StarDate

If you need some extra chills to go along with your trick-or-treating or other Halloween fun tonight, just look into the sky. It’s filled with ghosts, witches, and Gorgons — the snaked-headed sisters of mythology who turned anyone who looked at them to stone.

The Gorgons are four stars in Perseus, low in the northeast as night falls. The brightest of the four represents Medusa, one of the sisters. The other three arc to its right. The bright one is Algol, from an Arabic phrase that means “the demon’s head.” It may have received the name because it fades dramatically every three days or so — the result of a fainter star passing in front of a brighter one.

The Skull Nebula — the final gasp of a dying star — is in the southeast, in Cetus — the sea monster. And the Witch Head Nebula — a giant cloud of gas and dust — climbs into view before midnight, close to Rigel, the bright foot of Orion. It looks like the profile of the wicked witch in “The Wizard of Oz.”

Two nebulas are called “the Ghost,” and both are high in the northern sky. One is near the “house” outlined by the stars of Cepheus the king. The other is near the “W” outlined by the stars of his wife, Cassiopeia. Both are clouds of gas and dust. Part of the outline of the “kingly” ghost looks like demons with horns. And the outline of the “queenly” one looks like a ghostly sheet blowing on the wind — among the spooky sights in the sky on Halloween night.
 

Script by Damond Benningfield

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The star Algol is a good one for Halloween. It’s in the northeast as night falls, and climbs directly overhead in the wee hours of the morning. More important, though, is its name: “Algol” comes from the Arabic phrase “ras al-ghul” — the head of the demon.

Ancient skywatchers may have bestowed the name because Algol does something spooky: It fades and brightens over a period of about three days. And the change is obvious even to the unaided eye — something you can’t say for any other star.

It took a long time to figure out why that happens. It turns out that the system contains two stars in a tight orbit around each other. They line up so that, as seen from Earth, they eclipse each other. When the fainter star passes in front of the brighter one, the system fades to just a third of its un-eclipsed brightness.

Algol actually has a third star. But it’s so far away from the others that it doesn’t line up in a way that causes eclipses.

A study released a year ago said there could be as many as four more stars in the system. A scientist in Finland used a complicated mathematical model to simulate the motions of the known stars. The model suggested they could be tugged by the gravity of stars that take anywhere from a couple of years to a couple of hundred years to orbit them. But so far, no one has seen any other stars at Algol — a “demonic” star system for Halloween.

We’ll have more about Halloween tomorrow.
 

Script by Damond Benningfield

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The trunk of an elephant extends 20 light-years across the constellation Cepheus, the king. New stars are taking shape inside the trunk — especially in the nostrils. But the supply of gas that gives birth to stars is being worn away, so the starbirth won’t last long.

The trunk is part of a giant complex of stars, gas, and dust known as IC 1396. It’s a few thousand light-years away. Even so, it’s so big that it spans about five degrees in our sky — 10 times the width of the Moon. And under dark skies, it’s bright enough to see with the eye alone. It’s high in the northern sky at nightfall.

The entire complex is illuminated by a system of three hot, giant stars. Their ultraviolet light causes gas in the surrounding nebula to glow. Winds from those and other stars are blowing away much of that gas and dust. But they’re also squeezing some of that material, causing it to collapse and form new stars.

That’s what’s happening with the elephant’s trunk. It’s a tall pillar of bright gas and dark dust, with a big blob at the tip. The trunk contains many stars that are no more than a hundred thousand years old — so young that they’re not actually full-fledged stars yet. The blob at the tip appears to hold a couple of stars that are slightly older.

Before long, all the gas and dust will be blown away or incorporated into new stars, and the elephant’s trunk will disappear.

Tomorrow: the demon star.
 

Script by Damond Benningfield

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As twilight fades out this evening, many prominent stars fade in. There’s Fomalhaut, the lonely “autumn star,” low in the south-southeast. The stars of the Summer Triangle — Deneb, Vega, and Altair — are pinned high in the sky. And the bright orange stars Aldebaran and Betelgeuse climb skyward later on.

The stars are different ages, sizes, and types. But one thing they have in common is their names: all of them were adopted from Arabic.

The names were passed down in a couple of ways. Some of them were translations from the “Almagest,” a star catalog compiled by Greek astronomer Claudius Ptolemy around the year 150. Ptolemy included each star’s position in a star picture, such as the mouth of the fish. Centuries later, Arab astronomers translated those descriptions. So the mouth of the fish became “fam al-hut” — a name known today as foh-mahl-HOT or foh-mah-LOW.

In the 10th century, Persian astronomer al-Sufi created his own star catalog. He updated the Almagest, and created many new names. Over the centuries, his work was translated into European languages, and the star names entered common usage.

So today, we gaze upon Deneb, adapted from a phrase meaning “the tail of the hen;” Vega, “the swooping eagle;” Altair, “the flying eagle;” Aldebaran, “the follower,” because it follows the Pleiades; Betelgeuse, “the shoulder of the giant;” and stars with many other beautiful and ancient names.
 

Script by Damond Benningfield

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The neighborhood around a star can be dangerous. Comets, asteroids, and even planets can slam together. That can rip them apart and create massive clouds of dust and rock. And those clouds can be deceiving.

Consider Fomalhaut, the brightest star of the southern fish. It’s low in the southeast at nightfall and scoots across the south during the night. It’s the only bright star in that region of the sky, so it’s easy to pick out.

Fomalhaut is bigger, brighter, and heavier than the Sun — and billions of years younger. And it’s encircled by disks and rings of dust.

In 2008, pictures of the system from Hubble Space Telescope revealed a bright, compact object near one of those rings. For a long time, scientists thought it was a giant planet. They even gave it a name: Dagon. But a few years later, that pinpoint of light began to spread out. And before long, it vanished.

Continued study of the system suggested the object is really a cloud of dust that’s spreading out and growing fainter. It may be the debris from a collision between two “planetesimals” — big balls of rock and ice that are the building blocks of planets. It could also be the remains of a single planetesimal that passed too close to a giant planet and was ripped apart by the planet’s gravity. So Fomalhaut could have a planet — and perhaps several planets. But so far, we can’t see them.

Tomorrow: lyrical names for Fomalhaut and many other stars.
 

Script by Damond Benningfield

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Fish are always trying to fend off other creatures, from other fish to birds to people. That applies to fish that are in the stars as well. In fact, the southern fish, Piscis Austrinus, has been nibbled at several times over the centuries.

The constellation was established in ancient Babylon. Later, it was adopted by the Greeks, who tweaked its mythology. They said that a goddess either fell or threw herself into a river. She was rescued by a fish, which was placed in the heavens as a reward.

The original constellation was a stick-figure outline anchored by Fomalhaut, the fish’s only bright star. Later, astronomers began shifting things around. The star that originally represented the fish’s tail, for example, became the head of the new constellation Grus, the crane. Some stars that one astronomer assigned to the fish were later moved by other astronomers. They became part of a constellation that honored the microscope.

Today, the constellation has precisely defined borders. That keeps other constellations from poaching its faint stars.

Piscis Austrinus scoots quite low across the south on October and November evenings. Look for Fomalhaut — a name that means “the fish’s mouth.” Not only is it the brightest star in the constellation, it’s the brightest star in that whole region of the sky, so you can’t miss it. The rest of Piscis Austrinus extends to its right.

More about Fomalhaut tomorrow.
 

Script by Damond Benningfield

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Almost every galaxy is giving birth to at least a few stars. But a giant stellar nursery on the rim of M33, the Triangulum Galaxy, takes starbirth to the extreme. It is giving birth to thousands of stars — including many that are among the hottest, brightest, and most massive yet seen.

M33 is the third-largest member of the Local Group, a collection of scores of galaxies. The Milky Way and the Andromeda Galaxy are its largest members. M33 is about half the diameter of the Milky Way, and contains perhaps one-tenth as many stars.

Several loosely wound spiral arms wrap around its nucleus. The arms contain huge amounts of gas and dust — the raw materials for new stars. Much of it congregates in a collection of stellar nurseries.

The largest is NGC 604. It’s about 6,000 times brighter than the Orion Nebula, the closest major nursery to Earth.

NGC 604 is only a few million years old, but it’s already given birth to about 200 superstars — up to 120 times the mass of the Sun. Many of them will explode.

M33 is about three million light-years away, in the constellation Triangulum, which is low in the east-northeast as night falls. Under especially dark skies, the galaxy is just visible to those with good eyesight. Everyone else needs help to see this busy galaxy.
 

Script by Damond Benningfield

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Families can be hard to predict. An exception is families of eclipses. Astronomers can predict them centuries in advance — down to the second.

An example is a partial solar eclipse that will be visible across parts of the eastern hemisphere early tomorrow. The Moon will cover about 82 percent of the Sun’s disk, lowering temperatures and making the sky look a little dusky.

The eclipse is part of a family called Saros 124. It’s a sequence of eclipses that are all related.

The sequence is playing out in a predictable, orderly fashion. It began with a partial eclipse in the year 1049 that was visible across the Antarctic. Over the centuries, the eclipse path has moved slowly northward. From 1211 to 1968, the series included total eclipses, with the Moon completely covering the Sun. Now, we’re back to partial eclipses.

This is eclipse number 55 in the cycle. It’ll be visible across parts of Europe, northeastern Africa, and western Asia. It begins shortly before 4 a.m. Central Time, reaches its peak at 6, and ends about 8.

After this, the eclipses of Saros 124 will continue to move northward. The final eclipse in the cycle will take place on May 11th, 2347 — the last act of a predictable family.

Incidentally, a solar eclipse takes place two weeks before or after a lunar eclipse. In this case, there’ll be an eclipse on the night of November 7th, which will be visible across most of the United States.
 

Script by Damond Benningfield

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The Sun sometimes takes a nap. It can go for decades without producing many sunspots. That has a big impact on space weather, and maybe on Earth’s climate.

One of those naps is known as the Spörer Minimum. It was discovered by Gustav Spörer, a German astronomer who was born 200 years ago today.

Spörer earned his PhD by studying a comet. In his late 30s, though, he turned his attention to sunspots — dark blotches on the Sun. Today, we know they’re cool magnetic storms. At the time, though, their nature was unknown.

Astronomers had found that the spots follow an 11-year cycle. There are lots of spots at the cycle’s peak, but few at its low point. Spörer and others found that no two cycles are alike. Some are quiet, with few spots. And there can be periods with several quiet cycles in a row.

The most famous is the Maunder Minimum, discovered by Spörer and by Edward Maunder. It came in the late 17th and early 18th centuries. The Spörer Minimum came a couple of centuries earlier. There’s evidence that space weather — an interaction between Earth and the Sun — was quieter then. And Earth’s climate was a little cooler during those periods — an indication that the Sun’s energy output was lower than normal.

Spörer discovered that sunspots migrate from high latitudes toward the equator during the 11-year cycle. He also discovered that different latitudes of the Sun rotate at different rates — insights into the Sun and its long naps.
 

Script by Damond Benningfield

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Astronomical distances can be mind boggling. Our closest neighbor, the Moon, is a quarter of a million miles away — equal to about 10 trips around Earth’s equator. The closest planet, Venus, is always at least a hundred times farther. And the closest neighboring star, Proxima Centauri, is about a million times farther still.

Yet even that is just a hop compared to the distance to the most remote object that’s easily visible to the unaided eye. The Andromeda Galaxy is more than half a million times farther than Proxima Centauri — two-and-a-half million light-years.

Right now, the galaxy stands in the east-northeast, about half-way up the sky, at nightfall. It looks like a faint patch of light about as wide as the Moon. Binoculars bring it into better view.

Like our home galaxy, the Milky Way, Andromeda is a wide, flat disk. The visible part of the disk spans more than a hundred thousand light-years. But powerful telescopes reveal that stars taper off into space well beyond that, making the disk twice as wide as the Milky Way’s.

We see the galaxy almost edge-on, which raises another mind-boggling detail about astronomical distances. It takes the light from the far edge of the disk much longer to reach our eyes than the light from the near edge. So there’s no way to see the Andromeda Galaxy at a single point in time. Instead, we see different parts of it as they looked over a span of almost a hundred thousand years.
 

Script by Damond Benningfield

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