StarDate

Billy Henry
  • 4.6(262개의 평가)
  • 천문학
  • 매일 업데이트

StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.

에피소드

  1. 1일 전

    Degenerate Future

    The Sun faces a “degenerate” future. That’s not a value judgment – it’s physics. When the Sun can no longer produce nuclear reactions, its core will collapse. How far it collapses is limited by a type of pressure exerted by its atoms – degeneracy pressure. Today, the Sun is “fusing” atoms of hydrogen to make helium. When the hydrogen is gone, it’ll fuse the helium to make carbon and oxygen. But the Sun isn’t massive enough to extend that process, so its nuclear furnace will be extinguished. Fusion releases energy, which balances the pull of gravity. That keeps the Sun puffed up. Right now, it’s big enough to hold a million Earths. When fusion stops, gravity will win out. The core will shrink to the size of Earth itself. But it’ll still be about half as heavy as the present-day Sun. So a chunk the size of a sugar cube would weigh a ton. The dead core won’t shrink beyond that. That’s because the electrons in the core will exert their own pressure – degeneracy pressure. They can be squeezed only so much before they run out of “elbow room” and halt the collapse. That will leave a white dwarf – a dead cosmic cinder – to cool and fade over the eons. The galaxy is littered with white dwarfs, but none of them is bright enough to see with the eye alone. The closest one is a companion of Sirius, the brightest star in the night sky, which is low in the southwest as night falls – a star that faces its own “degenerate” future. Script by Damond Benningfield

    2분

  2. 2일 전

    May Day

    For centuries, the people of the British Isles marked the beginning of summer not on the solstice, in June, but on May 1st. It’s a cross-quarter day, which comes about half way between a solstice and an equinox. In Scotland and Ireland, the date was known as Beltane. People built bonfires to celebrate the longer days, and held rituals to protect their crops and livestock. And in England, the date became known as May Day. People celebrated with village fetes, and they danced around the maypole. Dancers grabbed ribbons attached to the top of the pole, then circled around it, getting closer with each circuit. Especially tall maypoles were erected in an area of London known as the Strand. The last of these poles was removed 300 years ago. But it found a new life – supporting one of the world’s largest telescopes. The maypole was acquired by Isaac Newton, who had formulated laws of gravity and motion. In April of 1718, he had the pole moved to a park outside London for use by James Pound, an astronomer and clergyman. Pound had the use of a large lens created by another astronomer. The telescope was created by mounting the lens on the maypole. The eyepiece was on the ground, linked to the lens by a long wire. With that telescope, Pound measured the positions of the moons of Jupiter and Saturn. Newton used those observations to calculate the moons’ orbits – measuring a celestial dance around the maypole. Script by Damond Benningfield

    2분

  3. 3일 전

    Desirable Stars

    The stars are quite literally desirable. That’s because the roots that make up the word desirable mean “to long for a star, heavenly body, or constellation.” Astronomy has a rich vocabulary: star, planet, galaxy, and many other words. Many of them also have non-astronomical meanings. A “galaxy of stars,” for example, might refer to an auditorium full of actors – though how many of them can be considered “stars” is a matter of opinion. Some words with heavenly connections seem obvious. “Lunatic” refers to the Moon. It comes from an ancient belief that the Moon’s influence could make people behave strangely. And “jovial” – to be full of good cheer – means “of Jupiter;” in ancient astrology, the planet was thought to exert a happy influence. Other words have more surprising connections to the stars. Consider “consider.” Its roots mean “to observe the stars.” “Sider” is from a Latin word that means “star, heavenly body, or constellation.” In fact, many words with some version of the root have a link to the stars – including desire. Disaster also comes from ancient astrology. It meant an unfavorable position for a star or planet. “Aster” was a Latin word for star. The word “influence” appeared in the 14th century. Dictionaries say it meant “streaming ethereal power from the stars when in certain positions, acting upon the character or destiny of men” – a good description of modern-day “influencers.” Script by Damond Benningfield

    2분

  4. 4일 전

    Moon and Spica

    To the eye alone, Spica is one of the 15 brightest stars in the night sky. And it really is brilliant. At visible wavelengths, it’s about 2,000 times brighter than the Sun. It looks white with a hint of blue. When you look at Spica with special instruments, though, it’s even more impressive. It consists of two stars, not one. Both are much bigger and heavier than the Sun. And when you add up all wavelengths of light, they shine about 20 thousand times brighter than the Sun. Most of that energy is in the ultraviolet – wavelengths that are too short for the human eye. Spica’s two stars produce so much of it because their surfaces are tens of thousands of degrees hotter than the Sun’s. In fact, the type of energy a star emits depends almost entirely on its surface temperature. And so does the star’s color. To the eye alone, the hottest stars look blue. But they emit huge amounts of ultraviolet. The coolest stars look orange or red. They emit huge amounts of infrared light – wavelengths that are too long for the human eye. Stars in the middle are white or yellow. They emit most of their light at visible wavelengths. So with a star like the Sun, we see most of the energy it produces – light that’s just right for the human eye. Spica is quite close to the Moon as darkness falls this evening. The Moon will slide away from the star during the night, but they’ll still be close as they set, around dawn. Script by Damond Benningfield

    2분

  5. 5일 전

    Venus and Aldebaran

    Aldebaran is like a reverse time capsule. Instead of preserving mementos from the past, the star shows us what we can expect in the distant future – the far, far distant future. It’s in a phase of life that the Sun will pass through in several billion years. Aldebaran marks the eye of Taurus, the bull. It’s low in the western sky as evening twilight fades. It’s a little to the left of Venus, the brilliant “evening star.” The Sun is in the prime phase of life. It’s steadily “fusing” the hydrogen atoms in its core to make helium. That produces the energy that makes our star shine. Aldebaran has already completed that phase. Its core has converted the hydrogen to helium. Now, the star is fusing the hydrogen in a thin layer around the core. This layer is especially hot. Its radiation pushes outward on the surrounding layers of gas. That’s caused Aldebaran to swell to about 45 times the Sun’s diameter. And that’s made the star more than 400 times brighter than the Sun. Over many millions of years, Aldebaran will use up that shell of hydrogen. Nuclear fusion will then fire up in the helium core, briefly making the star even bigger and brighter. After that, fusion in the core will begin to shut down. Aldebaran’s outer layers will blow away, briefly forming a colorful bubble. As the bubble dissipates, only the star’s now-dead core will remain – a final memento of a once impressive star. Script by Damond Benningfield

    2분

  6. 6일 전

    Superkilonova

    A giant star in a galaxy more than a billion light-years from Earth died a spectacular death. Then it might have died again – an event that was even more spectacular than the first. The double demise earned it a doubly impressive title: a superkilonova – two powerful explosions from a single star. The system was discovered last August. It produced a huge outburst of gravitational waves – ripples in spacetime. Astronomers first thought it was a kilonova – the violent merger of two super-dense corpses known as neutron stars. Such mergers produce huge amounts of the heaviest elements in the universe, including gold, platinum, and uranium. After a few days, though, the event began to look more like a type of supernova – the explosion of a star much heavier than the Sun. But as astronomers followed the outburst with a dozen telescopes on the ground, one team suggested that it might have been both. The supernova came first. The massive star’s core collapsed to make a neutron star. Its outer layers then blasted into space. But the collapsing core might have split apart to make two neutron stars, not one. Or the second neutron star might have come together from debris around the first one. Either way, the tiny but massive neutron stars quickly spiraled together. That set off the second blast – a kilonova. There are other possible explanations for the object. But for now, a superkilonova tops the list. Script by Damond Benningfield

    2분

  7. 4월 26일

    Crow and Cup

    A pair of ancient but faint constellations flows across the southern evening sky at this time of year. The two of them share a common story, which also involves a third constellation. Corvus and Crater have been around for more than two millennia. Their story, in fact, comes from ancient Greece. According to the myth, the god Apollo sent Corvus, the crow, to fill a cup – known as a crater – with water from a nearby spring. On the way, the crow saw a tree filled with unripe figs. Instead of fetching the water and coming straight back, he waited for the figs to ripen. When they did, he gorged on them. Corvus knew that Apollo wouldn’t be happy with him. So he filled the cup with water, then grabbed a water snake in his talons. He brought both back to Apollo, and blamed the snake for blocking his way. But Apollo wasn’t fooled. Instead, he was angry and vengeful. He cast crow, cup, and snake into the heavens, forming three constellations. As extra punishment, he decreed that the crow would suffer from thirst – with the water-filled cup forever just out of reach. The constellations are in the southeast at nightfall now. Corvus contains four moderately bright stars that outline the shape of a sail. Crater, to the upper right, looks like a goblet – but you need really dark skies to see it. Both of them sit on the back of poor Hydra, the water snake – an innocent victim of the wrath of the gods. Script by Damond Benningfield

    2분

  8. 4월 25일

    Moon and Regulus

    As seen from the eastern United States, there’s a “now-you-see-it, now-you-don’t” event in the early evening sky. The Moon will occult Regulus – passing in front of Leo’s brightest star and blocking it from view. The star will remain hidden for a few minutes. But its disappearance is almost instantaneous: Regulus is there one second, then gone the next. It does take a tiny fraction of a second for the Moon to cover the star. Astronomers make precise measurements of that timing. The length of time it takes a star to vanish reveals its apparent diameter – how big it looks in our sky. And that’s how the first good measurement of the size of Regulus came about. In 1933, a French astronomer recorded an occultation of the star on a rapidly spinning photographic plate. That told him how long it took Regulus to disappear. From that, he calculated the star’s apparent diameter. And he was close to the modern value. When astronomers combine that number with a star’s distance, they can calculate its true diameter. Regulus is 79 light-years away – and about four times the diameter of the Sun. Tonight’s occultation is best seen from the eastern U.S. The Moon and Regulus will be in the sky as seen from the rest of the country as well. But at least part of the event will take place during daylight, when Regulus is too faint to see without help. The star will shine close to the Moon after the occultation ends. Script by Damond Benningfield

    2분

  9. 4월 24일

    Pointing the Way

    It’s hard to ask for a better signpost for finding things in the night sky than the planet Venus. Right now it’s the brilliant “evening star,” low in the west as twilight fades. And it points the way to two other wonders: the planet Uranus and the Pleiades star cluster. The Pleiades is fairly easy to find on its own. Its brightest stars form a tiny dipper shape. In fact, the Pleiades is often mistaken for the Little Dipper. But that dipper is in the north, anchored by the North Star. Despite its prominence, the Pleiades is best appreciated with a technique known as averted vision – seeing it from the corner of your eye. And Venus offers a good chance to try it. Look at Venus, then see if you can see the sparkly cluster to its right. They’re separated by the width of a couple of fingers held at arm’s length. Uranus is about one finger width below Venus. It’s the third-largest planet in the solar system. But it’s so far away that it looks tiny and faint. It’s an easy target for binoculars or a small telescope, though. It looks like a faint star. A telescope reveals something interesting about Venus – it doesn’t look quite complete. That’s because it’s in a gibbous phase. If you watch the planet for months, you’ll see it get thinner and thinner. That’s because Venus will cross between Earth and the Sun in late October. Like the new Moon, it’ll be lost in the Sun’s glare no matter how you look at it. Script by Damond Benningfield

    2분

  10. 4월 23일

    Thick Ice

    Jupiter’s big moon Europa is one of the most likely bodies in the solar system to host life. The moon has a global ocean that holds more water than all of Earth’s oceans combined. The ocean might have sources of energy and chemical compounds that are needed to support microscopic life. But getting to that ocean won’t be easy. It’s covered by a crust of ice. And a recent study says the ice is pretty thick. The Juno spacecraft scanned part of Europa with an instrument that can probe conditions below the surface. It found that the average thickness of the ice is about 18 miles. That’s thicker than suggested by some earlier studies. Juno found many cracks in the ice. But they don’t penetrate anywhere close to the water. So there doesn’t appear to be a good way to get through the ice to study the ocean. That also could be a problem for any organisms in the ocean. Jupiter’s radiation zaps material on the surface, transforming it into possible nutrients. Without any holes or thin spots in the ice, there’s no direct way to flush the nutrients into the water. But another study found that large concentrations of nutrients could make blocks of ice denser than the surrounding ice. Over time, the heavier blocks could sink all the way through the ice – perhaps helping to sustain any life in Europa’s hidden ocean. Jupiter is high in the west at nightfall, and looks like a brilliant star. The twins of Gemini stand above it. Script by Damond Benningfield

    2분
  • 10개의 에피소드

호스트 및 게스트

4.6
최고 5점
262개의 평가

소개

StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.

정보

  • 제작진
    Billy Henry
  • 방송 연도
    2017년 - 2026년
  • 에피소드
    10
  • 등급
    전체 연령 사용가
  • 저작권
    © 2022 The University of Texas McDonald Observatory
  • 웹사이트 보기
    StarDate

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