Stardate Radio Broadcast - McDonald Observatory
StarDate: November 11, 2013

Antarctic Adventures

Back in 1969, as the Apollo astronauts were picking up pieces of the Moon, Japanese scientists were picking up pieces of other solar-system bodies in another hostile environment: the bitter cold of Antarctica. They found nine meteorites on the ice fields, all of which came from asteroids.

The discovery started a scientific treasure hunt that continues today. Teams of scientists from Japan, the United States, and elsewhere are getting ready for expeditions that’ll begin in a few weeks, as summer arrives in the southern hemisphere.

The first organized expedition took place in 1974. Since then, hundreds of meteor hunters have picked up more than 50,000 meteorites. Most of them are from asteroids, but a few are from Mars or the Moon.

The vast ice fields are a good site for meteor hunting because the Earth rocks are buried far below the ice. So there’s a good chance that any rock on top of the ice is from space.

Teams of hunters spend several weeks on the ice. Each day, they move slowly across the ice on snowmobiles or on foot. When they find a meteorite, they log its position, take its picture, and carefully store it inside a Teflon bag. At the end of the season, the American teams send their treasures to the Johnson Space Center for processing. After that, researchers from around the world can request samples for study — pieces of other worlds found in the otherworldly realm of Antarctica.

More about Antarctic science tomorrow.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/antarctic-adventures
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StarDate: November 12, 2013

Antarctic Adventures II

Many are looking forward to a little downtime over the Thanksgiving and Christmas holidays. But for some teams of scientists and engineers, the holiday season will be up time — time to send research balloons up to altitudes of 25 miles over Antarctica. Among other things, those balloons will study cosmic rays and the early history of the universe.

Balloons allow astronomers to loft their instruments above most of Earth’s obscuring atmosphere, at a fraction of the cost of a space mission. The instruments can also be recovered for use on later flights.

NASA launches several balloons each year from New Mexico and Texas. But most of those flights last no more than a day or two, because the payloads have to be brought down before winds push them away from the U.S. In Antarctica, on the other hand, winds push the balloons in a big circle around the continent’s perimeter. That means the flights can last for days or weeks. Last year, in fact, a balloon stayed aloft for a record 55 days.

This year the agency will launch three balloons, beginning in December, when there’s round-the-clock daylight. One will probe the early universe to learn more about cosmic inflation — a brief instant in which the newborn universe expanded at a phenomenal rate. Another will study cosmic rays — energetic particles from far outside our own solar system — from high above the frozen Antarctic.

And we’ll have more about Antarctic astronomy tomorrow.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/antarc...entures-ii
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StarDate: November 13, 2013

Antarctic Adventures III

A list of qualities that make a perfect site for a telescope would go something like this: It needs to be remote to avoid city lights and air pollution; dry, to provide a clear view of the heavens; high, to overcome the blurring effects of Earth’s atmosphere; and cold, to provide a good view of the infrared sky.

In other words, it would be a lot like the high plateaus of Antarctica. And in fact, astronomers are taking greater advantage of Antarctic skies all the time. They’re placing more telescopes there, which view the skies in many different ways.

The South Pole Telescope, for example, looks at wavelengths of light that reveal the “afterglow” of the Big Bang. Its observations help astronomers probe the early universe.

A telescope known as Ice Cube consists of strings of light detectors buried in the ice. They look for the phantom-like particles known as neutrinos, which come from stars and other sources.

And China is building a set of three visible-light telescopes to hunt for exploding stars, as well as planets in other star systems. The automated telescopes will operate at a remote site that sees few human visitors.

Most of Antarctica is bathed in constant sunlight right now, so some of the telescopes can’t do much observing. So this is when astronomers and engineers visit the continent to set up new instruments and service the existing ones — to get ready for the gloriously cold, dark skies of the Antarctic winter.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/antarc...ntures-iii
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StarDate: November 14, 2013

William Herschel

If not for a late-blooming interest in the heavens, William Herschel might be best known as a pretty good composer and musician. He wrote more than 200 works of music, including 24 symphonies. This one is his “Chamber Symphony in F Major,” performed by The Mozart Orchestra and provided courtesy of Newport Classic.

Herschel was born 275 years ago this week. He turned to astronomy in his mid-30s, and in five decades of work he discovered the planet Uranus, infrared energy, hundreds of binary star systems, and thousands of deep-space objects.

Before he became an astronomer, though, Herschel was a musician. He started as a member of a military band in his native Germany. He moved to England when he was 19 to avoid a war. He quickly became a church organist and director of public concerts in the city of Bath. He played violin and several other instruments, and taught music lessons.

Herschel also was a prolific composer. He wrote solos for various instruments, as well as sonatas, minuets, and many others.

Herschel scaled back his musical career after he earned an appointment as the King’s Astronomer for discovering the planet Uranus. In recent years, though, several of his symphonies have been recorded by modern orchestras — keeping alive the musical heritage of one of history’s greatest astronomers.

More about Herschel tomorrow.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/william-herschel
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StarDate: November 27, 2013

Sunward Bound

Assuming that it’s held together so far, Comet ISON is headed toward a spectacular and potentially fatal Thanksgiving Day encounter — a plunge near the surface of the Sun. It’ll pass about 700,000 miles above the Sun around mid-day. If it survives, it should put on a nice display in the morning sky beginning in just a few days.

Like all comets, ISON is a big ball of frozen gases and water mixed with rock and dust. As it approaches the Sun, the heat vaporizes some of the comet’s icy surface. That surrounds it with a cloud of gas and dust that can span a hundred thousand miles or more. The Sun pushes some of this material outward to form a glowing tail.

Many comets are basically big rubble piles — chunks of material that are loosely bound together. As they approach the Sun they can fall apart and vaporize — something that happens fairly often.

ISON appears to be fairly large as comets go — about three miles in diameter. And it’s probably making its first trip by the Sun after spending billions of years in the icebox of deep space. Those factors make it tough to predict what will happen as it approaches the Sun.

If it does survive, the extreme heat will vaporize a lot of ice, spewing much more gas and dust into space. So as ISON moves far enough from the Sun for us to see it, it’ll be a pretty sight, with its trail stretching far across the sky — so far that it could be visible in both evening and morning skies.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/sunward-bound
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StarDate: January 13, 2014

Hot Weather

The objects known as brown dwarfs are oddballs. They’re heavier than planets, but not heavy enough to trigger the nuclear reactions that would make them shine as true stars. In fact, they’re often described as failed stars.

Yet they share some traits with both stars and planets. Like stars, their surfaces are hot, with temperatures of up to several thousand degrees. But like planets, those surfaces may be topped by layers of clouds and giant storms.

Astronomers have discovered “weather” on the surfaces of several brown dwarfs. They can’t actually see the clouds and storms. But they know they exist because the brown dwarfs get fainter and brighter in different wavelengths as they rotate. The sometimes-dramatic change in brightness indicates that the surface of a brown dwarf consists of layers of clouds with embedded storm systems.

The clouds and storms are quite different from those on Earth, though. The clouds are so hot that they’d be made of small particles of iron or silicon, not water. And the storms might be a lot like Jupiter’s Great Red Spot — cyclones big enough to swallow an entire planet.

Indeed, a stormy brown dwarf might look a lot like Jupiter, with bands of clouds circling all the way around it, and big storms whirling through the clouds. But the brown dwarf would also provide its own inner glow — its heat would make it shine dull red or orange, with the clouds forming dark bands across its stormy surface.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/hot-weather
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StarDate: January 14, 2014

Moon and Jupiter

Jupiter blazes just to the left of the almost-full Moon this evening. The giant planet outshines all the other planets and stars in the sky at that hour, so it makes a brilliant counterpoint to the Moon.

Jupiter has a whole entourage of moons of its own, the largest of which puts our moon to shame. In fact, Ganymede is the largest moon in the entire solar system — half again the diameter of our moon, and bigger even than the planet Mercury.

Unlike Mercury and the Moon, though, Ganymede contains a lot of frozen water. The ice forms an outer layer that’s hundreds of miles thick. An ocean of liquid water may slosh about deep inside the ice.

The surface of Ganymede consists of two completely different types of terrain, which give it a streaky, blotchy appearance. Dark regions appear to be parts of the original crust, and they’re covered with lots of impact craters.

Light-colored regions appear to be younger. The main features in these areas are grooves that can be a couple of thousand feet tall and hundreds of miles long. They might have formed when the gravity of some of Jupiter’s other moons tugged at Ganymede. That cracked and folded the ice, wiping out any evidence of the original crust of this big, icy moon.

Ganymede and three other Jovian moons are visible through binoculars. They look like tiny stars arrayed near Jupiter. Around midnight tonight, they’re all on the left side of Jupiter, with Ganymede closest to the giant planet.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/moon-and-jupiter-35
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StarDate: January 15, 2014

Black Hole Collisions

It’s dangerous out there. Earth is threatened by asteroids and comets, storms on the Sun, and exploding stars, among other things. Fortunately, though, a recent study has some good news about another celestial danger: If a black hole hit Earth, you probably wouldn’t even notice it.

A black hole’s gravity is so powerful that nothing can escape its grasp — not even light. Some black holes are as massive as stars, while far heavier ones occupy the centers of many galaxies, including our own.

These black holes are so rare that Earth will probably never encounter one. But it’s possible that huge numbers of tiny black holes were created just after the Big Bang. These “primordial” black holes are as heavy as asteroids, but they’re smaller than an atom. If they exist, they outnumber all other types of black holes put together.

Scientists recently modeled what would happen if one of them hit Earth. Surprisingly, the answer is not much. The black hole would zip through our planet in less than a minute, shaking the surface just as an earthquake would. But the quake would be so weak that you might not even feel it.

And the risk of a collision is small. In fact, even if primordial black holes account for all of the universe’s mysterious dark matter, which outweighs normal matter, one would hit Earth only once every few million years. So black holes of any kind rank far down the list of cosmic threats.

More about black holes tomorrow.

Script by Ken Croswell, Copyright 2013
http://stardate.org/radio/program/black-hole-collisions
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StarDate: January 16, 2014

M101 ULX-1

Sometimes, astronomy can be just plain weird. The darkest objects in the universe can also be some of the brightest, for example, and many of the objects visible to our telescopes no longer exist.

Both of those apply to a star system in the Pinwheel galaxy, M101, which is about 22 million light-years away.

The star system is known as M101 ULX-1. It consists of two prominent objects.

One of them is a black hole, which recent observations suggest is about 20 to 30 times as massive as the Sun. A black hole’s gravity is so strong that not even light can escape from it. But as gas is pulled toward the black hole, it forms a superhot disk that produces enormous amounts of X-rays, making it an easy target for space telescopes.

Much of the gas in the disk appears to come from a bright, heavy companion star. The star blows a strong “wind” into space. Some of the hot gas in this wind is captured by the black hole.

A star like this one lives a short life. When its time is up, its outer layers explode, but its core collapses to form a black hole. In fact, that’s probably already happened to the bright star in M101 ULX-1, so what astronomers see through their telescopes no longer exists. We haven’t yet seen the star’s demise, though, because it takes 22 million years for light from the system to reach Earth. So somewhere between here and M101, the light of an exploding star may be racing toward us — showing us the birth of a black hole.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/m101-ulx-1
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StarDate: January 22, 2014

Moon and Spica

The Moon passes breathtakingly close to a bright star in the wee hours of tomorrow morning: Spica, the leading light of Virgo. At their closest, they’ll be separated by about the width of the Moon itself. And the bright orange planet Mars looks on from just above them.

Spica is one of only a handful of bright stars that can have such close encounters with the Moon. That’s because the Moon follows a narrow path across the sky — within a few degrees of the Sun’s path, known as the ecliptic. The stars all maintain fixed positions relative to the ecliptic, so only a few of them can greet the Moon each month.

But not all monthly encounters with the Moon are the same, because the Moon’s path is tilted slightly with respect to the ecliptic. So some months the Moon passes quite close to stars like Spica, and others it gives them a wide berth.

This month, the geometry is right for an especially close passage. As they climb into good view after midnight, Spica and the Moon will be separated by about a degree — less than the width of your finger held at arm’s length. At their closest, around 3 or 4 a.m. Central Time, they’ll be just half a degree apart. The exact separation depends on your location. They’ll appear a little closer together from northern latitudes than southern ones.

After that, the Moon will slowly move away from Spica, and they’ll be a degree or two apart at first light — headed toward another good encounter just four weeks later.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/moon-and-spica-12
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StarDate: January 23, 2014

Orion Nebula

One of the most remarkable astronomical objects that’s visible to the unaided eye is at its best on winter evenings. The Orion Nebula is in the southeast as darkness falls tonight, to the lower right of Orion’s well-known belt.

To the eye alone, the nebula looks like a big but faint star. But its true nature is far more impressive. Instead of a single star, it’s a stellar nursery — a light-years-wide complex of gas and dust that’s given birth to thousands of stars.

Many of the stars are less than a million years old, with some just a few tens of thousands of years old. Some of the youngest are also the hottest and most massive. Strong “winds” from these stars compress some of the nearby clumps of gas, causing them to collapse and form new stars. But the winds also blow away some of the gas and dust, preventing stars from taking shape.

In addition to the big boys, the nebula also contains thousands of smaller, fainter stars, plus the “failed stars” known as brown dwarfs. And many of the stars are encircled by disks of gas and dust — the raw materials for planets.

And there’s plenty of gas and dust for making more stars — giant clouds and streamers that can stretch across light-years. Some of them glow like fluorescent bulbs, energized by the radiation from hot stars, while others reflect the light from the nebula’s crowded stars. They fill the skies of these stars with light and color — the remarkable glow of a busy stellar nursery.

[Image: LLOri_hubble_4806.jpg]Vast wisps of gas and dust and scores of newborn stars glow brilliantly in this close-up view of a portion of the Orion Nebula, a stellar nursery that's about 1,500 light-years from Earth, from Hubble Space Telescope. It has already given birth to thousands of stars, with many more still taking shape. Much of the nebula is illuminated by a few hot, bright, massive stars at its center. Radiation from these stars also evaporates much of the surrounding material, shutting off star formation in the nebula's inner precincts. This image includes a detailed view of LL Orionis, a bright star at lower left, that is still in the process of forming. Its radiation and winds have cleared a small cocoon around the hot star. The Orion Nebula is bright enough to see with the unaided eye, beneath Orion's Belt. [NASA/ESA/Hubble Heritage Team]


Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/orion-nebula-0
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StarDate: January 24, 2014

Moon and Saturn

The planet Saturn looks tranquil enough. Clouds form wide stripes that encircle the entire planet. They’re colored in subtle shades of yellow and tan.

Yet if you were to plunge into those clouds, you’d find a world that can be far more violent than Earth is, with giant storms, powerful lightning, and fierce winds.

Saturn’s turbulent atmosphere is stirred up by energy from the Sun, energy from deep within the planet itself, and the planet’s high-speed rotation.

Saturn spins on its axis once every 10-and-a-half hours. That makes the planet bulge out at the equator. It also stretches the clouds into those globe-encircling bands. And it creates powerful winds — the jet stream at the equator blows at 1100 miles per hour.

Saturn is so far from the Sun that is receives fairly little solar heat. So most of the energy that drives Saturn’s weather comes from deep inside the planet itself. As the heat makes its way to the surface, it drives thunderstorms that can be as big as Earth, with lightning bolts thousands of times more powerful than anything on our planet.

The heat also powers super-storms that pop up every few years or decades. These storms can eventually encircle the entire planet and whirl through its turbulent atmosphere for many months.

Saturn is in great view at first light tomorrow. It looks like a bright star right next to the Moon — colored golden by its beautiful but violent atmosphere.

Script by Damond Benningfield, Copyright 2013

http://stardate.org/radio/program/moon-and-saturn-19
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StarDate: January 25, 2014

California Nebula

Some of the faintest stars that are visible to the unaided eye are really some of the most impressive stars of all. They look faint only because they’re a long way off. In fact, they’re so far away that they must be truly remarkable for us to see them at all.

A prime example is in the constellation Perseus, which is high in the south at nightfall.

To the eye alone, Xi Persei is faint. In fact, you can’t see it at all from a light-polluted city. In reality, though, the star is a stunner — more than 10,000 times brighter than the Sun. And when you add in the ultraviolet, it’s more than 300,000 times brighter than the Sun. It looks faint only because it’s about 1,800 light-years away.

Xi Persei is so bright in the ultraviolet because its surface is extremely hot; in fact, it’s one of the hottest stars that’s visible to the naked eye. That energy has an impressive effect on a nearby cloud of gas and dust: It causes the gas to glow like a fluorescent bulb. The visible part of the cloud spans about a hundred light-years, so Xi Persei’s radiation is energizing enormous amounts of material.

The cloud resembles the outline of the state of California, so it’s known as the California Nebula. But it won’t look that way forever. Some of its gas and dust are collapsing to make new stars. And Xi Persei is blasting away some of the material that’s closest to it like a celestial blowtorch — constantly resculpting the California Nebula.

[Image: IR_calif_nebula.jpg]
This infrared view from the WISE spacecraft shows details of the California Nebula, a vast complex of gas and dust in the constellation Perseus. Ultraviolet energy from Xi Persei, a bright star at upper left, causes much of the nebula's gas to glow. Strong winds from the star create a shockwave that heats the surrounding dust, shown in red. The green depicts lanes of dust in the nebula. Some of the dust and gas may collapse to give birth to new starsScript by

Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/california-nebula-0
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StarDate: January 28, 2014

Mirzam

The big dog trots across the southern evening sky this week. It’s quite easy to spot because it’s home to Sirius, the brightest star in all the night sky. It’s in the southeast in early evening, with the rest of the constellation below it and to the sides.

Sirius really is a fairly bright star, but it’s a mere firefly compared to some of the other stars of Canis Major. One example stands close to the right or upper right of Sirius during the early evening.

Mirzam looks much fainter than Sirius, but that’s a bit of a trick. The star is really thousands of times brighter than Sirius, but it’s also much farther — about 500 light-years, versus less than nine light-years for Sirius.

That means that Mirzam is quite a stunner. When you add up all forms of energy, it’s thousands of times brighter than Sirius, and tens of thousands of times brighter than the Sun.

The key to its brightness is the star’s great mass. It’s so heavy that its gravity squeezes its core tightly. That’s like mashing your foot down on the gas pedal of your car — it revs up the nuclear reactions in the star’s core, making it produce much more energy. But also like your car, mashing down the pedal uses up the fuel much more quickly. So despite its great size, Mirzam will live less than one percent as long as the Sun will. When its time is up, it’ll explode as a supernova — a brilliant ending for a brilliant star.

We’ll have more about the big dog tomorrow

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/mirzam
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StarDate: January 31, 2014

Evening Mercury

Rugged little Mercury, the smallest planet in the solar system, is putting in a quick but decent showing in the early evening sky right now. It’s especially easy to find tonight because it’s close to the upper left of the crescent Moon.

Mercury’s surface resembles the Moon’s — a desolate landscape marked by countless impact craters. But observations by the orbiting MESSENGER spacecraft show a few differences.

The main difference is the volcanic history of the two worlds. The Moon has been geologically “dead” for close to four billion years, so there’s been little volcanic activity. But Mercury stayed active for much longer. Relatively young volcanic plains fill much of the space between old craters — some of them formed just a couple of billion years ago.

By then, Mercury’s interior had cooled quite a bit, causing the entire planet to shrink. Mercury’s crust got thicker and stronger, shutting off the flow of molten rock to the surface and ending the planet’s volcanic activity.

The shrinking planet also created giant “wrinkles” in Mercury’s surface. These rounded cliffs can be up to a mile high and hundreds of miles long — features that are not found on the Moon.

And Mercury and the Moon are in good view shortly after sunset this evening. The planet looks like a bright star close to the Moon. But they’re so low in the sky that you need a clear horizon to see them. They drop from sight not much more than an hour after sunset.

Script by Damond Benningfield, Copyright 2013
http://stardate.org/radio/program/evening-mercury-1
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