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Double Cluster Oct 10, 2026

Show notes

A pair of big, young star clusters is one of the skywatching highlights of autumn evenings. Each cluster contains thousands of stars. And hundreds of those stars are especially impressive – supergiants that are many times the size and mass of the Sun, and many thousands of times brighter.

The clusters are NGC 869 and 884. Together, they’re known as the Double Cluster. They’re in the northeast at nightfall, in the constellation Perseus the hero. Under dark skies, they’re visible to the eye alone as a single smudge of light. Binoculars split them apart, revealing two sparkling collections of stars.

The clusters are more than 7,000 light-years away. They form the core of the Perseus OB1 Association – a huge complex of stars and clouds of gas and dust. The region has given birth to perhaps tens of thousands of stars.

All of the stars were born in the recent past, as measured on the astronomical time scale. The Double Cluster is only about 14 million years old, compared to four-and-a-half billion years for the Sun. One way astronomers determine that age is through the types of stars found in the clusters. The most-massive stars burn out in a hurry. But the clusters still contain many such stars.

Some of those monsters won’t last much longer, though – they’ll blast themselves to bits as supernovas – brilliant light shows in the Double Cluster.

Script by Damond Benningfield

Caroline’s Rose Oct 09, 2026

Show notes

Cassiopeia is an easy constellation to pick out. The stars of the queen form a prominent letter M or W, which is visible even through moderate light pollution. And under dark skies, binoculars reveal several star clusters around that pattern, all immersed in the glow of the Milky Way.

One of the highlights is NGC 7789. It was discovered in 1783 by Caroline Herschel – the first woman to be paid for her work as an astronomer. Through a telescope, the contours of the cluster and nearby clouds of dust resemble a rose. So NGC 7789 also is known as Caroline’s Rose.

The cluster is about 6800 light-years away, in the opposite direction from the center of the galaxy. And it’s packed with stars. It has 1300 confirmed members, with an estimated total of 3,000 stars or more.

The cluster’s age has been tough to pin down. A recent study says it’s one-and-a-quarter billion years old. Previous estimates are a little higher. Regardless of the exact age, the cluster has made several orbits around the center of the galaxy. By the time many other clusters have made that many orbits, they’ve been pulled apart by the gravity of the rest of the galaxy. The stars survive, but they head their separate ways. Caroline’s Rose is in the northeast at nightfall, just above Cassiopeia’s outline. It climbs high across the north during the night.

Script by Damond Benningfield

Quiet Monster Oct 08, 2026

Show notes

A quiet monster lurks in the heart of M31, the Andromeda Galaxy. Known as M31-star, it’s a black hole a hundred million times the mass of the Sun, and 25 times heavier than the black hole at the heart of the Milky Way.

Every large galaxy probably has a supermassive black hole. And many of them are quite bright.

The black hole itself is completely black – it swallows up all the matter and energy that falls into it, and nothing can come back out.

But the black hole’s gravity pulls in huge amounts of gas and dust, along with an occasional asteroid, star, or other large object. This debris forms a disk around the black hole. As material in the disk spirals closer to the black hole it gets extremely hot, so it shines brightly.

But M31-star is one of the quietest of all supermassive black holes – its disk produces very little energy.

That tells us that the black hole is not actively “feeding” – not much debris is falling into it. A distant ring of gas and dust encircles the black hole, with filaments of material spiraling into the disk. But the “feeding” rate is low, so M31-star remains quiet – a dark monster in the heart of M31.

Under dark skies, the Andromeda Galaxy is visible to the naked eye. It looks like a faint smudge of light that’s wider than the Moon. Right now, it’s about a third of the way up in the east-northeast at nightfall, and climbs high overhead later on.

Script by Damond Benningfield

Andromeda Galaxy Oct 07, 2026

Show notes

Two-and-a-half million years ago, Earth was going through some big changes. It was the start of the Pleistocene epoch – a period of major ice ages. And the ancestors of modern humans were just appearing.

That timescale puts a little perspective on the distance to M31, the Andromeda Galaxy – the closest major galaxy to the Milky Way. It’s two-and-a-half million light-years away. So when we look at the galaxy, we’re seeing it as it looked two-and-a-half million years ago.

Andromeda and the Milky Way are much alike. Both of them are barred spirals – they have a long bar of stars in the center, with spiral arms wrapping off the ends of the bar. They’re about the same mass – roughly one trillion times the mass of the Sun. Andromeda appears to be wider, although it’s hard to measure the size of the Milky Way from our location inside it.

Andromeda isn’t giving birth to as many stars as the Milky Way is. That may be because it collided with a smaller galaxy in the distant past. The collision triggered a huge wave of starbirth that used up most of the star-making material – limiting the future population of the Andromeda Galaxy.

M31 is well up in the east-northeast at nightfall. Under fairly dark skies, it looks like a faint smudge of light wider than the Moon – the most-distant object that’s easily visible to the eye alone.

We’ll have more about the Andromeda Galaxy tomorrow.

Script by Damond Benningfield

Moon and Regulus Oct 06, 2026

Show notes

The Moon has had a busy social calendar this week. It’s had meet-and-greets with the twins of Gemini and the planets Mars and Jupiter. And it has one more engagement tomorrow. Regulus, the heart of the lion, will stand above the Moon at dawn. In centuries past, people took a more literal view of lunar social activities. Many thought the Moon was inhabited – including some astronomers. In 1778, for example, William Herschel reported seeing towns on the lunar surface. Herschel was one of the top astronomers of the time – he discovered the planet Uranus – so people took him seriously. The idea of lunar life was especially common in the 19th century. In 1835, the New York Sun published a series describing a world teeming with life, including a civilization of “bat people.” The Sun attributed the discoveries to Herschel’s son, John – another famous astronomer. The whole thing was a hoax. But the idea of lunar life was so ingrained that the public ate it up. In 1838, another writer described seeing structures built by “lunarians.” And in 1901, H.G. Wells wrote about intelligent life in “The First Men in the Moon” – a race of insect-like creatures called Selenites. Today, we know that the Moon is devoid of life – at least for now. China and the U.S. have plans to establish permanent outposts on the Moon in the decades ahead – “lunarians” from right here on Earth.

Script by Damond Benningfield

Moon and Jupiter Oct 05, 2026

Show notes

For skywatchers across the eastern United States, the planet Jupiter will vanish early tomorrow – hidden behind the crescent Moon. The rest of the country will see an impressively close encounter between the two bodies.

The vanishing act is an occultation – from a Latin word that means “to hide.” Over the centuries, astronomers used these events to learn more about the Jovian system. Precise timing of occultations helped astronomers understand the planet’s orbit, which helped them zero in on Jupiter’s distance. And it takes a few seconds for the planet to vanish and reappear. The exact timing, combined with Jupiter’s distance, helped refine its diameter.

Occultation studies also have included radio waves. Jupiter’s magnetic field sculpts a teardrop-shaped “bubble” around the planet. It also creates powerful radiation belts. Watching Jupiter vanish behind the Moon revealed the extent of both.

Occultations are less important to scientists than they once were – but they’re still fun to watch.

This one plays out before or during dawn. Jupiter looks like a brilliant star. From the eastern U.S., it’ll wink out before dawn, with Jupiter and the Moon quite low in the sky. From a little farther west, the occultation will be in progress as they rise, with Jupiter popping into view shortly thereafter. Those in the western states will have to settle for an especially close encounter between Jupiter and the Moon.

Script by Damond Benningfield

Moon and Mars Oct 04, 2026

Show notes

To borrow from “Alice in Wonderland,” the case for life on Mars keeps getting curiouser and curiouser. Two rovers have discovered organic compounds there – the chemical building blocks of life – in locations that are thousands of miles apart. And some recent looks at results from the Viking landers of the 1970s suggests they, too, might have found organics. So it’s possible that microbes might have inhabited Mars in the past – and might do so even today.

Some of the best evidence comes from the Perseverance rover. In 2024, it studied a formation known as Bright Angel – layers of sediment deposited at the bottom of a river perhaps three and a half billion years ago.

A rock named Cheyava Falls contained a lot of organics. And a study earlier this year confirmed the finding. The compounds could have been produced by microscopic life. But there are several other possible explanations, including chemical reactions in the rocks themselves.

Perseverance stored a sample of Cheyava Falls for return to Earth. Laboratory analysis could tell us for sure how the organics were formed. But NASA has nixed a planned sample-return mission. So we’re a long way from satisfying our curiosity about life on Mars.

Look for Mars quite near the Moon early tomorrow. It looks like a bright star. They’re especially close as they climb into good view, around 2:30 or 3. We’ll talk about the Moon and another companion tomorrow.

Script by Damond Benningfield

Moon and Companions Oct 03, 2026

Show notes

The Moon will run a gauntlet of bright stars and planets the next few mornings, from the twins of Gemini to the heart of the lion. The twins are up first. Pollux and Castor will perch to the upper left of the Moon at dawn tomorrow. Pollux is the brighter of the two, and it’ll be closer to the Moon. On the following mornings, the Moon will slide past Mars, Jupiter, and Regulus. These encounters are possible because all of these objects are near the ecliptic – the Sun’s path across the sky. The stars all maintain the same position relative to the ecliptic from month to month and year to year. Regulus, for example, is less than half a degree away from it – less than the width of a pencil held at arm’s length. The planets, on the other hand, can shift from one side of the ecliptic to the other. That’s because their orbits around the Sun are tilted a bit. The Moon’s orbit is tilted as well, by about five degrees. So the Moon can swing a little farther from the ecliptic. Tonight, it’s a few degrees north of it. By Wednesday, when it’s closest to Regulus, it’ll be just south of it. Despite that wiggle room, the Moon passes close to each of these bright pinpoints during every month-long cycle of phases. And when the geometry is just right, it can even cover them up – which it will do to Jupiter on Tuesday. We’ll have more about that later in the week, and more about the Moon and Mars tomorrow.

Script by Damond Benningfield

Saturn Opposition III Oct 02, 2026

Show notes

Saturn is a “superior” planet. Among other things, it’s the second-largest and second-heaviest planet in the solar system. Technically, though, what makes it “superior” is its location. It’s the sixth planet from the Sun, so its orbit is outside Earth’s orbit.

Superior planets can line up opposite the Sun in our sky – a point known as opposition. And that’s what Saturn is doing now. It’ll reach that point early Sunday. So for a while, it’ll be in the sky all night, and shine brightest for the year. Only a few planets and stars will outshine it.

A planet looks especially bright at opposition for a couple of reasons. For one thing, it’s closest to Earth. Saturn, for example, will be about a hundred million miles closer than average.

Another reason is the viewing angle. At opposition, a planet is reflecting more sunlight directly toward Earth than at any other time. In effect, the planet is a more efficient “mirror.” We see the same effect with the Moon. A full Moon – which also is in a “superior” position – is about six times brighter than a half Moon. The change in the Moon’s brightness is complicated by other factors, but the principle is the same – a superior Moon puts in a superior show – just like the superior planet Saturn.

Saturn is low in the east at nightfall. It looks like a bright star. It climbs high across the south during the night, and is low in the west at dawn.

Script by Damond Benningfield

Saturn Opposition II Oct 01, 2026

Show notes

This isn’t a sound effect from a sci-fi movie. Instead, it’s the “voice” of the auroras on the planet Saturn – radio waves that have been shifted to wavelengths we can hear. They were recorded by the Cassini spacecraft as it closed in on Saturn two decades ago.

The radio waves are produced by the complex interplay between Saturn’s magnetic field and the solar wind – a steady flow of charged particles from the Sun.

Motions deep inside the planet generate the magnetic field, which is about as strong as Earth’s. But because Saturn is much bigger than Earth, its magnetic field is much bigger as well – it fills a huge volume of space.

The magnetic field forms a teardrop-shaped “bubble” around Saturn. That bubble deflects much of the solar wind. But some of the particles make it through. The lines of magnetic force guide some of them toward the magnetic poles. They spiral in, emitting radio waves as they do so. And when the particles hit the upper atmosphere, they create auroras – shimmering curtains powered by the Sun.

Saturn is putting in its best appearance of the year. It’s at opposition – it lines up opposite the Sun. It’s closest to Earth, so it shines brightest. And it’s in view all night. The giant planet looks like a bright golden star. It’s low in the east at nightfall, and climbs high across the south later on.

Script by Damond Benningfield

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