StarDate

The stars of the binary system SSN 7 are doomed, doomed, and doomed. Each of the two monster stars will collapse to form a black hole. And in the far-distant future, the black holes will merge to form a bigger one.

The system is about 200,000 light-years from Earth. It’s in a massive stellar nursery in the Small Magellanic Cloud, a companion galaxy to the Milky Way.

A recent study found that one star in the system is about 32 time the mass of the Sun, while the other is 55 times the Sun’s mass. That makes them some of the hottest, brightest, and heaviest stars in the universe. They’re only about four million years old — about one percent the age of the Sun. But because they’re so massive, they’re nearing the ends of their lives.

The study concluded that the stars are so close together that they’re touching each other. Not only that, but the heavier star is “stealing” hot gas from its companion. In as little as 700,000 years, the less-massive star will collapse to form a black hole. After a brief quiet period, it will begin pulling in gas from the surviving star, which will collapse as well. The entire scenario should play out in just a few million years.

After that, the black holes will spiral ever closer as they emit gravitational waves — “ripples” in space-time. The study forecasts that they’ll merge in about 18 billion years — several billion years longer than the current age of the universe.
 

Script by Damond Benningfield

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By Jove, the Moon and the planet Jupiter put on a good show the next couple of nights. They climb into good view by about 11 or 11:30. Jupiter looks like a brilliant star near the Moon — only the Moon and the planet Venus outshine it.

Jupiter is named for a Roman god — the equivalent of Zeus, the king of the Greek gods. Appropriately enough, Jupiter was a sky god. And like Zeus, he was in charge of everything — the leader of all the gods. He was considered a protector of Rome, so military commanders visited one of his temples after a successful battle to give thanks.

Jupiter was also known as Jove. The name is used in the phrase “by Jove!”, which indicates surprise or adds emphasis. According to Miriam-Webster, the phrase was mainly British, and it’s been largely abandoned.

“Jove” is still a part of daily language, though, mainly in the word “jovial” — showing “good-humored cheerfulness.” Other forms of the word include “jovialize,” which means “to make jovial,” and “jovialist” — someone who’s already jovial.

Look for Jove — or Jupiter — rising in late evening, near the gibbous Moon. The solar system’s biggest planet is to the lower left of the Moon tonight, and about the same distance to the right of the Moon tomorrow night. By Jove, the view is pretty much guaranteed to make just about anyone feel jovial — jovialists under the stars.

Tomorrow: a pair of giant stars with a non-jovial future.
 

Script by Damond Benningfield

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If that sounds like beating hearts, that’s because it is — in a way. It’s the sound of “heartbeat” stars. If you plot how the light from such a star changes, it looks like an EKG — like a beating heart. Scientists have converted some of those beats to sound, and sped them up to show the rhythm of the heartbeats.

The stars are actually binaries — pairs of stars locked in orbit around each other. Their orbits are stretched out — they’re long and thin. Depending on the system, each orbit takes a few days to a few weeks, so the system “beats” at up to a few times per month.

When the two stars are at their closest, the gravity of each star distorts the shape of the other, making the stars bulge toward each other. That creates more surface area for both stars, making the system brighter. At the same time, the surfaces of the stars vibrate like ringing bells. That also changes their brightness.

Astronomers have discovered about 1300 heartbeat systems. Most of them consist of stars that are bigger, brighter, and more massive than the Sun. Such stars are more likely to be born in pairs than Sun-like stars are.

Several heartbeat systems are in Cygnus. The swan’s brightest star, Deneb, is high in the east-northeast as night falls, and passes almost directly overhead later on — surrounded by stars that produce their own heartbeats.
 

Script by Damond Benningfield

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It looks like Roman calendar makers just ran out of gas. They named the first eight months of the year for gods and goddesses, or for emperors with godly ambitions. But after that, all they could come up with were numbers indicating a month’s position in the year.

September, for example, means “seventh month.” We know that Star Date listeners are pretty bright, so you’ve no doubt noticed that September is actually the ninth month of the year. But in the original Roman calendar, the year began in March, and lasted only 10 months. January and February were added later.

In other cultures, the calendar year began at different times. In Egypt, for example, it started in July, when Sirius returned to view in the morning sky.

Sirius is the brightest star in the night sky. Just as important to the Egyptians, it returned to view about the same time as the Nile’s annual life-giving floods. Using Sirius as a marker, the Egyptians established the first known 365-day calendar. Later, they added leap days to keep the calendar in sync with the seasons.

Much later, the Romans were fussing with a calendar that was a mess. Its months didn’t add up to a full year, so extra days or months were added at whim. So in 46 B.C., Julius Caesar ordered up a new calendar. Rome adopted the 365-and-a-quarter-day year — perhaps influenced by the Egyptian calendar. But it kept the Roman names for the months — including September.
 

Script by Damond Benningfield

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A supermassive black hole can be a powerhouse. Its gravity pulls in huge amounts of gas and dust, forming a superhot disk around the black hole. And magnetic fields within the disk can fire out “jets” of gas at almost the speed of light.

Some of the more impressive jets are in Hercules A — a giant galaxy that’s more than two billion light-years away. It’s in the constellation Hercules, which is high in the sky at nightfall.

Jets fire out of the middle of the galaxy, in opposite directions. From end to end, they span more than a million and a half light-years.

Hercules A is impressive. It’s a thousand times the mass of our home galaxy, the Milky Way. And the black hole in its heart is a thousand times the mass of the Milky Way’s black hole.

A lot of gas has funneled into the black hole — perhaps as the result of a merger with another galaxy. In fact, the black hole itself could have merged with the other galaxy’s black hole about 20 million years ago. That changed the angle of the black hole, which in turn changed the angle of the jets.

As the jets ram into the material around Hercules A, they produce huge amounts of radio waves and X-rays, making the jets billions of times brighter than the Sun. The jets also squeeze the surrounding material, which triggers the birth of new stars.

But there’s evidence that the activity around the black hole is slowing down — choking off the “powerhouse” at the center of Hercules A.
 

Script by Damond Benningfield

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The full Moon has a case of the blues tonight — it’s known as a Blue Moon.

There’s a passel of blue moon definitions. The phrase “once in a blue moon” is applied to something that happens rarely. In the calendar, a Blue Moon can be the 13th full Moon in a year, or the third of four full Moons in a calendar season. Today, Blue Moon usually refers to a second full Moon in a calendar month. And that’s what we get tonight.

There’s a slight difference between the Moon’s cycle of phases and the length of a month. A lunar cycle averages 29 and a half days. So in a month that has 30 days, a full Moon on the first of the month can be followed by another on the 30th. Months with 31 days can have full Moons on the 1st or 2nd, and again on the 30th or 31st.

The rarest of all blue moons are those that actually look blue. They happen when a big volcanic eruption or a major wildfire spews tiny bits of ash high into the sky. The ash scatters red light and allows bluer wavelengths to shine through — giving us a truly blue Moon.

And if you wonder where the modern definition of Blue Moon came from, we’re partially to blame — or credit. Writer Deborah Byrd discovered the definition in a 1946 magazine article, and used it in a Star Date episode in January 1980. The article was mistaken, but Byrd found no evidence of that. The definition later was used in the board game Trivial Pursuit — ingraining the Blue Moon in popular culture.
 

Script by Damond Benningfield

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Two “full” solar-system bodies huddle close together tonight and tomorrow night: the Moon and the planet Saturn. Saturn looks like a bright golden star. It’s to the left of the Moon as darkness falls tonight, and closer to the upper right of the Moon tomorrow night.

Saturn and the Moon are full for the same reason — both are at opposition — they line up in the opposite direction from the Sun. At opposition, the Sun fully lights up the side of a body that’s facing our way, so the object is at its brightest.

Saturn reached opposition a couple of days ago. Now, it’s beginning to move out of that alignment. But it’s a slow process, so Saturn will stay at its peak brightness for a while.

The Moon will reach opposition tomorrow night. It’s the second opposition this month — the second full Moon — which makes it a Blue Moon; more about that tomorrow.

It’s also the closest full Moon of the year. Tomorrow morning — about 10 hours before the moment of full Moon — the Moon will be about 17,000 miles closer than average. It’ll still be quite close at the precise moment it’s full, tomorrow night.

You might think the Moon is always closest when it’s full, but that’s not so. There’s a difference of a couple of days in the periods of the Moon’s orbit around Earth and its cycle of phases. So sometimes the full Moon is farther than average. But that’s not the case tomorrow night — the night of a big, bright, blue Moon.
 

Script by Damond Benningfield

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[AUDIO: exoplanet sonification]

That sound represents the first confirmed exoplanets — planets that orbit stars other than the Sun. At the end of 1992, only two such planets were known — orbiting the dead heart of an exploded star. The first planets orbiting a star similar to the Sun were announced in 1995.

By last spring, the number had passed 5,000, with thousands more possible planets awaiting confirmation. NASA put together an audio track as a timeline of all the discoveries. Each note represents a confirmed planet, with the pitch representing the planet’s distance from its star.

The pace of discovery really picked up in 2009, with the launch of the planet-hunting Kepler space telescope. It found thousands of planets that astronomers have confirmed with additional observations, and thousands more that they’re still trying to lock down. And although Kepler shut down five years ago, it still accounts for a majority of the planets discovered to date.

A successor, known as TESS, has discovered hundreds more, and is still scanning the skies. So are other telescopes in space and on the ground — adding to the “music of the spheres” — exoplanet style.
 

Script by Damond Benningfield

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Nothing lasts forever. That appears to include the rings of Saturn. They could disappear in as little as a hundred million years. Considering Saturn’s age of four and a half billion years, that’s not long.

Scientists have debated the age of the rings for decades. Some say the rings formed along with Saturn itself. But the Cassini spacecraft, which orbited Saturn for more than a decade, found evidence that they could be as little as a hundred million years old. They may be debris from a collision that destroyed a small moon or a passing comet.

At the end of its mission, Cassini passed between Saturn and the inner edge of the rings. It found that material is “raining” from the rings into Saturn’s atmosphere. Most of the rain consists of tiny bits of ice, which makes up the bulk of the rings, but it also includes grains of dust.

If the rainfall rate holds steady, the rings could disappear in anywhere from a hundred million to a few hundred million years. But the rings could be refreshed by more collisions between moons, comets, or asteroids. So we can’t be sure how long the rings will last — only that they won’t last forever.

Saturn is at its best for the year right now. It rises at sunset and is in view all night, in Aquarius. It’s brightest for the year as well, so it looks like a bright golden star. Look for it low in the east-southeast at nightfall, and scooting across the south during the night.
 

Script by Damond Benningfield

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It’s the start of a new season on Saturn: spoke season. Early this year, Hubble Space Telescope saw dark “spokes” in the planet’s beautiful rings. They appear to come and go with the seasons.

Saturn’s main rings span roughly three-quarters the distance from Earth to the Moon. They’re made of bits of ice, with a smattering of dust. From afar, they look smooth and even. But close-up views reveal many small features.

Some features are sculpted by small moons that orbit inside the rings. The gravity of the largest of these moons pulls at the ring particles, creating waves that ripple through the rings.

The smallest moons are only a few hundred feet across, so their gravity is weak. But it’s strong enough to create features known as propellers. These are gaps in the rings where the moonlets are, with streaks of ring material in front of and behind the moons.

The spokes appear to be unrelated to the moons. They’re clouds of dust particles that levitate above the rings. They can be thousands of miles long. The particles may get an electric charge from the solar wind, pushing them away from the rings. The spokes are most commonly seen around the equinoxes — the start of spring and fall. And the northern fall equinox is approaching — bringing “spoke season” to Saturn’s rings.

Saturn looks like a bright golden star. It’s low in the east-southeast at nightfall, and slides across the south later on.

More tomorrow.
 

Script by Damond Benningfield

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