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Moon, Antares, Saturn

Sun, 22 Jan 2017 06:00:00 +0000

The crescent Moon will slide past several bright companions over the next few mornings. Tomorrow, the bright orange star Antares is to the lower right of the Moon at first light, with the golden planet Saturn to the lower left of the Moon.




Moon, Antares, Saturn

Sun, 22 Jan 2017 06:00:00 +0000

Early risers, take note: The crescent Moon will slide down past several bright companions over the next few mornings, creating some beautiful configurations in the pre-dawn sky.

First up are the star Antares and the planet Saturn. Bright orange Antares stands to the lower right of the Moon at first light, with golden Saturn about the same distance to the lower left of the Moon.

Antares and Saturn are among the few objects in the night sky to show any color. Antares looks orange because of its surface temperature — it’s thousands of degrees cooler than the surface of the Sun. Saturn, on the other hand, looks yellow because of the composition of its upper atmosphere.

The giant planet is a big ball of hydrogen and helium gas, with a tiny mixture of other chemical elements. Those elements combine to form layers of clouds at the top of the atmosphere.

The clouds in the top layer are made of ammonia. Those in the layers below probably are made of water, ammonia, and a compound that includes ammonia and sulfur.

These compounds are all white. But above Saturn’s visible cloudtops, several compounds react with sunlight to form hydrocarbons, which have an orange or red color. Tiny amounts of them fall into the ammonia clouds, adding a bit of color. When we see Saturn in the night sky, the colors blend together to give the giant planet a subtle golden hue — a rare bit of color in the starry night sky.

More about Saturn and the Moon tomorrow.

 

Script by Damond Benningfield

StarDate: 
Sunday, January 22, 2017
Teaser: 
Subtle color for a giant planet



Leading the Dog

Sat, 21 Jan 2017 06:00:00 +0000

Two “dog stars” hunker low in the east and southeast as night falls at this time of year. From most of the U.S. one of them, Procyon, rises a bit before the Dog Star Sirius, the brightest star in the night sky. The name Procyon means “before the dog.”




Leading the Dog

Sat, 21 Jan 2017 06:00:00 +0000

Two “dog stars” hunker low in the east and southeast as night falls about now, and scamper higher across the sky later on. One of them rises a bit earlier than the other — a fact reflected in its name: Procyon means “before the dog.”

Procyon is the brightest star of Canis Minor, the little dog. It rises a few minutes earlier than Sirius, the brightest star in all the night sky. Sirius is also the leading light of Canis Major, the big dog, so it’s known as the Dog Star.

Because of their relative locations in the sky, Procyon always rises before Sirius — but only from north of roughly 30 degrees north latitude. Below that line, Sirius rises first.

Although Procyon isn’t as bright as Sirius, it’s still one of the most prominent stars in the night sky. In fact, the two stars look so bright for the same reasons — they are fairly bright, but more important, they’re both close neighbors.

Sirius is about 26 times brighter than the Sun, but it’s also less than nine light-years away — closer than only a few other star systems. Procyon is only about a third as bright as Sirius, and it’s about three light-years farther, so it looks a good bit fainter as it leads the Dog Star across the night sky.

The two stars are quite low as the sky gets good and dark tonight. Procyon stands due east, with Sirius well to its right, posing a little lower in the sky as seen from most of the United States.

Tomorrow: subtle color for a big planet.

 

Script by Damond Benningfield

StarDate: 
Saturday, January 21, 2017
Teaser: 
One dog leads another across the sky



More Fornax

Fri, 20 Jan 2017 06:00:00 +0000

The constellation Fornax, which is low in the south at nightfall, has only one modestly bright star, Alpha Fornacis. Binoculars show that it consists of two stars. One is bigger and heavier than the Sun, while the other is smaller than the Sun.




More Fornax

Fri, 20 Jan 2017 06:00:00 +0000

There’s no fountain of youth to make people look younger. But there is one for stars. It’s a process that sounds like a story from a 1950s B movie — “stealing” life from another star.

A good example of a rejuvenated star is in the constellation Fornax, which is low in the south as night falls. It has only one modestly bright star, Alpha Fornacis, which is 46 light-years away.

To the eye alone, it’s not much to look at. Binoculars, though, reveal that it consists of two stars. One of them is bigger and heavier than the Sun. It’s nearing the end of its life, even though it’s almost two billion years younger than the Sun.

The other star of Alpha Fornacis is smaller than the Sun, and its surface is cooler than the Sun’s, so it glows orange. Yet it should be even redder than it is. And that’s where the story of rejuvenation comes in.

The star has been identified as a blue straggler. That means its color shifted to slightly bluer wavelengths as the star aged. It might have done so by merging with another star, which would rev up its nuclear reactions, making it hotter and bluer. On the other hand, it might have changed color by simply stealing gas from a third star in the system.

And there is some evidence of a third member of Alpha Fornacis — the corpse of a once-normal star. If it’s there, it may be about half as massive as the Sun, and quite close to the blue straggler — a dead star that gave part of its life to a stellar companion.

 

Script by Damond Benningfield

 

StarDate: 
Friday, January 20, 2017
Teaser: 
Drinking from the fountain of youth



Giant Storm

Thu, 19 Jan 2017 06:00:00 +0000

A sunspot forms a dark blotch on the Sun in this recent image from ALMA, a set of telescopes in Chile that look at the universe in millimeter and submillimeter wavelengths, a portion of the radio spectrum. Sunspots are relatively cool magnetic storms on the Sun's surface. The number of spots waxes and wanes on a roughly 11-year cycle. The Sun is currently on the downward slope of one such cycle, so few sunspots have been observed in recent years. This spot is roughly twice the diameter of Earth. [ALMA (ESO/NAOJ/NRAO)]

(image)



Fornax

Thu, 19 Jan 2017 06:00:00 +0000

Fornax, the furnace, is quite low in the south as night falls right now. Created in the 17th century, it originally was called Fornax Chemica, after a small heater that was used for chemistry experiments. The name was shortened a few decades later.




Fornax

Thu, 19 Jan 2017 06:00:00 +0000

Almost a century ago, astronomers partitioned the celestial sphere into 88 constellations. Most of them — the famous ones — date from ancient times. But 14 of them — none of which is famous — were created by a single man, in the 18th century.

Nicolas Louis de la Caille was a French astronomer. In 1751, he set up an observatory at the Cape of Good Hope in South Africa to study the stars of the southern hemisphere. Over the following year, he cataloged about 10,000 stars. And later, he used those stars to draw new constellations in regions of the sky that weren’t visible from most of Europe.

He called one of them Mons Mensa — table mountain. It honored a feature near la Caille’s observatory. He named all the others for tools that had scientific uses, such as the telescope and microscope, or artistic uses, such as the painter’s easel.

One of those constellations is Fornax, the furnace, which is quite low in the south as night falls right now.

It was originally called Fornax Chemica, after a small heater that was used for chemistry experiments. Another astronomer shortened the name a few decades later.

Fornax isn’t much to look at — at least not with the eye alone. It contains only one modestly bright star, Alpha Fornacis, which we’ll talk about tomorrow. But a telescope reveals many treasures within its borders, including some beautiful individual galaxies, plus a giant cluster of galaxies — fiery visions in the celestial furnace.

 

Script by Damond Benningfield

StarDate: 
Thursday, January 19, 2017
Teaser: 
Firing up a celestial furnace



Morning Mercury

Wed, 18 Jan 2017 06:00:00 +0000

Mercury, the solar system’s smallest planet, will be at its greatest distance from the Sun in the morning sky tomorrow. It looks like a fairly bright star quite low in the southeast as dawn brightens, to the lower left of Saturn, another planet.




Fast Bursts

Wed, 18 Jan 2017 06:00:00 +0000

When astronomers find a new type of object that goes “boom,” it takes a while to explain it. They have to figure out how far away the objects are, which reveals how bright they are. And they have to see them at different wavelengths to understand what they’re doing.

They’re just starting that process for a class of objects known as fast radio bursts — blasts of radio waves that last no more than a few thousandths of a second. The first was discovered in 2007, and a few dozen others have been seen since then.

Theorists have proposed several explanations for the bursts — from mergers between stellar corpses, to flares on the surfaces of highly magnetized corpses.

The effort to understand them has been stymied because astronomers hadn’t seen any of the bursts at other wavelengths. But that changed with a burst that was discovered in November of 2013.

A space telescope was looking at the same region of sky where the radio burst was discovered. An analysis, reported late last year, showed that the burst was accompanied by a blast of gamma rays, which are produced by some of the most violent events in the universe.

That means that this particular burst took place far outside our home galaxy, so it had to be extremely energetic. That eliminates some possible explanations for the burst. But astronomers say that different bursts could have different causes. So it’ll take a while to fully understand the diverse nature of fast radio bursts.

 

Script by Damond Benningfield

 

StarDate: 
Wednesday, January 18, 2017
Teaser: 
Explaining a new kind of outburst



Orion Nebula

Tue, 17 Jan 2017 06:00:00 +0000

The Orion Nebula is a fuzzy patch of light just below the three bright stars that represents Orion’s Belt. The nebula is a vast cloud of gas and dust that has given birth to thousands of stars over the last few million years.




Super Supernovae II

Tue, 17 Jan 2017 06:00:00 +0000

A supernova that was discovered a couple of years ago has astronomers doing a lot of head scratching. The explosion appears to be a couple of hundred times brighter than a typical supernova. But none of the models of how stars explode can fully explain why the blast was so bright.

Supernova 15LH is thought to be the violent death of a massive star. Such a star dies when it can no longer produce energy in its core. The core collapses, and the surrounding layers are blasted into space.

It’s not easy to explain a blast as powerful as 15LH, though — but that hasn’t stopped the theorists from trying.

One team, for example, says that the energy could be coming from the interaction between the supernova blast wave and a shell of gas and dust around the star. The material would have been expelled from the star long before the explosion, and was moving away from the star.

Other groups have come up with other ideas. One says that the supernova was powered by a magnetar — the star’s collapsed core. The super-dense, highly magnetized core would be spinning about a thousand times per second, pumping energy into the material around the core with each turn.

And yet another idea says that 15LH wasn’t a supernova at all. Instead, it was the death throes of a star that was ripped apart by a supermassive black hole.

With all these competing ideas, it’s likely to take a while to explain Supernova 15LH.

We’ll talk about another stellar blast tomorrow.

 

Script by Damond Benningfield

StarDate: 
Tuesday, January 17, 2017
Teaser: 
Explaining a brilliant explosion



Last Walk

Mon, 16 Jan 2017 22:02:55 +0000

Eugene Cernan, the last astronaut to walk on the Moon, died on January 16, at age 82. Cernan, shown here with the Moon's Taurus mountains in the background, commanded the Apollo 17 mission, which landed on the Moon in December 1972. Cernan and crewmate Harrison Schmitt, a geologist, spent three days in the Taurus-Littrow Valley, and conducted three long moonwalks. They also used a lunar rover (at right) to cover about 22 miles during their explorations. Cernan also piloted the Gemini 9 mission, during which he conducted a spacewalk that left his visor fogged and his heart rate at dangerous levels. He also served as lunar module pilot for Apollo 10, which was a dress rehearsal for the first landing mission, Apollo 11. [NASA]

(image)



Aries

Mon, 16 Jan 2017 06:00:00 +0000

One of the dimmest but best-known constellations of the zodiac is in fine view right now. Aries, the ram, stands high in the sky at nightfall, and drops down the western sky during the evening.




Super Supernovae

Mon, 16 Jan 2017 06:00:00 +0000

Every supernova is a brilliant beacon — a stellar explosion that can outshine an entire galaxy. But in recent years, astronomers have logged a few dozen supernovae that take “brilliant” to extremes — they shine anywhere from about 10 to hundreds of times brighter than a typical supernova. And theorists are still trying to understand why.

The first examples of “superluminous” supernovae were discovered more than a decade ago by Robert Quimby, a graduate student at the University of Texas at Austin. He was looking for supernovae across large patches of the sky when he discovered a couple of exceptionally bright examples. Since then, other astronomers have joined the search, leading to many new discoveries.

These super-bright explosions appear to come in two varieties. One contains a lot of hydrogen — the element that makes up the bulk of most stars. The other type shows no hydrogen.

The hydrogen-rich variety may involve a shell or bubble of hydrogen gas around the star that was expelled from the star before it exploded. If the bubble has expanded to just the right size, then the collision with the debris from the supernova could make it extremely hot. At such high temperatures, it would radiate enormous amounts of light — making it a superluminous supernova.

The hydrogen-poor variety is a bit more mysterious. Theorists have proposed several explanations — from the magnetic cores of dead stars to stellar encounters with black holes. More about that tomorrow.

 

Script by Damond Benningfield

StarDate: 
Monday, January 16, 2017
Teaser: 
Making a super-duper supernova



Bright Stars

Sun, 15 Jan 2017 06:00:00 +0000

From southern latitudes of the U.S., the two brightest stars in the night sky line up in the south tonight. The brighter star is Sirius, which is high in the south in late evening. The other is Canopus, which is well below Sirius and a little to the right.




Scary Asteroids

Sun, 15 Jan 2017 06:00:00 +0000

Astronomers compile catalogs of all kinds of objects: variable stars, black holes, binary stars, and many others. One of their most important catalogs keeps getting bigger — it passed 15,000 entries a couple of months ago.

The catalog lists N-E-Os — Near-Earth Objects. These asteroids and comets follow paths that approach or cross Earth’s orbit around the Sun. Such objects have the potential to hit our planet, so it’s important to find and track them. With enough warning, it might be possible to deflect an object that’s on a collision course.

Most of that work is done by automated searches in Arizona and Hawaii, which scan the sky most clear nights of the year. A new search is scheduled to begin next year in Europe, with another, using a giant new telescope in Chile, to follow soon after.

Scientists estimate that they’ve found more than 90 percent of NEOs that are at least a kilometer in diameter. Such giant space rocks could cause widespread damage if they hit us. In fact, just such an impact is thought to be responsible for the demise of the dinosaurs.

In recent years, searchers have been looking for even smaller objects. Such objects wouldn’t be big enough to trigger global problems if they hit, but they could destroy a city. But smaller objects are also fainter, so it takes much more effort to find them.

So far, the searches haven’t discovered any problems — none of the 15,000 cataloged NEOs is on a threatening course.

 

Script by Damond Benningfield

StarDate: 
Sunday, January 15, 2017
Teaser: 
Cataloging scary space rocks



Moon and Regulus

Sat, 14 Jan 2017 06:00:00 +0000

Look for Regulus, the heart of Leo, quite near the Moon as they climb into view in mid evening, and a little farther to the right of the Moon at first light tomorrow.




Moon and Regulus

Sat, 14 Jan 2017 06:00:00 +0000

Regulus is one of the brightest stars in the night sky, so people have been looking at it since the beginning. And astronomers have been studying it since the invention of the telescope. And it’s quite close — less than 80 light-years away. So you might think that we’ve known all the important details about it for a long time. You’d be wrong. Astronomers continue to learn about the system. Less than a decade ago, for example, they found that the bright star we see as Regulus has a close companion. That star tells us a lot about the bright star’s history. The companion is small, faint, and quite close to the bright star, which is known as Regulus A. So it’s impossible to see the companion directly. Instead, astronomers detected it by measuring the system’s individual wavelengths of light. They reveal a slight shift in the star’s motion caused by the gravitational tug of the companion. The companion is a white dwarf — the tiny corpse of a once-normal star. That star had to be born with more mass than Regulus A, so it aged faster. It puffed up, then dumped much of its outer layers of gas onto Regulus A. That made Regulus A bigger and hotter, and it made the star spin much faster. That discovery shows that there’s still a lot to learn about the stars — even the ones we think we know well. Look for Regulus just above the Moon as they climb into view in mid-evening, and a little farther to the right of the Moon at first light tomorrow.   Script by Damond Benningfield Keywords: Binary and Multi-Star SystemsLifecycle of StarsRegulusStarsStarDate: Saturday, January 14, 2017Teaser: Learning about a familiar star[...]



Auriga

Fri, 13 Jan 2017 06:00:00 +0000

Auriga, the charioteer, rides high across winter’s evening skies. To find it, look for its brightest star, Capella, which stands high overhead around 10 or 11 p.m. Capella is one of the brightest stars in the night sky, and shines pale yellow.




Local Supercluster

Fri, 13 Jan 2017 06:00:00 +0000

The structure of the universe is like a Russian matryoshka doll — each bit is nested inside a larger one. In our case, for example, Earth is a member of the solar system, which in turn is a member of the Milky Way galaxy, which is a member of a family of galaxies known as the Local Group.

And the nesting doesn’t end there. The Local Group is a member of a much larger collection of galaxies known as the Local Supercluster. It spans more than a hundred million light-years, and contains tens of thousands of galaxies.

The supercluster was discovered and named more than half a century ago, by Gerard de Vaucouleurs. It’s centered roughly on the Virgo Cluster, which contains a couple of thousand galaxies.

Most of the supercluster’s galaxies appear to form a flat disk, with a few in a wide halo around the disk.

The mass of all these galaxies is equal to a million billion Suns. But most of that mass is invisible. Instead of glowing stars and gas clouds, it consists of dark matter — material that produces no detectable energy, but that exerts a gravitational pull on the visible matter around it. It may consist of subatomic particles, although physicists have had a hard time finding them.

The nested dolls may not end with the Local Supercluster, though. A study a couple of years ago found that it may be part of an even bigger supercluster — one that spans half a billion light-years — one more layer in the structure of the universe.


Script by Damond Benningfield

 

 

StarDate: 
Friday, January 13, 2017
Teaser: 
“Nesting” the structure of the universe



Andromeda Galaxy

Thu, 12 Jan 2017 06:00:00 +0000

From a dark skywatching location, the Andromeda galaxy is visible to the unaided eye. It looks like a tiny smudge of light. At this time of year, it stands high in the west as night falls.




Local Group IV

Thu, 12 Jan 2017 06:00:00 +0000

Crash Course A series of images shows the collision and merger of the Milky Way and its nearest large galactic companion, M31, the Andromeda galaxy. Top left shows the galaxies still far apart, with M31 a tiny disk at upper left and the starry band of the Milky Way forming the bright streak across the night sky. M31 grows bigger in the next two images, then slams into the Milky Way, stirring up the stars of both galaxies and triggering a violent burst of starbirth. In the bottom row, the newly merged galaxies settle into life as a giant elliptical, with a bright haze of starlight filling Earth's night sky. The collision won't happen for several billion years, though. [NASA/ESA/Z. Levay and R. van der Marel (STScI)/T. Hallas/A. Mellinger] The Milky Way is doomed. Our home galaxy will collide with the Andromeda galaxy. The collision will scramble both of them, ejecting many of their stars. The two galaxies will then merge — and the Milky Way as an individual galaxy will be no more. Andromeda and the Milky Way are the biggest members of the Local Group, a small family of galaxies. Both are giant spiral galaxies that contain hundreds of billions of stars. Right now, they’re about two and a half million light-years apart. But they’re caught in each other’s gravitational grip. So every hour, they move about a quarter of a million miles closer — the distance from Earth to the Moon. As they get closer, their approach will accelerate. In about four billion years, the galaxies will ram together. Individual stars are so widely spaced that collisions between stars are unlikely. But the gravity of all the stars and gas clouds will stir things up. It’ll eject big streamers of stars from the galaxies, and cause clouds of gas and dust to slam together, giving birth to millions of new stars. Over the following billion years or so, Andromeda and the Milky Way will merge to form a single galaxy — one of the most impressive in all the cosmos. Andromeda is pretty impressive even now. From a dark skywatching location, it’s visible to the unaided eye. It looks like a tiny smudge of light. At this time of year, it’s high in the west as night falls — a glimpse at our galactic future.   Script by Damond Benningfield   Keywords: Andromeda Galaxy, M31Galaxy Formation and MergersMilky Way GalaxyStarDate: Thursday, January 12, 2017Teaser: A collision course for the Milky Way [...]



Crash Course

Wed, 11 Jan 2017 06:12:15 +0000

A series of images shows the collision and merger of the Milky Way and its nearest large galactic companion, M31, the Andromeda galaxy. Top left shows the galaxies still far apart, with M31 a tiny disk at upper left and the starry band of the Milky Way forming the bright streak across the night sky. M31 grows bigger in the next two images, then slams into the Milky Way, stirring up the stars of both galaxies and triggering a violent burst of starbirth. In the bottom row, the newly merged galaxies settle into life as a giant elliptical, with a bright haze of starlight filling Earth's night sky. The collision won't happen for several billion years, though. [NASA/ESA/Z. Levay and R. van der Marel (STScI)/T. Hallas/A. Mellinger]

(image)



Evening Venus

Wed, 11 Jan 2017 06:00:00 +0000

The planet Venus, which shines as the brilliant “evening star” right now, stands farthest from the Sun for its current evening appearance. That means it stands highest in the sky at sunset, and remains in view longer than at any other time.




Local Group III

Wed, 11 Jan 2017 06:00:00 +0000

Astronomers have spotted what may be the puniest galaxy ever seen. It has so few stars that it emits just 180 times as much light as the Sun. That’s a far cry from our home galaxy, the Milky Way, whose many stars produce tens of billions of times more light than the Sun. The dim new galaxy provides insight into how the Milky Way formed. Current theory holds that giant galaxies like the Milky Way grew as lesser galaxies rammed together. But the theory predicts that hundreds or even thousands of satellite galaxies should orbit the Milky Way. So far, though, we know of only about 50. The new galaxy is one of them. It’s about 280,000 light-years away, in Virgo, which is halfway up the southern sky at first light. Its brightest star, Spica, is just below the brilliant planet Jupiter. The galaxy is named Virgo I. It’s just a few hundred light-years across, compared to a hundred thousand light-years for the Milky Way. Its discovery hints that the Milky Way could have many other dim satellites. Virgo I turned up after astronomers had used the giant Subaru Telescope in Hawaii to search only a quarter of one percent of the sky. That suggests that hundreds more of these super-faint satellite galaxies orbit the Milky Way. If that many satellites are found, their discovery will lend support to the leading idea for how giant galaxies came to be. The Milky Way may merge with another giant galaxy in the distant future; more about that tomorrow.   Script by Ken Croswell, Copyright 2016   Keywords: Local GroupMilky Way GalaxyVirgo, the VirginStarDate: Wednesday, January 11, 2017Teaser: A faint satellite of the Milky Way[...]



Twilight

Tue, 10 Jan 2017 06:00:00 +0000

Twilight has precise beginning and ending points. Civil, nautical, and astronomical twilight begin or end when the Sun lies six, 12, and 18 degrees below the horizon, respectively. Astronomical twilight requires the darkest skies.




Local Group II

Tue, 10 Jan 2017 06:00:00 +0000

The Milky Way is like a high-ranking politician or a popular music star: it travels with a big entourage. Astronomers have discovered about four dozen possible companion galaxies. A couple of them are visible to the unaided eye, but most are quite small and faint. The Milky Way and its entourage are all members of the Local Group — dozens of galaxies that are bound by their mutual gravitational pull. The Milky Way and another big spiral, the Andromeda galaxy, are its largest members. The Milky Way’s most prominent satellites are the Large and Small Magellanic Clouds. Each contains several billion stars, plus lots of gas for making more stars. From southern skies, they’re visible to the eye as small, glowing clouds. Most of the Milky Way’s other satellites are much smaller. In fact, the smallest contain only a few thousand stars. Although a few of these satellites have been known for a while, most were discovered only in the last few years. These late discoveries are quite faint, so you have to look carefully to see them. And a few others have been hidden behind clouds of stars or dust in the Milky Way. Some of these little guys are being pulled apart by the Milky Way, which is taking their stars and gas for itself — a fate that’s probably befallen many other small satellites during the galaxy’s long lifetime. A recently discovered satellite suggests that there could be many more of them out there even now. More about that tomorrow.   Script by Damond Benningfield       Keywords: Galaxy ClusterLocal GroupMagellanic CloudsStarDate: Tuesday, January 10, 2017Teaser: The Milky Way’s galactic entourage[...]



More Moon and Aldebaran

Mon, 09 Jan 2017 06:00:00 +0000

The star Aldebaran stands to the upper right of the Moon this evening. The bright orange star represents the eye of the bull. It is near the end of its life, so it has bloated to dozens of times the diameter of the Sun.