StarDate

The center of the galaxy is dangerous. It’s dominated by a supermassive black hole. And to make things more hazardous, one of its closest neighbors is a magnetar — the ultra-dense corpse of a once-mighty star. It spins once every 3.8 seconds, emitting a “pulse” of energy with each spin. That makes it a pulsar. And it has a magnetic field that may be a trillion times stronger than Earth’s — fatal at a range of thousands of miles.

Quite a few pulsars inhabit the galaxy’s core. But the magnetar is the closest one to the black hole. Astronomers are trying to find out if there's a connection — if there's something about the environment near the black hole that favors the formation of a magnetar.

Using a giant radio dish in Australia, they’ve already found that the magnetar’s pulses are spread out — like looking at a bright light through frosted glass. That could mean that the pulses are passing through a cloud of charged particles. And there’s a difference between pulses, which could be revealing details about how the magnetar works.

We can't see the galaxy’s heart because it’s behind clouds of dust. But we can see its location. It’s above the “spout” of the teapot formed by the stars of Sagittarius, which is low in the southeast at first light. And right now, the brilliant planet Jupiter is passing in front of the core — pointing the way to the galaxy’s dangerous heart.

Script by Damond Benningfield

You don’t want to get close to a magnetar. From a distance of hundreds of miles, the universe’s most powerful magnets would tug at the electrons in your body’s atoms, pulling the atoms out of shape — and causing you to fall apart.

The first magnetar was discovered 40 years ago today. A wave of gamma rays swept across the solar system — the most powerful outburst seen to that time. It was detected by spacecraft in Earth orbit and beyond, allowing astronomers to pinpoint the source: clouds of debris from an exploded star.

It took a while for astronomers to understand what they were seeing, though: the star’s highly magnetized corpse, now called a magnetar.

A magnetar forms at the end of a massive star’s life. The star can no longer produce energy in its core, so the core collapses. The core is about twice the mass of the Sun, but it’s compressed into a ball only about a dozen miles across. The resulting “corpse” is known as a neutron star.

As the core shrinks, its magnetic field intensifies. The “squeezed” field can be more than a million million times the strength of Earth’s magnetic field.

The field is strong enough to trigger “quakes” in the star’s ultra-dense surface. These tremors produce intense outbursts of gamma-rays — like the one detected in 1979.

A magnetar’s magnetic field decays quickly. So in about 10,000 years, the magnetar loses most of its field — and settles into life as a “normal” neutron star. More tomorrow.

Script by Damond Benningfield

Pulsars don’t play well with others. Some of them are destroying their companions, earning them an unflattering nickname: black widows.

Pulsars are the ultra-dense corpses of once-mighty stars. They’re up to a couple of times as massive as the Sun, but no bigger than a city. They’re called “pulsars” because they spin rapidly — up to hundreds of times per second — and we see “pulses” of energy with each spin.

Some pulsars have companions — stars or the stellar wannabes known as brown dwarfs. The pulsars bombard these unlucky mates with radiation and charged particles. That strips away material from the surface of the companion, creating a “wake” of hot gas behind it. Over time, that process may vaporize the companion. So like a female black widow spider, the pulsar destroys its mate.

The first black-widow pulsar was discovered in 1988. It’s about twice as massive as the Sun, and spins more than 600 times a second. Its companion is a brown dwarf — a “failed” star just two percent the Sun’s mass. They’re a little more than a million miles apart.

The brown dwarf eclipses the pulsar during each orbit. As the pulsar passes behind the brown dwarf’s wake, the charged particles amplify its pulses.

Eventually, though, the eclipses will end — as the pulsar whittles away its unlucky mate.

More about pulsars tomorrow.

Script by Damond Benningfield

One of the jewels of the winter Milky Way stands high in the northwest this evening. It’s actually two jewels that are quite close together — a pair of star clusters known as the Double Cluster. And they really do represent jewels — the jeweled handle of the sword of Perseus, the hero.

Individually, the clusters are cataloged as NGC 884 and 869. Although they were known to ancient skywatchers, their true nature wasn’t discovered until the 18th century, when William Herschel studied them through a telescope.

Both clusters are about 7500 light-years away. Quite a few clusters are closer, but not many of them are brighter. That’s because both members of the Double Cluster appear to be less than 15 million years old. At such a young age, they still contain some heavy stars, which burn especially hot and bright. Such stars burn out quickly, though, leaving their parent clusters with less-massive stars that shine longer but less brightly.

Under dark skies, the Double Cluster is easily visible to the unaided eye, immersed in the faint glow of the Milky Way. It’s a smudge of light above Cassiopeia, whose brightest stars form the outline of a letter M or W. But the clusters really shine when you view them through binoculars, which reveal the individual clusters as well as dozens of their individual stars — some extra jewels for the sword of the hero.

Tomorrow: black widows.

Script by Damond Benningfield

A brilliant young star in the Orion Nebula apparently doesn’t want any more brothers or sisters. It’s blowing an intense “wind” that’s clearing out much of the gas around it — pushing away the raw materials for making more stars.

The star is known by the somewhat clumsy name of Theta-1 Orionis C. It’s the heaviest member of the Trapezium — a cluster of hot, massive young stars. The star is many times heavier than the Sun, tens of thousands of degrees hotter, and hundreds of thousands of times brighter.

The Trapezium is at the center of the Orion Nebula, a giant stellar nursery more than 1300 light-years away. The nebula has given birth to thousands of stars, with many more still being born.

But the Trapezium itself is surrounded by the Orion Veil — a giant bubble with relatively little gas.

Astronomers recently studied the bubble with SOFIA, an airborne observatory. They found that Theta-1 Orionis C is blowing the bubble. Hot winds from its surface are causing the bubble to expand at about 30,000 miles per hour. The remaining gas inside the bubble is so sparse that there’s not much left for making more stars. But gas is piling up the bubble’s edge, which could trigger the birth of stars — far away from the Trapezium.

Orion is in the south as night falls right now. The Orion Nebula is visible to the unaided eye. It looks like a fuzzy star below Orion’s Belt. Binoculars will reveal the Trapezium, near the center of the nebula.

Script by Damond Benningfield

Beauty doesn’t always last. Consider the rings of Saturn. These bands of ice and dust are among the most beautiful features in the solar system. Yet they may be doomed — they could disappear in a few hundred million years.

The rings are constantly changing. Collisions pulverize larger chunks of material, while smaller bits can stick together to form bigger ones — all the way up to the size of small moons.

And ring particles “rain” onto Saturn, adding water to the planet’s atmosphere — which is why the rings may disappear.

Researchers recently took a new look at some old observations of Saturn. They found changes in the planet’s ionosphere — a layer of the atmosphere that contains particles with an electric charge. The changes correspond to dark bands in Saturn’s atmosphere seen in other observations.

The changes may be caused by bits of ice in the rings falling toward Saturn. The particles have their own electric charge, so they’re guided by Saturn’s magnetic field. As they hit the atmosphere, they wash away particles of haze — leaving dark bands.

The researchers calculated that this icy “rain” could make the rings vanish in about 300 million years — only a few percent of the age of Saturn itself.

Saturn just peeks into view at dawn right now. Tomorrow, it’ll stand to the upper right of the Moon, with brilliant Venus close to the left of the Moon. They’ll be in view by about an hour before sunrise, low in the southeast.

Script by Damond Benningfield

Odd little February — the shortest month of the year — comes to an end today. Historians aren’t exactly sure just why it’s so short. But tracing the evolution of this abbreviated month gives us a capsule history of the evolution of the calendar.

The modern western calendar is a descendant of the earliest Roman calendar. It included only 10 months, beginning with March. The official months were followed by about 60 days that weren’t part of any month.

That system didn\'t work very well, though, so two months were added to the end of the year — January and February. February was named, incidentally, for the god of purification.

The lengths of the 10 original months were changed to leave 56 days for the newcomers. But the Romans feared even numbers, so they added a day to January to give it 29. February was the month for festivals of repentance and for honoring the dead, so it stayed at an unlucky even number.

But this version of the calendar contained only 355 days. So an extra month was added every other year. In those years, the last five days of February were dropped.

After that, February remained unchanged until 46 B.C., when Julius Caesar introduced the basic calendar that’s in use today. He might have lengthened February to 29 days; if so, it was cut back to 28 by Augustus Caesar, who took the extra day for the month that bears his name: August.

Script by Damond Benningfield

Pamela Lyndon Travers saw a bit of the world. The creator of “Mary Poppins” traveled from Australia to the British Isles to the United States. And late last year, she traveled even farther — or at least her name did. A hundred-mile-wide crater on the planet Mercury was named in her honor.

So far, astronomers have named more than 500 features on Mercury — mostly impact craters mapped by Mariner 10 and Messenger, the only spacecraft ever to visit the planet.

Different types of features have different naming themes. Craters are named for people from the creative arts: authors, painters, musicians, and others. The list includes Dr. Seuss, Johann Sebastian Bach, French painter Paul Cezanne, Mexican painter Diego Rivera, Walt Disney, and Imhotep, architect of the first pyramids of ancient Egypt.

Some types of ridges are named for scientists and engineers who contributed to the study of Mercury, such as Gerard Kuiper, a one-time director of McDonald Observatory. Tall cliffs are named for famous ships that explored the world. And wide volcanic plains are given the names for Mercury from different cultures.

And the Sun’s closest and smallest planet is in view in the early evening sky the next few days. It’s quite low in the west as twilight fades away. But it looks like a fairly bright star. So if you have a clear horizon, you should be able to spot Mercury — a little planet with a distinctly artistic flair.

Script by Damond Benningfield

The planet Jupiter huddles below the Moon at first light tomorrow. It looks like a brilliant star. But it’s really the solar system’s largest planet — a ball of gas about 11 times the diameter of Earth.

A quarter of a century ago, Jupiter was bombarded by the fragments of a shattered comet. The impacts were visible to telescopes on Earth. And the scars of the impacts remained visible for months.

A telescope has been watching impacts on the Moon as well. But none of them has been anywhere close to the magnitude of those on Jupiter.

The project is conducted by the European Space Agency. It uses a 48-inch telescope in Greece to record flashes of light on the dark portion of the lunar disk — the part where it’s nighttime. The project began in March of 2017, and recently was extended through January of 2021.

The flashes are produced by small asteroids — chunks of rock that orbit the Sun. Each flash is visible for only a fraction of a second. And each gouges a small crater on the lunar surface — a pit that can remain for billions of years.

From the number of flashes recorded so far, scientists estimate that there should be a couple of impacts across the entire Moon every hour.

Earth gets pelted by even more space rocks. Most of them burn up in the atmosphere. But the observations of the lunar impacts should help scientists determine the risks from impacts by bigger space rocks — ones that could harm our fragile planet.

Script by Damond Benningfield

A star and an onion might not seem to have much in common. But as the heaviest stars near the ends of their lives, they’re put together a lot like an onion.

All stars begin their lives by “fusing” atoms of hydrogen in their cores to make helium. When they’ve used up the hydrogen, gravity squeezes the cores more tightly, making them hotter, so they fuse the helium to make carbon and oxygen.

For stars like the Sun, that’s as far as it goes — they can’t get hot enough to make heavier elements. But stars that are at least 8 to 10 times the mass of the Sun can.

Gravity squeezes them even tighter, allowing the carbon to fuse to make neon and other elements, which takes hundreds of years. It then takes perhaps a year or less for the neon to make oxygen, and as little as weeks for the oxygen to make silicon. Each of these steps leaves a layer of the earlier elements, creating the onion-like structure.

The final step takes just days. The silicon fuses to make iron. It takes more energy than the core can produce for the iron to fuse to make even heavier elements, so the reactions stop. The core collapses, and the outer layers blast into space as a supernova.

One star that will undergo that fate is Antares, which is below the Moon at first light tomorrow, far to the right of the bright planet Jupiter. It’s probably fusing helium in its core right now, so the clock is ticking toward its demise — sometime in the next million years.

Script by Damond Benningfield