StarDate

Early risers are in for a skywatching treat at first light tomorrow — a close pairing of the crescent Moon and the planet Venus. Venus looks like a dazzling star just to the left or upper left of the Moon.

Venus is the second planet out from the Sun, while Earth is third. Because of that, Venus has a limited range in our sky. At best, it’s visible for a few hours before sunrise or after sunset.

Also because of that arrangement, Venus shows phases, just as the Moon does — from a bare crescent to almost full. It’s a crescent around the time it passes between Earth and Sun, and almost full just before it passes behind the Sun. We don’t see it when it’s full because it’s too close to the Sun then.

Right now, the planet is roughly at a right angle to the Sun, so it’s about half full. So if you look at it with a telescope, you’ll see that half of the hemisphere that faces our way is in sunlight, while the other half is in darkness.

You might expect the planet to be brightest when it’s full, and faintest when it’s a crescent, but that’s not so. Venus is much closer to us when it’s a crescent, so it covers a larger fraction of the sky. We also catch more of its reflected sunlight then. So Venus is at its brilliant best a little before and after it passes between Earth and the Sun.

Venus is always bright, though, so it’s an easy target. For now, look for it in the east at first light — tomorrow, near the crescent Moon.

Script by Damond Benningfield

The stars that dust the night sky are all moving around the center of the galaxy at hundreds of thousands of miles per hour. Yet they’re so far away that their motion is imperceptible across not just a human lifetime, but hundreds of lifetimes. In fact, even one of the fastest stars as seen from Earth will move just one degree over the next 5,000 years — less than the width of a finger held at arm’s length.

Altair is the brightest star of Aquila, the eagle. In fact, the name “Altair” means “the flying eagle.” The star is in the east at nightfall, at the lower right corner of the bright, widespread Summer Triangle.

Altair is only about 17 light-years away — closer than all but a handful of the stars that are visible to the unaided eye. That’s the main reason it’s moving in such a hurry. It’s like watching race cars on opposite sides of a track. Although the cars are all moving at about the same speed, those on the side closest to you cover a larger angle in the same amount of time than those on the far side.

Yet that motion is too tiny to plot with the eye alone. Instead, astronomers make extremely precise measurements of its position against the background of more-distant stars. Comparing Altair’s position over a period of years reveals its apparent speed across the sky.

Again, look for Altair almost due east at nightfall, climbing high across the south during the night, and almost due west at first light.

Script by Damond Benningfield

One of the most beautiful and inspiring regions in the galaxy climbs across the south on summer nights. Binoculars reveal some of its stars, and a telescope shows its hazy outline. But its true glory comes through best in long-exposure images.

The Eagle Nebula is a vast complex of stars, newly forming stars, and the raw material for stars — clouds of gas and dust. The nebula was discovered by comet hunter Charles Messier. But it was made famous a couple of decades ago by an image from Hubble Space Telescope, known as the Pillars of Creation.

The pillars of cold gas and dust span several light-years. They’re sculpted by winds and radiation from hot, young, massive stars. The stars erode the outer regions of the pillars, but they also create shock waves that squeeze them. The shock waves compress dense knots of gas and dust, helping them collapse to form new stars.

The nebula has given birth to hundreds of stars in a wide variety of sizes and masses.

There’s evidence that one of its heavy stars has exploded as a supernova. If so, then a shockwave from the star is racing outward. In fact, it’s probably already plowed through the pillars, blasting away most of the material for making more stars. Because the system is about 6500 light-years away, though, we won’t see that happen for another millennium or so. That means we can enjoy the inspiring beauty of the Eagle Nebula for many more centuries.

Script by Damond Benningfield

Most constellations bear little resemblance to their namesakes. You need a great imagination to see a king in the stars of Cepheus, for example, or a “sea goat” in Capricornus.

One constellation that does resemble its namesake is the dolphin, Delphinus. It’s a small grouping of stars that’s low in the east at nightfall, and swims high across the south later on. And that little group of stars really does look like a dolphin jumping through the edge of the starry Milky Way.

In Greek mythology, Delphinus carried a poet to safety when he jumped overboard to escape some nasty sailors. The poet and the dolphin were commemorated in several coins that were issued around 500 B.C. And the dolphin gained longer-lasting recognition through its own constellation.

None of the individual stars of Delphinus is particularly interesting. The brightest is Beta Delphini. It’s near the center of the constellation, and marks the end of the dolphin’s torso. The dolphin’s body stretches to the left as it climbs higher in the sky, and its tail to the right.

Beta Delphini is actually a binary. The two stars were born from the same cloud of gas and dust, and they remain bound to each other by their mutual gravitational pull. They orbit each other once every 27 years.

Look for the beautiful dolphin swimming into view in the east as darkness falls, and climbing high across the south during the night.

Script by Damond Benningfield

Many stars and constellations are named for people, but only a few of those people were real. One of them was an Italian astronomer who published a star catalog. And thanks to a practical joke, he has not one star named after him, but two.

Nicolo Cacciatore was assistant director of Palermo Observatory in Sicily. In the early 1800s, he began compiling a new edition of the Observatory’s star catalog.

When the catalog was released in 1814, it included two star names that no one had ever seen before: Sualocin and Rotanev. They were attached to the brightest stars of Delphinus, the dolphin. Before that, the stars had been known simply as Alpha and Beta Delphini. Other astronomers didn’t know what the names meant, and Cacciatore wasn’t telling.

Three decades later, though, a British astronomer solved the mystery of the names. The English version of Cacciatore’s name would be Nicholas Hunter. When that name is converted to Latin, it becomes Nicolaus Venator. Spell the two names backwards, and you get Sualocin and Rotanev — a bit of immortality for Nicolo Cacciatore.

Delphinus is a small constellation, and its stars are all faint. Even so, under a moderately dark sky it’s fairly easy to pick out. That’s because its outline really does look like a dolphin, swimming gracefully through summer skies. It’s about a third of the way up the eastern sky at nightfall, and soars high across the south later on.

We’ll have more about the dolphin tomorrow.

Script by Damond Benningfield

When NASA set out to send people into space, it handed the job to its oldest facility. Langley Research Center had been operating on the banks of Chesapeake Bay for four decades. To handle the new task, its engineers formed the Space Task Group. The group oversaw the design and construction of the Mercury spacecraft, and selected and trained the original astronauts — the center’s first big step into space exploration.

Langley is commemorating its hundredth anniversary this week. Construction began on its first facility in July of 1917. It wasn’t part of NASA at the time, though — NASA didn’t even exist. Instead, it was part of the N-A-C-A — the National Advisory Committee on Aeronautics.

Langley was the first civilian aviation research center in the country. It built a series of wind tunnels for testing airplanes and their systems. That work helped improve aircraft performance and safety.

When NASA was formed, in 1958, it inherited the NACA facilities. Langley continued its aviation work, but also branched out into space.

Its engineers developed the concept that Apollo used for getting the Moon. They managed a set of robotic orbiters that mapped the lunar surface, and built simulators to help astronauts maneuver in space and land on the Moon. Langley also managed the successful Viking missions to Mars.

Langley continues its work today, with projects involving aviation, space, and other fields — a century after its birth.

Script by Damond Benningfield

A scorpion’s most fearsome feature isn’t its claws, although those are pretty scary-looking. Instead, its the stinger — the part that injects venom. And the celestial scorpion has a good one: two stars at the end of its curving tail.

Scorpius is low in the south as darkness falls. The stinger is well to the lower left of Antares, the scorpion’s bright orange heart. It consists of two stars that are side by side, with the one on the left a bit brighter than the one at the stinger’s tip.

Both stars are almost 600 light-years away. The fact that they’re visible to the unaided eye from that distance means they’re extremely bright — among the brightest stars in the galaxy.

The brighter star is Lambda Scorpii. It consists of three stars. Two of them are Class “B” stars — among the hottest and brightest in the galaxy. And at least one of them is destined to explode as a supernova.

The third member of the system is so young that it’s not yet shining as a true star. Instead, it’s a protostar — an object that’s still collapsing to become a star. It should ignite the fires of nuclear fusion before long, joining its older siblings as full-fledged stars.

The stinger’s fainter star is Upsilon Scorpii. It’s a single star. And like the main members of Lambda Scorpii, it’s class B, so it shines many thousands of times brighter than the Sun. It, too, is fated to explode as a supernova — briefly adding to the fearsomeness of the scorpion’s stinger.

Script by Damond Benningfield

Everything about Scorpius is impressive. It’s a prominent constellation that really does resemble its namesake. Its leading light, Antares, is one of the brightest stars in the night sky. And its wide “head” contains many stars, some of which are destined for brilliant final acts.

Scorpius is in the south at nightfall. The scorpion’s head stands to the upper right of bright orange Antares, and is outlined by three stars. From top to bottom, they’re Beta, Delta, and Pi Scorpii.

Beta is actually a system of at least six stars, which are divided into two tight-knit groups. A couple of the stars are more than 20,000 times brighter than the Sun. Delta Scorpii consists of two stars, and one of those also shines fiercely. And Pi Scorpii has at least three stars, including one more brilliant beacon.

All or most of these stars formed from a vast complex of gas and dust that spans Scorpius and the nearby constellation Centaurus. In the last 15 million years or so, it’s given birth to thousands of stars. And quite a few of them are especially heavy, which makes them especially hot and bright.

The stars at the top end of the weight scale will live short lives — in fact, some of them probably will expire in the next few million years. And when they die, they’ll blast themselves to bits. For a while, such a conflagration will outshine anything in the night sky except the Moon — briefly adding to the impressiveness of the scorpion.

Script by Damond Benningfield

Our brains tend to find patterns just about everywhere. Some of them are real, but many are just imagined. A cloud, for example, might look like a dragon or a fairy-land castle. An eroded mesa on Mars can look like a human face. And patterns of stars might look like a dolphin, a lion, or a scorpion.

In fact, the celestial scorpion is one of the highlights of summer nights. It’s in the south as darkness falls, quite low above the horizon, and wheels across the southwest later on. Many cultures have seen a wide head, a slightly curved body, and a sharply curved tail complete with stinger — the perfect outline of a scorpion.

The outline itself is just a coincidence. But the fact that so many bright stars appear in that part of the sky isn’t. Scorpius is embedded in the hazy band of light known as the Milky Way — the glow of countless stars that define the disk of the Milky Way galaxy. And it’s roughly in the direction of the galaxy’s heart, where we’re looking into a great thicket of stars. So it’s like gazing into the densest part of a forest — there are big trees everywhere you look.

Clouds of gas and dust in that direction are giving birth to many new stars. Many of these newborns are especially big and bright — stars that really stand out. Several of these standouts are among the stars that form the pattern that we see as the scorpion.

Three of these stars form the scorpion’s head, and we’ll have more about them tomorrow.

Script by Damond Benningfield

Two of the most striking objects in the night sky are meeting in the east before dawn over the next couple of weeks: the planet Venus and the star Aldebaran. Venus is the brilliant “morning star,” so you can’t miss it. And Aldebaran shines bright orange — the baleful eye of the celestial bull.

Tomorrow, Venus will stand almost directly above Aldebaran. Over the next few days, though, Aldebaran will pass Venus as it climbs higher into the sky. And after that, it’ll pull away from the brilliant planet, quickly leaving it behind.

Their motions are different because of their different positions relative to Earth.

Aldebaran and the other true stars are so far away that they appear to move across the sky as a group — the relative positions of any two stars always stays the same. But Venus is a planet, so it’s much closer to us. In fact, it’s the closest planet of all.

Venus orbits the Sun inside Earth’s orbit. So Venus and Earth are like two runners on a circular track, with Venus on the inside lane and Earth farther out. Because Venus has a shorter distance to cover, it takes less time to complete each lap. So its position against the background of more-distant objects — the stars — changes from day to day. The change is especially noticeable when Venus is passing by an especially bright star such as Aldebaran.

So watch Venus and Aldebaran as they cruise past each other in the early morning sky over the next couple of weeks.

Script by Damond Benningfield