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StarDate Online - Your guide to the universe





 



Vanishing Planets

Thu, 27 Jul 2017 05:00:00 +0000

A star in Cygnus, the swan, is entering the final stages of life, so it’s starting to puff up like a giant balloon. And that’s trouble for two of its planets. Over the next couple of hundred million years, they’ll be roasted and then engulfed by the dying star.

The system is known as Kepler 56. It’s about halfway between bright Vega, which is high in the east at nightfall, and slightly fainter Deneb, the tail of the swan, to the lower left of Vega.

The star is younger than the Sun, but it’s also heavier, so it’s quickly converted the original hydrogen fuel in its core to helium — a process that will continue in the Sun for several billion years. Today, the core of Kepler 56 is quiet, with nuclear reactions taking place only in a thin shell around the core.

In response to that change, the outer layers are puffing outward, toward two planets. Both worlds are much closer to Kepler 56 than Mercury, the innermost planet in our own solar system, is to the Sun. And both are quite large and puffy — similar to the giants of the solar system.

As Kepler 56 continues to evolve, its outer layers will expand even more. As the star’s surface approaches the planets, their atmospheres will vaporize and stream off into space, leaving only their dense cores. Eventually, those bare chunks of rock and metal will fall into Kepler 56 — and the two planets will vanish from the universe.

 

Script by Damond Benningfield

StarDate: 
Thursday, July 27, 2017
Teaser: 
Doomed planets around a dying star



Zone of Death

Thu, 27 Jul 2017 05:00:00 +0000

Stellar time bombs shine in tonight’s sky. Among the brightest are Antares, the heart of Scorpius, which is low in the south, and Deneb, the tail of the swan, in the northeast. Each will end its life with a titanic blast known as a supernova.




Black Hole Reality

Wed, 26 Jul 2017 05:00:00 +0000

Black holes are among the most popular objects in the universe. But they’re also among the most misunderstood. Among many misconceptions, they’re not as voracious as they’re often portrayed.

A black hole is an object with such powerful gravity that nothing can escape from it, including light. Some were born from the collapse of supergiant stars, and are several times as massive as the Sun. Millions of these objects may speckle the Milky Way galaxy.

When a star becomes a black hole, though, it doesn’t automatically suck up all the planets and other objects around it.

If the Sun were to become a black hole, for example — something that’s not possible, by the way — Earth and the other planets wouldn’t “feel” anything different. Even though the black-hole Sun would be just a few miles in diameter, Earth would continue to orbit at the same speed and distance as it does today. So would Mars and Jupiter and Halley’s Comet.

The point is that while the Sun’s size and energy output would change dramatically, its mass would remain the same, and it’s mass that determines an object’s gravitational pull, not its size.

Objects that got too close to the black hole would be torn apart, and their remains would form a hot disk. As this material spiraled into the black hole, it would get extremely hot, so it would glow brightly. Beyond that close range, though, the rest of the solar system would go on as before — undisturbed by the nearby black hole.

 

Script by Damond Benningfield

StarDate: 
Wednesday, July 26, 2017
Teaser: 
The reality about black holes



V404 Cygni

Wed, 26 Jul 2017 05:00:00 +0000

A star system in the celestial swan can’t seem to settle down. Every few decades, V404 Cygni flares to thousands of times its normal brightness, the result of likely feeding frenzies by a black hole.




Beryllium

Tue, 25 Jul 2017 05:00:00 +0000

In the movie “Galaxy Quest,” a starship is powered by a sphere of beryllium, one of the lightest chemical elements. That may be strictly Hollywood fantasy, but beryllium is an important component in many spacecraft.

Beryllium comes in several forms, but only one of them is stable. That form is produced between the stars, when cosmic rays zap atoms of heavier elements, splitting the atoms apart.

A tiny bit of beryllium was incorporated into Earth’s crust. And it has a lot of uses. It’s combined with copper or other elements, for example, to make alloys that are especially strong and durable.

Beryllium doesn’t block X-rays or most other forms of radiation, so it’s used in many scientific settings. It forms the pipes that surround the particle beams in the Large Hadron Collider. When the particles in those beams ram together, the radiation and particles they produce pass right through the pipes so they can be recorded by scientific instruments.

Beryllium also frequently finds its way into space. It’s used in some rocket nozzles, and was a key component in the brakes and windshields of the space shuttles.

And because it doesn’t expand or contract much as it changes temperature, it’s also great for the mirrors of space telescopes. All the mirrors aboard Spitzer Space Telescope are made of beryllium, and so are the giant mirrors of the new James Webb Space Telescope — “powering” the continued exploration of the universe.

 

Script by Damond Benningfield

StarDate: 
Tuesday, July 25, 2017
Teaser: 
A key element in fact and fantasy



M71

Tue, 25 Jul 2017 05:00:00 +0000

The tiny arrow known as Sagitta is in the east as night falls and arcs high overhead later on. Under dark skies you can just make out the arrow, not far to the upper left of Altair, the bright star at the southern point of the Summer Triangle.




On the Downslope

Mon, 24 Jul 2017 05:00:00 +0000

Water, ice, or wind may have carved this notch in the rim of Endeavour crater, which was photographed by the Opportunity Mars rover in June. The rover's tracks are visible heading toward the notch, known as Perseverance Valley. The rover will move farther down the valley in August, after Mars emerges from behind the Sun and communications are restored. [NASA/JPL/Cornell/Arizona State]

(image)



Oxygen

Mon, 24 Jul 2017 05:00:00 +0000

Oxygen is one of the most important elements on Earth. It makes up about one-fifth of the mass of the atmosphere, nine-tenths of the mass of water, and two-thirds of the mass of the human body. It’s a by-product of plant life, and a necessity for animal life. And it combines with other elements to make everything from water to rocks.

All of the oxygen atoms on Earth — and throughout the universe, for that matter — were made by stars.

When a star is born, it’s made mainly of hydrogen, the simplest chemical element, which was forged in the Big Bang. For most of its life, the star fuses the hydrogen in its core to make helium. At the end of its life, a star as massive as the Sun or heavier fuses the helium to make heavier elements. A star like the Sun makes carbon and oxygen, while heavier stars make even more elements — all the way up to iron.

Over the 14-billion-year history of the universe, stars have made more oxygen than any other element, so it now accounts for about one percent of all the atoms in the universe.

When a star dies, it expels much of its gas into space. Stars like the Sun do so in a fairly gentle process, creating beautiful clouds that eventually dissipate. More massive stars do it more explosively, blasting out debris at a few percent of the speed of light. This mixture of elements can then be incorporated into new stars and planets — and at least in the case of our own Earth, into living organisms as well.

 

Script by Damond Benningfield

StarDate: 
Monday, July 24, 2017
Teaser: 
Breathing a creation of the stars



Southern Sky

Mon, 24 Jul 2017 05:00:00 +0000

Many amateur astronomers turn their telescopes toward the south on summer evenings. The region of the sky around Sagittarius and Scorpius contains some prominent star clusters, which are popular targets.




Emptiness

Sun, 23 Jul 2017 05:00:00 +0000

It’s lonely out here in the galactic suburbs. The closest neighbors are light-years away — distances that are truly astounding. The distance to the Sun’s nearest stellar neighbor, Proxima Centauri, is almost 29 million times the Sun’s diameter. At that same scale, if you live in a house that’s 50 feet wide, your nearest neighbor would be more than a quarter-of-a-million miles away — farther than the Moon.

That’s a pretty typical gap between star systems in this part of the galaxy — although not necessarily between individual stars. While the Sun is alone, many other stars have close companions. Proxima Centauri, for example, belongs to a system of three stars.

The space between the stars isn’t completely empty. It contains wisps of hydrogen and helium gas, plus a tiny smattering of heavier elements. On average, there’s about one atom of gas for every cubic centimeter of space.

There’s a lot more stuff packed together in the giant clouds known as nebulae. If they have enough gas and dust, they can give birth to new stars. Even so, by earthly standards a nebula still qualifies as a hard vacuum.

The stars are all following their own orbits around the center of the galaxy, so over time, the distances between them varies. In 10,000 years, for example, Proxima Centauri will no longer be our closest neighbor. Instead, it’ll be Barnard’s Star, at just 3.8 light-years — about half a light-year closer than Proxima Centauri is today.

 

Script by Damond Benningfield

StarDate: 
Sunday, July 23, 2017
Teaser: 
The emptiness between the stars



Wild Duck Cluster

Sun, 23 Jul 2017 05:00:00 +0000

The star cluster Messier 11 is more than 6,000 light-years away, in the constellation Scutum, the shield. The cluster’s brightest stars outline the letter V, which resembles a flight of wild ducks. So M11 is also known as the Wild Duck Cluster.




Far, Far Away

Sat, 22 Jul 2017 05:00:00 +0000

It’s a long way from Earth to the center of the galaxy. But the exact distance is uncertain — measurements vary by several thousand light-years.

The most accurate method of measuring astronomical distances is called parallax. To understand how it works, hold out a finger and look at it with first one eye, then the other. The finger appears to shift against the background. The angle of the shift reveals how far the finger is from your eyes.

Astronomers determine parallax by looking at an object when Earth is on opposite sides of the Sun. The change in position causes a target to shift a tiny bit compared to the background of more-distant objects.

As the distance increases, though, the angle gets smaller. Eventually, it gets so small that it’s almost impossible to measure. That’s especially true when you’re looking through Earth’s atmosphere, which blurs the view. New technology has sharpened the view, but there’s still a lot of wiggle room in the measurements.

Another technique looks at how certain stars change in brightness. There’s a relationship between the length of each brightness cycle and the star’s true brightness. But clouds of dust between Earth and the center of the galaxy absorb a lot of light, complicating the measurements.

So when you take all the difficulties into account, different studies yield a distance of between about 24,000 and 28,000 light-years away — a long jaunt any way you look at it.

 

Script by Damond Benningfield

StarDate: 
Saturday, July 22, 2017
Teaser: 
Mapping the distance to the galactic center



Scutum

Sat, 22 Jul 2017 05:00:00 +0000

A small, faint “shield” of stars climbs high across the south tonight. Scutum represents the coat of arms on the shield of John Sobieski, a 17th-century king of Poland and one of that country’s national heroes.




Black Widows

Fri, 21 Jul 2017 05:00:00 +0000

Black widows lurk among the stars. They slowly destroy their companions, ingesting part and sweeping away the remains.

These nasty-sounding objects are pulsars — the spinning corpses of once-mighty stars that blasted themselves apart. All that’s left is their crushed cores, known as neutron stars. Some neutron stars spin, emitting beams of energy that sweep across the cosmos like a lighthouse. From Earth, we see such a beam as on-and-off pulses — hence the name “pulsar.”

Some pulsars have companions — “normal” stars like the Sun, or perhaps the “failed” stars known as brown dwarfs. Radiation from the pulsar heats the companion, causing it to puff up and lose its grip on the hot gas at its surface. Some of the gas is pulled in by the pulsar, causing it to spin faster — up to hundreds of times per second.

But pulling material off the surface of its companion is only half of the story of a black widow.

In some cases, the pulsar’s radiation also erodes the surface of its companion like a blowtorch, with gas streaming away from the pulsar. Over time, the combination of accretion — pulling material into the pulsar — and erosion — blasting stuff away from the pulsar — can completely destroy the companion.

So far, astronomers have caught only a handful of black widows in the process of destroying their companions. But they suspect that many more have already finished the deed — dead stars that have devoured their mates.

 

Script by Damond Benningfield

StarDate: 
Friday, July 21, 2017
Teaser: 
Celestial creepy-crawlies



One Month Away

Fri, 21 Jul 2017 05:00:00 +0000

A spectacular total solar eclipse is just one month away. It will be visible across a narrow path that stretches from Oregon to South Carolina, with the rest of the United States seeing a partial eclipse.




Hot Weather

Thu, 20 Jul 2017 05:00:00 +0000

Clouds rotate across the surface of a brown dwarf in this series of images snapped by the Very Large Telescope in Chile. The images were snapped roughly 48 minutes apart. The brown dwarf, known informally as Luhman 16B (after its discoverer), is about six light-years from Earth. It is more massive than a planet, but not massive enough to ignite nuclear fusion in its core and shine as a star. Like a star, though, it is made of gas. It is cool enough for molecules to condense to form solid particles in its upper atmosphere. These particles then form clouds. Astronomers have discovered clouds on several other brown dwarfs as well. [ESO/I. Crossfield]

(image)



Hot Weather

Thu, 20 Jul 2017 05:00:00 +0000

Hot Weather Clouds rotate across the surface of a brown dwarf in this series of images snapped by the Very Large Telescope in Chile. The images were snapped roughly 48 minutes apart. The brown dwarf, known informally as Luhman 16B (after its discoverer), is about six light-years from Earth. It is more massive than a planet, but not massive enough to ignite nuclear fusion in its core and shine as a star. Like a star, though, it is made of gas. It is cool enough for molecules to condense to form solid particles in its upper atmosphere. These particles then form clouds. Astronomers have discovered clouds on several other brown dwarfs as well. [ESO/I. Crossfield] The objects known as brown dwarfs are oddballs. They’re heavier than planets, but not heavy enough to trigger the nuclear reactions that would make them shine as true stars. In fact, they’re often described as failed stars. Yet they share some traits with both stars and planets. Like stars, their surfaces are hot, with temperatures of up to several thousand degrees. But like planets, those surfaces may be topped by layers of clouds and giant storms. Astronomers have discovered “weather” on the surfaces of several brown dwarfs. They can’t actually see the clouds and storms. But they know they exist because the brown dwarfs get fainter and brighter in different wavelengths as they rotate. The sometimes-dramatic change in brightness indicates that the surface of a brown dwarf consists of layers of clouds with embedded storm systems. The clouds and storms are quite different from those on Earth, though. The clouds are so hot that they’d be made of small particles of iron or silicon, not water. And the storms might be a lot like Jupiter’s Great Red Spot — cyclones big enough to swallow an entire planet. Indeed, a stormy brown dwarf might look a lot like Jupiter, with bands of clouds circling all the way around it, and big storms whirling through the clouds. But the brown dwarf would also provide its own inner glow — its heat would make it shine dull red or orange, with the clouds forming dark bands across its stormy surface.   Script by Damond Benningfield Keywords: Brown DwarfWeather and Atmospheric PhenomenaStarDate: Thursday, July 20, 2017Teaser: Hot weather on failed stars [...]



Lagoon Nebula

Thu, 20 Jul 2017 05:00:00 +0000

The Lagoon Nebula is visible low in the southern sky tonight. To find it, look south around 10 p.m. for Sagittarius, a pattern of stars that forms a teapot. The Lagoon Nebula is visible through a small telescope just above the teapot’s spout.




Moon and Venus

Wed, 19 Jul 2017 05:00:00 +0000

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

Keywords:

StarDate: 
Wednesday, July 19, 2017
Teaser: 
A brilliant early morning encounter



Moon and Venus

Wed, 19 Jul 2017 05:00:00 +0000

Beautiful Venus, the brilliant “morning star,” stands close to the upper left of the Moon at dawn tomorrow. The planet is brighter than any other object in the night sky other than the Moon, so it’s hard to miss.




Altair

Tue, 18 Jul 2017 05:00:00 +0000

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

StarDate: 
Tuesday, July 18, 2017
Teaser: 
Zipping across the night sky



Moon and Companions

Tue, 18 Jul 2017 05:00:00 +0000

The Moon is closing in on two bright points of light in the dawn sky: the star Aldebaran and the planet Venus. Aldebaran stands to the lower left of the Moon at first light tomorrow, with Venus, the “morning star,” farther along the same line.




Eagle Nebula

Mon, 17 Jul 2017 05:00:00 +0000

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

StarDate: 
Monday, July 17, 2017
Teaser: 
Inspirational beauty in the southern sky



Milky Way

Mon, 17 Jul 2017 05:00:00 +0000

The hazy band of the Milky Way arches high overhead tonight. It represents the muted glow of millions of stars in the disk of our Milky Way galaxy. Even so, it is impossible to see if you are surrounded by artificial light sources.




Red Eye

Sun, 16 Jul 2017 05:00:00 +0000

The Juno spacecraft snapped this image of Jupiter's Great Red Spot on July 10, when it flew just 5,600 miles (9,000 km) above the giant storm. The storm currently spans more than 10,000 miles (16,000 km), which is wider than Earth. It has been shrinking in recent decades, though; at its peak, it was more than twice Earth's diameter. The image contrast has been enhanced to bring out subtle features in the clouds of the Great Red Spot and the surrounding atmosphere. [NASA/JPL/MSSS]

(image)



The Dolphin II

Sun, 16 Jul 2017 05:00:00 +0000

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

StarDate: 
Sunday, July 16, 2017
Teaser: 
The beautiful, graceful dolphin



Delphinus II

Sun, 16 Jul 2017 05:00:00 +0000

A pretty binary climbs across the southern sky tonight. Gamma Delphini is at the snout of Delphinus, the dolphin, which is in the east as night falls. Under dark skies, Gamma Delphini looks like a single point of light, but a telescope reveals two stars.




The Dolphin

Sat, 15 Jul 2017 05:00:00 +0000

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 Keywords: AstronomersDelphinus, the DolphinHistory of AstronomyNaming and Classification of StarsStarDate: Saturday, July 15, 2017Teaser: A practical joke in the night sky[...]



The Dolphin

Sat, 15 Jul 2017 05:00:00 +0000

Although the small constellation Delphinus, the dolphin, is faint, under a moderately dark sky it’s fairly easy to pick out. That’s because its outline really does look like a dolphin. It’s about a third of the way up the eastern sky at nightfall.




Centennial Celebration

Fri, 14 Jul 2017 05:00:00 +0000

NASA's Langley Research Center celebrates its centennial this month. Construction began on its first building, near Chesapeake Bay in Virginia, in July 1917, when the center was part of the National Advisory Committee for Aeronautics, the precursor to NASA. The center has supported the Apollo missions to the Moon, the Viking missions to Mars, and other space projects. This illustration, by sixth-grade student Apoorva Panidapu of Evergreen, California, was the winning entry in the center's centennial student art contest. [NASA/LRC]

(image)