StarDate

Billy Henry
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  • ASTRONOMY
  • UPDATED TWICE WEEKLY

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

Episodes

  1. 1 DAY AGO

    Kepler’s Supernova

    In October of 1604, a brilliant “new” star blazed to life in the constellation Ophiuchus. It was bright enough to see in the daytime for weeks. German astronomer Johannes Kepler kept a close eye on it until it faded from the night sky, in 1606. So today, it’s known as Kepler’s Supernova. It’s the last known supernova in the Milky Way Galaxy. A space telescope has been keeping a close eye on the aftermath of that event for the past 25 years. That’s revealed a lot about the supernova and the environment around it. The supernova flared to life when a stellar corpse known as a white dwarf tipped above its weight limit. The star either stole gas from a companion star, or it merged with another white dwarf. Either way, the star was blasted to bits. The explosion expelled a huge cloud of debris – a nebula that today spans about a light-year. It’s extremely hot, so it produces a lot of X-rays. Chandra X-Ray Observatory has taken many looks at the nebula. It’s found that one side of it is expanding at about two percent of the speed of light. The opposite side is moving only one-third that fast. The slower side is also hotter. That’s because it’s running into more gas and dust around the nebula. Chandra will keep an eye on the nebula for as long as it can – telling us much more about the violent death of a star. The nebula is at the southern edge of Ophiuchus. At dawn tomorrow, it’s to the upper right of the Moon. Script by Damond Benningfield

    2 min

  2. 2 DAYS AGO

    SMILE

    The Sun sprays Earth with a constant shower of charged particles – the solar wind. But the shower sometimes becomes a storm – a barrage that can damage satellites, overload power grids, and cause other mischief. Predicting such storms can save a lot of grief. But better predictions require a better understanding of the Sun, Earth’s magnetic field, and how they interact. A mission scheduled for launch as early as this week should help. SMILE is a joint project of Europe and China. The craft will orbit up to 75,000 miles from Earth. From that high perch, it’ll be able to see Earth’s magnetopause – the zone where the solar wind rams into Earth’s magnetic field. It will monitor that zone for up to 40 hours at a time – far longer than any glimpses we’ve had before. Earth’s magnetic field deflects most of the particles in the solar wind. But some of them get through. They create the auroras – the colorful northern and southern lights. Powerful storms on the Sun blast out huge amounts of particles. They can overwhelm the magnetic field, creating intense bouts of “space weather.” Among other effects, that causes especially intense auroras, which can appear in regions where they’re seldom seen. SMILE will watch the auroras to see how they change with the level of solar activity. SMILE’s observations will tell us a lot more about how Earth and the Sun get along – improving our ability to protect ourselves from solar storms. Script by Damond Benningfield

    2 min

  3. 3 DAYS AGO

    Moon and Antares

    If we could send a spacecraft to the supergiant star Antares, it could take a really close look. In fact, it’s not hard to imagine that we could build a probe that could safely plunge into the star’s outer layers. Although those layers are hot, they’re also quite thin – a fairly decent vacuum. So a probe might be able to descend millions of miles below the surface and survive. Antares is a monster. It’s roughly a dozen times the mass of the Sun, and 700 times the Sun’s diameter. So its average density is less than one-billionth of the Sun’s. And most of its mass is concentrated deep in the core, which is where the star generates its energy. That means the outer layers are extremely thin – so thin that it’s tough to define the surface – it blends into the background. The surface temperature of Antares is about 6100 degrees Fahrenheit, compared to 10 thousand degrees for the Sun. We’ve already built a probe that can approach to within a few million miles of the Sun. It has a shield that can withstand temperatures of about 2500 degrees. A plunge into Antares would be hotter, but building a shield to take the heat doesn’t seem impossible – providing a way to get an up-close look at this monster star. Antares climbs into good view by 1 or 1:30 a.m. It’s close to the lower left of the Moon as they rise, with the Moon inching closer to the star before dawn. Script by Damond Benningfield

    2 min

  4. 4 DAYS AGO

    Beta Monocerotis

    Eighteenth-century astronomer William Herschel described the star system Beta Monocerotis as “one of the most beautiful sights in the heavens.” It’s one of the hidden beauties of Monoceros, the unicorn. The constellation is well up in the southwestern sky in early evening. It’s wedged between brilliant Orion and the “little dog” star Procyon. There’s not much to see in Monoceros with the eye alone. But telescopes reveal a bounty of beautiful sights. And Beta Monocerotis straddles both domains. It’s faintly visible to the unaided eye as one of the unicorn’s two brightest stars. But to see the same beauty that Herschel did, you need a telescope. That view reveals three stars, not one, all with a fetching blue-white color. The color comes from the temperatures of the stars – their surfaces are many thousands of degrees hotter than the Sun’s. And all three stars are much more massive than the Sun. That revs up the nuclear reactions in their cores, which is what makes them so hot. It also makes the stars extremely bright – as much as 3200 times as bright as the Sun. So the stars are visible across 700 light-years of space. The two faintest members of the system probably form a wide binary, with the third star orbiting around them. Combined, they make Beta Monocerotis a beautiful skywatching sight – a vision in blue for an early-spring night. Script by Damond Benningfield

    2 min

  5. 5 DAYS AGO

    Stellar Interactions

    We never know everything there is to know about a person from the first glance – or anything else, for that matter. And that includes the stars. It takes a lot of time, and a lot of looks with different instruments, to piece together the whole story. One example is the system Gaia BH2. It consists of two known objects. But there might once have been a third object – a star that was gobbled up. The system was discovered by Gaia, a space telescope. It revealed two objects: a black hole about nine times as massive as the Sun, and a giant star about 1.2 times the Sun’s mass. They orbit each other once every three and a half years. Ground-based telescopes revealed the composition of the giant. Its chemistry looked like that of an ancient star. But observations by TESS, another space telescope, suggested otherwise. The satellite measured “starquakes” on the surface of the giant star. Sound waves bounce around inside the star and back to the surface. So just as an earthquake tells us what’s happening below the surface of Earth, a starquake tells us what’s happening deep inside a star. The quakes revealed that the star spins faster than expected. That suggests it was spun up by interactions with something else. It might have swallowed debris that encircled the black hole. Or it might have swallowed another star, changing the chemistry at its surface – prematurely “aging” this giant star. Script by Damond Benningfield

    2 min

  6. 6 DAYS AGO

    Moon and Spica

    The stars of Spica may be headed for a breakup. One of the two stars is likely to explode as a supernova. That may send the stars careening into the galaxy on their own. Spica is the brightest star of Virgo. It rises just above the Moon early this evening. The system consists of two big, heavy stars. The primary star, Spica A, is about 10 times the mass of the Sun. Spica B is about seven times the Sun’s mass. The stars are so close together that they whirl around each other once every four days. Within a few million years, Spica A will consume all the nuclear fuel in its core. The core will collapse, probably forming a neutron star – an object up to twice the mass of the Sun, but only as big as a city. Its outer layers then will blast into space at a few percent of the speed of light – a supernova. The companion star should survive, although it might lose some gas from its surface. But what happens next is tricky. Supernovas sometimes explode asymmetrically – the blast can be off-centered. That can give the neutron star a big kick. And the neutron star will be only a fraction as massive as the original star. That means its gravitational grip on its companion will be much weaker. The neutron star could zip off at high speed – perhaps fast enough to escape the galaxy. And even if that doesn’t happen, the stars are likely to move farther apart – a bigger gap between these impressive stars. Script by Damond Benningfield

    2 min

  7. 1 APR

    Morning Mercury

    Mercury is just peeking into view in the dawn sky. The little planet is in the east in the waxing twilight, and looks like a bright star. It’ll stand highest in the sky on Friday. But because of the angle at which it rises, it’s hard to spot. In fact, from much of the United States, you probably can’t see it at all. The view is best from south of about Dallas. That difficulty illustrates how tough it’s been for scientists to study Mercury. It’s never in view for long – no more than a couple of hours before sunrise or after sunset. And it’s so low in the sky that we always see it through a thick layer of air, so the view is murky – like trying to make out the shapes of clouds from the bottom of a swimming pool. In the late 1800s and the early 1900s, astronomers did make a few crude maps of Mercury’s surface. But there was a lot they couldn’t figure out. That included the length of the planet’s day. At first, it appeared that Mercury completed one turn on its axis in 88 Earth days – the same length as its year. In the early 1960s, though, astronomers bounced radio waves off the surface. That work showed that a day lasts 59 Earth days. So Mercury completes three turns on its axis for every two orbits around the Sun – three days for every two years. Again, look quite low in the east not long before sunrise for elusive little Mercury – a planet that’s been hard to get to know. Script by Damond Benningfield

    2 min

  8. 31 MAR

    Alioth

    For skywatchers, tonight’s a time for old friends. There’s an almost-full Moon, so its glare overpowers most of the stars in the night sky. But the brighter stars shine through – the most familiar ones. That includes the stars of the Big Dipper, which are in the northeast at nightfall. The dipper’s leading light is Alioth. It’s the first star in the handle. It’s about 80 light-years away. But it’s an easy target because it’s about a hundred times brighter than the Sun. That’s because it’s bigger and hotter than the Sun. Alioth is classified as a “peculiar” star – its chemical makeup is unusual. Astronomers measure its chemistry by breaking the star’s light into its individual wavelengths. Each element in the star imprints its own “barcode” in that pattern of light. But the mixture of elements in Alioth is different from most stars. Some elements are especially common, while others are unusually rare. And the mixture changes as the star turns on its axis. That behavior is caused by the star’s odd magnetic field. It’s tilted so far that the magnetic poles lie roughly along the star’s equator. Thanks to that alignment, the magnetic field pulls some elements to the surface, and concentrates them in specific locations. It pushes other elements down, so we can’t see them. So Alioth is both familiar and peculiar – an old friend that’s easy to pick out through the glare of the full Moon. Script by Damond Benningfield

    2 min

  9. 30 MAR

    Making Contact

    Astronomers have been trying to hear from other civilizations for two-thirds of a century. So far, not a peep. But finding E-T might be the easy part. Actually having a conversation might be a lot harder. We wouldn’t know what the other folks were saying – or whether they were interested in talking at all. To gain some insight, scientists have been studying some “non-terrestrial” intelligences here on Earth – whales and dolphins – species that live in the oceans instead of on land. Many of them have complex communications with each other. And some of them interact with humans. One example is humpback whales. They’re playful and curious, and they often approach boats and divers. And a recent study suggested that they might be trying to have a conversation. Researchers found a dozen times when humpbacks blew special bubbles while they were near people. The bubbles looked like smoke rings, a few feet across. The bubbles were different from those associated with other behavior, such as courting or “corraling” fish. In most cases, a whale first approached the people, then moved away a bit and blew one or more rings. Some of the whales poked their heads up through the rings. The researchers said the whales might have been trying to play, or to see how the people responded. But the bubbles could have been an attempt to communicate – starting a conversation between terrestrial and non-terrestrial life. Script by Damond Benningfield

    2 min

  10. 29 MAR

    Moon and Regulus

    The star Regulus leads the Moon across the sky tonight. The bright heart of the lion is close to the upper right of the Moon at nightfall, with the gap increasing as the hours roll by. Regulus is about 79 light-years away. That means the light you see from Regulus tonight actually left the star about 79 years ago. So when a particle of light from Regulus hits your eye, it’s ending a journey of 79 years. As with many things astronomical, though, it’s all relative. For the particle of light itself – a photon – the trip took literally no time at all. That’s because the photon was traveling at the speed of light – 670 million miles per hour. Nothing can travel faster than that. And only photons can travel at that speed. That’s because photons have no mass – they weigh nothing at all. If anything else were to travel at lightspeed, it would become infinitely massive. So physical objects are limited to just below lightspeed. As an object moves faster, time appears to slow down for it as viewed by an outside observer – its clock would tick more slowly. So if you could accelerate a starship to just a fraction below lightspeed, it could travel for thousands of years as measured by a clock back on Earth – but just a few years or even less as measured by its own clock. So as you look at Regulus tonight, remember that the photons are completing a journey of both 79 years – and no time at all. Script by Damond Benningfield

    2 min
  • 10 Episodes

Hosts & Guests

About

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

Information

  • Creator
    Billy Henry
  • Years Active
    2017 - 2026
  • Episodes
    10
  • Rating
    Clean
  • Copyright
    © 2022 The University of Texas McDonald Observatory
  • Show Website
    StarDate

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