter how light polluted your observing site is, and it won’t matter that Thursday morning’s pass happens in a sky brightening from the approaching sunrise.

Although it is not hard to spot the ISS, you will likely see it sooner—and have more fun—if others look with you. So you might practice ambush astronomy on any visiting relatives and haul them outside with you. Set your watch accurately, and don’t give up if you don’t notice the ISS in the first minute or two.

Be sure not to mistake the International Space Station for:

  • a plane (the ISS does not have red or green blinking lights)
  • a bright planet (Venus and Saturn are currently in the morning sky, but they won’t appear to be trucking across it)
  • a bright star (no star rivals the apparent brightness of the ISS this Thursday or Saturday, or appears to move across the sky over a few minutes)

Because predictions of where and when to look can change, you may wish to check Heavens-Above or NASA’s sighting opportunities page the night before for updated predictions. Also check one of these sites if you will be somewhere other than the Triangle area. For either Web site, you must specify your observing location (for Heavens-Above see the “Configuration” heading).

Amy Sayle is definitely not a morning person but is considering waking up Thursday in time to see the space station.

If you have watched the early evening sky over the past weeks, you may have noticed Venus, Mars, and Saturn engaging in a slow planet dance.

On August 12 and 13, the Moon joins the party. Look for this striking sight soon after sunset in the same direction the Sun went down. You will likely see the crescent Moon and super bright Venus first. As the sky darkens further, notice Mars and Saturn near Venus. (Mercury will be lower, dimmer, and much harder to spot.)

If you’d like to see these celestial objects through a telescope, join Morehead for our skywatching session this Thursday, August 12, from 9 to 11 p.m. Weather permitting, we’ll be at Jordan Lake, Ebenezer Church Recreation Area. Come near the beginning of the session to view the Moon and planet trio. Then stick around for a chance to see some Perseid meteors.

If the skywatching session is canceled, we will post a message around 4 p.m. at the Morehead Web site — please check before you head out to Jordan Lake.

Amy Sayle hopes to spot a few Perseid meteors from Jordan Lake during Paddling Under the Stars. Although the paddle is sold out, the skywatching session is free and open to all.

Starlight from Arcturus opened the 1933 Chicago World's Fair.

Starlight from Arcturus opened the 1933 Chicago World's Fair.

If you want to wish on the first star you see tonight, there’s a good chance it’ll be Arcturus.

As you make your wish, you can also think about how Arcturus became famous in 1933 when its starlight opened the Chicago World’s Fair. On May 27, at 9:15 p.m. central time, several observatories aimed telescopes at Arcturus and focused its light onto photocells. The current that was generated resulted in the flipping of a master switch for the fair’s lights.

According to an article published the next day in the New York Times, “the grounds, pavilions and waterways of the fair were drenched with light. Thousands of awed beholders broke into cheers.”

Why was Arcturus chosen for this honor? It was thought to be 40 light years away, meaning that the light reaching Earth in 1933 would have left Arcturus forty years earlier, in 1893—when Chicago previously hosted a World’s Fair.

Unfortunately, they picked the wrong star. We now know that Arcturus is actually about 37 light years away.

So if you spot Arcturus tonight, you see it as it looked 37 years ago, in 1973, when the light left it. Looking deep into space is like having a time machine into the past.

To learn to identify Arcturus and other stars and constellations, come to Morehead’s skywatching session on Saturday, June 19. Or register for Starry Summer Nights; this class for adults takes place Tuesday evening, June 22, under the planetarium dome.

Arcturus is probably pretty much the same now as in 1973, but it’s still fun to think about.

Evening planets on May 24, 2010

Three planets are visible in the current evening sky: Venus, Mars, and Saturn.

But how do you tell a planet from a star?

1)      By how it looks.

Whereas stars twinkle, planets generally shine more steadily. Planets can also look very bright—especially Venus. Currently in the western evening sky, it’s the brightest object other than the Moon. Also in the evening sky are Mars and Saturn, which are roughly as bright as the brightest stars appearing near them.

2)      By where it is.

Stars appear all over the sky, but you won’t find planets just anywhere. Because they orbit the Sun in roughly the same plane, planets always appear within a certain band in our sky—the zodiac. Right now Venus appears to be near the feet of the Gemini Twins, Mars is about to munched on by Leo the Lion, and Saturn looks like Virgo the Maiden’s earring. (Side note: Many people are familiar with the 12 astrological signs of the zodiac, but there are more than 12 astronomical constellations of the zodiac that planets can appear in. Mercury, for example, was recently hanging out inside the boundary of Cetus the Sea Monster.)

3)      By how it moves over time.

Watch a planet night after night, and eventually you’ll notice it appears to wander against the background of the stars. Learn to identify the zodiacal constellations, and then you’ll know that any “extra” star is probably a planet. For an animation of the changing positions of the planets over the next few weeks, view the May 15th Carolina Skies segment on WRAL.

Over the next few months Venus, Mars, and Saturn will appear to close in on one another. See their progress at Morehead Planetarium and Science Center’s next skywatching session on Saturday, June 19. Weather permitting, we’ll be at Jordan Lake’s Ebenezer Church Recreation Area from 9 to 11 p.m.

Amy Sayle is Morehead's Science 360 manager.