Sunday, July 10, 2016

Last Call for Leo

     Leo isn't long for this world. At least not for the world of the evening sky. He's about to suffer the fate of all zodiacal constellations, slipping behind the Sun and rendered invisible by the dazzling light. This will happen in August and September.
     Over the next week or so you can watch the lion diving towards the western horizon as dusk fades. Between 10:00 and 10:30 pm is about right. A few nights ago I was out watching the holiday fireworks. The neighbors put on a great show and I could see other, more distant flashes. But then things started to settle down and the sky darkened to reveal the best fireworks of all - the stars and planets.

Sky and Telescope illustration

     A pair of Leo's brightest stars - Regulus and Algieba were just above the tree line. The trio that marks his butt was higher up while the familiar sickle of the lion's mane was hard to pick out - lost in twilight and haze. And that very bright star below his tail? That's not a star at all, but the the planet Jupiter which has been keeping Leo company all year.
     The constellation makes its first appearance in the evening sky in late winter, rising in the east. It's a hopeful sign that another spring is on the way. Earth's orbit shifts his position up each night placing Leo high overhead in May and finally sending him westward towards an annual rendezvous with the Sun. Fall and winter will come and go before we see him in the evening again.
     While most of us see a pattern that does indeed resemble a crouching lion, astronomers see much more. Regulus, the "star" of the constellation, is actually four stars gravitationally bound whose light merges as one to our eyes. There are double stars, variable stars, dwarfs and giants as well as flare stars and a carbon star or two. Algieba is known to have a planet in orbit as do a dozen other Leo stars. There are also galaxies sprinkled across the sky in Leo. Huge clans of billions of stars, they are massive but too distant to be seen by the eye alone.

     Much closer and more occasional is the Leonid meteor shower which seems to radiate from here in mid-November. It occurs when the Earth's orbit intersects with that of Comet Tempel-Tuttle and debris frictions and fires up in the atmosphere. Most years it's kind of duddy, some years absolutely spectacular.
     Jupiter also offers much more than meets the eye. There are four large Galilean moons that can be seen with binoculars. These got their namesake astronomer in trouble with the Church when he suggested that not everything orbits around the Earth. Beyond the four biggies are dozens of smaller moons (over 60 and counting). When we look at Jupiter's colorful bands and spots we're seeing the top of its thick atmosphere. It's mostly hydrogen and helium, the same elements that make up the Sun. Indeed, you could almost call Jupiter a "failed" star because it's not quite massive enough to create the pressures and temperatures needed for fusion, the process that produces the intense heat and light which defines stellar.

Damian Peach photo from Sky and Telescope

     It's not known for certain if Jupiter has a solid rocky core. It could just be gases that take on strange properties under the conditions that exist deep within the planet. Think hydrogen atoms compressed so tightly they turn into a dense metallic liquid. In any case we'll soon know more thanks to Juno, a NASA spacecraft that swung into orbit here on the Fourth of July. Check here for photos and updates.

Artist's illustration of Juno approaching Jupiter

     Though Leo and Jupiter are dropping out of the picture there's still plenty to see in the night sky. The Milky Way (our home galaxy) flows high overhead on these July evenings. Look for the summer triangle of bright stars - Vega, Deneb and Altair - embedded in the band with Arcturus further west. Hint: follow the curve of the Big Dippers handle to "arc" to Arcturus.

Sky and Telescope illustration

     Above the southern horizon Mars, Saturn and the star Antares form a shifting arrangement in the constellation Scorpius. Mars has looked distinctly orange all spring. It seems about the same brightness as Jupiter and it's also a place NASA has visited, with Curiosity up there roving as we gaze from down here.

Curiosity sees its shadow on Mars

     We all need to belong. To something, to someplace. It's one of the deepest human desires. We start families. We join churches, teams and organizations. We have school spirit, civic pride and patriotism for our country. We long for land, a place to put down roots. All good and natural urges. On some nights, when the sky is dark and clear and the stars seem close yet infinite, I find myself stretching the idea of "belonging". I imagine belonging to the universe, about as inclusive a concept of place as one can conjure. Out there are exploding stars and colliding black holes, extremes of heat and chill beyond measure, incredible violence and absolute stillness. I sense unlimited worlds to discover and unknowable mystery.
     When it starts to overwhelm I scurry back to our cozy little village solar system where you can peek out the window and watch the antics of those crazy next door neighbor planets. All in all, not a bad place to call home.

Star Girl
     Obviously I love astronomy and star gazing so I have to tell you how lucky I am to know a real live astronomer. Dr. Adele Plunkett is a good friend of Holly's. They skied and ran together at school and Adele has been up to the farm several times to visit. Earlier this year Adele won the Robert L. Brown Outstanding Doctoral Dissertation Award for her research on how stars form in families from molecular clouds. She used the ALMA radio telescope for her work. It's located in northern Chili and is the most complex astronomical observatory ever built. I believe Adele is currently an ALMA Fellow at the European Southern Observatory.
     After four years at Middlebury (2005-2009) she continued her education at Yale, eventually earning a PhD in astronomy. This involved many trips to Chili for telescope time. Amazingly, she also ran marathons, did triathlons and X-C ski raced during that time. She even allowed Holly to talk her into doing the Stowe Derby and has since forgiven my daughter!
     With Adele chasing down clues I'll bet we know more about how stars form in the near future. Congratulations Adele for all your hard work and achievement and thanks for being my "real live astronomer".
     Adele has two blogs you might want to check out: Adele en Chili and The Observing(b)Log

Dr. Adele Plunkett

Suggested Reading
     For a fun look at Jupiter and all its little solar system siblings I'ld recommend Dava Sobel's The Planets. It's science with a light lyrical touch and lots of interesting and unexpected anecdotes.

Suggested Viewing

     Click here for a great shot of Jupiter, its moons and a familiar old friend.

In case of clouds

From the web

     Ok, it's not always clear skies and twinkling stars. But there's often fireflies to take up the slack. Lots of nights this summer there has been both and I've enjoyed double dipping - looking up for awhile and then out across the meadows. Lightning bugs are nocturnal winged beetles. Their family name Lampyridae comes from the Greek "lampein" - to shine. They create light by combining chemicals in their abdomen/tail and this is called bioluminescence. There are over 2000 species but not all produce light. The flashes are a form of communication, a way for males and females of a species to connect and make sparks fly. It's an insect even an astronomer can love!


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