A pair of hunting dogs chases high across the north on May evenings. The hounds are pursuing Ursa Major, the great bear, which stands below them at nightfall. You’ll recognize the bear because it contains the stars of the Big Dipper. The dogs are held in leash by Boötes, the herdsman.
The dogs form the constellation Canes Venatici. Unlike Ursa Major and Boötes, which date from antiquity, the hunting dogs are fairly recent. Polish astronomer Johannes Hevelius drew the constellation in the 17th century to fill in some gaps between more prominent star patterns.
As a result, Canes Venatici is small and faint. You need fairly dark skies to see its stars, and a great imagination to picture a pair of hounds. The constellation’s three brightest stars form a wide-spread letter V, with its point aiming south.
Canes Venatici’s brightest star is Cor Caroli — the “heart of Charles.” Famed astronomer Edmond Halley named it for England’s King Charles the Second. Binoculars or a telescope show that it’s really two stars. The brighter one is hotter and brighter than our own Sun, and it’s the star that’s visible to the eye alone.
The constellation’s next-brightest star is Chara, and it’s similar to the Sun. It’s about the same color, temperature, and brightness. In fact, it looks almost exactly like the Sun would appear if we could view it from the same distance — about 30 light-years.
Look carefully for the stars of the hunting dogs as they pursue the great bear across the night.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
Ligeia Mare, one of the largest lakes on Saturn's moon Titan, looms still and dark in this false-color image from the Cassini spacecraft. New research suggests that as the seasons change on Titan, stormy skies could bring big waves or even hurricanes to this and other large lakes, which are filled with ethane, methane, and other liquid hydrocarbons. This image was compiled by Cassini's radar system, which peers through a hydrocarbon smog that cloaks Titan's surface from view. [NASA/JPL/ASI/Cornell]
Text ©2013 The University of Texas at Austin McDonald Observatory
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
The planet Saturn perches to the left of the Moon as night falls this evening. It looks like a bright golden star. The true star Spica stands to their upper right.
Spica is the brightest star of Virgo. And Saturn has been inside that constellation’s borders for most of the last four years.
One reason is that Virgo is one of the largest constellations. Another is that Saturn is so far away from the Sun that it takes the planet almost 30 years to complete a single orbit. So as seen from Earth, it takes that same amount of time for Saturn to complete one circle against the background of stars.
That “circle” isn’t smooth, though. Instead, for a few months each year, Saturn reverses its normal eastward motion and heads westward.
That’s because each year or so, Earth catches up to Saturn and passes it by. As that happens, our viewing angle to the planet changes. It’s like passing another runner on a jogging trail. When you’re behind the other runner, she appears to move forward compared to objects in the distance, such as buildings or mountains. As you catch up and pass her by, though, she briefly appears to move backward against that same background — a result of your changing viewing angle.
Saturn actually moved into the adjoining constellation Libra for a few months, but its reverse motion brought it back into Virgo. It’ll remain there for about three more months, when it’ll once again leave Virgo behind — not to return until the year 2038.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
The Moon takes aim at one of the brightest stars in the night sky tonight: Spica, the leading light of the constellation Virgo. The star is close to the lower left of the Moon as night falls, and even closer to the Moon as they set in the wee hours of the morning. They’ll be at their closest for skywatchers on the West Coast, where they’ll be separated by the width of your finger held at arm’s length.
The gap between them gets smaller because of the Moon’s orbital motion around Earth. It takes 27-and-a-third days for the Moon to make one full loop against the background of stars. At that rate, it covers a distance equal to its own diameter in about an hour.
Keep in mind, of course, that the gap between the Moon and Spica is only a projection effect — the two bodies just happen to line up in the same direction in the sky.
In reality, they’re far apart. The Moon is a bit more than one light-second away — the distance that light covers in a little more than one second, or about a quarter-of-a-million miles. The distance to Spica, on the other hand, is 250 light-years — about six billion times farther than the Moon.
To look at it another way, it took the Apollo astronauts about three days to reach the Moon. At that same average speed, it would take about 50 million years to reach Spica.
So keep an eye on Spica — a star that looks like it’s close to the Moon — throughout the evening and into the early morning.
Script by Damond Benningfield, Copyright 2013
For more skywatching tips, astronomy news, and much more, read StarDate magazine.
The two brightest planets, Venus and Jupiter, will help you find a fainter one, Mercury, as all three shine together in the western twilight about half an hour after sunset Saturday and for a few days after, according to the editors of StarDate magazine.
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