Published by Billy Henry
StarDate, the longest-running national radio science feature in the U.S., tells listeners what to look for in the night sky.
Listen on Apple Podcasts2 min
The formal name for a planet almost 50 light-years from Earth is Kua’Kua – a Costa Rican name that means “butterfly.” But there’s nothing beautiful or delicate about this world. Its surface is a desolate landscape of volcanic rock. The planet is in the system LHS 3844. Its star is a cool, faint ember known as a red dwarf. Kua’Kua – LHS 3844 b – is a super-Earth. It’s bigger and heavier than Earth, and it’s made of rock and metal. The planet is only about half a million miles from the star, and the same hemisphere always faces the star. So the dayside sizzles at more than 1300 degrees Fahrenheit. Every 11 hours, the planet passes behind the star as seen from Earth. Astronomers have watched several passages with Webb Space Telescope. Watching before and after a passage revealed the combined make-up of the star and planet. But when the planet disappeared, that left only the star in view. Comparing the readings revealed details about the surface of the planet. In fact, it’s the first “exoplanet” for which we have such a close look. The surface appears to be made of dark volcanic rock that could have been deposited recently, making it fairly smooth and unbroken. But the surface also could be much older. In that case, a constant pounding by radiation and meteorites could have pulverized the surface. Either way, Kua’Kua is not a good place to go hunting for butterflies. Script by Damond Benningfield
2 min
There’s just one place to catch a wave outside Earth: Titan, the largest moon of Saturn. It’s the only other world in the solar system with bodies of liquid on its surface. And the waves there could reach heights of 10 feet. But future surfers will need to dress carefully; the surface temperature is almost 300 degrees below zero. Titan is half-again the size of Earth’s moon, and it has a dense atmosphere. Rain fills its lakes and seas with liquid methane, ethane, and nitrogen. The largest sea covers about 200,000 square miles – twice the area of all the Great Lakes combined. It could be several hundred feet deep. The Cassini spacecraft used radar to measure Titan’s ponds. It saw waves of no more than an inch or so high. But a recent study says the waves could get a lot bigger. Based on 20 years of observations of waves on Lake Superior, scientists built a computer model of how waves might work on other worlds. The model accounted for gravity, the pressure of the atmosphere, and the properties of the liquid. When the model was applied to Titan, it showed that even gentle breezes could whip up some big waves. But the waves would move more slowly than those on Earth – a slow-motion trip across the sea. Saturn looks like a bright star close to our moon the next couple of mornings. It’ll stand to the left of the Moon at dawn tomorrow, and the lower right of the Moon on Tuesday. Script by Damond Benningfield
2 min
The dawn twilight has a bright visitor the next few mornings – the planet Mercury. It’s farthest from the Sun for its current morning appearance. It looks like a bright star, but it’s so low in the sky that it’s tough to find. Mercury holds an important spot in the history of astronomy and physics. It provided some of the first confirmation of General Relativity – Albert Einstein’s theory of gravity. Mercury’s orbit around the Sun is lopsided, so the planet’s distance from the Sun varies. For a long time, astronomers had seen that the orbit’s closest point shifted a tiny bit over time. Isaac Newton’s laws of gravity explained most of the difference. But there was still a tiny amount that couldn’t be accounted for. Einstein’s theory of gravity held that massive bodies warp the space around them. Since Mercury is the Sun’s closest planet, its orbit is influenced by that “warpage” more strongly than any other planet’s. In fact, general relativity accounted precisely for the shift in the orbit. So Mercury’s orbit provided some of the first evidence to support general relativity – a new way of thinking about gravity. Look for Mercury quite low in the eastern sky during the waxing twilight. It’ll shine a little brighter each day over the next few mornings. But it’ll also drop a little closer to the Sun, so you’ll need a clear horizon to spot it. Tomorrow: catching waves. Script by Damond Benningfield
2 min
The Sun is getting bigger, hotter, and brighter. The change isn’t enough to notice during a human lifetime – or even a thousand lifetimes. It plays out over hundreds of millions of years. And it’s all the result of changes deep inside our star. Like all stars in the prime phase of life, the Sun is “fusing” atoms of hydrogen in its core to make helium. That generates the energy that makes the Sun shine. As the amount of helium builds up, the core gets denser, so gravity squeezes it more tightly. That speeds up the fusion reactions, making the core even hotter. Radiation from the hotter core pushes on the Sun’s outer layers, making the Sun bigger. It also makes its surface hotter. The combination of bigger and hotter makes the Sun brighter. So over its four-and-a-half-billion-year lifetime, our star has grown about 15 percent wider, and perhaps 40 percent brighter. That should mean that the young Earth would have been an iceball. But studies suggest the atmosphere was much thicker when Earth was young. The atmosphere also contained much more carbon dioxide and other greenhouse gases. They trapped more heat, keeping Earth from freezing over. The Sun’s bigger-hotter-brighter trend will continue. In perhaps a billion to two billion years, it’ll be so hot and bright that Earth’s air and oceans will boil away. That will reduce our planet to a bare cinder. Script by Damond Benningfield
2 min
Eta Aquilae is big, bright, and unsteady. Over a bit more than seven days, the star pulses in and out like a beating heart. That causes its brightness to change. How it changes makes the star a good “standard candle” – a type of object that astronomers use to measure the scale of the universe. Eta Aquilae is a Cepheid variable – the first one ever discovered. Such stars brighten and fade in a predictable way. By timing the cycle, astronomers can determine the star’s true brightness. Comparing that to how bright the star looks allows them to calculate the star’s distance. Cepheids are bright enough to see hundreds of millions of light-years away – in galaxies beyond the Milky Way. To go even farther, astronomers rely on another type of standard candle: the exploding stars known as Type Ia supernovas. Like the Cepheids, the way they brighten and fade reveals their true brightness. Some of them appear in galaxies with Cepheids, where we already know their distance. That provides a way to calibrate all of the supernovas, which can be seen from billions of light-years away. Of course, it’s all a little more complicated than that. There are different classes of Cepheids, for example. So astronomers have to understand all the details – making sure that a standard candle really is a good distance marker. Eta Aquilae is high above the Moon in early evening, near Altair, its constellation’s brightest star. Script by Damond Benningfield
2 min
Saturn feels like it has a big region of the early morning sky practically to itself right now. The giant planet climbs into good view after midnight, and stands high in the south at first light. It looks like a bright golden star. You have to scan a long way in every direction to find another planet or star that rivals it. Saturn is traveling through Pisces, skimming along the border with Cetus. That region of the sky is well below the Milky Way – the hazy band of light that outlines the disk of the Milky Way Galaxy. When we look at the Milky Way, we’re looking into the most heavily populated part of the galaxy. So not only are there a lot more stars in and around that band, there are a lot more bright stars. At the same time, Saturn’s location is a quarter of the way around the sky from the center of the galaxy, which is in Sagittarius. Again, that means we’re looking into more thinly settled parts of the galaxy. It’s like looking toward the suburbs of a major city instead of its busy downtown – there’s just a lot less to see. Saturn is so far from the Sun that it takes the planet about 30 years to make one full circle against the starry background. So the planet will stay in this dimly settled region of the sky for a couple of years – making it especially easy to find as you look into the darkness. Tomorrow: bright “mile markers” for measuring the scale of the universe. Script by Damond Benningfield
2 min
Gliese 710 isn’t much to look at. It’s smaller and lighter than the Sun, and just one-tenth as bright. So from its current distance of 62 light-years, it’s much too faint to see with the eye alone. But come back in about 1.3 million years and it’ll be a different story. The star will shine about three times brighter than Sirius, the night’s current brightest star. All the stars are on the move. Like the Sun, they’re orbiting the center of the Milky Way Galaxy. Each star follows its own path, so its direction and speed are a little different from all the other stars. Some stars are moving toward us, while others are moving away. Gliese 710 is moving toward the Sun at more than a quarter of a billion miles per year. Studies have shown that it’ll pass just one-sixth of a light-year away – just four percent the distance to the current closest neighbor. That’s closer than any other star will approach the Sun over the next several million years. Gliese 710 will pass through the Oort Cloud – a huge shell of rocky, icy bodies that surrounds the Sun. That will push many of those objects toward the Sun. Some of them could slam into Earth – some un-neighborly gifts from a close neighbor. Gliese 710 is in Serpens, the serpent. The star is about half way up the south-southeastern sky at nightfall. You need a telescope to see it – for now. Script by Damond Benningfield
2 min
In April, engineers had to shut down one of the scientific instruments aboard the Voyager 1 spacecraft. The device had been studying charged particles in the interstellar medium – the space between the stars. But Voyager is slowly losing power, so the instrument was shut down to help extend the craft’s life. Voyager 1 is the most-distant object ever sent into space – 16 billion miles from Earth. At that range, it takes almost 24 hours for its radio transmissions to reach Earth. The craft and its twin, Voyager 2, were launched in the summer of 1977. Their mission was to study the giant planets Jupiter and Saturn. Voyager 2 continued on to Uranus and Neptune. Since then, both craft have just kept on going. In 2012, Voyager 1 became the first craft to leave the solar system. It passed outside the magnetic “bubble” generated by the Sun. Voyager 2 followed in 2018. Both Voyagers are powered by the radioactive decay of plutonium. Today, that generates less than half as much energy as it did at launch. So as the power levels have dropped, engineers have shut off most of the scientific instruments. Two instruments are still going on Voyager 1 – studying the space between the stars. In 300,000 years, the craft is expected to fly about one light-year from a small, faint star that’s 47 light-years away – a dead emissary from the people of Earth. Script by Damond Benningfield
2 min
The religion of ancient Egypt said that when a king died, his soul ascended to the heavens to join with the god Osiris, in the modern-day constellation Orion. His tomb was filled with items he might need to help him on his way. And in the case of at least one pharaoh, some of those items probably came from the heavens. The tomb of King Tutankhamen contained thousands of artifacts. Many of them were made of gold, including a dagger buried inside his coffin. But the boy king also had a second dagger, made of iron. When Tut was buried, more than 3300 years ago, Egypt hadn’t started to work with iron ore, so the dagger probably was made from an iron meteorite – a space rock that fell to Earth. The composition of the dagger’s metal is much like that of a metallic meteorite – a mixture of iron and nickel, with a pinch of cobalt. Another Tut artifact was an elaborate piece of jewelry known as a pectoral. Its centerpiece is a scarab beetle carved from yellow glass. The glass formed about 26 million years ago, when an asteroid or comet plunged toward Earth. It either hit the surface or exploded in the atmosphere. Heat from the explosion melted some of the desert sand, creating chunks of glass. One of those chunks eventually made its way to an Egyptian artist, and then to Tut’s tomb – a piece of glass from the heavens for a king traveling to the heavens. Tomorrow: into the void. Script by Damond Benningfield
2 min
Planetary scientists have had a hard time classifying a world that orbits a faint star in Ophiuchus. Since the planet’s discovery in 2009, they’ve described it as a super-Earth, a mini-Neptune, and a super-Venus. In other words, it’s not like anything in our own solar system. The planet orbits the star GJ 1214. It’s in the serpent bearer, which is high above the Moon this evening. The star is less than 50 light-years away. But it’s less than one percent as bright as the Sun, so you need a good-sized telescope to see it. A few years ago, the International Astronomical Union assigned formal names to both the planet and the star. The names come from Kenya, from the Maa language. The star is Orkaria, from the name of a red pigment used by warriors in tribal ceremonies – the color of the star. The planet is Enaiposha – a word for lake or sea, or for their stormy nature. The planet is bigger and heavier than Earth. That led to its early classification as a super-Earth. But it’s not very dense, which makes it more like a miniature version of Neptune – the smallest of the Sun’s giant planets. Enaiposha has a thick atmosphere, which is hot because the planet is quite close to the star. Observations by Webb Space Telescope suggest the atmosphere contains a lot of carbon dioxide. That hot C-O-2 atmosphere makes the planet like Venus – one of several identities for this hard-to-classify world. Script by Damond Benningfield
2 min
Cygnus X-1 contains the first black hole ever confirmed. And it recently recorded another first. Astronomers measured the details of twin “jets” of particles that shoot into space from its poles. The jets are firing at almost half the speed of light. And they have the power of 10,000 Suns. The system consists of the black hole and a supergiant star. The black hole, which was discovered in 1964, is 20 times the mass of the Sun. The star is twice that mass. The star is extremely hot and bright. It blows a thick wind of hot gas into space. The black hole captures some of the gas, which forms a swirling, super-hot disk around it. Magnetic fields grab some of the gas before it falls into the black hole, and fire it back into space through the jets. Astronomers have seen jets from many black holes. But this is the first time they’ve precisely measured a jet’s power and speed. Those details are important because the jets can have a big influence on the surroundings. They can blow away gas and dust, preventing the birth of more stars. Or they can squeeze clouds of gas and dust, triggering the birth of stars. So the details help us understand the role of black holes in the evolution of entire galaxies. Cygnus is in the eastern sky at nightfall. Although Cygnus X-1 is too faint to see, it’s about half way between the swan’s bill and the intersection of its body and wings. Script by Damond Benningfield
2 min
Stars follow a life-long weight-loss program. They blow hot gas off their surfaces. Over time, the amount of material in these “winds” can add up. Heavier stars, in fact, can expel enough gas to make several stars as massive as the Sun. An example is Antares, the leading light of Scorpius. It’s in good view tonight, to the left of the Moon as night falls. Antares is a supergiant – one of the biggest and brightest stars in the galaxy. It’s more than a dozen times the Sun’s mass. And it’s so big that if you placed it at the center of the solar system, it would extend past the orbit of Mars. But when Antares was born, about 11 million years ago, it was even heavier. Studies in recent years have placed its initial mass at about 15 to 17 times the Sun’s mass. Most of the difference has been blown into space on the star’s winds. Antares has lost so much of its original weight because it was heavy to begin with. A massive star “burns” through its nuclear fuel quickly, making its core extremely hot. Radiation from the core causes the star’s outer layers to puff outward. That far from the core, the surface gravity is fairly low, so it’s easy for radiation to push gas out into space. Antares is fated to expel even more of its mass. At the end of its life, its core will collapse, causing its outer layers to explode as a supernova – blasting most of its remaining gas out into the galaxy. Script by Damond Benningfield
2 min
A new era in the exploration of Mars opened 50 years ago this week, when the first of two Viking landers touched down there. The probes measured the weather and the composition of the Martian rocks and dirt. They looked for evidence of life. And they gazed into the sky, showing a reddish tint for most of the day, but blue at sunrise and sunset. That color is caused by dust in the atmosphere. The tiny dust grains are reddish brown. They scatter some of the sunlight – mostly red light, which makes the sky glow in shades of red. Depending on the time of day, the amount of dust, and other factors, the sky can range from butterscotch to apricot to bright pink. But as the Sun rises and sets, its light passes through a much thicker layer of the atmosphere. That filters out most of the red light, making the Sun and the sky look blue. There’s a lot of dust in the sky, and much of it floats quite high above the surface. So sunlight reflecting from the high-altitude dust extends the twilight, making the sky bright even when the Sun is well out of view. Mars is inching higher into our morning sky. It looks like a fairly bright orange star. It’s in the east at dawn. The star Elnath – the tip of one of the horns of Taurus – stands to the left of Mars. The bull’s eye, Aldebaran, is to the right of Mars. It’s a little brighter than Mars, but about the same color – the color of the Red Planet. Script by Damond Benningfield
2 min
One of the main goals of the twin Viking landers, which touched down on Mars 50 years ago, was to search for life. They found it. But then they didn’t. But maybe they really did. If that sounds confusing – well, it is. Scientists have been debating the findings since the beginning – and the debate is still going on. Viking 1 landed on July 20th, 1976, in a smooth plain north of the equator. It was the first fully successful landing. Viking 2 touched down six weeks later and 4,000 miles away. Both landers conducted several experiments to look for life. They scooped up some of the powdery dust and dumped it into chemical laboratories for analysis. In one experiment, they added water, nutrients, and a radioactive form of carbon. Any microbes in the samples should gobble up the nutrients and “exhale” the carbon. And that’s what appeared to happen – a sign of life. But other experiments came up empty. They looked for organic compounds – the building blocks of life. And they found nothing. According to most scientists at the time, that ruled out the possibility of life. Instead, the positive results were interpreted as complex chemical reactions. But many scientists continue to say the landers did find life. And over the past decade, there’s been a lively conversation about the results. So life at the Viking landing sites remains an open question. Script by Damond Benningfield
2 min
In a field of volcanic rocks and red dunes on the planet Mars, an emissary from Earth sits quietly. Powdery dust may coat its white surface, possibly hiding the American flag and Bicentennial logo from view. Extreme cold might have cracked some of its lenses and other components. But if humans ever colonize Mars, they’ll certainly visit this relic – the first craft to successfully land on the Red Planet. The Viking 1 lander touched down 50 years ago today. It was one of four craft in the Viking project – two landers and two orbiters. Viking 1 wasn’t the first probe to touch down on Mars. The Soviet Union’s Mars 3 had landed in 1971. But it died less than two minutes later, so it didn’t return any information about Mars. The Viking 1 and 2 landers snapped thousands of pictures. They monitored the weather and measured the composition of the soil and atmosphere. The landers also looked for signs of life. Their cameras saw no moving objects on the surface, and no growing plants. Chemical laboratories found no organic molecules in the soil. They did find chemical reactions like those produced by microorganisms on Earth. But scientists at the time decided the reactions were produced by the soil, not life; more about that tomorrow. The Viking 1 lander operated for three Mars years – more than six Earth years. Scientists continue to study its findings to learn more about the intriguing Red Planet. Script by Damond Benningfield
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