StarDate

You might forgive Pollux if it feels disrespected. It’s the brightest star of Gemini – twice as bright as Castor, its “twin.” But the designation that’s most often used by astronomers is Beta Geminorum. And the Greek letter “Beta” usually is applied to a constellation’s runner-up.

That naming system was created by German astronomer Johann Bayer, in 1603. He used the Greek alphabet to name most of the stars in a constellation. Usually, the brightest star was given the first letter, Alpha. The next-brightest was Beta, and so on.

But in some cases, Bayer switched things up. He labeled the stars based on their location in the constellation’s classical outline, or on some other category. So for Gemini, Pollux became the “Beta” star even though it’s clearly brighter than “Alpha.”

Pollux really is an impressive star. It’s moved into the red-giant phase of life. In fact, it’s the closest red giant to the Sun, at a distance of just 34 light-years.

It’s puffed up to about nine times the diameter of the Sun, so it shines almost 40 times brighter than the Sun. And it has a distinctively orange tint – a beautiful look for an impressive star.

Pollux and Castor line up to the upper left of the Moon at nightfall this evening. Pollux is closer to the Moon. The planet Jupiter is farther to the upper right of the Moon. Jupiter outshines all the true stars in the night sky – even the brightest light of Gemini.

Script by Damond Benningfield

If you head for orbit around Jupiter, you might want to take along your dust mop. Wide but thin rings encircle the planet. And they’re made of tiny particles of dust.

Jupiter’s rings are nothing like the magnificent set that encircles Saturn. The rings are so faint, in fact, that they weren’t discovered until 1979, when the Voyager 1 spacecraft flew close to Jupiter.

The system consists of four main rings. The inner ring, known as the halo, contains especially tiny particles, like a thin haze. The particles in the main ring are a little larger, but still quite small. And the two outer rings – known as gossamer rings – are wide and thick, but still don’t add up to much.

The particles that make up the rings probably were chipped off of some the small moons that orbit close to Jupiter. Chunks of ice and rock slam into the moons, blasting out clouds of debris.

The particles in the rings spiral into Jupiter quickly – within hundreds or thousands of years. So the rings are being constantly replenished by more impacts – adding to the dusty environment around the solar system’s largest planet.

Jupiter teams up with the Moon and the twins of Gemini tonight. The planet looks like a brilliant star below the Moon at nightfall. It’s far brighter than any of the true stars. Gemini’s twins – the stars Castor and Pollux – line up to the lower left of the Moon.

More about this beautiful grouping tomorrow.

Script by Damond Benningfield

The first solar flare ever observed was also by far the biggest yet seen. But such a monster storm will happen again. And when it does, it’s unlikely that even a single spacecraft in Earth orbit will come out unscathed. And many could be destroyed.

The benchmark storm so far was the Carrington Event. It was observed by British astronomer Richard Carrington, in 1859. He saw a brilliant flash of light erupt from a dark sunspot. The eruption produced beautiful displays of the northern and southern lights. It also zapped telegraph wires, disrupting transmissions and even starting fires in some stations.

Scientists at the European Space Agency recently simulated what would happen to satellites if such a monster storm hit us today. They concluded that it would be bad – really bad.

Over a period of about a day, GPS systems would fail. Satellite instruments would glitch or fail, entire satellites would be destroyed, and some ground stations would be knocked out.

Earth’s outer atmosphere would expand dramatically, dragging satellites down. That would increase the risk of collisions, and reduce the time in orbit for any survivors.

Operators can take some actions to protect their satellites. But that requires good forecasts of space weather. And future satellites could be equipped with better shielding. Even with those precautions, though, no satellite would be unaffected by the fury of a monster storm on the Sun.

Script by Damond Benningfield

Anything that’s in Earth orbit faces the constant threat of radiation – energy and charged particles from the Sun and beyond. It can cause instruments to glitch or fail, and even destroy a satellite. And it poses a health risk for astronauts.

The threat is greatest in a zone in the southern hemisphere – the South Atlantic Anomaly. It covers several million square miles above South America and South Atlantic Ocean. It’s a weak spot in Earth’s magnetic field that allows intense radiation to penetrate closer to the surface. And it’s getting bigger.

The magnetic field can deflect many of the charged particles that bombard our planet. That protects orbiting satellites and astronauts. It also protects the surface from power blackouts and other effects.

But the field is offset a bit from the center of the planet. It extends a little farther into space in some regions, but dips closer to the surface in others. And the South Atlantic Anomaly is the biggest dip of all. Spacecraft that are passing through the region often have to switch off some of their instruments to protect them from the harsh radiation.

A recent study found that the anomaly has gotten bigger over the past decade – by about half the area of continental Europe. So the space above that part of Earth is getting nastier – a bigger “danger zone” in the southern hemisphere.

We’ll have more about radiation hazards tomorrow.

Script by Damond Benningfield

To the eye alone, the Pleiades cluster looks like a small dipper of about seven stars – a few more if you have nice, dark skies. But when Galileo Galilei looked at it with his first small telescope, he saw a few dozen stars. It was one of the first indications that there’s far more to the universe than meets the eye.

You can share Galileo’s view with a basic pair of binoculars – no telescope required. They’re especially helpful tonight because of the Moon. It passes through the outskirts of the cluster, so it points the way. But the moonlight makes it tougher to see the stars.

The Pleiades is a family of perhaps a couple of thousand stars. The stars were all born together, from the same cloud of gas and dust. That makes the cluster a good laboratory. Since the stars all started with the same mix of elements, any differences among them are the result of their evolution – changes within the stars themselves. That helps astronomers understand how all stars change over the eons.

The cluster probably is a little more than a hundred million years old. That means it’s completed only about half an orbit around the center of the galaxy. During that time, it’s lost many of its original stars. And before it can complete one full orbit from its current location, it’s likely to evaporate – pulled apart by the gravitational tug of the rest of the galaxy.

Tomorrow: a growing “danger zone.”

Script by Damond Benningfield