Thursday, May 28, 2009

The Pond

Last week, we looked at one of my favorite spring star patterns, Three Leaps of the Gazelle. We learned that ancient Arabic star lore holds that the gazelle leapt from a spot in the sky known as the “Pond.” We can view that spot with the naked eye, as it is the well-known Coma Star Cluster in the constellation Coma Berenices (KOH-mah bare-uh-NIGH-seez).

Coma Berenices means Berenice’s Hair. Queen Berenice was a real person, a monarch of ancient Egypt. The Greek legend associated with Her Highness relates that she pledged her hair to the gods if they would keep her husband safe in battle. When he returned in one piece, she cut off her locks as promised and placed them in a temple. By the following day, they had disappeared. The court astronomer— apparently as politically astute as he may have been scientifically minded— determined that they had ascended to the heavens and could be seen as the spangled patch near Leo the Lion’s tail.

Let’s comb the sky for the queen’s tresses.

1) About an hour after your local sunset time, face south. 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 right shoulder to the west, and you’ll be facing approximately south.

Star map created with Your Sky

2) Tilt your head back and look at the zenith, the point in the sky that’s directly overhead. Near the zenith, or a bit below it toward the southern horizon, you should spot a fuzzy patch of stars. It will be slightly above and slightly east of Leo the Lion’s tail. This is the Coma Star Cluster (also known by its catalog designation Melotte 111)— what the Greeks saw as a bejeweled head of hair.

This star cluster is the most prominent naked-eye feature of Coma Berenices, and it’s the best way to tell when you’ve navigated into that particular constellation.

3) If you have binoculars or a small, wide-field telescope like the Starblast Astro, examine the cluster a bit more closely. Use your lowest power eyepiece (highest mm number) in your telescope. This is a really big object, so you don’t want to put much magnification on it.

Coma Star Cluster
© T. Credner & S. Kohle,

The Coma Star Cluster is an open cluster, a collection of stars that formed around the same time in the same nebula, or cloud of gas and dust. This cluster is believed to have around 40 member stars. You may want to think of them as a sort of family group.

Coma Galaxy Cluster
Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)

Coma Berenices doesn’t really have any other notable star patterns. Its other crowning glory, the Coma Galaxy Cluster, lies hidden to the unaided eye. The dense cluster contains thousands of galaxies, some of which can be observed by an amateur with a large-aperture reflecting telescope.

Astronomy Essential: The planets orbit the Sun at different speeds.

As the planets of our solar system orbit the Sun, they travel at different speeds. The closer the planet’s orbit is to the Sun, the greater its speed. The farther the planet’s orbit from the Sun, the slower its speed. Therefore Mercury, the nearest planet to the Sun, travels at an average orbital speed of 29.7 miles per second, whereas Neptune, the most distant planet, travels at a much slower average orbital speed of 3.3 miles per second.

The acceleration of planets that are closer to the Sun occurs because the closer the planet is, the greater the gravitational force the Sun exerts on it.

The “average orbital speed” is given here because, during its orbit, each planet speeds up when it is nearer the Sun and travels more slowly when it is far from the Sun. This variation in distance from the Sun occurs because the planets travel in elliptical orbits, not perfectly circular ones.

Thursday, May 21, 2009

Three Leaps of the Gazelle

Between two of the boldest naked-eye star patterns in the spring sky lies a third more demure pattern that’s one of my personal favorites. It’s quite easy to spot when you know where to look, so let’s go stargazing, shall we?

1) About an hour after your local sunset time, face west. 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— close enough for our purposes.

2) Tilt your head back and look at the zenith, the point in the sky that’s directly overhead. A little to the north (right), you should spy the distinctive seven-star pattern of the Big Dipper. The Big Dipper is an asterism, a recognizable star pattern, and it lies in the constellation of Ursa Major the Big Bear.

Star maps created with Your Sky

3) Now look a little south (left) and west from the zenith. Look for the Sickle, the curved asterism that marks the head of Leo the Lion. The Sickle looks a bit like its namesake, the old-fashioned farm implement, or like a backwards question mark. Spot it? Great.

4) Look in the space between the curved top of the Sickle and the bottom of the bowl of the Dipper for three pairs of stars widely spaced from one another. Each pair is around the same distance from the other pairs, and the spacing between the two stars of each pair is around the same. In addition, the stars are all around the same magnitude of brightness. This similarity of pattern helps the little pairs to stand out from the stars around them.

These form the asterism known as Three Leaps of the Gazelle. The three star pairs all lie within the constellation of Ursa Major the Big Bear, and they mark three of the bear’s paws.

Ancient Arabic star lore relates that the gazelle was startled by the lash of the lion’s tail when it sprang from “the Pond,” what we know as the Coma Star Cluster in the constellation Coma Berenices (Berenice's Hair). You can spot the Pond naked eye from a dark site; it looks like a large, bright patch just off Leo's tail.

5) Starting at the Pond, the first set of hoofprints you come to are the stars Alula Australis and Alula Borealis. Alula (uh-LOO-luh) is from the Arabic for first leap; Australis and Borealis are Latin for southern and northern, referring to the respective position of each star.

The middle set of hoofprints are the stars Tania Australis and Tania Borealis. Tania (TAH-nih-yuh) is from the Arabic for second leap.

The final set of hoofprints are the ones farthest from the Pond. The northernmost star is Talitha (TAH-lith-uh), from the Arabic for third leap. Its companion has no traditional name, so we know it simply as Kappa, its star catalog designation.

Can you imagine the swift gazelle leaving behind those three pairs of watery hoofprints as it leapt between twin perils of lion and bear?

Astronomy Essential: The Milky Way galaxy belongs to a galaxy group.

The Milky Way, our home galaxy, is a member of a group of galaxies called the Local Group. It contains around 30 galaxies. The two that are closest to the Milky Way are called the Large Magellanic Cloud and the Small Magellanic Cloud. They are much smaller than the Milky Way and can be seen with the naked eye from the Southern Hemisphere.

Another well-known member of our Local Group is the Andromeda Galaxy, which can be seen naked eye from the Northern Hemisphere. The Andromeda Galaxy is the closest large galaxy to our Milky Way; it lies around two and a half million light years from Earth.

Galaxies throughout the universe tend to cluster into groups. The members of these galaxy groups interact gravitationally and sometimes collide.

Thursday, May 7, 2009

Science v. Poetry

Recently a fifteen-year-old girl told me she hated science because it was so analytical. Once you break something down into all those little pieces and examine them, she complained, you lose the poetry of the thing.

As someone striving to communicate astronomy and science in a (hopefully) vibrant and accessible way, hearing this stopped me in my tracks. It was all I could do to stammer, "But the little pieces are the poetry!" She seemed not in the least bit convinced.

So I’ve been thinking about this problem a lot lately. How does one convince a creative-minded teenager (she’s in a performing arts school) that science is relevant to her life? Or at least that poetry and science aren’t mutually exclusive? How does one convince anyone of this?

In seeking thoughtful answers to these questions, I must first consider my own science education.

I too was far more drawn to poetry than science when I was growing up. In fact, memorable science experiences are few and far between. I can remember dissecting a frog in a biology class (the icky factor does prevail). I can remember feeling wonder at growing some sort of bacteria in an agar-filled petri dish (probably because it was a hands-on activity). I can remember learning the names of the (then) nine planets in orbital order from the Sun, and seeing a diagram of the concentric planetary orbits.

Everything else–all those science lessons I passively ingested and regurgitated without any real understanding–has been lost.

At home, I would drag a chaise lounge into the middle of my semi-rural backyard at night and find the constellations with the help of my little field guide. But this was hardly a science experience. Other than a twinkling point of light, I hadn’t a clue what a star was. I was initially drawn to stargazing through my love of Greek mythology. Tracing the star patterns was another way to indulge in the romance of those legends. Poetry again.

In my daily orbit, there was no astronomy club, no person with a telescope, no person who’d even seen a telescope. The overt message from teachers was, "Girls do not excel in math and science." In my home, however, there was a love of nature and a reverence for the natural world that has stayed with me, deepened over the years, and fueled my quest for science literacy.

Second, I must consider the current science learning environment in the school the fifteen-year-old attends, a high school in one of the largest cities in the nation. Because it’s an underperforming school, freshmen must take a science course called Integrated Coordinated Science, which covers topics in Earth Science, Physics, Chemistry, and Biology. This ostensibly prepares them for full-blown Physics, Chemistry, and Biology courses over the next three years.

The textbook purports to support an inquiry-based program: the learning of science by asking questions, digging deeper, and inquiring further. This is the current state of the art in science education. I suppose the textbook is better than some. I’ve just never been a big fan of textbooks, and browsing this one didn’t compel me to become one. Although I’m not a trained educator, the curriculum seemed to me to be rather dry and, well, superfluous. Clearly, it wasn't working for the fifteen-year-old. How much science minutiae do students need to absorb if they’re not going to pursue science-related degrees or careers? How many formulaic hoops should they have to jump through?

Yes, I get that there are byproducts of mental discipline and deductive reasoning skill produced in the process of doing the textbook’s prescribed activities and calculations. But wouldn’t it be far more valuable for kids to leave the experience inspired and intrigued, on fire to know more, with a reverence for the scientific approach to life and an understanding that science represents the underpinnings of absolutely everything? To see the intricately beautiful architecture of chemistry and physics when they peel the cover off of anything? To see the light of long-extinct supernovas shining out from their friend’s eyes and imagine the Milky Way spinning like a pinwheel in the vastness of expanding space? To see the poetry in an atom’s electron cloud and a tree’s transpiration of water vapor from its leaves? In short, to fully integrate the truths of scientific knowledge with the poetry of human vision?

This week, go outside and look at the night sky in a new way. See the stars as they are: nuclear reactors transforming hydrogen fuel into helium in their cores, gigantic spinning spheres of unimaginably hot gasses, bubbling cauldrons of light and heat energy. Then imagine them as the swollen, blazing stars of Van Gogh’s masterpiece, Starry Night.

In the battle between science and poetry, we must at least hope for a draw.

Equipped with his five senses, man explores the universe around him and calls the adventure Science. ~Edwin Hubble

Astronomy Essential: We are made of star stuff.

Our bodies are composed of elements forged in the nuclear furnaces of stars.

About three minutes after the Big Bang, the cosmos was a primordial cloud of hydrogen, helium, and lithium. The early generations of stars that formed from this cloud were massive and short-lived. They burned themselves out quickly and ended in cataclysmic explosions called supernovas. These supernovas spread the original three elements, plus additional elements forged in the stars’ nuclear cores, throughout the universe. In addition, more exotic elements that can only form in the extreme conditions of a supernova explosion were created and spewed into the cosmos.

Many of these elements ended up in the nebula (cloud of gas and dust) where our Sun and its attendant planets formed. The life forms that emerged on planet Earth were, therefore, also composed of these elements that came from the stars.