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StarDate Online - Your guide to the universe





 



Hyperactive Galaxy

Tue, 22 Aug 2017 05:00:00 +0000

Our home galaxy, the Milky Way, is a giant spiral that contains hundreds of billions of stars. And every now and then, one of its stars explodes as a supernova. The last time astronomers saw that happen was more than 400 years ago, but that may be because we can see only a small portion of our vast galactic home. If we were outside the Milky Way, astronomers estimate, we’d see about two supernova explosions per century.

We’ve seen supernova explosions in many galaxies beyond our own. But one prolific galaxy puts all the others to shame. It’s a beautiful spiral in the constellation Cepheus known as NGC 6946. During the past hundred years, astronomers have seen a record 10 supernovae in this one galaxy.

The galaxy owes those fireworks to its impressive star-spawning ways. Its gas and dust are giving birth to large numbers of new stars. The most massive of these stars explode a few million years after their birth, producing the fireworks we see.

As galaxies go, NGC 6946 is fairly close — about 20 million light-years from Earth. That means these stars actually died 20 million years ago, but it’s taken that long for the light of their explosions to reach us. Astronomers first saw a supernova in this galaxy a hundred years ago, back in 1917. The most recent popped off just a few months ago.

The supernova count might have gone even higher, but instead of exploding, one massive star collapsed to form a black hole. More about that tomorrow.

 

Script by Ken Croswell, Copyright 2017

Keywords:

StarDate: 
Tuesday, August 22, 2017
Teaser: 
A galaxy with lots of fireworks



Microscopium

Tue, 22 Aug 2017 05:00:00 +0000

A faint scientific instrument scoots low across the south at this time of year. Microscopium was one of 12 constellations created by Nicolas Louis de Lacaille in the 18th century. Its stars are quite meager, so you need dark skies and a starchart to pick it out.




Brilliant Beads

Mon, 21 Aug 2017 18:48:06 +0000

Brilliant beads of sunlight, known as Baily's Beads, shine through mountains on the Moon in this photograph of the August 21 eclipse from Madras, Oregon. [NASA/Aubrey Gemignani]

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Eclipse Day

Mon, 21 Aug 2017 05:00:00 +0000

Many skywatchers have been planning for this day for years. The Moon will pass directly between Earth and Sun today, creating a total solar eclipse from Oregon to South Carolina. Day will turn to night, and stars and planets will pop into view. And tens of millions of Americans are expected to see the spectacle in person.

A solar eclipse is the result of a complex ballet involving Earth, the Moon, and the Sun.

The Moon pirouettes against the background of stars and planets every 27 and a half days. But because the Sun is also moving against that background, it takes a couple of days longer for the Moon to catch up to it.

While the Moon passes the Sun roughly once a month, most months it doesn’t cause an eclipse. Instead, it usually glides a little above or below the Sun, because its orbit is tilted relative to the Sun’s path across the sky. A solar eclipse occurs only when the new Moon crosses that path. And even then, most eclipses are only partial: the Moon covers only part of the Sun’s disk, which is what most Americans will see today.

Total eclipses occur an average of about 18 months apart, although the gap can range from a few months to more than two years. The next total eclipse will take place in 2019, visible from parts of South America.

And there’ll be another eclipse over the U.S. on April 8th of 2024, from Texas to Maine. So if you miss out on today’s show, start planning for the next one — another disappearing act for the Sun.


Script by Damond Benningfield


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StarDate: 
Monday, August 21, 2017
Teaser: 
Two chances to see an eclipse



Eclipse Day

Mon, 21 Aug 2017 05:00:00 +0000

The Moon will pass directly between Earth and Sun today, creating a total solar eclipse from Oregon to South Carolina. Day will turn to night, and stars and planets will pop into view. From the rest of the country, the Moon will cover only a portion of the Sun.




Anatomy of an Eclipse

Sun, 20 Aug 2017 05:00:00 +0000

Day will briefly turn to night for parts of the United States on August 21 during a total solar eclipse. The Moon will completely cover the Sun's disk, blocking the sunlight but allowing the Sun's pearly outer atmosphere, the corona, to shine through. This multiple-exposure image shows the entire sequence of an eclipse as the Moon slowly encroaches on the Sun's brilliance, covers the Sun (center), then retreats. While the total eclipse is safe to look at with the eye alone, the Sun is still so bright at all other phases of the eclipse that looking at it without proper protection can result in eye damage. [Rick Fienberg/TravelQuest International/Wilderness Travel]

More information about the eclipse:

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Ready for the Eclipse

Sun, 20 Aug 2017 05:00:00 +0000

Anatomy of an Eclipse Day will briefly turn to night for parts of the United States on August 21 during a total solar eclipse. The Moon will completely cover the Sun's disk, blocking the sunlight but allowing the Sun's pearly outer atmosphere, the corona, to shine through. This multiple-exposure image shows the entire sequence of an eclipse as the Moon slowly encroaches on the Sun's brilliance, covers the Sun (center), then retreats. While the total eclipse is safe to look at with the eye alone, the Sun is still so bright at all other phases of the eclipse that looking at it without proper protection can result in eye damage. [Rick Fienberg/TravelQuest International/Wilderness Travel] More information about the eclipse: For millions of skywatchers in the United States tomorrow, day will briefly turn to night as the Moon passes in front of the Sun, eclipsing its light. The Sun’s outer atmosphere, the corona, will shine silvery-white around the dark Moon. And the stars and planets will shine through the dark as well. Regulus, the heart of the lion, will perch closest to the Moon. It’s usually lost from view at this time of year as the Sun crosses Leo’s borders. The planet Mercury will shine brightly a little farther away, with reddish Mars on the other side of the Sun. Brilliant Venus and Jupiter will be farther from the Sun, with Sirius, the brightest star in the night sky, low in the southwest. You may be tempted to shoot pictures and videos throughout the show. But a total solar eclipse is a once-in-a-lifetime experience, so most veterans say it’s best to simply drink in the spectacle. And it’s one that involves most of your senses — the air will get cooler, and you’ll hear the sounds of birds and other animals preparing for night. There are a few safety tips to keep in mind. It’s completely safe to look at the Sun when it’s fully eclipsed, but not at other times; it’s so bright that it can damage your eyes. And highway patrols around the country remind drivers not to stop on busy highways. Instead, find a park or some other safe spot to enjoy the sights and sounds of this amazing lightshow. We’ll have more about this skywatching spectacle tomorrow. Script by Damond Benningfield More information about the eclipse:     Keywords: Eclipses, Occultations and TransitsStargazing and SkywatchingStarDate: Sunday, August 20, 2017Teaser: Getting ready for the big event [...]



Ready for the Eclipse

Sun, 20 Aug 2017 05:00:00 +0000

The Moon will eclipse the Sun tomorrow, briefly turning day to night across part of the United States. It’s completely safe to look at the Sun when it is fully eclipsed, but not at other times; it’s so bright that it can damage your eyes.




Eclipse Predictions

Sat, 19 Aug 2017 05:00:00 +0000

The Great American Eclipse is coming up on Monday. The Moon will briefly cover the Sun, turning day to night across a narrow slice of the United States.

The timing of the eclipse is known down to the second, and has been for decades. And today, astronomers can predict eclipses far into the future. But making such predictions isn’t easy. It requires a detailed knowledge of the Moon’s orbit around Earth, Earth’s orbit around the Sun, and even the shapes of Earth and the Moon.

Scientists had been trying to predict eclipses for a long time. Just when they first succeeded is a bit unclear, though.

There’s no doubt that people have been predicting lunar eclipses for thousands of years. But lunar eclipses are easier to predict. Earth’s shadow is roughly a hundred times wider than the Moon’s, so you don’t need as high a level of precision to get it right.

There are stories that the Chinese were predicting solar eclipses more than 4,000 years ago, but no confirmation. An eclipse in 585 BC that stopped a war supposedly was predicted by Thales, a Greek scientist. Many modern-day scientists doubt that, however.

The first confirmed prediction was made by Edmond Halley, using the laws of gravity devised by Isaac Newton. Halley forecast that an eclipse would cross England on May 3rd, 1715. And he was right. So the eclipse of 1715 is known as Halley’s Eclipse — honoring the prediction of an astronomical spectacle.

More about eclipses tomorrow.

 

Script by Damond Benningfield

More information about the eclipse:

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StarDate: 
Saturday, August 19, 2017
Teaser: 
Predicting a skywatching spectacle



More Eclipse

Sat, 19 Aug 2017 05:00:00 +0000

The Great American Eclipse is coming up on Monday. The Moon will briefly cover the Sun, turning day to night across a narrow slice of the United States. The rest of the country will see a partial eclipse, with the Moon covering only a portion of the Sun’s disk.




Safety First!

Fri, 18 Aug 2017 05:00:00 +0000

The August 21 solar eclipse will be one of nature's grandest spectacles. But it requires special protection for safe viewing, such as special eclipse glasses (shown) or dark welder's glass (No. 14 or darker). Sunshades, exposed photographic film, and other makeshift solutions do NOT provide adequate protection for viewing the partial phases of the eclipse. The only time it's safe to view the eclipse without protection is during totality, when the Moon completely covers the solar disk. [Jay Pasachoff]

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Eclipse Watching

Fri, 18 Aug 2017 05:00:00 +0000

Safety First! The August 21 solar eclipse will be one of nature's grandest spectacles. But it requires special protection for safe viewing, such as special eclipse glasses (shown) or dark welder's glass (No. 14 or darker). Sunshades, exposed photographic film, and other makeshift solutions do NOT provide adequate protection for viewing the partial phases of the eclipse. The only time it's safe to view the eclipse without protection is during totality, when the Moon completely covers the solar disk. [Jay Pasachoff] Venus, the “morning star,” looks down on the Moon at first light tomorrow. It’s one of the most beautiful of all astronomical encounters. But the Moon is headed toward an even more spectacular encounter on Monday, when it crosses in front of the Sun, creating a total solar eclipse. It’ll be visible across a narrow path from Oregon to South Carolina. But the couple of minutes when the Sun disappears are only part of the eclipse experience. The Moon will partially eclipse the Sun for about an hour and a half before and after totality. In fact, a partial eclipse will be visible across the entire United States, with the Moon covering most of the Sun’s disk across most of the country. It’s completely safe to look at the total phase of the eclipse — when the Sun is totally covered. But it’s dangerous to look at any other phase. The Sun is so bright that even a sliver of it can damage your eyes. But there are ways to safely view the partial eclipse. One is to look through special eclipse viewers or a piece of welder’s glass — number 14 or darker. Another is to poke a hole in a piece of cardboard and let the sunlight shine on the ground or a piece of paper; the hole creates an image of the eclipse. So do the leaves of a tree. If you stand beneath a tree with lots of leaves, but not so many that they block out the sky, you can see hundreds of eclipses projected on the ground — a safe and beautiful way to enjoy an astronomical spectacle.   Script by Damond Benningfield More information about the eclipse: Keywords: Eclipses, Occultations and TransitsStargazing and SkywatchingStarDate: Friday, August 18, 2017Teaser: Safety tips for a skywatching spectacle [...]



Eclipse Watching

Fri, 18 Aug 2017 05:00:00 +0000

Venus, the “morning star,” looks down on the Moon at first light tomorrow. The Moon is headed toward an even more spectacular encounter on Monday, when it will cross in front of the Sun, creating a total solar eclipse.




Chasing a Shadow

Thu, 17 Aug 2017 05:00:00 +0000


The Sun sets behind a NASA research aircraft, a WB-57F Canberra, at its base near Houston. Two of NASA's three Canberras will chase the Moon's shadow during the August 21 total solar eclipse. They will carry instruments to monitor the Sun's corona, its hot outer atmosphere. They also will study the planet Mercury, which will become visible during the eclipse, and scan the space between the Sun and Mercury for small asteroids, known as Vulcanoids. [NASA/JSC]

We have much more about eclipse science in the July/August issue of StarDate magazine. Order online or by calling 1-800-STARDATE (8 a.m.-4 p.m. Monday-Friday).

 

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More Eclipse Science

Thu, 17 Aug 2017 05:00:00 +0000

Chasing a Shadow The Sun sets behind a NASA research aircraft, a WB-57F Canberra, at its base near Houston. Two of NASA's three Canberras will chase the Moon's shadow during the August 21 total solar eclipse. They will carry instruments to monitor the Sun's corona, its hot outer atmosphere. They also will study the planet Mercury, which will become visible during the eclipse, and scan the space between the Sun and Mercury for small asteroids, known as Vulcanoids. [NASA/JSC] We have much more about eclipse science in the July/August issue of StarDate magazine. Order online or by calling 1-800-STARDATE (8 a.m.-4 p.m. Monday-Friday).   The B-57 Canberra has been taking to the skies since the Korean War. Today, only three of the aircraft remain. All three fly research missions for NASA. And on Monday, two of them will be chasing the shadow of the Moon during a total solar eclipse. The aircraft will conduct experiments for the Southwest Research Institute in Colorado. They’ll look at the Sun’s outer atmosphere, known as the corona. It’s so faint that it’s visible only during a total eclipse. But it’s extremely hot, and astronomers aren’t sure just why. They’re pretty sure it’s caused by the Sun’s magnetic field. But just how that works is being debated. One idea says it’s caused by “mini-flares” — a constant series of small explosions near the surface, which transfer energy from the magnetic field to the corona. Another idea says it’s caused by waves that travel through the corona, depositing heat. The twin Canberras will carry high-speed video cameras to capture detailed images. Those pictures could reveal any waves that might be rippling through the corona. An infrared telescope will map small regions of the corona. And another instrument will capture the light from electrically charged atoms of iron. The iron outlines the magnetic field, which can form loops that are bigger than Earth. These experiments, along with many others, should provide a better understanding of the Sun’s mysterious corona. More about the eclipse tomorrow.   Script by Damond Benningfield More eclipse information Keywords: Airborne ObservatoriesEclipses, Occultations and TransitsSunSunspots and Solar FlaresStarDate: Thursday, August 17, 2017Teaser: Chasing a shadow from the sky [...]



Moon and Venus

Thu, 17 Aug 2017 05:00:00 +0000

The “morning star” stands to the lower left of the crescent Moon before dawn tomorrow. Although it looks like a brilliant star, it’s really Venus, our nearest planetary neighbor.




Solar Mystery

Wed, 16 Aug 2017 05:00:00 +0000

Astronomers will pay special attention to the Sun's hot outer atmosphere, the corona, during Monday's solar eclipse. It will form a silvery halo around the intervening Moon. The corona is millions of degrees hotter than the Sun's surface, but astronomers are not yet certain what heats it. They will be watching the eclipse from the ground and from aircraft to try to gather clues about this solar mystery. [Luc Viatour]

We have much more about eclipse science in the July/August issue of StarDate magazine. Order online or by calling 1-800-STARDATE (8 a.m.-4 p.m. Monday-Friday).

 

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Eclipse Science

Wed, 16 Aug 2017 05:00:00 +0000

Solar Mystery Astronomers will pay special attention to the Sun's hot outer atmosphere, the corona, during Monday's solar eclipse. It will form a silvery halo around the intervening Moon. The corona is millions of degrees hotter than the Sun's surface, but astronomers are not yet certain what heats it. They will be watching the eclipse from the ground and from aircraft to try to gather clues about this solar mystery. [Luc Viatour] We have much more about eclipse science in the July/August issue of StarDate magazine. Order online or by calling 1-800-STARDATE (8 a.m.-4 p.m. Monday-Friday).   Astronomers have been studying the Sun for so long that you might think they know everything there is to know about it. And they do know quite a bit. It’s a hot ball of gas that’s 865,000 miles wide. It’s powered by nuclear reactions deep in its core. And it’s been shining for billions of years, and will keep going for billions of years more. Yet there are still some mysteries about the Sun. At the top of the list is what heats its outer atmosphere, the corona. Although it’s quite thin, it’s millions of degrees hotter than the surface of the Sun, and scientists aren’t sure why. The corona most likely is heated by energy from the Sun’s magnetic field. The field creates dark sunspots, powerful explosions, and outbursts of billions of tons of charged particles. Those events impart some energy to the corona, but not nearly enough to account for its temperature. Solving the mystery requires more observations of the corona, but they’re hard to get. The Sun’s disk is a million times brighter than the corona, so it overpowers the faint wisps of gas. Satellites can block out the Sun, but they block the inner part of the corona as well. So the only time scientists get a good look at the corona is during a total solar eclipse — like the one coming up on Monday. As the Moon covers the Sun, the corona will shine around the Moon. So astronomers will probe the corona with telescopes on the ground, in the air, and in space; more about that tomorrow.   Script by Damond Benningfield For more about the eclipse, visit our special eclipse site Keywords: Eclipses, Occultations and TransitsSunStarDate: Wednesday, August 16, 2017Teaser: Studying a solar mystery [...]



Solar Corona

Wed, 16 Aug 2017 05:00:00 +0000

Skywatchers along a narrow path across the U.S. will see a rare sight on Monday: the Sun’s corona, its hot, faint outer atmosphere. It will look like a silvery curtain around the Sun during a solar eclipse, which will be visible from Oregon to South Carolina.




Moon on the Move

Tue, 15 Aug 2017 05:00:00 +0000

The Moon will pass by several prominent companions over the next week. Tomorrow, the bright star Aldebaran, the eye of the bull, will stand just above the Moon at first light. On Friday and Saturday, the Moon will pass by the planet Venus, the “morning star.” And it’ll end its week of companionship on Monday, when it lines up with the Sun — creating a total solar eclipse. Over the centuries, eclipses have helped astronomers learn a lot about the Sun and the universe. During an eclipse in 1868, for example, French and British astronomers discovered a new element in the Sun’s atmosphere. It was named “helium” for Helios, an ancient Greek Sun god. Later observations revealed that it’s the second-most-abundant element in the universe, after hydrogen. Perhaps the most famous eclipse discovery came in 1919. Just a few years earlier, Albert Einstein had published his theory of gravity, known as general relativity. Among other things, it predicted that the gravity of a massive object like the Sun would “warp” the space around it. To test that idea, British astronomer Arthur Eddington led an expedition to an island off the coast of Africa. His team photographed the eclipse, as well as stars that appeared near the Sun in the darkened sky. The apparent positions of those stars were shifted a tiny bit by the Sun’s gravity — confirming general relativity, and turning Einstein into an international celebrity. More about this year’s eclipse tomorrow.   Script by Damond Benningfield Visit our special eclipse web site https://stardate.org/nightsky/2017-solar-eclipse Keywords: Eclipses, Occultations and TransitsHistory of AstronomyRelativityStarDate: Tuesday, August 15, 2017Teaser: The Moon moves across the sky[...]



Moon on the Move

Tue, 15 Aug 2017 05:00:00 +0000

The Moon will pass several bright objects over the next week. Tomorrow, bright Aldebaran, the eye of the bull, will stand just above the Moon at first light. And on Friday and Saturday, the Moon will pass by the planet Venus, the “morning star.”




The Right Path

Mon, 14 Aug 2017 05:00:00 +0000

The Great American Eclipse is coming up on August 21. This map shows the circumstances of the eclipse across the entire United States. The path of totality, where the Moon will completely cover the Sun, is a shaded strip from Oregon to South Carolina. [NASA/Scientific Visualization Studio]

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Solar Eclipse

Mon, 14 Aug 2017 05:00:00 +0000

The Right Path The Great American Eclipse is coming up on August 21. This map shows the circumstances of the eclipse across the entire United States. The path of totality, where the Moon will completely cover the Sun, is a shaded strip from Oregon to South Carolina. [NASA/Scientific Visualization Studio] Check your tires and your gas gauge and get ready to hit the road for nature’s most spectacular sky show: a total solar eclipse. It takes place a week from today, and will cover a narrow slice of the United States, from Oregon to South Carolina. And be sure to allow plenty of time to get there — millions of Americans are expected to travel to the eclipse path. That should make it the most-viewed solar eclipse in history. A solar eclipse occurs when the new Moon passes directly between Earth and the Sun, covering the Sun’s disk. Day briefly turns to night, and the Sun’s corona — its hot but faint outer atmosphere — encircles the intervening Moon. The Moon’s shadow covers a narrow path. For this eclipse, the maximum width will be about 70 miles, over Illinois and Kentucky. That’s where the eclipse will last longest — two minutes and 41 seconds. About 12 million people live along that path. But almost 90 million live within a couple of hundred miles of that region. So millions of people may travel to see it. In towns near the centerline of the eclipse, where totality lasts longest, the population could triple. So if you’re among the travelers, eclipse veterans and state highway patrols recommend that you plan your route in advance, leave plenty of time to get there, and check the weather forecast — you don’t want clouds to spoil the most spectacular of all skywatching events. We’ll have more about the eclipse tomorrow.   Script by Damond Benningfield  For more details, visit our special eclipse pages  Keywords: Eclipses, Occultations and TransitsStarDate: Monday, August 14, 2017Teaser: A journey from day to night [...]



Solar Eclipse

Mon, 14 Aug 2017 05:00:00 +0000

A total solar eclipse will take place on August 21. It will cover a narrow slice of the United States, from Oregon to South Carolina. Millions of Americans are expected to travel to the eclipse path, making it the most-viewed solar eclipse in history.




Flashy Star

Sun, 13 Aug 2017 05:00:00 +0000

A star in Sagittarius, known as Sakurai's Object, has undergone a "rebirth" of sorts, as it produced an intense outburst a couple of decades ago. The outburst took place when the star began "burning" a shell of helium surrounding its hot, dead core. Known as a "final flash," it produced a strong wind of gas that has surrounded the star with a glowing ring, as shown in this image from the European Southern Observatory. [ESO]

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Sakurai’s Object

Sun, 13 Aug 2017 05:00:00 +0000

Flashy Star A star in Sagittarius, known as Sakurai's Object, has undergone a "rebirth" of sorts, as it produced an intense outburst a couple of decades ago. The outburst took place when the star began "burning" a shell of helium surrounding its hot, dead core. Known as a "final flash," it produced a strong wind of gas that has surrounded the star with a glowing ring, as shown in this image from the European Southern Observatory. [ESO] A dying star in Sagittarius isn’t going quietly. A couple of decades ago, it was “reborn” with an intense outburst of energy. It’s faded from view since then, but it’s starting to return. Sakurai’s object long ago used up the hydrogen fuel in its core, triggering a series of changes. Those changes culminated when the star expelled its outer layers of gas into space, forming a glowing bubble. That left only its hot core, made of carbon and oxygen topped by thin shells of hydrogen and helium. The core was cooling off to form a white dwarf — the final phase of life for stars that are similar to the Sun. In the 1990s, though, Sakurai’s object flared up — it grew more than 10,000 times brighter. That’s because it was going through a phase called a “final flash”: There was enough helium to ignite a new series of nuclear reactions at the star’s surface. The new reactions produced a strong “wind” of gas. As this material surrounded the star, it cooled and clumped together to form a cloud of dust. That blocked the star’s light, so it vanished from view. Today, though, the dust is getting thinner. That’s allowed astronomers to start watching it again. In fact, they’ve seen that it seems to be blowing giant bubbles into space from above its poles — a final act for a dying star. Although we can’t see the star, we can see its location. It’s above the “teapot” formed by the brightest stars of Sagittarius, which is low in the south at nightfall.   Script by Damond Benningfield Keywords: Lifecycle of StarsSagittarius, the ArcherStarDate: Sunday, August 13, 2017Teaser: A “rebirth” for a dying star [...]



Sakurai’s Object

Sun, 13 Aug 2017 05:00:00 +0000

Sakurai’s Object, a dying star in Sagittarius, was “reborn” a couple of decades ago as it began “burning” helium around its core. Although it is too faint to see, it is above the teapot formed by the brightest stars of Sagittarius, which is in the south as night falls.




Black-Hole Blobs

Sat, 12 Aug 2017 05:00:00 +0000

The black hole at the heart of the Milky Way galaxy is one of the quietest around. It’s not pulling in much material, so there’s nothing to heat up and produce light. Every once in a while, though, the black hole pulls apart an unlucky star, creating a powerful display of fireworks — including some “cannonballs” as big as planets. The black hole is called Sagittarius A-star. It’s about 27,000 light-years away. It’s above the spout of the teapot formed by the bright stars of Sagittarius, which is low in the south at nightfall. The black hole is about four million times the mass of the Sun — rather small for a galactic hub. It’s encircled by a thin disk of gas and dust, which emits a trickle of energy. When the black hole grabs a star, though, it produces some major pyrotechnics. It rips the star to shreds, producing a torrent of energy. Some of the material enters the disk before it plunges into the black hole. But some of it, accelerated by the black hole’s powerful gravity, shoots back out into space. Earlier this year, a study said that some of that hot gas coalesces to form blobs as big as planets. They’ve moving so fast that they’ll eventually leave the galaxy behind. A few of these blobs could be passing through our galactic neighborhood. Right now, there’s no way to tell them apart from planets drifting through space on their own. But future telescopes might be able to track down these blobs from the Milky Way’s dark heart.   Script by Damond Benningfield Keywords: Black HoleMilky Way GalaxySagittarius, the ArcherStarDate: Saturday, August 12, 2017Teaser: A black hole fires some rockets[...]



Steamy Skies

Sat, 12 Aug 2017 05:00:00 +0000

Sagittarius scoots low across the south on summer nights. Its brightest stars form the outline of a teapot, with clouds of stars rising from its spout like steam. Those clouds conceal the busy center of the Milky Way galaxy.




Future Resident

Fri, 11 Aug 2017 05:00:00 +0000

Sagittarius marks the center of our home galaxy, the Milky Way. So the constellation is packed with stars, star clouds, and star clusters. But one of the clusters doesn’t belong to the Milky Way at all — at least not yet. It’s in a small, puffy galaxy on the far edge of the Milky Way’s disk. Messier 54 is a globular cluster. It’s a ball-shaped region a few dozen light-years across, packed with hundreds of thousands of stars. Native globulars are among the Milky Way’s oldest residents — they were born with the galaxy itself, more than 10 billion years ago. But a few of these clusters are interlopers — they were born in other galaxies, then were absorbed when their galaxies were consumed by the Milky Way. For a long time, astronomers thought that M54 was a charter member of the Milky Way — one of its early globular clusters. A couple of decades ago, though, they found that it’s near the center of a newly discovered galaxy, the Sagittarius Dwarf, so it’s outside the Milky Way’s disk. But the Milky Way is pulling in the smaller galaxy, and eventually will incorporate all of its stars. So M54 will become a member of the Milky Way — one of its newest — and oldest — residents. Sagittarius scoots low across the south on summer nights. Its brightest stars form the outline of a teapot, with clouds of stars rising from its spout like steam. M54 is at the lower left corner of the teapot, although you need a telescope to pick it out.   Script by Damond Benningfield Keywords: Messier ObjectsSagittarius, the ArcherStar ClustersStarDate: Friday, August 11, 2017Teaser: A future resident of the Milky Way[...]