StarDate

Any residents of a galaxy in the constellation Serpens have a big problem: They’re being blasted by a death ray from a black hole.

The galaxy is a companion to a bigger galaxy, known as 3C321. They’re more than a billion light-years away.

A supermassive black hole inhabits the heart of the larger galaxy. It’s surrounded by a giant disk of gas that’s heated to millions of degrees. Powerful magnetic fields funnel charged particles from the disk into jets. They squirt away from the poles of the black hole at almost the speed of light.

One of those jets is firing toward the companion galaxy, which is just 20,000 light-years away. Observations by telescopes on the ground and in space show that the jet is hitting the edge of the companion, creating a hotspot. The encounter deflects the beam off its original course, but the beam continues for hundreds of thousands of light-years.

The particles and radiation in the beam could destroy the ozone layer of any planet the beam hits. That would leave the planet exposed to radiation from the beam itself, and from other cosmic sources. So anything living on the planet would be in danger.

And the situation is getting even worse. The smaller galaxy appears to be just entering the black-hole jet. Over time, more of the galaxy will pass through the jet – possibly exposing even more planets to this “death ray” from another galaxy.

Script by Damond Benningfield

The sky is divided into 88 official constellations. In fact, though, it’s more like 88 and a half. That’s because the constellation Serpens consists of two disconnected parts – a head and a tail. They wrap “behind” the body of Ophiuchus the serpent bearer.

Serpens is in full view in the east and southeast by a couple of hours after sunset. The half that represents the head is highest, above Ophiuchus, with the tail below the serpent bearer.

The front of the snake, Serpens Caput, is the more prominent half. It has several stars that are fairly easy to see. The brightest is Alpha Serpentis, also known as Unukalhai – “the serpent’s neck.” It’s a red giant – an old, bloated star that’s much bigger and brighter than the Sun. Its surface is much cooler than the Sun’s, so the star looks yellow-orange.

The back half of the snake, Serpens Cauda, is tougher to spot. Its brightest star, Eta Serpentis, is the second-brightest star in the whole constellation. It’s about half as bright as Alpha. But the two stars are quite similar. Eta is also a giant – a puffed-up star that’s nearing the end of its life. It’s a little farther along than Alpha, so it’s a little bigger and brighter. It looks fainter because it’s farther away.

The two stars will end their lives in the same way. Each will cast its outer layers into space, leaving behind a hot but tiny corpse known as a white dwarf.

More about Serpens tomorrow.

Script by Damond Benningfield

Venus and Jupiter are staging one of the top skywatching events of the year – an especially close encounter of the two brightest points of light in the night sky. It plays out in the west over the next few evenings.

Venus is the beautiful “evening star” – the brightest object in the night sky after the Moon. Jupiter is the next-brightest. Even so, right now it’s only about one-seventh as bright as Venus, so it’s easy to tell them apart.

The two planets can pass especially close because both of them stay near the ecliptic – the Sun’s path across the sky. They pass by each other every year or so. But both worlds wander a little bit to either side of the ecliptic, so they usually just miss each other. And even when they are close, they’re sometimes so near the Sun that we can’t see them.

At times, though, Venus can pass in front of Jupiter, blocking it from view That last happened in 1818. It’ll happen again in 2065. But that’s one of those times when they’ll be too close to the Sun to see.

Tonight, Jupiter is close to the upper left of Venus. But over the coming evenings, Venus will overtake it. They’ll stand side by side on Sunday, and be especially close on Monday and Tuesday – separated by about the width of your finger held at arm’s length. They don’t drop from view until about 10:30 or 11, so there’s plenty of time to watch this impressive planetary encounter.

Script by Damond Benningfield

The night sky can sometimes look like a tie-dyed T-shirt flapping on a clothesline. Ribbons and swirls of bright color ripple through the sky. They can change appearance in seconds – blown by the solar wind.

The colorful display is an aurora – the northern and southern lights. An aurora flares to life as charged particles from the Sun run into Earth at high speed.

Earth’s magnetic field funnels the particles toward the magnetic poles. When particles hit atoms and molecules high above the surface, they knock atoms out of their usual configuration. When they return to normal, the atoms emit light.

The color of an aurora depends on what the charged particles hit, and where they hit it. Most auroras are green. They switch on when particles hit oxygen molecules at altitudes of about 60 to 200 miles. Red auroras are fed by oxygen that’s even higher.

The lower fringes of a display can appear pink or dark red – the result of collisions with nitrogen at lower altitudes. Collisions with hydrogen and oxygen create blue and purple auroras. But they’re not very common, and they’re hard for the eye to take in. They’re easier to see in photographs.

Most of the time, the northern lights stay close to the magnetic pole. When the Sun spews out more particles, though, they can spread outward, shining in regions where they’re seldom seen. And the colors can get more intense – dramatically “tie-dying” the night sky.

Script by Damond Benningfield

The goddess of the dawn has given millions of Americans a rare treat the past couple of years: brilliant displays of the northern lights in regions where they’re seldom seen. Today, we know that these colorful curtains of light are powered by storms on the Sun. Bigger storms expand the viewing area. But in centuries past, cultures around the globe created their own explanations.

In Scandinavia, for example, the northern lights might have represented Bifrost, the “rainbow bridge” that connected Earth to Asgard, the home of the gods. In some of the islands of Scotland, the lights represented a pair of chieftains fighting for the hand of a “merry dancer.”

In southern England, they were considered omens of misfortune. Some saw the lights as clashing swords; red lights were streamers of blood. During an intense outburst in March 1716, at the end of a civil war, people ran into the streets in their nightclothes, and some thought it was judgment day. One writer said that some “read in its glaring visage, the fate of nations and the fall of kingdoms.”

The name for the northern lights – the aurora borealis – was bestowed in 1619 by Italian astronomer Galileo Galilei. Aurora was the Roman goddess of the dawn. Boreas was the Greek god of storms and the north wind – one of the namesakes of the always beautiful, sometimes frightening northern lights.

More about the aurora tomorrow.

Script by Damond Benningfield