StarDate

A giant planet in the constellation Hercules sounds like it would make a sweet snack for the strongman. It’s about as dense as cotton candy. In fact, it may be the “puffiest” planet yet seen.

HAT-P-67b is about 1200 light-years away. Its star — HAT-P-67 — is bigger, brighter, and heavier than the Sun. And the star and planet are quite close together — a tiny fraction of the distance from Earth to the Sun. That means the planet is getting roasted. The temperature at its cloud tops is at least 3,000 degrees Fahrenheit. And some recent work says it could be 8500 degrees or higher — hotter than most of the stars in the galaxy.

The heat has caused the planet’s outer layers to puff up. HAT-P-67b is about a third as massive as Jupiter, the giant of our own solar system. But it’s more than twice Jupiter’s diameter. That means it’s big and puffy. It’s only about five percent as dense as water — roughly the density of cotton candy.

The parent star may be blowing away the planet’s atmosphere — a process that could make the planet even puffier.

The HAT-P-67 system is in Hercules, which is high in the west at nightfall. The system stands to the right of the Keystone — four moderately bright stars that outline the strongman’s body. But the system is too faint to see without a telescope.

Tomorrow: “computing” a career in astronomy.
 

Script by Damond Benningfield

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    LAUNCH CONTROL: 3, 2, 1, and liftoff of Osiris-Rex. Its seven-year mission, to boldly go to the asteroid Bennu and back.

The seven years are up. Osiris-Rex flew to the asteroid Bennu, kept pace with it for two and a half years, and kicked up some dust and pebbles from its surface. It grabbed some of that debris. And tomorrow, it’s scheduled to drop a canister filled with those samples into Earth’s atmosphere, where it will parachute to a soft landing in Utah.

Bennu is both a scientific treasure and an existential threat.

The asteroid is about a third of a mile in diameter. It contains a lot of organic compounds — the chemical building blocks of life. Asteroids like Bennu could have pounded the young Earth, providing some of the key ingredients for life on our planet. So the samples could tell us more about the development of life on Earth.

On the other hand, Bennu’s orbit comes close to Earth’s orbit. That means Bennu could someday slam into our planet, causing massive destruction. Some close encounters with Earth in the 22nd century could put Bennu on a collision course. Learning about the asteroid could help future generations deflect it from such a path.

Osiris-Rex probably collected at least a pound of material from Bennu, and possibly four pounds or more. The sample container will be taken to Johnson Space Center in Houston, where its treasures will be parsed out to scientists around the world.
 

Script by Damond Benningfield

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People have been following the motions of the Sun for thousands of years. They’ve even built special observatories for the job.

One of the more impressive ones is at Dengfeng in China. Astronomers built a giant sundial there almost 750 years ago. The city was a center of science, religion, education, and politics for centuries. So it became known as “the center of heaven and earth.” That made it a perfect spot for following the Sun.

Astronomers built a smaller sundial there more than five centuries earlier — part of a network of sites across the country. From the different lengths and motions of the shadows cast by the Sun, astronomers measured the length of the year to within about a half-minute of its true value — the most accurate measurement by anyone up to that time. The findings were used to create a calendar, and to measure the extent of different territories.

The observatory built in the 13th century consisted of a tall platform shaped a bit like a pyramid. A pole atop the platform cast a shadow along a hundred-foot scale on the ground.

The observatory is still there — the centerpiece of a World Heritage site — a site for following the Sun.

And this is a good time to follow the Sun because tonight is the equinox — the beginning of autumn in the northern hemisphere. The Sun rises due east and sets due west across the whole planet — a key point for skywatchers across the globe — and across the centuries.
 

Script by Damond Benningfield

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Dozens of robotic spacecraft have studied the worlds of the solar system from up close. They’ve told us a lot about those worlds, and about the birth and evolution of the entire solar system. But to really get down to the nitty-gritty, you need the nitty-gritty — samples of dust and rock to study in the lab.

So far, space missions have collected samples of four worlds other than Earth: the Moon, two asteroids, and a comet. Astronauts and robots have collected almost half a ton of samples from the Moon. The samples of the others are tiny.

Still, those bits are treasures. In the lab, scientists can study the samples with the most advanced equipment yet devised — stuff that could never be flown in space. Different groups can study the samples, applying different techniques to help confirm the results. And some of the samples can be stored for future scientists, who will have equipment and techniques that haven’t yet even been dreamed of.

The most recent samples were captured by a Japanese mission to the asteroid Ryugu. It delivered five grams of material to Earth in 2020. From those tiny bits of rock and dust, scientists have learned that Ryugu dates back to the birth of the solar system. They’ve also found that some minerals on the surface formed in a wet environment, and much more.

Scientists are scheduled to get samples of another asteroid this weekend, when a NASA mission parachutes to Earth.
 

Script by Damond Benningfield

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Landing on the Moon is hard. Most attempts to reach our satellite world in recent years have ended with crashes. And many other landing missions have been delayed by months or years.

Two landers crashed in 2019 — one from India, the other from a private company in Israel. They were victims of bad software or faulty gyroscopes. And a Japanese lander crashed earlier this year, also most likely because of a software problem.

Several companies in the United States are developing landers as well. Some of them will include rovers, and several will land near the south pole, where there should be large deposits of ice. But all of the missions have been delayed — some by years. So the launch queue is getting stacked up with missions to the Moon.

The most successful Moon landers in recent years were launched by China. One touched down on the lunar farside, in 2018 — the first landing on the side of the Moon we never see. The other landed in late 2020. It gathered about four pounds of rocks and dirt and brought them back to Earth for study.

India dispatched a new lander in July, for landing in August — another try at a hard-to-do landing on the Moon.

The target for all of these missions is in the southwest as night falls now. And it has a bright companion: Antares, the heart of the scorpion. The star is close to the left of the Moon this evening, and to the lower right of the Moon tomorrow night.
 

Script by Damond Benningfield

Editor's Note: India's mission successfully landed on the Moon after this program was recorded, while Russia's Lune 25 was launched and then crashed attempting a landing.

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Historically, mid-September is the peak of hurricane season here in North America. The most powerful storms generate sustained winds of more than 150 miles per hour, with stronger gusts — strong enough to flatten anything in their path. Yet that’s like a soft spring breeze compared to the winds of Neptune, the Sun’s most remote major planet. Winds there can reach almost 1300 miles per hour.

Neptune is about four times the diameter of Earth. It has a thick atmosphere that’s bright blue. Cold clouds form bright white bands high in the sky.

By tracking the clouds, scientists have measured sustained wind speeds of up to 700 miles per hour. And some gusts are almost twice that speed.

Just what drives the winds isn’t well understood. The planet’s weather is powered mainly by heat coming from inside Neptune. But there’s no clear indication of why the giant planet would have such high-speed winds.

James Webb Space Telescope has found one other interesting feature in the atmosphere — a band of warmer air at the equator. Global circulation patterns may move the atmosphere toward the equator, where it sinks and heats up — creating a hot “girdle” around this giant planet.

Neptune lines up opposite the Sun in our sky this week. It rises at sunset, in the constellation Pisces, remains in view all night, and shines at its brightest. It’s so far away, though, that you need binoculars or a telescope to see it.
 

Script by Damond Benningfield

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One of the giants of the outer solar system is at its best this week. Neptune lines up opposite the Sun in our sky. From that position, it rises at sunset and is in the sky all night. And it shines at its brightest. It’s the Sun’s most remote major planet, though — about 2.7 billion miles away — so you need good binoculars or a telescope to see it.

Neptune is the fourth-largest planet in the solar system — roughly four times the diameter of Earth. But it’s the third most-massive planet, just eking past Uranus.

Neptune and Uranus are “ice giants.” Neptune has a small, dense core that’s roughly as massive as Earth. And it has a thick atmosphere of hydrogen, helium, and a dab of methane, which contributes to its bright blue color.

Between the core and atmosphere are layers of compounds that are classified as “ices” — mainly water, methane, and ammonia. The ices aren’t cold, though. Neptune’s gravity squeezes them tightly, heating them to hundreds or thousands of degrees. The great pressure deep within Neptune keeps these layers from boiling away. In fact, the layer directly below the atmosphere could be a deep ocean of super-hot water.

Neptune’s atmosphere has some of the strongest winds in the solar system, and we’ll have more about that tomorrow.

The giant planet is in Pisces, the fishes. As darkness falls, Neptune stands below the pentagon of stars that outlines the head of one of the fish.
 

Script by Damond Benningfield

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Venus, the “morning star,” is at its absolute best right now. The planet is in the east at first light. It’s so bright that you might think it’s an airplane or some other flying craft. That brightness is a combination of its distance from Earth, and the portion of its Earth-facing hemisphere that’s lit up by the Sun.

Venus is completely blanketed by bright clouds, which hide the surface. In fact, our only maps of the surface have come from radar — especially from a radar aboard the Magellan spacecraft, in the 1990s.

The clouds top an atmosphere that’s extremely thick and hot. It protects the surface from impacts by asteroids. All but the biggest ones burn up or explode before they can hit the ground.

But some of those explosions can be powerful enough to damage the surface. We’ve seen it happen on Earth several times since the early 20th century. Because Venus’s atmosphere is so much thicker than Earth’s, though, the damage can be more extensive.

A recent study found almost 300 “scars” from these airbursts. A pressure wave from the explosion slams into the surface, scouring out a shallow depression. The feature looks dark to the radar, with a brighter “halo” around it.

Scientists are studying those features in detail. That should help them better understand the history of Venus’s surface, which has been sculpted by huge volcanic eruptions — a violent past for the beautiful Morning Star.

Script by Damond Benningfield

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If we could speed up our view of the galaxy NGC 7469, it might look like halftime at the Super Bowl — flashes going off everywhere. In this case, the flashes represent the births of new stars. The galaxy contains more than a hundred star clusters that are no more than two million years old — mere newborns on the cosmic timescale. And each cluster contains hundreds to thousands of stars.

NGC 7469 is about 200 million light-years away. It’s in Pegasus, which is in the east at nightfall and climbs high across the sky later on.

The galaxy is a barred spiral — it has a “bar” of stars in its middle, with spiral arms curling off the ends of the bar. And it has a supermassive black hole in its heart. The black hole is encircled by a disk of superhot gas, which shines brightly.

The bar and spiral arms contain huge amounts of gas and dust — the raw materials for making stars. There’s also a huge ring of gas and dust around the black hole. Most of the new stars are being born in clusters in the ring, bar, and arms. Last year, James Webb Space Telescope found more than 60 young clusters, doubling the known population. Some of the clusters are just a million years old, and are still giving birth to stars.

Starbirth is driven in part by the black hole. Radiation and “winds” from the disk squeeze clouds of gas and dust. The clouds collapse to make more stars — flashes of starbirth in a busy galaxy.
 

Script by Damond Benningfield

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A recently discovered planet in a star system 130 light-years away is on the border — the dividing line between a planet and a brown dwarf.

HD 206893c is the third member of its system. The main member is a star that’s bigger and heavier than the Sun. It has a distant companion known as a brown dwarf — an object that’s more massive than a planet but not massive enough to shine as a star.

The planet was hinted at by Gaia, a space telescope that’s observing more than a billion stars. A big telescope on the ground provided more details on the system, and even snapped the planet’s picture.

HD 206893c is a little bigger than Jupiter, the giant of our own solar system — and almost 13 times as heavy. That puts it on a border line. Anything less massive is definitely a planet, while anything heavier is most likely a brown dwarf.

Yet the planet is much brighter than most big planets. That suggests that it’s “fusing” a form of hydrogen in its core — something that usually happens in light-weight brown dwarfs. So studying this odd object may help scientists nail down the definitions of both planets and brown dwarfs — and the dividing line between them.

HD 206893 is low in the southeast at nightfall, and is bright enough to see through binoculars. It’s in the constellation Capricornus, not far to the upper right of the planet Saturn, which looks like a bright golden star.
 

Script by Damond Benningfield

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