CFHT CLOUD CAM TIME LAPSE SUNRISE JUNE 11, 2012 June 11 The Moon is at last quarter today. That means it is three-quarters of the way through its four-week cycle of phases. At last quarter, sunlight illuminates exactly half of the lunar hemisphere that faces our way. June 10 The summer Milky Way is climbing into good view. It forms a hazy band quite low across the eastern sky in mid evening and arcs high overhead in the wee hours of the morning. It will climb higher each evening, becoming more prominent as it does so. AQUILA, THE EAGLE (ALTAIR) Aquila glides on outstretched wings through the glowing band of the Milky Way. Look for it high in the south in late summer. The brightest star in Aquila is a white star about 17 light-years from Earth called Altair, the Arabic word for eagle. Altair is the southern point of a pattern of three bright stars called the Summer Triangle. Deneb, in the constellation Cygnus, forms the triangle's northeastern point. Vega, in Lyra, the harp, is in the northwest. Altair is nice and bright and easy to find right up to the beginning of winter. Altair is about twice as massive as the Sun, so it will live only about two billion years to the Sun's 10 billion. Despite its size, Altair appears to turn on its axis once every 10 hours, versus about four weeks for the Sun. One of the effects of Altair's high-speed rotation is that its gas is forced outward at the equator, giving the star a flattened appearance -- it is about 14 percent wider through the equator than through the poles. If Altair spun about twice as fast as it does now, it would fly apart. Astronomers refer to Aquila's two "tail" stars as Zeta and Epsilon Aquilae. Together, they also have an older Arabic name: Deneb al Okab, which means "the eagle's tail." The northern star in the tail is actually a system of three or more stars. Only one of them is bright enough to see with the unaided eye. It's a type of star known as a red giant. That means it's in the final stages of life. Its core is getting hotter and denser, while its outer layers are puffing out and getting cooler. That's the same process that awaits the Sun in several billion years. The southern star is a multiple-star system, too. Its brightest star is fairly early in life. It's bigger, heavier, and hotter than the Sun, and it spins close to 200 times faster than the Sun. That means the star bulges out at the equator, so it looks like a squashed beachball. PISCES, THE FISH In the lore of the sky, spring is associated with the constellation Aries, the ram. Yet at the moment of the vernal equinox, which marks the beginning of spring in the northern hemisphere, the Sun actually stands within the borders of the next constellation over -- Pisces, the fishes. Several thousand years ago, when the zodiac was first drawn, the Sun stood inside Aries at the time of the equinox. And today, the March equinox is still known as the "first point of Aries." Yet the Sun has moved from Aries into Pisces because of an effect known as precession. It is a wobble in Earth's rotation caused by the gravitational pull of the Sun and Moon. As a result of this wobble, the point of the equinox moves all the way around the sky. That means that as the centuries roll by, the Sun appears against different stars at the equinox. Pisces, which is best viewed during autumn and winter evenings, is one of the constellations of the zodiac. Despite this claim to fame, though, Pisces is tough to see. Even its brightest stars are no match for the light pollution from many cities and suburbs. Pisces is one member of the "celestial sea," a group of constellations that are all related to water. These constellations probably were associated with water because the Sun passed across them during the rainy season in the ancient Middle East. Spiral galaxy M74 although none of its stars is particularly impressive, Pisces is home to several beautiful galaxies. One of the most prominent is M74, a spiral galaxy that we view almost exactly face on. It's just 24 million light-years away. M74 resembles a slightly smaller version of the Milky Way, so it looks like a glowing cosmic pinwheel. Its spiral arms contain clouds of gas and dust that create new stars. The brightest and hottest of these new stars are blue, giving the spiral arms a blue tint. Traffic Report on 11 June '12 Three visitors are reported to be within ten lunar distances (LD) of our planet today. Risk-listed 2012 LJ exits Earth's Hill sphere, moving from 1.87 to 5.41 LD. Out further, 2012 LT comes its closest to Earth on this passage, reaching 5.18 LD at 1008 UTC, and 2012 LA is outbound from 9.57 to 9.82 LD. Coming to the neighborhood next, 2012 LU arrives inside ten LD on June 16th. This report was generated at 1452 UTC. hohmanntransfer.com/news.htm, stardate.org, space.com, nasa.com, spaceref.com, skyandtelescope.com

• published: 11 Jun 2012
• views: 3173