StarDate

A young “cotton-candy” planet is hastening its own demise. As it dips close to its star, it appears to trigger giant explosions that erode the planet’s atmosphere. The planet orbits HIP 67522, a star roughly 400 light-years from Earth. The star is a little bigger and heavier than the Sun, but less than one percent the Sun’s age. Such young stars generate strong magnetic fields. Lines of magnetic force tangle and snap, producing powerful flares. The planet, HIP 67522 b, orbits just a few million miles from the star, so it already receives hefty doses of radiation and charged particles. A European space telescope, Cheops, has seen 15 flares that are tied to the planet’s orbit around the star. The planet may gather magnetic energy as it whips around the star. Waves of magnetic force ripple outward like the wake of a ship. When the waves hit a stormy spot on the star, they trigger a giant flare. That douses the planet with six times more radiation than it would receive otherwise. HIP 67522 b is almost as big as Jupiter, the giant of our own solar system. But it’s only about one-quarter of Jupiter’s mass. That makes the planet especially puffy, like cotton candy. But as it’s zapped by the star, some of its atmosphere is blown away. In a hundred million years or so, it could shrink to less than half its current size – a shrinkage caused by its close orbit around the star. Script by Damond Benningfield

A visitor from far beyond the solar system is getting better acquainted with the Sun this week. Tomorrow, it’ll make its closest approach to the Sun – just 126 million miles. After that, it’ll head back toward interstellar space. The visitor is 3I/ATLAS. It was discovered on July 1st by an automated telescope that looks for comets and asteroids. Calculations of its orbit quickly showed that it came from outside the solar system. That makes it the third known visitor from interstellar space. It originated in the galaxy’s “thick disk.” That’s a region that sandwiches our part of the disk. It contains stars that are far older than the Sun. Estimates say 3I/ATLAS could be three billion years older than the solar system, so it could preserve a chemical record of an earlier era in galactic history. 3I/ATLAS is a comet – a ball of rock and frozen gases a few miles in diameter. As it’s closed in on the Sun, some of its gas has vaporized, releasing bits of dust as well. Observations will reveal the composition of this material, telling astronomers about conditions in the region where it formed. Unfortunately, astronomers can’t see 3I/ATLAS at all right now – it’s hidden in the Sun’s glare. It’ll return to view in December – but only when viewed through a telescope. It’ll pass closest to Earth on December 19th – almost 170 million miles away. Script by Damond Benningfield

Big “wobbles” in Earth’s magnetic field more than 40,000 years ago could have made the cultures of the time feel wobbly as well. Early modern humans might have adapted to the wobbly field better than Neanderthals. Earth’s magnetic field protects the surface from high levels of solar radiation. But during a period known as the Laschamp Excursion, which began 42,000 years ago, the field weakened to just 10 percent of its current intensity. And instead of acting like a bar magnet, with strong north and south poles, it generated smaller poles all across the planet. As the field wobbled, it produced brilliant auroras in regions where they had seldom been seen. It also allowed more radiation to zap the upper atmosphere. That destroyed some of Earth’s protective ozone. It also changed climate patterns across the planet. This turbulent period lasted about 1800 years. A new study found changes in the behavior of Neanderthals and modern humans in Europe and Asia during this period. The changes suggest these cultures were trying to protect themselves from the dangers of the weakened field, including sunburn, higher rates of skin cancer, and eye damage. The early humans apparently adjusted better than Neanderthals. Many factors were involved in the behavioral changes. Even so, researchers say the Lashcamp Excursion might have spurred early humans to respond to their changing environment. Script by Damond Benningfield

As seen from most of the United States, the Big Dipper is plunging toward the northern horizon as night falls, as if it’s about to dip into a pail of water. If you line up the stars at the outer edge of the dipper’s bowl, and follow that line to the upper right, the first moderately bright star you come to is Polaris, the Pole Star or North Star. Earth’s north pole aims toward it, so Polaris forms the hub of the northern sky – all the other stars appear to rotate around it. And it’s always at the same point above the horizon – night and day, all year long. There’s a southern pole star, too. It’s not as prominent as Polaris, though. In fact, it’s barely visible. The star is Polaris Australis. It’s also known as Sigma Octantis because it’s in the constellation Octans, which depicts a navigational instrument known as an octant. Polaris Australis isn’t as impressive as Polaris mainly because Polaris is huge and brilliant. Compared to most stars, though, the southern pole star is impressive, too. It’s more than half again the mass of the Sun. It’s expanding as it nears the end of its life, so it’s several times wider than the Sun. And its outer layers puff in and out, so it brightens and fades a tiny bit every couple of hours. On average, it’s more than 40 times brighter than the Sun. But it’s almost 300 light-years away. So that keeps Polaris Australis from being a better pointer to the celestial south pole. Script by Damond Benningfield

The Blue Danube has been performed for some pretty lofty audiences – kings and queens, emperors and empresses, presidents and prime ministers. But a performance earlier this year topped them all: it was aimed at the stars. The waltz was composed by Johann Strauss II, who was born 200 years ago today. His birthday was one of the motivations for the performance. The other was the 50th anniversary of ESA – the European Space Agency. So the broadcast was mostly symbolic – not a real attempt to contact other civilizations. The waltz was performed by the Vienna Symphony Orchestra in late May. It was transmitted to space by one of ESA’s tracking stations. The waltz was beamed toward Voyager 1. It’s the most-distant working spacecraft in history – more than 15 billion miles from Earth – so far that it took 23 hours for the waltz to reach it. Voyager carries a golden phonograph record inscribed with several musical works – but not the Strauss waltz. Voyager is passing through Ophiuchus, near the constellation’s brightest star, Rasalhague. It’s about half way up in the west-southwest at nightfall, and it’s easy to see. It’s a bit more than 48 light-years away. So if anyone there happens to point a radio telescope toward Earth in late 2073, perhaps they’ll hear the strains of The Blue Danube waltzing through the galaxy. Script by Damond Benningfield

A giant companion to a giant star faces an uncertain fate. The star is dying. As it expires, it will blast the companion, drag it inward, zap it with radiation, then loosen its grip on whatever remains. Mirach is the second-brightest star of Andromeda. It’s passed through the prime phase of life, and now is in the red-giant phase. It’s puffed up to about 85 times the diameter of the Sun, making it shine about 1700 times brighter than the Sun. Two years ago, astronomers discovered that Mirach has a companion. It’s probably a “failed star” known as a brown dwarf. It’s twice as far from Mirach as Earth is from the Sun. Before long – astronomically speaking – the star’s outer layers will flow into space at tens of thousands of miles per hour. That will “sandblast” the companion, stripping away some of its bulk. And friction from that material will drag the companion toward the star. After that, only the star’s hot but dead core will remain – a white dwarf. It’ll pelt the companion with ultraviolet radiation, vaporizing more of it. But the white dwarf will be much less massive than the present star, so it will loosen its gravitational grip on the companion. No one knows for sure how all of this will play out, so we can’t predict the fate of Mirach’s giant companion. Mirach is a third of the way up in the east-northeast at nightfall. It’s easy to see, even from most light-polluted cities. Script by Damond Benningfield

The black hole at the heart of a distant quasar has the biggest appetite astronomers have ever seen. It gobbles down the equivalent of one Sun per day – more than any other known black hole. It’s fed by the widest disk of gas and dust yet seen. And it outshines everything else in the known universe – 500 trillion times the Sun’s brightness. The quasar is so far away that we see it as it looked when the universe was a little more than one-tenth of its current age. It was discovered in the early 1980s, but astronomers thought it was a star. They deciphered its true nature just a couple of years ago. The heart of the quasar is a black hole 17 billion times the mass of the Sun. That’s not a record, but it’s near the top of the list. The black hole’s enormous gravity pulls in gas, dust, and stars. They form a spinning disk around the black hole. The disk is seven light-years across – half again the distance from the Sun to its closest neighboring star. As material in the disk funnels toward the black hole, it’s heated to millions of degrees. So the disk shines brilliantly – allowing us to see it across most of the visible universe. The quasar is in Pictor, the painter’s easel. For skywatchers in the far-southern United States, the constellation is barely in view, low in the south, before dawn. Despite the quasar’s great power, though, it’s much too faint to see without a telescope. Script by Damond Benningfield

We got our first picture from the surface of another planet 50 years ago today, when the Soviet Union’s Venera 9 landed on Venus. It transmitted data from the surface for 53 minutes, including a wide panorama. Venus is completely covered by thick clouds, so we can’t see its surface from Earth, or even from orbit around Venus – orbiters use radar to peer through the clouds. Venus also has a hot, dense atmosphere, so landing there is tough. Venera 9 parachuted through the clouds, measuring their thickness and composition. At the surface, it measured the density of the atmosphere – about 90 times the density of Earth’s atmosphere. And it measured the surface temperature – about 900 degrees Fahrenheit. The lander was supposed to take a full 360-degree view of the landscape. But the lens cap on one of its cameras didn’t pop off as planned, so Venera photographed only half of the scene around it. The image revealed a flat landscape covered with wide, flat rocks. And the lighting was comparable to a cloudy summer day on Earth. Venera 9 relayed its findings to Earth through an orbiter. Communication ended when the orbiter moved out of range – ending our first direct view of the surface of Venus. Venus is the beautiful “morning star” this month. It’s low in the east at dawn, and slowly fades from view in the waxing twilight. Tomorrow: the most ravenous black hole. Script by Damond Benningfield

A star in the constellation Cetus brightens and fades dramatically every 11 months. At its brightest, it’s fairly easy to see. At its faintest, it’s visible only through a telescope. Because of that change, a 17th-century astronomer called the star Mira – from the Latin word for “wonderful.” The star changes because it pulses in and out like a beating heart. Mira’s in the final stages of its red-giant phase of life. Its core is no longer producing nuclear reactions. Instead, it’s fusing hydrogen and helium in thin shells around the core. Mira’s outer layers are puffed up by radiation from the shells. At the maximum, that inflates the star to about 400 times the diameter of the Sun. That’s also when its surface is coolest and faintest. As the outer layers cool, they fall inward, making the surface hotter and brighter. At minimum, the star is about 330 times the Sun’s diameter. Each time it puffs up, Mira loses a little of the gas at its surface. Within the next million years or so, it’s likely to expel all the gas in its outer layers. That will leave only its hot but dead core – a white dwarf. Astronomers have discovered thousands of stars like Mira. And many others will undergo the same phase, including the Sun – in about six billion years. Mira climbs into view in the east by 8:30 or 9. But it’s in the “fading” part of its cycle, so you need a telescope to see it. Script by Damond Benningfield

Algol does something amazing. Every 2.9 days, the star fades to just one-third of its usual brightness. In centuries past, the stars were thought to be unchanging. A star that changed so blatantly was a bit scary. So it was given a name to match: “Algol” comes from an Arabic phrase that means “head of the demon.” But the star’s odd behavior isn’t scary it all – Algol fades as the result of eclipses. The system consists of three stars. Two of them form a tight binary. The members of the binary orbit each other once every 2.9 days. We see the system edge-on, so the two stars eclipse each other. One star is much brighter than the other. When the fainter star crosses in front of it, the system fades dramatically. When the bright star covers up the faint one, though, the difference is tiny – much too subtle to see with the eye alone. Astronomers have cataloged hundreds of eclipsing binaries. And the eclipses are important. They reveal the relative sizes and masses of the two stars, details about their orbit, and more. So there’s nothing to fear from these up-and-down star systems. Algol is low in the northeast at nightfall, in Perseus. It should be at its brightest tonight. The faint part of its cycle will happen during daylight for the next few cycles. It’ll be visible during nighttime later in the month. Sometimes, a star can change brightness all on its own, and we’ll have more about that tomorrow. Script by Damond Benningfield

The Orionid meteor shower should be at its most active the next few nights. And there’s no Moon to get in the way, so it should be a pretty good show. The shower is named for Orion because its meteors appear to “rain” into the sky from Orion the hunter. The constellation climbs into good view after midnight, so that’s when the shower is at its best – between midnight and dawn. You don’t have to look at Orion to see the meteors, though – they can blaze across any part of the sky. The meteors are bits of debris from Comet Halley. The comet sheds grains of dust as it orbits the Sun. When Earth crosses the comet’s path, some of those grains plunge into the atmosphere. They instantly vaporize, creating the streaks of light known as meteors. Most of the dust grains are no bigger than pebbles. But a few are larger. They form brilliant streaks that are visible even in a somewhat light-polluted sky. And some of them can leave glowing trails that remain visible for a couple of minutes. The shower has been declining in recent years. Halley’s Comet is near its greatest distance from Earth, so there aren’t as many bits of comet dust in this part of its orbital path. Even so, the shower could produce 20 or more meteors per hour at its peak. To watch the Orionids, find a dark but safe site away from city lights. Bundle up against the autumn chill, then sit back and watch the sparks from Halley’s Comet. Script by Damond Benningfield

Venus doesn’t have any moons. But it does share its orbit around the Sun. Astronomers have discovered 20 asteroids known as “co-orbitals,” but there could be many more. These big space rocks follow roughly the same path as Venus. But they won’t stay in that lane forever. And when they leave it, they could threaten Earth. These objects are nudged along by the gravity of Venus and the Sun. They generally stay well ahead of or behind Venus. Only one follows exactly the same orbit as the planet. The others move in and out a bit, getting closer to the Sun, then moving farther away. Over the long term, though, their orbits aren’t stable, so they can break free and head elsewhere. A recent study found that of the 20 known objects, six could threaten Earth within the next 12,000 years. And three of them are especially dangerous. All three are at least a thousand feet in diameter, so they could cause major damage if they hit our planet. A study also found that there could be many more of these Venus groupies. They stay so close to the Sun in our sky that they’re hard to see through the solar glare. And they move quickly, making them even harder to find. But a new telescope in Chile might pick out some of them – helping us find potential threats far in advance. Look for Venus near the Moon in the dawn sky tomorrow. It’s the brilliant “morning star,” so you can’t miss it. Tomorrow: an autumn meteor shower. Script by Damond Benningfield

California is the land of the stars. It’s also in the stars as the California Nebula – a cloud of gas and dust that looks like the outline of the state. It’s more than a thousand light-years away, in Perseus. The nebula belongs to a giant star-forming complex – the Perseus O-B-2 association. The region has given birth to many class O and B stars – the biggest and brightest of all stars. The California Nebula probably is energized by one of those stars, known as Xi Persei. The star is more than 30 times the mass of the Sun, and tens of thousands of degrees hotter. At that temperature, it produces huge amounts of ultraviolet energy. When that radiation zaps hydrogen atoms, it splits them apart. When they link back up, the atoms produce red light – the main color of the nebula. Oxygen and other elements produce their own colors, but they’re not nearly as common as hydrogen. The California Nebula probably is about a hundred light-years long. It’s likely to split into smaller clumps that will collapse to form even more stars. But radiation and winds from Xi Persei and other big stars will blow away much of the nebula’s material – limiting the number of new stars for this cosmic California. Perseus climbs into good view, in the northeast, in early evening. Xi Persei is visible to the naked eye, near the bottom of the constellation. But you need a telescope to see the faint outline of the California Nebula. Script by Damond Benningfield

Xi Persei doesn’t look all that imposing. The star shines at fourth magnitude, so it’s visible under dark skies, but not from cities and towns. But that’s only because it’s a long way off – about 1200 light-years. In reality, it’s one of the most impressive stars visible to the human eye. Perseus climbs the eastern sky on autumn evenings. It consists of a couple of ribbons of stars that join at Mirfak, the constellation’s leading light. And it contains the most famous variable star in the sky: Algol, the Demon Star, which fades and brightens every three days. Yet neither can compare with Xi Persei, which is near the bottom of the longer ribbon. At visible wavelengths, it’s about 13,000 times brighter than the Sun. But it’s tens of thousands of degrees hotter than the Sun, so it emits most of its light in the ultraviolet. When you add that in, Xi Persei is a quarter of a million times the Sun’s brightness. The key to that showiness is the star’s mass – roughly 30 times the Sun’s mass. At that great heft, gravity squeezes its core tightly, revving up its nuclear engine. Energy works its way to the surface, making Xi Persei hot and bright. Before long, it’ll get even hotter and brighter. It’ll explode as a supernova, briefly shining brighter than billions of normal stars – a brilliant demise for an impressive star. Xi Persei energizes a nearby cloud of gas, and we’ll have more about that tomorrow. Script by Damond Benningfield

For decades, Regulus had astronomers fooled. The star is bright, hot, and blue – an indication that it was quite young. Most estimates put its age at no more than a hundred million years – about two percent the age of the Sun. Instead, it’s at least a billion years old. But like a vampire, it’s been rejuvenated by taking the life’s blood of a companion, making it look much younger. The star we see as Regulus is about four times the size and mass of the Sun, and more than 300 times brighter. A few decades ago, astronomers discovered its companion – a “dead” star known as a white dwarf. The two stars are so close together that the corpse was hidden in the glare of the bright star. The presence of the companion means the system has to be at least a billion years old – old enough for the companion to evolve to its present state. As it evolved, it puffed up. Gas flowed from its surface over to the other star. That made the star we see today much bigger and heavier. It also made the star hotter, which made it bluer. Hot blue stars usually are quite young. So astronomers were fooled into thinking that bright Regulus was still a youngster – not an older star that’s been rejuvenated. Look for Regulus close to the Moon at dawn tomorrow. The distance between them will narrow as you move westward. They’ll be especially close as seen from Alaska or Hawaii. Script by Damond Benningfield

The Milky Way is a giant among galaxies – a hundred thousand light-years in diameter. But a few galaxies make the Milky Way look like a mere bauble by comparison. They span millions of light-years – puffed up by the action of supermassive black holes. These monsters are known as giant radio galaxies. Not only are they large, but they produce enormous amounts of radio waves. The black hole in such a galaxy’s heart is encircled by a massive disk. As material in the disk spirals into the black hole, magnetic fields fire “jets” of some of its particles like water from a firehose. These jets can streak far into space. They end as they plow into the material between galaxies, forming “lobes” that are bright sources of radio waves. A recent study found 15 of these giants. They’re in the constellation Sculptor, which creeps low across the south on October evenings. The largest of them spans more than 12 million light-years. The galaxy itself is wider and heavier than the Milky Way. But the jets puff up its overall size. It actually has two sets of jets – one nested inside the other. The longer set is older – powered up by the black hole millions of years ago. But the black hole might have slowed down its eating for a while, shutting off that flow of particles. Later, it started chowing down again, powering the second set of jets, which continue to expand – sustaining this galactic monster. Script by Damond Benningfield

Deneb, the brightest star of Cygnus, stands high overhead as night falls at this time of year. And it really is a brilliant star – tens of thousands of times brighter than the Sun. But if we could tune our eyes to see radio waves, Deneb wouldn’t even register. Instead, the swan’s leading light would be Cygnus A – one of the brightest radio galaxies in the universe. A radio galaxy produces huge amounts of radio waves. It’s usually a large elliptical galaxy, which looks like a fat, fuzzy football. It has a supermassive black hole at its center. Gas, dust, and stars spiral into the black hole. But powerful magnetic fields eject some of that material back into space. It forms “jets” that fire out at almost the speed of light. The jets can span hundreds of thousands of light-years. Electrons spiral through a jet’s magnetic field, producing radio waves. Eventually, the jets plow into gas and dust between galaxies, forming wide bubbles that emit even more radio waves. Cygnus A was the first radio galaxy ever discovered, in 1939. It’s about 760 million light-years away. Its black hole is two and a half billion times the mass of the Sun. The entire complex – galaxy, jets, and bubbles – spans more than 600,000 light-years. That’s six times the diameter of our home galaxy, the Milky Way – one of the biggest, brightest radio galaxies in our part of the universe. More about radio galaxies tomorrow. Script by Damond Benningfield

Floating through the clouds at Jupiter’s equator sounds like a celestial carnival ride. The equator spins at about 28,000 miles per hour – 28 times faster than Earth’s equator. So the Sun, moons, and stars would zip across the sky in a hurry. Jupiter is the largest planet in the solar system – 11 times Earth’s diameter. It also spins faster than any other planet – so fast that it bulges outward at the equator. At that speed, a day on Jupiter is less than 10 hours long. So the equator always sees about five hours of daylight followed by five hours of darkness. It might not sound right, but Jupiter spins so fast because it’s so big. As it swept up more material while it was taking shape, gravity compressed it, making it smaller. The planet had to spin faster to balance the books – like a skater spinning faster as it pulls in its arms. Some studies have suggested that Jupiter might actually have been slowed down early on by its magnetic field. The young planet was encircled by a disk of gas and dust that gave birth to its moons. As the gas swirled through the magnetic field, some of it developed an electric charge. The charged-up gas grabbed on to the field, acting like a brake – slowing down the solar system’s biggest and still fastest planet. Jupiter looks like a brilliant star below the Moon at dawn tomorrow. The twin stars of Gemini are closer to the left and lower left of the Moon. Script by Damond Benningfield

If you’d like to thank your lucky stars for a bit of good fortune, we have two stars for you to look at. They’re the brightest stars of Aquarius. Both of them have names that mean “lucky.” The brighter of the two is Sadalsuud. The name comes from an Arabic phrase that means something along the lines of “luckiest of the lucky.” When the name was bestowed, the star first appeared in the dawn sky around the spring equinox. The days were getting longer and warmer, and spring rains were settling in – bringing life-giving water to the fields. So the star was considered a sign of good fortune. The other lucky star is Sadalmelik – “luck of the king.” The exact reason for its name is unclear, although it, too, may relate to the seasons. Both stars are class-G supergiants. They’re about the same temperature and color as the Sun, but much bigger, heavier, and brighter. Both stars have passed through the prime phase of life, so their luck is running out – they’re nearing the end. Each will shed its outer layers and leave behind a massive white dwarf – a corpse about as heavy as the Sun, but only as big as Earth. Aquarius is in the southeast at nightfall. The “lucky” stars line up parallel to the horizon, with Sadalmelik on the left. The stars are separated by about the width of your fist held at arm’s length. But they’re so far from us that they don’t look all that bright – a bit of bad luck for skywatchers. Script by Damond Benningfield

Stars like the Sun go through several distinct phases of life, from embryo to corpse. Consider Aldebaran, the bright eye of Taurus, which accompanies the Moon tonight. It’s more than six billion years old – older than the Sun. And it’s well into “old age.” Aldebaran was born when a cloud of gas and dust collapsed. For millions of years, it shined as a result of the heat generated by that collapse – its “embryonic” phase. Eventually, its core got hot enough to ignite the fires of nuclear fusion, and Aldebaran entered the prime phase of life – fusing hydrogen to make helium. A few hundred million years ago, it used up the hydrogen in the core. The core got smaller and hotter, and Aldebaran began fusing the hydrogen in a shell around the core. At the same time, its outer layers puffed up, so Aldebaran is more than 40 times wider than the Sun. This is the giant phase of life. Eventually, the core will get hot enough to fuse the helium to make carbon and oxygen. But when the helium is gone, fusion will stop. The core will get smaller and hotter, and its radiation will push the star’s outer layers into space. Only the hot, dead core will remain – a white dwarf. Even that isn’t the end, though. The white dwarf will cool and fade. Hundreds of billions of years from now – and perhaps much longer – it’ll stop producing any visible light at all. That will make it a black dwarf – the final stage for the eye of the bull. Script by Damond Benningfield