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StarDate Online - Your guide to the universe





 



Procyon B

Sun, 21 Jan 2018 06:00:00 +0000

The star known as Procyon B is a faint cosmic ember. It’s only a bit bigger than Earth — roughly one percent the diameter of the Sun. And it’s quite close to a bright companion star, Procyon A. That makes it almost impossible to see, even through a big telescope.

That would not have been the case when Procyon B was born. It probably was about twice as massive as the Sun — bigger and heavier than Procyon A is today. That would have made it brighter than Procyon A, too.

Because Procyon B was heavier, it evolved faster. More than a billion years ago, it expelled its outer layers into space, leaving only its dead core — a white dwarf.

The two stars were closer together then. So as Procyon B evolved, it probably had an effect on its companion. As its core died, for example, Procyon B expelled more than two-thirds of its mass; some of that material fell onto its companion.

The extra gas made Procyon A heavier, so it probably accelerated the star’s evolution. As a result, “A” will live a shorter life than it would have otherwise. In fact, it’s already starting to change. In another hundred million years or so, it, too, will shed its outer layers, leaving only its dead core. So the system we know as Procyon will consist of two white dwarfs, shining meekly through the cosmic night.

For now, look for Procyon low in the east as night falls. It rises a little earlier than Sirius, the brightest star in the night sky, which is lower in the southeast.

 

Script by Damond Benningfield

StarDate: 
Sunday, January 21, 2018
Teaser: 
Better days for a cosmic ember



Procyon

Sat, 20 Jan 2018 06:00:00 +0000

Sirius, the Dog Star, is in the southeast this evening. It’s the night sky’s brightest star, so it’s hard to miss. And it’s led into the sky by another bright light — Procyon, the little dog star. It’s to the left of Sirius and a little higher, so it precedes Sirius across the evening sky.

Procyon is among the dozen brightest stars in the night. That’s mainly because it’s just 11 and a half light-years away.

It’s actually a system of two stars. The main star is known as Procyon A. It’s about one and a half times as massive as the Sun, about twice as big, and about seven times as bright.

The star is nearing an important transition point. It’s converted most of the original hydrogen fuel in its core to helium. That’s made the core get smaller and hotter, which in turn has caused its outer layers to puff outward a bit.

Before long, all the hydrogen in the core will be gone, and the star will swell up to giant proportions. It’ll then start converting the helium to carbon and oxygen. Once that process is complete, the nuclear reactions in the core will shut down. Procyon A then will cast its outer layers into space, leaving behind only the dead core — a tiny ember known as a white dwarf.

That’s already happened to the second star in the system, Procyon B. It’s so faint and so close to Procyon A that it’s almost impossible to see, even through a big telescope. But it once was even bigger and brighter than Procyon A. More about that tomorrow.

 

Script by Damond Benningfield

StarDate: 
Saturday, January 20, 2018
Teaser: 
A star at a transition point



Crescent Moon

Fri, 19 Jan 2018 06:00:00 +0000

For many people, one of the most common sights in the night sky is also one of the most confusing. It’s the crescent Moon — a phase in which only a small fraction of the hemisphere that faces Earth is illuminated.

Many folks think the dark portion of the Moon is darkened by Earth’s shadow, but it’s not. The only time the Moon passes through the shadow is during an eclipse. And that happens only during full Moon, when the Moon lines up opposite the Sun.

Instead, the cycle of lunar phases is caused by the Moon’s orbital motion. As the Moon orbits Earth, the angle between Earth, Moon, and Sun changes. That means that sunlight illuminates different fractions of the hemisphere that faces Earth.

The Moon was new on Tuesday, as it passed between Earth and the Sun. The far side of the Moon was facing the Sun then, so the hemisphere that faces Earth was dark.

Today, the Moon has moved away from the Sun, but it still lines up in the Sun’s general direction. At that angle, sunlight illuminates only a few percent of the part of the Moon that faces our way. The rest of the disk is in its own shadow, so it’s nighttime.

If you could stand on the Moon and look toward Earth right now, our planet would be almost full. It’s dozens of times brighter than a full Moon, so it lights up the lunar night. We see that effect as earthshine — a subtle glow across the dark part of the crescent Moon, which is low in the southwest at sunset tonight.

 

Script by Damond Benningfield

Keywords:

StarDate: 
Friday, January 19, 2018
Teaser: 
Shedding light on the crescent Moon



Water Worlds IV

Thu, 18 Jan 2018 06:00:00 +0000

Flying saucers and alien abductions aside, there’s no evidence that Earth has been visited by life from other worlds. In fact, we haven’t found any evidence of intelligent life anywhere else in the universe.

To Enrico Fermi, that lack of neighbors was puzzling. Decades ago, the physicist considered the likely number of planets, the age of the universe, and other factors. And he calculated that everywhere we look, aliens ought to be looking back.

That could mean that we’re alone, or that we’re just not looking hard enough. And according to one present-day scientist, it could also mean that many of the aliens don’t know the rest of the universe exists.

Alan Stern heads New Horizons, a mission that flew past Pluto a couple of years ago. The craft found that an ocean of liquid water could lie below Pluto’s crust. Similar oceans probably exist on several moons of the giant outer planets, and perhaps on other solar-system worlds as well. That makes them much more common than worlds with water on the surface — Earth is the only one.

If such worlds are as common in other star systems, Stern says they could be common homes for life as well. With a solid crust above it, such life might not know that its home world has a “surface,” or that there are other worlds beyond. Such a civilization would be trapped, unable to explore or communicate with the rest of the universe — limiting the number of aliens in our own cosmic neighborhood.

 

Script by Damond Benningfield

StarDate: 
Thursday, January 18, 2018
Teaser: 
Alien life in alien environments



Cold fountains

Wed, 17 Jan 2018 08:34:29 +0000

Fountains of water and ice squirt into space from the near the south pole of Enceladus, one of the moons of Saturn, as depicted in this diagram. The water may come from an underground ocean that contains the chemistry and energy needed to support microscopic life. [NASA/JPL]

(image)



Water Worlds III

Wed, 17 Jan 2018 06:00:00 +0000

Cold fountains Fountains of water and ice squirt into space from the near the south pole of Enceladus, one of the moons of Saturn, as depicted in this diagram. The water may come from an underground ocean that contains the chemistry and energy needed to support microscopic life. [NASA/JPL] The most impressive water fountain in the solar system squirts out from the south pole of Enceladus, a moon of Saturn. Water and ice shoot hundreds of miles into space. The fountain may be powered by Saturn itself. The distance between Saturn and Enceladus varies. As the gap widens and narrows, Saturn’s gravity squeezes the interior of Enceladus. Friction from the constant flexing heats the moon’s core. That generates enough energy to melt some of the ice around the core, creating a deep ocean of liquid water between the core and the crust. And a recent study says that process could have been going on for billions of years. The study’s authors created models of the interior of Enceladus to help explain the jets of water and ice detected by Cassini, a craft that orbited Saturn for more than a decade. The models show that water from the ocean may drip through cracks in the core. As the water descends it’s heated, which makes it rise back toward the surface. The hot water percolates through the rocks, picking up bits of minerals. It then squirts back into the ocean through vents on the ocean floor. Plumes of warm water slowly rise through the ocean and melt some of the ice above it, forming thin spots in the crust. Cracks in the thinner crust then allow some of the water to squirt out into space — forming the solar system’s most impressive water fountain. We’ll talk about water worlds in other star systems tomorrow.   Script by Damond Benningfield Keywords: Saturn's MoonsWater and Water IceStarDate: Wednesday, January 17, 2018Teaser: Forming an impressive water fountain [...]



Water Worlds II

Tue, 16 Jan 2018 06:00:00 +0000

An ocean may once have covered much of Ceres, the largest body in the asteroid belt. And much of that ocean may still be there. It doesn’t pool on the surface, though. Instead, some of its water may have mixed with rock and minerals to make up Ceres’ crust. And some may lie below the surface — perhaps in liquid form, or mixed with other materials.

Ceres is about 600 miles in diameter — roughly a quarter the size of the Moon. It’s been studied in detail by Dawn, a spacecraft that’s been orbiting Ceres for the last three years. Dawn has revealed a surface that’s covered by craters. Bright white features highlight the floors of some of the craters — possible salts from an underground ocean.

Dawn’s observations have shown that the rims of some of the craters, as well as the only tall mountain on Ceres, have “slumped” over the eons — they’re not as tall and sharp as they once were. Yet the little world’s crust should be quite rigid. It’s made of frozen water — possible remnants of an ancient ocean — mixed with other ices, salts, and solid rock — a composition that should allow surface features to hold their shape.

That suggests that there’s a “squishy” layer below the crust. It could be partially liquid — water from the ancient ocean mixed with rock and ice. That would have enough “give” to allow the surface features to slump — reshaping a surface that might once have held an ocean.

We’ll talk about water on another world tomorrow.

 

Script by Damond Benningfield

StarDate: 
Tuesday, January 16, 2018
Teaser: 
Tracing a vanished ocean



Water Worlds

Mon, 15 Jan 2018 06:00:00 +0000

Our planet is a water world — the wet stuff covers more than two-thirds of Earth’s surface. But that may be the proverbial drop in the bucket compared to some other worlds. Vast oceans may hide beneath the surfaces of several bodies in the solar system. And even bigger oceans may cover planets in other star systems.

Missions to the other planets in the solar system have found evidence of water on several moons, as well as two “dwarf” planets.

At least three of those water worlds are moons of Jupiter. The most intriguing is Europa. It appears to have a sub-surface ocean that could be miles deep. The ocean might hold several times as much water as all of Earth’s oceans combined. Hot, mineral-rich fountains might squirt up from far below the ocean floor — perhaps providing conditions that are comfortable for life.

Water is squirting out of a subsurface ocean on Enceladus, a moon of Saturn. And a huge ocean could lurk far below the surface of Saturn’s biggest moon, Titan.

There’s also evidence of water on Pluto, the little world that’s just beyond the realm of the major planets, and on Ceres, the largest member of the asteroid belt; more about that tomorrow.

And a recent study suggests that oceans could almost completely cover some planets in other star systems. Dry land might make up just 10 percent of the surface of such a planet. So if anyone wants a home planet with almost unlimited ocean views, there could be plenty to choose from.

 

Script by Damond Benningfield

StarDate: 
Monday, January 15, 2018
Teaser: 
Water worlds near and far



Icy Mars

Sun, 14 Jan 2018 08:58:13 +0000

This color-enhanced image shows layers of ice (in blue) exposed on a steep cliff on Mars. The layers of frozen water are about 260 feet (80 meters) thick. They probably were deposited as snow million of years ago, when Mars was tilted at a different angle on its axis, producing a wetter climate. Such layers could provide a resource for Mars colonists. They also could help scientists learn about Mars's climate history by preserving conditions that were present in different periods in the planet's past. The image was snapped by a camera aboard Mars Reconnaissance Orbiter. [NASA/JPL/UA/USGS]

(image)



Eridanus Cluster

Sun, 14 Jan 2018 06:00:00 +0000

If you look south two or three hours after sunset tonight, you’ll be gazing into one of the largest of all the 88 constellations — Eridanus, the river. It’s long and winding, and not easy to see. It hosts one of the brightest stars in the sky, but the star is so far south that it’s out of sight for most Americans.

Eridanus also is home to a cluster of galaxies. The galaxies spread over a range of distances, but the center of the cluster is probably about 75 million light-years from Earth.

The cluster is a grander gathering than the Local Group, the collection of galaxies that includes our home galaxy, the Milky Way. For one thing, the Eridanus cluster has more galaxies. For another, its largest galaxies have more diversity: some are elliptical galaxies and some are spirals. In contrast, the only two giants in the Local Group are both spirals.

One of the most impressive members of the Eridanus cluster is NGC 1300. It’s a breath-taking barred spiral that looks like a backward letter S. It has two enormous spiral arms that are spawning new stars. The spiral arms emerge from opposite ends of a long bar, which houses mainly older stars. The Milky Way is also a barred spiral, but its bar is much less prominent.

Next door to the Eridanus cluster is the better-known Fornax cluster, which is slightly closer to us. Both clusters are part of a long filament of galaxies, which stretches across the southern sky tonight.

 

Script by Ken Croswell

StarDate: 
Sunday, January 14, 2018
Teaser: 
Galaxy clusters in the southern sky



River’s End

Sat, 13 Jan 2018 06:00:00 +0000

Because the Sun is a spinning ball of gas, it’s wider through its equator than through the poles. The difference is so small, though, that you really can’t see it.

For the brightest star of Eridanus, the river, though, it’s a different story. Achernar is more than half again as wide through its equator as through the poles. So it looks not like a ball, but like an M&M.

Achernar is much bigger and heavier than the Sun, and thousands of times brighter. And it has a smaller companion star. They orbit each other once every 15 years or so.

Achernar is so flattened because it’s spinning like crazy: A spot at its equator rotates at about 1.3 million miles per hour, hundreds of times faster than the Sun.

That fast rotation has a couple of interesting consequences. For one thing, because Achernar’s poles are much closer to its core — the source of the star’s energy — they’re thousands of degrees hotter than the equator. That heat creates “winds” of gas from Achernar’s poles. Gas also is flung away from the equator by the fast rotation. That surrounds the star with a cloud of gas and dust — a veil around a stellar whirling dervish.

Achernar is at the southern tip of Eridanus. In fact, its name means “river’s end.” It’s so far south that it’s not visible north of about Dallas. The rest of Eridanus is in better view. It begins next to the foot of Orion, which is in the southeast at nightfall, then curls to the right and down to the horizon.

 

Script by Damond Benningfield

StarDate: 
Saturday, January 13, 2018
Teaser: 
A star with a bulging waistline



Beta Ceti

Fri, 12 Jan 2018 06:00:00 +0000

Cetus, the whale or sea monster, is in the south and southwest at nightfall. Its brightest star, Beta Ceti, is the second-brightest star in a wide swath of sky. It’s outshined only by Fomalhaut, which is quite low at that hour.




Beta Ceti

Fri, 12 Jan 2018 06:00:00 +0000

One of the highlights of a solar eclipse is the chance to see the corona — the Sun’s outer atmosphere. Its thin gas reaches millions of degrees, producing a faint, silvery glow around the Sun.

A corona also encircles the brightest star of Cetus, the sea monster. It’s even bigger and hotter than the Sun’s. But it may not be produced in the same way.

Beta Ceti is in the southwest at nightfall. It’s the second-brightest star in a wide swath of sky. It’s outshined only by Fomalhaut, which is quite low at that hour.

Beta Ceti is a giant — it’s almost 20 times wider than the Sun. It got that big after it ended its “normal” lifetime. It consumed the original hydrogen fuel in its core, converting it to helium. The core then got smaller and hotter, allowing it to begin fusing the helium to make heavier elements. The hotter core pushes on the outer layers of gas, causing the star to puff up to giant proportions.

About a decade ago, space telescopes discovered that Beta Ceti is producing a lot of X-rays. They come from the star’s corona.

The Sun’s corona is produced by a magnetic dynamo. Different layers of the Sun rotate at different rates, generating a magnetic field. It guides charged particles from the surface out into space, forming the corona.

Beta Ceti, though, probably has a weak dynamo. Instead, its magnetic field is at least partly a leftover from the star’s earlier life — a magnetic fossil that helps create a giant corona around this giant star.

 

Script by Damond Benningfield

StarDate: 
Friday, January 12, 2018
Teaser: 
The imprint of a magnetic “fossil”



Camelopardalis

Thu, 11 Jan 2018 06:00:00 +0000

Camelopardalis, the giraffe, is one of the largest constellations, covering a big wedge of the northern sky. But it isn’t very bold. All of its stars are so faint that you need to get away from city lights to see them.




Speed of Gravity

Thu, 11 Jan 2018 06:00:00 +0000

It’s hard to think of gravity as something that travels. Instead, we think of it as a force that pulls objects together, and that’s true enough. But it moves through space as waves, just as light does. And a recent discovery has allowed scientists to make the most accurate measurement of how fast those waves are moving. Back in August, scientists detected gravitational waves produced by the violent merger of two neutron stars — the ultra-dense cores of exploded stars. As the stars got closer and closer, they whipped up the space around them, producing ripples in space and time — gravitational waves. Scientists converted the waves to sound. And less than two seconds after the waves reached Earth, telescopes in space detected gamma rays from the merger. The fact that the two types of waves arrived at Earth at almost the same instant — from an event that happened 130 million light-years away — tells us that they traveled at the same speed: the speed of light. In fact, the difference in their speed is no more than one part in a million billion. Albert Einstein’s theory of gravity had predicted that gravity should move at the speed of light. It’s been impossible to measure that speed, though, because it’s been impossible to capture gravitational waves. But over the last couple of years, detectors in the United States and Europe finally detected them — a discovery that won last year’s Nobel Prize in Physics. Script by Damond Benningfield Keywords: Gravitational WavesGravityNeutron StarsNobel PrizeRelativityStarDate: Thursday, January 11, 2018Teaser: Measuring the speed of gravity[...]



Moon and Planets

Wed, 10 Jan 2018 06:00:00 +0000

The Moon and two bright planets form a beautiful triangle at dawn tomorrow. Brilliant Jupiter stands to the right of the Moon, with fainter orange Mars close below them.




Moon and Planets

Wed, 10 Jan 2018 06:00:00 +0000

The Moon and two bright planets form a beautiful triangle at dawn tomorrow. Brilliant Jupiter stands to the right of the Moon, with fainter orange Mars close below them.

The surfaces of the Moon and Mars have been sculpted in part by collisions with asteroids — big space rocks that orbit the Sun. The impacts have gouged craters. And on the Moon, they punched holes in the crust that allowed molten rock to bubble up from below, creating dark volcanic plains.

Jupiter gets hit by asteroids, too. In fact, because it’s a bigger target and has a stronger gravitational pull, it gets hit a lot. Over the last quarter of a century, in fact, astronomers have seen several asteroids and comets slam into the planet.

Jupiter doesn’t have a solid surface, though, so the impacts don’t leave permanent scars. Instead, they leave temporary markings — dark splotches in the planet’s upper atmosphere. They can persist for weeks or even months, and stretch across thousands of miles. Eventually, though, the atmosphere heals itself and the scars disappear.

Jupiter and Mars have received many asteroid visitors because they flank the asteroid belt — a wide band of debris left over from the birth of the planets. In fact, the gravity of nearby Jupiter kept the pieces from clumping together to make a planet.

Collisions between asteroids may send debris zipping out of the belt and toward the planets — creating potential hazards for these and other worlds.

 

Script by Damond Benningfield

StarDate: 
Wednesday, January 10, 2018
Teaser: 
Hazards to planetary navigation



Vanishing Venus

Tue, 09 Jan 2018 06:00:00 +0000

Venus will pass behind the Sun today, so it is lost from view in the Sun’s glare. It will return to view next month, when it will shine as the brilliant Evening Star.




Last Surveyor

Tue, 09 Jan 2018 06:00:00 +0000

Scientists compiled this panorama of the lunar landscape from pictures snapped by Surveyor 7, America's final robotic lunar lander, in January 1968. The craft landed near the rim of Tycho Crater, which is visible in the background. The ground is covered with boulders and smaller rocks blasted out by the impact that formed the crater. Surveyor 7 was the only mission in the Surveyor series dedicated strictly to science. The primary goal of the earlier missions was to make sure that it was safe for Apollo astronauts to land on the Moon. [NASA]

(image)



Last Surveyor

Tue, 09 Jan 2018 06:00:00 +0000

Last Surveyor Scientists compiled this panorama of the lunar landscape from pictures snapped by Surveyor 7, America's final robotic lunar lander, in January 1968. The craft landed near the rim of Tycho Crater, which is visible in the background. The ground is covered with boulders and smaller rocks blasted out by the impact that formed the crater. Surveyor 7 was the only mission in the Surveyor series dedicated strictly to science. The primary goal of the earlier missions was to make sure that it was safe for Apollo astronauts to land on the Moon. [NASA] The Surveyor program of the 1960s was designed to prove that it was safe for Apollo astronauts to land on the Moon. So the first few missions touched down on the smooth volcanic plains where the first astronauts would land. By the time the final Surveyor took flight, though, Apollo planners had all the intel they needed to land safely. So Surveyor 7 was dedicated strictly to science. The three-legged craft landed on the Moon 50 years ago tonight, on the flank of Tycho, a big, bright crater in the southern hemisphere. The crater was gouged by an impact more than 100 million years ago. On the airless Moon, that’s fairly recent — the crater looks fresh, and it’s surrounded by bright “rays” of material blasted out by the collision. Surveyor 7 landed in that debris field, which included boulders gouged from deep below the surface. Over the following few weeks, Surveyor snapped more than 21,000 pictures of its surrounding landscape — the roughest seen by any Surveyor. Just as important, it carried instruments for digging into the powdery lunar dirt and analyzing the dirt and rocks. Those instruments found that the chemistry around Tycho was similar to that of the volcanic plains, with a little less iron and related elements. Surveyor 7 also saw a glow above the horizon at sunset. That could have been caused by grains of electrically charged moondust levitating above the surface — a bonus discovery from America’s final robotic lander on the Moon.   Script by Damond Benningfield Keywords: Earth's MoonLunar ExplorationLunar SurfaceStarDate: Tuesday, January 9, 2018Teaser: A final trip to the Moon [...]



Last-Quarter Moon

Mon, 08 Jan 2018 06:00:00 +0000

The Moon is at last quarter today at 4:25 p.m. CST. Sunlight will illuminate half of the lunar hemisphere that faces Earth. The illuminated fraction will continue growing smaller until the Moon is new, on January 16.




Frank Watson Dyson

Mon, 08 Jan 2018 06:00:00 +0000

It’s been almost 80 years since British astronomer Frank Watson Dyson passed away. But the people of Great Britain are reminded of his accomplishments every day. Some BBC Radio stations broadcast a set of six tones every hour — the “six pips.” The final tone marks the top of the hour — a precise time signal that was important to the nation in the days before electronic clocks. The system was instituted by Dyson.

Dyson was born 150 years ago today, in Leicestershire. He became an astronomer at the Royal Greenwich Observatory at age 26, and its director — England’s Astronomer Royal — in 1910 — a post he held for 23 years.

Dyson studied the Sun and the structure of the Milky Way. And he organized two historic eclipse expeditions in 1919. As the Sun vanished from view, the expeditions measured a slight shift in the positions of stars near the Sun. That confirmed a prediction of Albert Einstein’s theory of gravity. The discovery made Einstein an international star, and led to wide acceptance of his theory.

In the 1920s, Dyson began organizing signals to transmit the precise Greenwich Mean Time — the international time standard. The signals were beamed out every quarter-hour through a radio station operated by the Post Office. And in 1924, he arranged to transmit the signals to the BBC, which in turn broadcast them to the nation and, eventually, the world — six “pips” that helped keep Britain on time for decades.

 

Script by Damond Benningfield

StarDate: 
Monday, January 8, 2018
Teaser: 
Keeping a nation on time



Taurus

Sun, 07 Jan 2018 06:00:00 +0000

Taurus, the bull, passes high overhead this evening. Its brightest stars form a long, thin wedge, with its brightest star, orange Aldebaran, at its southeastern corner. Taurus is at its highest around 9 p.m.




Orion’s (Other) Belt

Sun, 07 Jan 2018 06:00:00 +0000

Orion strides boldly across the southern sky on winter nights. The big, beautiful constellation is low in the east and southeast at nightfall. Its most conspicuous feature is a short line of three bright stars known as Orion’s Belt. It points almost straight up into the sky in early evening.

The people of Corpus Christi, Texas, don’t have to wait for night to see Orion’s Belt — it’s in view all the time, day and night. That’s because the belt’s three stars — Alnitak, Alnilam, and Mintaka — are represented by a public sculpture.

It was created more than 15 years ago by Robert Perless, who has designed many of his works to interact with the wind.

Orion’s Belt consists of three dagger-like wind vanes atop tall poles. Each vane is 55 feet long, and looks a bit like a 1950s concept of a star liner. The vanes move with the winds that buffet the coastal city. They’re sensitive to even a whisper of a breeze.

Perless has done some other works with a cosmic theme. In 2008, for example, he created “Dream Weaver,” based on string theory. It consists of ribbons of aluminum coated with a holographic material. The surface of the ribbons looks like a spectrum — a rainbow of colors.

His Corpus Christi work also incorporates many of Orion’s other bright stars. They\'re represented by stainless steel disks embedded in sidewalks around the city. The disks are arranged just as Orion’s stars are in the sky — some bright markers around Orion’s Belt.

 

Script by Damond Benningfield

StarDate: 
Sunday, January 7, 2018
Teaser: 
Sculpting a starry belt



Orion’s Belt

Sat, 06 Jan 2018 06:00:00 +0000

Orion is in the eastern sky at nightfall. Its three-star belt points straight up from the horizon, with Orion’s other bright stars arrayed to its left and right. From top to bottom, the stars of the belt are Mintaka, Alnilam, and Alnitak.




Shiny Belt

Sat, 06 Jan 2018 06:00:00 +0000

Glowing clouds of gas and dust surround the three stars of Orion's Belt in this long-exposure photograph of the region. From left, the stars of the belt are Alnitak, Alnilam, and Mintaka. All three are supergiant stars that will explode as supernovae. The nebulosity around the stars includes the Horsehead Nebula, a dark notch in the red cloud close to the lower left of Alnitak. [Rogelio Bernal Andreo/Wikimedia]

(image)



Orion’s Belt

Sat, 06 Jan 2018 06:00:00 +0000

Shiny Belt Glowing clouds of gas and dust surround the three stars of Orion's Belt in this long-exposure photograph of the region. From left, the stars of the belt are Alnitak, Alnilam, and Mintaka. All three are supergiant stars that will explode as supernovae. The nebulosity around the stars includes the Horsehead Nebula, a dark notch in the red cloud close to the lower left of Alnitak. [Rogelio Bernal Andreo/Wikimedia] Being a member of a popular group can make you famous — just not as yourself. Consider three stars at the center of Orion the hunter. They’re some of the biggest, brightest stars in the galaxy. Yet almost no one pays attention to them as individuals. Instead, we think of them as a group: Orion’s Belt. Orion is in the eastern sky at nightfall. The belt points straight up from the horizon, with Orion’s other bright stars arrayed to its left and right. From top to bottom, the stars of the belt are Mintaka, Alnilam, and Alnitak. The names are from ancient Arabic. Mintaka and Alnitak refer to the “Belt of the Great One” — a giant figure whose origin is unknown. Alnilam refers to an alternate name for the belt — the “string of pearls.” There’s no doubt that these stars are among the most impressive jewels in the entire Milky Way. Alnitak is a binary. It consists of two supergiant stars, which are much bigger and heavier than the Sun, and tens of thousands of times brighter. And Mintaka appears to consist of at least four stars, all of which are among the biggest and brightest in the galaxy. The stars in the Belt are all much younger than the Sun — only a few million years old, compared to a few billion years for the Sun. Even so, they’re closer to the ends of their lives. They’re burning through their nuclear fuel in a hurry, and will expire soon — perhaps by blasting themselves to bits. We’ll talk about an Orion’s Belt here on Earth tomorrow.   Script by Damond Benningfield Keywords: Orion's BeltOrion, the HunterStarDate: Saturday, January 6, 2018Teaser: Paying attention to a celestial trio [...]



Mars and Jupiter

Fri, 05 Jan 2018 06:00:00 +0000

The planets Mars and Jupiter are in the east at first light right now. Jupiter is the brightest point of light in the sky at that hour, with fainter Mars close to the right of Jupiter tomorrow and below Jupiter the next day.




Mars and Jupiter

Fri, 05 Jan 2018 06:00:00 +0000

Two siblings with little family resemblance are getting together for a bit of a reunion right now. They’re in the east at first light, and they’re so bright and so close together that you just can’t miss them. The brighter of the siblings is Jupiter, while the other is Mars. Fainter orange Mars will stand a bit to the right of Jupiter tomorrow. But Jupiter will have moved above Mars by the next day, with the two worlds still separated by just a fraction of a degree. Jupiter is the largest planet in the solar system — about 11 times Earth’s diameter. Mars, on the other hand, is only a bit more than half the size of Earth. The main reason for the difference is that the planets were born in different parts of the solar system. Mars was born close to the Sun, where it was bathed in solar radiation and a strong “wind” of charged particles. That swept away much of the planet-making materials — hydrogen and helium gas, and frozen water and other ices. That left less material to make planets — bits of relatively heavy elements. Jupiter was born several times farther from the Sun. Temperatures were colder there, and the solar wind was less intense. Small bits of rock and ice stuck together to make larger bodies, which in turn stuck together to make the core of Jupiter. As the planet grew, its gravity swept up lots of hydrogen and helium, surrounding the core with gas. So Jupiter grew to immense proportions, while Mars stayed fairly scrawny.   Script by Damond Benningfield Keywords: JupiterMarsStargazing and SkywatchingStarDate: Friday, January 5, 2018Teaser: Sibling worlds cross in the dawn[...]



Moon and Regulus

Thu, 04 Jan 2018 06:00:00 +0000

The Moon will will pass close to Regulus, the star that marks the heart of Leo, the celestial lion, tonight. And for skywatchers from Alaska and other high northern latitudes, the Moon briefly will pass in front of the star, blocking its light.