StarDate

Be careful what you say — a single phrase can define a legacy.

Consider Frances Baily. He served four terms as president of the Royal Astronomical Society and compiled some of the most important star catalogs in history. But he’s best known for five little words: “like a string of beads.”

Baily was born 250 years ago today, in England. As a young man, he traveled to the wilds of North America, then joined the London Stock Exchange. He was especially good at the mathematical side of things, compiling guides about annuities and life insurance. He made a fortune, then retired in 1825 to spend all of his time on astronomy.

Baily had already helped establish the forerunner of the royal society. He used his skills from his days in business to compile star catalogs — work that required a lot of tedious calculations. One of them was the leading publication of its time.

In 1836, Baily watched a solar eclipse from Scotland. Just before the Sun vanished, he noticed little points of light around the edge of the Moon. Edmond Halley had seen the same thing more than a century earlier. Halley even explained those points: they’re sunlight shining through gaps between lunar mountains and craters.

To his fellow astronomers, Baily described them as “a row of lucid points, like a string of beads.” So today, the points are known as “Baily’s beads” — insuring a bit of immortality for an insurance expert-turned-astronomer.

Script by Damond Benningfield

Russian astronomer Friedrich Wilhelm von Struve discovered and catalogued thousands of binary stars — pairs of stars that are gravitationally bound to each other. But a system that he first saw in 1829 was so striking that he gave it a special name: Pulcherrima — “the most beautiful.” It honors the contrasting colors of the two stars. One looks pale orange, while the other looks blue-white or even green.

The system is also known by an even older name: Izar, “the girdle,” because it represents the middle of Boötes, the herdsman. Regardless of what you call it, most skywatchers agree with Struve: Seen through a telescope, the pair is quite beautiful.

The orange star is a giant. It’s burned through its original hydrogen fuel and is nearing the end of its life. As a result, it’s puffed up to many times the diameter of the Sun. That “puffiness” caused the star’s outer layers to cool, which is why it looks orange.

Its companion is much hotter, so it shines almost pure white. It looks blue or green only when it’s compared to the orange star. It’s less massive than the companion, so it has a lot longer to go before it reaches its own “giant” phase.

Boötes is in the east as night falls. Look for its brightest star, brilliant yellow-orange Arcturus. Izar is the first noticeable star to the left of Arcturus. To the eye alone, it looks like a single point of light. But a telescope reveals the true nature of this colorful duo.

Script by Damond Benningfield

The brightest star in the night sky is getting ready to leave it for a while. Sirius, the Dog Star, is low in the southwest as night falls. Over the next few weeks, it’ll sink deeper into the twilight, then disappear from view.

Sirius is almost nine light-years away. And it actually consists of two stars, not one. The one we see is a good bit bigger, brighter, and heavier than the Sun. The other is about the same mass as the Sun, but a whole lot smaller — only as big as Earth.

That star is a white dwarf. It’s the crushed core of a star that originally was more massive than its companion. Because of those extra pounds, the star aged more quickly. It puffed up to giant proportions. When it could no longer produce energy in its core, it cast off its outer layers, leaving only the dead core. The white dwarf is so small and faint that it’s visible only through a telescope.

The bright star of Sirius eventually will suffer the same fate. And so will the Sun — but not for several billion years.

Sirius will return to view — in the morning sky — in August, with the exact date depending on your location. From ancient Egypt, it disappeared for about 70 days. Sirius was important in both religious and secular life. So 70 days became the length of time set aside to prepare a dead king’s body for the afterlife. And the star’s reappearance marked the start of a new year — in a calendar regulated by the Dog Star.

Script by Damond Benningfield

Stars are huge — anywhere from about 10 times the diameter of Earth to a hundred thousand times or more. Such a scale is just hard to fathom. One way to envision it is to consider how long it would take you to make one turn around such a giant body.

An extreme example is Antares, the bright orange heart of Scorpius. It’s to the lower left of the Moon as they climb into good view tonight, after midnight, and about the same distance to the upper right of the Moon tomorrow night.

Antares is a supergiant — one of the biggest stars in the galaxy. It’s also one of the brightest and heaviest. The exact numbers are a bit uncertain. In part, that’s because its outer layers are extremely thin — they just kind of taper off into space. And Antares is blobby instead of perfectly round. But a good estimate says it’s almost 600 million miles in diameter — about 75 thousand times wider than Earth.

To get a better picture of that, imagine flying around Antares in a passenger jet at 600 miles per hour. At that speed, you could circle the Moon in about 11 hours, and Earth in about 40. And it would take six months to circumnavigate the Sun.

For Antares, though, you’d need to pack a lot of movies on your mobile device. That’s because it would take 350 years to make one full turn around it — a whole bunch of frequent-flier miles for circling around a supergiant star.

Script by Damond Benningfield

Over the millennia, stars acquire a lot of names. Some make sense, some don’t. And some of them might have gotten mixed up along the way.

An example is the fourth-brightest star of Leo, the lion, which is about 58 light-years away. It represents the lion’s hip. A few centuries ago, it was assigned the name “Delta Leonis” — an indication of its ranking within the constellation. But it also has some older names, including Zosma and Duhr.

Zosma comes from ancient Greek. It means “the girdle.” But that may be a mixed-up version of the original word, which meant “hip” or “back” — the star’s correct position in the lion’s anatomy. Duhr comes from ancient Arabic. It’s a shortened version of a phrase that means “the lion’s back.”

Regardless of the name, Zosma is a pretty impressive star. It’s more than twice the size and mass of the Sun, and about 15 times brighter. And its surface is thousands of degrees hotter.

Studies have shown that Zosma could be up to three-quarters of a billion years old. Stars of its mass burn through their nuclear fuel much faster than stars like the Sun. As a result, they live much shorter lives. Zosma should end its “prime-of-life” phase and head into old age in a few hundred million years. It’ll shine hundreds of times brighter than it does now — giving the lion a brilliant hip.

Zosma is high in the sky at nightfall. It’s well to the right of Regulus, the lion’s brightest star.

Script by Damond Benningfield

Immanuel Kant is best known for his ideas about philosophy, from ethics to the nature of knowledge. But he also played a role in the development of an idea about how planets are born. And while many of the details were off, his basic idea was sound.

Kant was born 300 years ago this week, in the German state of Konigsberg. And during his 80 years, he never left it.

He enrolled in the University of Konigsberg at age 16. But his father died, and he was forced to leave the university. He became a tutor for well-to-do families. He was able to return and finish his education in 1755.

Kant was interested in just about everything — including science. Soon after completing his degree, he wrote about earthquakes, the weather, and more. One of his early works was “Universal Natural History and Theory of the Heavens.” In it, he described a “nebular” hypothesis for the formation of planets.

A scientist in Sweden had conceived the idea a couple of decades earlier. Kant developed it further. He wrote that the Sun and planets were born from a nebula — a giant spinning cloud of gas and particles. Gravity caused the cloud to flatten, forming a disk. Material in the disk stuck together to make larger and larger chunks — eventually forming planets.

Today, scientists have worked out more of the details. But the basic idea remains the same — Kant’s hypothesis provides a basic description of how planets are born.

Script by Damond Benningfield

Few constellations have as many backstories as Virgo, the virgin. In ancient Greece and Rome, it was linked with several goddesses, each with her own story.

In one story, she was Dike, the goddess of justice. She lived when the gods known as the Titans ruled the land. Everything was peaceful, it was always spring, and living was easy. But after Zeus and the Olympians defeated the Titans, life got much more complicated. The goddess had to work a lot harder to maintain peace. Eventually, things got so bad that she turned her back on humanity and settled among the stars.

In another story, Virgo was Demeter, the goddess of agriculture and the harvest. The Sun entered that region of the sky in the fall, around the time of the harvest, strengthening the connection.

Virgo’s brightest star is Spica — a name that means “an ear of grain.” It’s the only truly bright star around. It’s about 250 light-years away, and consists of two stars in a tight orbit around each other. The more massive of the two is likely to end its life as a supernova — a titanic blast fit for the early gods of ancient Greece.

Spica stands just a whisker away from the full Moon tonight. They’re low in the southeast as twilight fades, separated by about half a degree — less than the width of a pencil held at arm’s length. They arc low across the south during the night, and set around dawn.

Tomorrow: an early recipe for a system of planets.

Script by Damond Benningfield

If you look straight up as the sky gets dark this evening, you won’t see much of anything. The region that’s high overhead is populated by some especially faint stars and constellations. But there’s a ring of brighter stars around it.

The point directly overhead is called the zenith. And most of the time, unless you’re lying on a blanket and just watching the stars, you’re not likely to pay it much attention. It’s just too uncomfortable to tilt your head back that much. Instead, most of us look at what’s closer to eye level.

Sometimes, it’s worth looking up there. Tonight really isn’t one of those times. The constellations near the zenith at nightfall include Leo Minor, the little lion; Lynx, a constellation so faint that you need the eyes of a cat to see it; and the part of Ursa Major that includes the feet and legs of the great bear, which are faint. And there’s an almost-full Moon in the sky, which overpowers dimmer stars.

But if you look a little below the zenith, the view is more impressive.

High in the south, for example, there’s Regulus, the bright heart of Leo, the big lion. And about the same height in the west, you’ll find Pollux and Castor, the “twin” stars of Gemini.

Finally, in the northeast, you’ll find perhaps the most famous star pattern of all: the Big Dipper. Its stars outline the body and tail of Ursa Major. They’re the easy-to-spot parts of the great bear, standing high in the sky — just not at the zenith.

Script by Damond Benningfield

The Little Dipper is famous for the star at the tip of its handle: Polaris, the North Star. Earth’s axis points in that direction, so all the other stars in the night sky appear to circle around it.

The second-brightest star in the dipper is Kochab, at the lip of the bowl. It isn’t nearly as famous as Polaris, but it’s almost as bright.

Kochab is a giant — more than 40 times the Sun’s diameter, and almost 400 times its brightness. It’s so big because it’s nearing the end of its life. The nuclear reactions deep inside the star push on the surrounding layers of gas, making them puff outward.

Just when a star enters the giant phase of life depends on its mass. Heavier stars age much faster, so they “burn out” more quickly. And Kochab is more massive than the Sun.

But just how massive has been the subject of debate. Studies using different techniques have yielded estimates of about 1.3 to 2.5 times the Sun’s mass. If Kochab had a companion star, it would be easy for scientists to measure the masses of both stars. For solitary stars like Kochab, though, astronomers rely on models of how stars behave. Today, the models seem to indicate a mass of about 2.2 times the Sun’s. But that isn’t completely settled. Until it is, we won’t know the complete story of Kochab.

Kochab is moderately bright, and stands to the right of Polaris at nightfall. It rotates directly above the Pole Star in the wee hours of the morning.

Script by Damond Benningfield

The Lyrid meteor shower is building toward its peak, on Sunday night. The Moon will be almost full then, so its glare will wash out all but the brightest of the “shooting stars.”

The shower is the offspring of Comet Thatcher 1861. The comet orbits the Sun once every 415 years or so.

As Thatcher approaches the Sun, some of the ice at its surface vaporizes. That releases small bits of dirt and rock into space. This debris spreads out along the comet’s path. Earth flies through this path every April. Some of the comet dust slams into our atmosphere and burns up — forming meteors.

At least, most of it does. It’s likely that some of the grains fall to the surface. In fact, a recent study might have found some of those grains at the bottom of New York’s Hudson River.

Researchers sifted through layers of sand and mud deposited thousands of years ago. The layers included fossils of microscopic organisms that were coated with tin — an element that likely came from outside Earth. The scientists also found other elements that probably originated outside our planet as well. The layers were laid down at roughly 400-year intervals — suggesting a possible connection with Comet Thatcher and the Lyrid meteors.

The findings are preliminary. So we don’t know for sure whether there’s a link between the sediments at the bottom of the Hudson River and the streaks of light in April’s night skies.

Script by Damond Benningfield