by Kim Malville
The night sky of May
Summer is coming! Now is the time to start spending more time outside at night. The most brilliant star in the evening skies looking south is ruddy Arcturus, halfway up the sky. Arcturus is similar in mass to the sun but it is nearly 3 billion years older. Because of that it has exhausted all of the hydogen in its core and has grown larger to become 25 times larger than the sun and nearly 200 times brighter. It is the brightest star north of the celestial equator.
Arcturus can be located using the bent handle of the Big Dipper: follow its arc southward to reach the star. If you continue south you will move downward to Spica, the brightest star of Virgo. Beyond Spica you can continue the curve to Corvus the Crow. Beyond Corvus are the fainter constellations of Crater and the water monster Hydra. To the right of Spica is Leo the Lion with Regulus its brightest star, and just beyond it is Jupiter.
Arcturus is particularly interesting because prehistoric Polynesian navigators used it to guide them on the voyage from Tahiti to Hawaii. They called Arcturus Hōkūle’a, the “Star of Joy”. Arcturus is the zenith star of the Hawaiian Islands. Using Hōkūle’a and other stars, the Polynesians launched their double-hulled canoes from Tahiti and the Marquesas Islands. Traveling east and north they eventually crossed the equator and reached the latitude at which Arcturus would appear directly overhead in the summer night sky. Knowing they had arrived at the exact latitude of the island chain, they sailed due west on the trade winds to landfall. If Hōkūle’a could be kept directly overhead, they landed on the southeastern shores of the Big Island of Hawai’i. For a return trip to Tahiti the navigators could use Sirius, the zenith star of that Tahiti. Since 1976, the Polynesian Voyaging Society’s Hōkūle‘a has crossed the Pacific Ocean many times under navigators who have incorporated this technique in their non-instrument navigation.
In the early evening Venus is the brightest object above the western sky. Below it and to the right you should be able to see Mercury about an hour after sunset. Higher in the sky is Jupiter. And then to the left of Spica is Saturn. Venus and Jupiter move toward each other (Venus moves faster since it is closer to the earth) until a magical evening on June 30 when they will come together in a spectacular conjunction.
May 1: For two weeks Mercury should be visible below Venus just after sunset. Just beyond Mercury you might be able to spot the Pleiades at one hour after sunset.
May 4: The moon will be close to Saturn near the head of Scorpius.
May 21: The crescent moon is on the bent knee of Pollux and close to Venus in the constellation of Gemini.
May 23: The moon has moved just below Jupiter.
May 30: The moon will be moving toward Spica, getting closer and closer throughout the night.
Organics circling a young star
Organic molecules have been found in a disk of gas, dust, and ice swirling around a very young star. This is the kind of disk that produces planets and comets. Using the radio telescope known as the Atacama Large Millimeter Array (ALMA) in Chile, astronomers have found large amounts of methyl cyanide—(CH3CN), cyanoacetylene (HC3N) and hydrogen cyanide (HCN) in the proto-planetary disk surrounding a very young star roughly twice the size of the sun, which is located about 455 light-years from Earth. The ratios of these molecules are similar to those is found in comets in our solar system. These are the kind of molecules that form the building blocks of life.
This research demonstrates that these gaseous disks, wherever they are, function as engines of chemical synthesis, creating environments vital for building the chemical complexity of biological life. All this happens long before a planetary surface is created. This kind of “pre-biotic” chemistry found in asteroids and comets in the solar system seems to be replicated in other young planetary systems in our galaxy. The building blocks of carbon-based life are thus not only found all over our solar system in the comets that sweep in toward the sun and in the asteroids that occasionally fall to earth, they exist throughout our galaxy. As we are discovering more and more often these days, it’s no great leap to imagine carbon-based life, like us, thriving amongst the hundred billions of galaxies in our universe.
Glaciers on Mars
When you hike over glacial moraines in the Sangre de Cristos this summer, think Mars! The red planet has thousands of glaciers buried beneath its dusty surface. Mars apparently contains enough frozen water in its glaciers to blanket the planet with a layer of ice 3’-4’ deep. If you are a doubter, look at this photo of a rock-covered Martian glacier with its lateral and terminal moraines.
Radar data, collected by Mars-orbiting satellites, combined with computer models of ice floes show the planet has about 5.3 trillion cubic feet of water locked in the ice.
What is it that transformed Mars from a warm, wet and presumably Earth-like planet early in its history into the cold, dry desert that exists today?
Billions of years ago, Mars lost its global magnetic field when its core, smaller than Earth’s, cooled. Without a protective magnetic field much of its atmosphere was stripped away by the solar wind. The atmospheric pressure on Mars is now so low that water ice sublimates and becomes water vapor. But when glaciers are protected by a thick layer of dust, they can survive.
It is a strange and disturbing thought that when our planet warms up and all glaciers on the earth have all melted, glaciologists can continue their research on Mars.
Mars has lost about 87% of the water it once had due to evaporation into its thin atmosphere. The planet probably had an ocean more than a mile deep covering almost half of its northern hemisphere.