Thursday, May 22, 2008

Mother and Child

we remember Stephanie Keese, 1980-2008

Some deep-sky objects never lose their allure, even for veteran observers who have gazed at them hundreds or thousands of times through binoculars or telescopes. One of these is the magnificent Whirlpool Galaxy, 31 million light years away.

This spectacle of the northern sky is a showstopper at public star parties and observatory events. No one can forget his or her first telescopic glimpse of two galaxies interacting, one large and one small. It’s an iconic pairing I like to call “Mother and Child.”

Although I don’t normally venture outside of our own Milky Way galaxy in this blog, I will occasionally make an exception. This is one of those times.

The Whirlpool Galaxy is also known as M51, shorthand for Messier 51. This is its designation in the deep-sky catalog of the famed 18th century French comet-hunter Charles Messier (pronounced MESS ee yay). Technically, M51 refers to the large spiral galaxy only; the small, irregular companion galaxy has its own catalog number, NGC 5195. But in practice, most of us refer to these interacting galaxies collectively as M51, since they’re something of a package deal.

Messier himself discovered the ‘mother,’ and the ‘child’ was discovered by an astronomer pal of his. However, because of the limited resolving power of their telescopes, they thought the objects were nebulae (pronounced NEBB-you-lee; plural of nebula), clouds of gas and dust.

The 19th century English astronomer Lord Rosse discovered M51’s spiral nature through his whopping, six-foot-diameter “Leviathan” telescope in Ireland. It was the first time spiral structure had been recognized in a celestial object. But it was the great 20th century American astronomer Edwin Hubble who ultimately determined that many of the objects called “nebulae” (including M51) which were thought to be emerging solar systems were in fact galaxies--immense star systems lying beyond the Milky Way.

Restored Leviathan at Birr Castle, Ireland
Courtesy of Birr Scientific and Heritage Foundation

A dark site away from urban and suburban lighting is required to see the galactic twofer in all its glory. This is an ideal time of year to view this object, as it’s high in the sky. You can spot the Whirlpool Galaxy using binoculars, but you’ll need a telescope to see detail. Its proximity to the Big Dipper makes it fairly easy to locate.

1) You’ll need to face north, so if you don’t know the cardinal directions at your location and you don’t have a compass, make note of where the sun sets on the horizon. That spot is approximately west. Stand with your left shoulder to the west, and you’ll be facing approximately north.

2) Wait at least one hour after sunset to begin observing, so that twilight’s over and your sky’s good and dark. On Friday, May 23, you’ll have a couple hours of dark before the Moon rises. For the rest of the observing week, the Moon will rise even later each subsequent night.

3) Facing north, locate the Big Dipper, the distinctive seven-star asterism (recognizable star pattern) that looks like a giant, long-handled saucepan. It will be due north and somewhere between the zenith, the point directly above your head, and the northern horizon. The saucepan will be oriented upside-down. Point your binoculars or telescope at the point marked on the star map below, just off Alkaid (pronounced AL-kayd), the final star in the saucepan’s handle.

Chart created with Your Sky

Although just off the handle of the Big Dipper, which is part of the constellation Ursa Major the Great Bear, the Whirlpool Galaxy is actually in the lesser-known constellation of Canes Venatici the Hunting Dogs (pronounced KAY-neez vee-NATT-uh-sigh).

4) In binoculars and with good sky conditions, you should see an elongated fuzzy blob with two bright cores. A telescope will help you separate the blob into two distinct objects. In an eight-inch-diameter or larger reflector, you should clearly see spiral structure in the large galaxy. A large-aperture telescope and good sky conditions are needed to see “the Bridge,” the arm of the spiral galaxy that appears to reach out and touch the little galaxy.

In reality, the little galaxy is passing behind the large galaxy and has been doing so for hundreds of millions of years. But the gravitational pull of this galactic glide-by has disturbed and excited gas clouds in the spiral galaxy’s arms, setting off maelstroms of star formation. In the Hubble Space Telescope image below--the most detailed ever taken of M51--the new stars can be seen as bright blue clusters sprinkled along the sweeping arms.

It seems the child in this family portrait is quite precocious.

Thursday, May 15, 2008

Top Ten Moon Myths - Part 2

Last month, I gave you my picks for Numbers 10 through 6 of the top ten moon myths of all time. This week, to celebrate the Full Moon on Monday (Moon Day), May 19, let’s finish up the list with my selections for Numbers 5 through 1.

5) Plant growth is influenced by moon phases. The practice of lunar gardening or lunar agriculture--planting and harvesting according to moon phases--is ancient. Many cultures around the world have subscribed to it, and it’s a mainstay of folkloric tradition. A surprising number of modern folks practice it too; references can even be found in modern farmer’s almanacs.

The practice hinges on the belief that the Moon’s gravitational force exerts an influence on the flow of moisture in soil and plants. Lunar gardeners believe, for example, that crops producing their yield above ground should be planted during the waxing (growing) moon. The time to plant root crops is during the waning (shrinking) moon. However, no planting should be done on the New Moon or Full Moon--or, strangely, on any Sunday.

There is no body of scientific data that supports the claims of the lunar gardeners. At some point in prehistory, the use of the lunar calendar as a planting calendar--a simple tool to ensure crops went in at the right time--may have evolved into a belief system linking the Moon to agricultural success. And we humans do cling tenaciously to our belief systems, don’t we?

4) The Apollo moon landings were a hoax. Let’s see: the testimony of the astronauts who went there, the hundreds of pounds of unique moon rocks that have been examined by scientists around the world (as well as displayed in museums), the voluminous number of archived mission photographs, in other words, overwhelming evidence to the contrary. Most of the ‘hoax evidence’ claims are skillfully debunked here.

And that's all I have to say about that.

Image source: NASA

3) There is a link between the Full Moon and an increase in mentally disturbed behavior, criminal activity, women going into labor, etc. Notwithstanding that the word lunatic comes from the Latin word for moon, numerous studies have found no definitive link between mental hospital admissions and the Full Moon. There have been many studies conducted on the possible link between the Full Moon and crime, with no clear pattern emerging. Some have postulated that the Full Moon may simply create the optimum lighting condition for nighttime mischief-making, rather than influence behavior. Finally, no link supported by scientific studies has been found between the Full Moon (or any moon phase) and birthrates.
Anecdotal evidence is plentiful and proliferative, but perception is most assuredly not the same thing as objective analysis of reliable data (what we like to call “science”).

2) We can see the American flag on the Moon’s surface from Earth. I hear it all the time at star parties when the Moon is out: “Show me the flag on the Moon!” Some folks actually get incensed when I explain to them that I can’t: “But you just showed me a galaxy millions of light years away. Why can’t you show me the flag?!”

I’m sure the conspiracy theorists would say: “Aha. We can’t see it because it was never there.” But the truth is the smallest feature we can see on the Moon--using even the orbiting Hubble Space Telescope--is about 300 feet across. We would need an immensely large telescope to possess the light-gathering capability that is needed to see such a small, dim object like a flag--one that doesn’t produce light, but only reflects it. A galaxy, on the other hand, although tremendously more distant, is gargantuan compared to a flag. In addition, it emits the collective light of several hundred billion stars.

And the number one moon myth of all time:

1) The Moon is made of green cheese. One of the earliest references to a cheesy moon has been attributed to the 16th century French satirist Francois Rabelais: “Thought the moon was made of green cheese.” Green, in his time, meant new, non-aged cheese, and--clever writer that he was--he cast the Moon's dark maria or seas (basalt-filled craters) as the bubbles in a wheel of cheese. In a different time and place, however, the green was misinterpreted as the color, and so began the charming--albeit silly--practice of befuddling small children by telling them the moon is made of green (sounds pretty yucky) cheese.

The 17th century clergyman John Wilkins wrote: “You may as soon persuade some country peasants that the Moon is made of green cheese…as that 'tis bigger than his cart wheel.” Apparently, 17th century country bumpkins were not to be hoaxed by tales of lunar edibleness, even if they couldn't be convinced of lunar immenseness.

Image source: NASA

Thursday, May 8, 2008

The Pink Planet

Speedy Mercury, closest planet to the Sun, zips around our nearest star in only 88 days, compared to Earth’s 365-day orbit. The fleet planet was named for the Roman god of travel, traditionally shown in stylin’ winged sandals.

Image by Mary Ann Sullivan

Mercury is an inferior planet. This does not mean it isn’t quite as good as the rest of the planets. “Inferior” simply means that it orbits closer to the Sun than Earth does (Venus is also an inferior planet).

Of the five naked-eye planets, Mercury is the most challenging to spot, for several reasons:

a) Mercury is a moving target. Its speedy orbit means it quickly changes position relative to the Sun. Throughout the year, it alternates between being a morning planet, visible in our eastern sky just prior to sunrise, and being an evening planet, visible in the west shortly after sunset. In either case, it’s visible for only two to three weeks at a time. If you’re not paying attention, you’ll miss it.

b) Because Mercury orbits so close to the Sun, it is sometimes hidden in the Sun’s glare. Note: It is very dangerous to attempt to locate Mercury while the Sun is above the horizon. You could unintentionally look directly at the Sun and permanently damage your eyes. Don’t try it!

c) Because Mercury hangs tight with the Sun, it typically sets soon after the Sun sets or rises shortly before the Sun rises. This limits your windows of opportunity for spotting it.

Now for the good news. We are currently enjoying the best evening apparition of planet Mercury in 2008. This observing week, Mercury reaches its greatest elongation east. This means that, from our perspective on Earth, Mercury and the Sun are about as far apart as they can get during an evening apparition. This separation helps with both (b) and (c) above.

Here’s your chance to bag the smallest and swiftest for your planetary trophy case!

1) Find an observing spot with an unobstructed view of the western sky, i.e. no tall buildings, trees, big hills, etc. Get there just before sunset, so you can make note of where on the horizon the Sun sets. Remember that spot, using a natural or manmade visual marker. Never stare directly at the Sun!

2) Now find the crescent moon in the sky, because you can use it to locate Mercury. As I’ve mentioned in a number of previous posts, the Moon and the planets can be found along the ecliptic. The ecliptic is the imaginary line that represents the path the Sun appears to take across the sky, as seen from Earth. So, if you know where the Sun set, and you see the Moon in the sky, and you draw an imaginary line between the two, you can approximate the ecliptic. Along that line is where you’ll find bright planet Mercury.

3) On the evening of Friday, May 9th, Mercury will be a bit lower than halfway from the Moon to the spot where the Sun sets. Depending on your eyesight and your ability to spot star-like objects while the sky is still illuminated by twilight, it might take up to half an hour after sunset before you spot Mercury. By then, it should be dark enough for anyone to spot it. Don’t worry, you’ll have plenty of time to find it; Mercury won’t set until about two hours after sunset. Obviously, if there are any clouds in the western sky, Mercury could be obscured. If so, try again another night this week.

4) About half an hour after sunset, Mercury’s altitude, that is, its distance above the horizon, will be around the height of your fist. Make a fist and hold it at arm’s length in front of you, with your thumb at the top. Place the bottom of your fist at the horizon. Look for a bright star-like object at or slightly above the top of your fist. Mercury will be the second brightest “star” in the western sky. Only Sirius the Dog Star, low in the southwest, will be brighter. Find it yet? Congratulations on your planetary conquest!

By the way, the bright star just below and to the left of Mercury is Aldebaran, aka the Eye of the Bull, in the constellation Taurus.

5) At the same time each night after the 9th, the Moon will be a bit higher in the sky, but Mercury will be around the same altitude above the western horizon. You’ll simply need to draw a longer imaginary line to connect the Moon and the sunset point.

6) Mercury is known as the “Pink Planet.” I looked askance at the first person to tell me that, but darned if it doesn’t look pink or peach every time I observe it. Do you see any color? Compare Mercury to stars around it. Try comparing it to bright Sirius, which is blue-white in color. Sometimes comparison will help you see its subtle pink or peach hue. Of course, if you are of the male persuasion, you may--like my significant other--relentlessly dispute that pink and peach are even different colors.

Thursday, May 1, 2008

My Favorite Flicks with Astronomy or Space Themes

This one’s just for fun. Post your picks for favorite films with an astronomy or space theme, or comment on mine. Hmmm, I’m getting a sudden, strong craving for Red Vines and Raisinets…

5) Red Planet (2000) Stars Val Kilmer, Carrie-Anne Moss, and Benjamin Bratt. I found this film very entertaining, and it really transported me to a somewhat believable Mars, unlike some other contemporary films set on Mars. Moss in a great strong woman role, and the usually annoying Kilmer well directed as a wolfish underling who is ultimately sympathetic. Good edge-of-your-seat, old-fashioned outer space flick.

4) 2001: A Space Odyssey (1968) Stanley Kubrick's enigmatic masterpiece, and a defining film of the Space Age. Required viewing for 20th Century cultural literacy. Rent it.

3) The Right Stuff (1983) Sweeping epic of the Space Race and the first Apollo missions. Stellar cast and larger-than-life characterizations. An exciting ride.

2) Contact (1997) Entertaining, thought-provoking, and inspiring. A terrific story with a cosmic perspective, from the novel by the late great astronomer and astronomy popularizer Carl Sagan. Passionate, intelligent performance by Jodie Foster. It's got heart, it's got soul, it's got brains. OK, it’s got some silly Hollywood science too, like radio astronomers ‘listening’ with headphones. But I love that it was partially filmed at the Very Large Array in my home state of New Mexico.

1) Local Hero (1983) A quirky but unforgettable little film by Scottish director Bill Forsyth, with pitch-perfect performances by Peter Riegert and the late great Burt Lancaster. Terrific supporting cast, bonny Scottish locales, evocative score by Mark Knopfler of Dire Straits, wry humor, and the magic of the aurora borealis. Astronomy wins in the end, and that alone is worth the price of admission.