Archive for November, 2007

Leo: In the Spotlight

November 17, 2007

On Oct. 25 I posted a blog featuring the constellation Orion, adhering to the advice in  Pathways to Astronomy for beginning stargazers to learn the star lore of a constellation to improve their ability to locate it in the night sky.  And I have to say, it worked for me!  Since posting that blog, I’ve successfully spotted Orion three times.   (It was unexpected at first:  I was out lying on the dock at Lake Joy in Duvall, enjoying the night with a couple of friends, when I identified the three stars of Orion’s Belt.  But instead of stopping there, as in the past, I traced the sky for the outline of Orion’s body.  “I did it!” I said.  It was a very proud moment.)  As promised, this is the second installment.

The constellation in the spotlight:  Leo.

Leo is a spring-winter constellation and, thus, most visible in both the spring and winter months.  (Leo rises in the east around midnight in November.)  And just like Orion, the Leo region is host to a meteor shower this month.  The Leonids will peak in activity at 1 a.m. on Nov. 18.  However, interested stargazers should be warned:  According to FOXNews.com, while the Leonid meteor shower has been spectacular in the past, this year’s display will be modest.

On Nov. 14 I talked with Dr. Ana Larson, a senior lecturer of astronomy, about the Leo constellation.  “It’s one of the few that really looks like what it’s supposed to represent,” Larson said.  “It sort of looks like a lion.”

Stargazers shouldn’t have too much trouble spotting Leo, Larson said.  “Even if you’re in a bright city, it’s actually one of the easiest constellations to point out, because it’s one of the largest,” she said.  “Not as big as Orion, but it’s pretty large.  And there’s not many bright stars around it, so it really sticks out at night around midnight.”

Larson said the easiest way to spot the Leo constellation is to first find the Big Dipper.  Instead of following the imaginary line of the pointer stars to Polaris, extend the line southward.  It will point to the middle of Leo’s back, she said.  Or stargazers can also look for a backward question mark, an asterism called the Sickle, which forms Leo’s head. 

Other interesting components of the Leo Constellation:

  • Regulus (a white-blue star at Leo’s shoulder) is often eclipsed by the Moon.
  • Saturn (the sixth planet from the Sun) is currently in the middle of the Leo constellation.  “It’s one of the brightest things in the constellation, so it won’t be hard to miss,” Larson said.  “It has a sort of yellowish glow.  It’s right in the middle– right in the belly of Leo.”

Again, instead of butchering the story behind the Leo constellation in a summary, I’ve posted an excerpt.  Here is one version of the legend of Leo the Lion, courtesy of the Legg Middle School Planetarium Web site:

“Hercules’ first labor was to kill the Nemean lion, a fierce beast who descended to Earth from the Moon in the form of a meteor and ravaged the countryside of Corinth.  The lion had hide so tough that neither spear nor arrow nor any other weapon could pierce it.  So well known was the beast that Hercules had no trouble finding its lair, a cave with two entrances.  As Hercules approached, the lion showed itself and Hercules sped an arrow toward its heart.  The arrow merely bounced off and fell to the ground.  Hercules now knew that arrows or spears were useless against the beast.  He then sealed of one of the entrances to the cave and pursued the lion inside through the other entrance.  So great was his strength that Hercules seized the lion and strangled it to death by ramming his fist down its throat.  He then flung it over his shoulder and returned to show King Eurystheus that he had fulfilled his first labor.  The cowardly king was terrified at the sight of the beast and fled.  Hercules then [used the beast’s own claws to skin] the lion, and used its [pelt as a cloak of invulnerable armor and donned the lion’s head as a helmet].  So angry was Hera at Hercules’ success that she raised the soul of the lion high into the sky.”

Don’t forget to check out StarDate Online’s seven-day star forecast for the nights Nov. 18 to Nov. 24.

Question: Why do stars twinkle?

November 9, 2007

On Nov. 3 a fellow stargazer posted a question for astronomy graduate student Matt Davis on the Interview with Matt Davis page of this blog.  The question:  Why do stars twinkle?  I e-mailed Davis the next day about the inquiry, as promised.   (Thanks, Jay!)

The answer:  “Stars twinkle because we are looking at them through a thick, constantly moving layer of air:  Earth’s atmosphere,” Davis said.

Davis gave a great analogy of the twinkle-star effect:  “Imagine you are out in the desert on a hot day, looking down a straight road,” he said.  “As you look down the road, the line on the road seems to shift around and the air looks like it’s shimmering and moving.  This is because the air next to the road is very hot and it’s rising, as hot air does.  This means that the air is changing density and moving along your line of sight, and this causes things you see through that air [to] appear to move and shimmer.”

“This is the same effect we see as we look at stars or the distant lights of a city,” Davis said.  “All of the air between you and a star or [the] light is moving around.   Different parts of [the air] have different temperatures and different densities so it bends the light around, making it look like it’s twinkling.”

The twinkle-star effect is the main reason astronomers put telescopes (like the Hubble Space Telescope) in orbit around Earth, he said.  Above the atmosphere “the stars … no longer twinkle and we can take much clearer pictures,” Davis said.

“Interestingly, planets do not appear to twinkle the way stars do because they have an actual finite size because they are so much closer to us than the stars,” he added.  “If you look at a planet through binoculars you will see that it has a disk, [whereas] stars still just look like points.  This makes it so that the light from a planet gets kind of averaged out so that we don’t see it twinkle.”

For another good answer to why stars twinkle, read what volunteers in the Astronomy Department of Cornell University had to say on the Ask an Astronomer Web site.

Again, please post any questions about stargazing to this blog.  I’m happy to work as an intermediary for other interested stargazers.  Davis, a self-proclaimed “extragalactic distances guy,” encourages inquiries about celestial phenomena outside of the Milky Way galaxy.

Oh, and check out StarDate Online’s seven-day star forecast for the nights Nov. 8 to Nov. 14.

Stargazer Top Five: A list of stargazing must-sees

November 5, 2007

In my interview with astronomy graduate student Matt Davis on Oct. 16, I asked him to suggest his favorite stars and constellations for amateur stargazers to look for in the night sky.  Davis responded by giving me a list of celestial phenomena he thinks stargazers shouldn’t miss.  Below is the Stargazer Top Five, a list of stargazing must-sees, devised from his suggestions:

1.  The Milky Way galaxy.  “If I had to make a list of all the things [stargazers] should see, the Milky Way tops the list,”  Davis said. 

I knew the Milky Way is the galaxy of our solar system, but I wanted to know:  Why does the Milky Way look the way it does from Earth?  The Milky Way is a combination of billions of stars and dust, Davis said.  “The Milky Way is a fuzzy glow of so many stars shining at us that we can’t distinguish any of the stars,” he said.  “It’s combined light from all of the stars of the Milky Way that we can’t see individually.  We are orbiting perpendicular to the galaxy, so that’s why we kind of see it overhead.  And you can’t tell, but the center of our galaxy is in the constellation Sagittarius.  When you’re looking at the constellation Sagittarius, you’re looking at the direction of the center of our galaxy.”

2.  The planets.  “It’s always cool to identify the planets,” Davis said.  According to StarDate Online, the planets Mercury, Venus, Mars, Jupiter and Saturn are visible to the naked eye.  For information on when and where to view the planets, see StarDate Online’s planet viewing guide.

3.  The Pleiades star cluster.  What’s most interesting about the Pleiades star cluster– or any star cluster– is that unlike the stars in a constellation, “those stars are actually physically associated with each other,” he said.  “It’s a cluster of young, bright stars born at the same time, in the same location.”  Stargazers can find Pleiades in the Taurus constellation.

4.  The star Sirius.  Sirius should be easy to spot because it is the brightest star in the sky, Davis said.  “Because Sirius is so bright, the light sensitivity of your eye will actually try to determine the color of the star,” he said.  “It’s very pretty.”  To learn more about Sirius, see StarDate Online’s radio program transcript of a discussion on the star.  Stargazers can find Sirius in the Canis Major constellation.

5.  The Delphinus constellation.  Davis said Delphinus is the best constellation in the sky.  “It’s cute– it’s a dolphin,” he said.  But to him, Delphinus looks more like a kite.  (Funny thing:  My friends and I have spotted the ‘kite’ numerous times while stargazing, not knowing it was an actual constellation.)  Using my star map, I figured out that Delphinus lies near the celestial equator, just east of the Milky Way.  It is surrounded by the Pegasus, Equuleus, Aquila, Vulpecula and Sagitta constellations.

Remember to check StarDate Online’s seven-day star forecast for the nights Nov. 4 to Nov. 10.  Fellow stargazers may also want to go to stardate.org to see an overview of stargazing opportunities in November.