StarDate

Pilots at the airport in Wichita, Kansas, will notice some changes this year. All three of the airport’s runways will get new names. Runway 14/32 will become 15/33, for example, while 1 Left/19 Right will become 2 Left/20 Right.

The change is needed because of changes in Earth’s magnetic field. Runways are designated by their compass headings. As the magnetic field changes, though, so do those directions. So the runways need new names to reflect the direction to the north magnetic pole.

And the pole is shifting in a hurry. Since the 1990s, it’s moved an average of about 35 miles per year. It’s moved from northern Canada into the Arctic Ocean, not too far from the geographic pole. It’s headed for Siberia.

Earth’s magnetic field is generated by motions deep within the planet. The outer core is made of liquid iron, which flows as Earth rotates on its axis. That process isn’t smooth and predictable, though. Currents within the core come and go. And blobs of material can move in sudden “jerks” — something that happened a few years ago.

The recent shift is so big that scientists released a new model of Earth’s magnetic field earlier this year — a year earlier than scheduled. The military and other agencies use that model to help navigate around the world. It’s even used in some smartphones. So the early update will help keep many people headed in the right direction — not just pilots.

Script by Damond Benningfield

The Crab Nebula stands high in the west as night falls. It’s far above Aldebaran, the bright orange star that marks the eye of Taurus, the bull. The nebula is the debris from an exploded star — and the brightest source of X-rays in the night sky.

Hitomi, an X-ray space telescope, took a look at the Crab in March of 2016. It was the last thing the Japanese craft ever saw. As it turned toward a new target, its pointing system failed. That led to a series of problems that resulted in the craft spinning so fast that it ripped itself apart.

The whole episode might have been triggered by radiation. Hitomi was flying through the South Atlantic Anomaly — a region from southern South America to South Africa where Earth’s magnetic field is weak. That allows the radiation belts that surround Earth to dip to within about a hundred miles of the surface.

Spacecraft that travel through the region get zapped by charged particles. So Hubble Space Telescope and other craft shut down when they’re passing through.

The anomaly can be a problem for people, too. Astronauts have reported seeing “shooting stars” when they passed through. In fact, the International Space Station carries extra shielding to protect crew members from the radiation.

Recent research suggests the South Atlantic Anomaly has been around for tens of thousands of years. So it’s not likely to leave spacecraft alone anytime soon.

More about Earth’s magnetic field tomorrow.

Script by Damond Benningfield

The hottest ride in the solar system is really sizzling right now. Parker Solar Probe will pass just 15 million miles from the Sun tomorrow — about 12 million miles closer than any other spacecraft. But it’s setting up for even closer encounters in the years ahead.

The craft’s mission is to study the Sun’s thin outer atmosphere, the corona. It’s millions of degrees hotter than the surface of the Sun, and scientists are trying to understand why that’s the case. The corona probably is heated by the Sun’s powerful magnetic field, but the details are still hazy.

Parker is also studying the region where the solar wind is born. This flow of charged particles breezes through the solar system at a million miles per hour or faster. When it reaches Earth, it creates the aurorae. Intense winds can cause trouble. A better understanding of how the wind gets started should help scientists produce better forecasts of how the winds will affect us here on Earth.

Parker Solar Probe was launched last August. It made its first close pass by the Sun in November — also at around 15 million miles — and began its second orbit around the Sun in January. Plans call for it to make 24 orbits in all, getting closer to the Sun on each circuit. In 2025, it’ll pass less than four million miles from the Sun — the hottest moment for the solar system’s hottest ride.

We’ll talk about Earth’s magnetic field tomorrow.

Script by Damond Benningfield

It’s been a quiet couple of years for the Sun. The dark magnetic storms known as sunspots have been rare. Most days last year, in fact, the Sun showed no sunspots at all. And the number of sunspots is expected to stay low for at least a few months more.

The Sun goes through an 11-year cycle of magnetic activity. At a cycle’s peak, sunspots are common, and so are giant outbursts that shower Earth with radiation and charged particles.

The current magnetic cycle reached its peak in 2014. It was especially quiet, though — lower than astronomers had seen in many decades. And since then, solar activity has ramped down even more. The Sun is either in or nearing what’s called solar minimum — the quietest period of an entire cycle.

The Sun’s impact on Earth is at a minimum, too — fewer disruptions to satellites, power grids, and other technologies. And the northern and southern lights are at their puniest.

The reduced solar energy cools the top of Earth’s atmosphere, so the atmosphere shrinks. There’s less air to slow down satellites, so they need fewer rocket firings to keep them on track.

On the other hand, a quieter Sun allows more cosmic rays to enter the solar system. These particles from exploding stars and other sources can also damage satellites, and are hazardous to astronauts — an unpleasant side effect of a quiet Sun.

One satellite is getting close to the Sun this week, and we’ll have more about that tomorrow.

Script by Damond Benningfield

Two of the most popular sights in the night sky are teaming up right now — the planet Mars and the Pleiades star cluster. They’re due west as darkness falls, about a third of the way up the sky. Mars looks like a modest orange star. The dipper-shaped Pleiades is close to the right.

Mars is popular not just to look at, it’s popular to explore. Almost a score of American spacecraft have studied the Red Planet from up close. As of early March, in fact, five of those craft were still at work. And so were three other missions, from Europe, Russia, and India.

One American mission went silent last year. The Opportunity rover landed in January 2004, and operated for more than 14 years. But a massive dust storm blanketed Mars last year, turning day to night. The solar-powered rover hunkered down, using its batteries to keep itself warm. When the storm cleared, though, Opportunity didn’t wake up. Months of attempts to contact it produced no results.

The most recent Mars explorer touched down in November. InSight is probing the Martian interior. It’s listening for Marsquakes, and taking the planet’s temperature. That should provide the best picture yet of how Mars is put together.

Today, several countries are preparing the next round of Mars missions. As many as five could launch in the summer of 2020 — a combination of orbiters, landers, rovers, and even a small helicopter — new explorations of a popular planet.

Script by Damond Benningfield

The two brightest orbs in the night sky perch close together at first light tomorrow. The Moon will stand quite low in the southeast at dawn. The planet Venus — the brilliant “morning star” — will be close to the lower left. But there’s not a lot of time to watch them before daylight overpowers their glow.

The surface of the Moon is covered with craters — big round holes blasted out when big space rocks plowed into the Moon. The process has been going on for billions of years. That’s long enough for the older craters to have been partially destroyed by more recent impacts. So pictures of the Moon show craters on top of craters on top of more craters.

There are craters on Venus, too — about a thousand have been cataloged. Unlike the Moon, though, they all look young and fresh. That’s because volcanic activity “repaved” Venus a few hundred million years ago. So all the craters we see on Venus today have been carved since that resurfacing. And the planet’s atmosphere is so thick that it prevents most space rocks from reaching the surface — keeping Venus’s craters looking pristine.

Again, look for Venus and the Moon during morning twilight tomorrow. The view gets better as you go farther south, because the Moon and Venus rise at a steeper angle, so they climb higher into the sky. They’ll be closer together on Tuesday, but the Moon will be lower, making the viewing window even tighter.

Script by Damond Benningfield

The tail of the lion has left its family behind it. The star escaped from the cluster where it was born. Today, it travels through the galaxy alone. Yet it hasn’t given up all traces of home. It moves through the galaxy in the same way as dozens of other stars — an indication that they may be related.

Denebola — a name that means “the tail of the lion” — is the third-brightest star of Leo. It’s in the east as night falls, at the bottom of the figure that outlines the lion. It’s almost twice as massive as the Sun, and about 15 times brighter.

Studies in recent years have suggested that it belongs to a group known as the Argus association. The stars in the group don’t all belong to a star cluster. But they all move through the galaxy in the same way. Their chemical composition is about the same, too. And they all appear to be quite young — roughly 40 million years old — just one percent the age of the Sun. In fact, several of the stars, including Denebola, are encircled by rings of dust left over from their formation — another indication of their youth.

Most members of the Argus association are in a small star cluster. But others are well outside the cluster, including Denebola. Those stars may have been born in the cluster, but later escaped. Denebola is the brightest of the bunch, mainly because it’s one of the closest to Earth — just 36 light-years away — hundreds of light-years closer than most members of Denebola’s family.

Script by Damond Benningfield

Before a star like the Sun becomes a star like the Sun, it goes through a busy infancy. It forms from a collapsing cloud of gas and dust. Most of the material clumps together in the center, getting hotter and hotter, forming the baby star. Much of the remaining gas and dust forms a disk around the star. And bigger clouds of material from the star’s nursery lurk nearby.

A couple of star-cloud pairings are in the west and southwest as night falls. Both clouds vary in brightness as a result of the activity around the young stars.

T Tauri is near the top right point of the “V” that forms the face of Taurus, the bull. It’s only a few hundred thousand years old, so it’s still coming together — it’s not actually shining as a true star.

Next door to it is Hind’s Variable Nebula. It shines by reflecting light from T Tauri. The nebula changes brightness over a period of weeks or months — the result of changes in the star and its encircling disk.

The star R Monocerotis is to the upper left of Orion. It’s in the same stage of life as T Tauri.

A triangular nebula points away from the star. It’s known as Hubble’s Variable Nebula after Edwin Hubble, for whom Hubble Space Telescope is named. The nebula varies when dense blobs of dust pass in front R Monocerotis, casting shadows.

The nebula was the subject of the first photograph taken with the giant Palomar Telescope in California, 70 years ago. The picture was taken by Edwin Hubble.

Script by Damond Benningfield

The planet Saturn stands close to the upper right of the Moon at first light tomorrow. It looks like a bright golden star.

Saturn has dozens of moons of its own. Titan, the biggest, has a thick atmosphere and lakes of liquid methane. And geysers of water and ice shoot into space from a distant moon, Enceladus.

Another moon is a lot less active, but it has some interesting features nonetheless: Straight lines up to hundreds of miles long that lie parallel to its equator.

Dione is Saturn’s fourth-largest moon. It’s about 700 miles in diameter, and orbits about 200,000 miles above Saturn\'s cloudtops. Its surface is made of ice. It’s scarred by impact craters and jagged cracks.

The stripes were revealed by photos from the Cassini spacecraft, which orbited Saturn for a decade. The stripes were studied by researchers from the Planetary Science Institute and the National Air and Space Museum.

The scientists found that the stripes are no more than three miles wide, but up to hundreds of miles long. They’re brighter than the surrounding landscape, and they’re completely straight — like stripes painted down a highway.

The researchers say the stripes probably were created by something other than Dione itself. They could have been deposited by a “rain” of ice from Saturn’s rings, or by passing comets. Or they could consist of material blasted off nearby moons by small space rocks — sprays of ice forming sporty stripes on Dione.

Script by Damond Benningfield

A sculpture in Florida that looks like an alien metallic flower will cast a shadow around a plaque today. The plaque commemorates the possible first sighting of Florida by European explorers, on this date in 1513.

The sculpture is named “Solar Rotary.” It’s on the campus of the University of Southern Florida in Tampa. It’s one of many sculptures around the country that have special solar alignments.

One is the Soleri Bridge in Scottsdale, Arizona. It’s a pedestrian bridge with tall pylons at its end. The Sun shines through a narrow gap between the pylons at certain times, lighting a stripe on the bridge. The pylons cast no shadow at noon on the summer solstice.

Another, in Honolulu, is called Sky Gate. It’s a wavy ring atop three legs. The Sun stands directly above it at local noon on two dates each year. At those moments, the sculpture casts a perfectly round shadow on the ground below.

Solar Rotary was created by artist Nancy Holt. A campus astronomer calculated the site’s precise latitude and longitude, and the angle of the Sun on key dates.

The sculpture is 20 feet tall. It consists of eight steel legs. They all curve inward and meet at a seven-foot ring near the center.

At the summer solstice, the ring forms a circular shadow around the base of the sculpture. It encircles five small plaques on other dates, which are important in local history. That includes the first visit by Europeans — marked with the help of the Sun.

Script by Damond Benningfield