StarDate

For Charles Messier, star clusters were a nuisance. The French astronomer was mainly interested in comets. In the 18th century, finding a comet could bring fame and fortune – kings sometimes awarded medals and fat stipends for their discovery.

Through a telescope, star clusters could resemble comets. Messier and others might spend time following a cluster, only to find out that it wasn’t the prize. So Messier compiled a catalog of clusters and similar nuisances – a list of objects to ignore.

Four of the clusters follow a narrow path near Canis Major, the big dog: M46, 47, 48, and 50 – a Messier “highway.”

Although they’re close together in our sky, the clusters are not close together in space. Their distances range from about 1600 light-years to more than five thousand. So there’s no relationship among them.

They appear close together because they all lie along the Milky Way – the glowing outline of the disk of the Milky Way Galaxy. In that direction, we’re looking into the most densely populated region of the galaxy, so we see many more stars and star clusters – including the “pesky” clusters cataloged by Charles Messier.

The clusters are in the southeastern quadrant of the sky as night falls. Look for Sirius, the brightest star in the night sky, due south. The clusters spread out to the left and upper left of Sirius. All of them are easy targets for binoculars.

Script by Damond Benningfield

Winter brings out the big dogs – some of the most prominent constellations of all. And one of those really is a dog: Canis Major, the big dog. It’s best known for Sirius, the Dog Star – the brightest star in the night sky. It’s a third of the way up the southern sky at nightfall.

But there’s much more to Canis Major than just Sirius. It includes several bright stars, most of which are below or to the right of Sirius. When you link them up, they do form the outline of a dog.

Like all constellations, Canis Major consists of more than just a connect-the-dots pattern of stars, though. It covers a patch of sky that includes everything within its borders. And in that area, you can find several deep-sky objects – objects like star clusters, which are far beyond most of the individual stars visible in Canis Major.

Perhaps the best known is Messier 41. It’s not far below Sirius, and it’s an easy target for binoculars. It’s about 2300 light-years away, and includes a hundred or more stars.

The cluster probably is about 200 million years old. At that age, its biggest, heaviest stars have expired. They’ve left behind small, dense corpses known as white dwarfs. The next-heaviest stars soon will follow the same path. Those stars have puffed up to become red giants. They’re easily visible through binoculars – sparkling red and orange jewels along the “collar” of the big dog.

More about Canis Major tomorrow.

Script by Damond Benningfield

A magazine that first hit newsstands 100 years ago today was unlike anything readers had seen before. Its cover featured a brightly-colored painting of people ice-skating on a comet as it zoomed past Saturn. Its founding editor, Hugo Gernsback, called it “a new sort of magazine” – “a magazine of ‘scientifiction'” – a genre known today as science fiction.

Amazing Stories was the first magazine dedicated solely to the genre. Its debut issue, which was dated April 1926, carried reprints of stories by Jules Verne, H.G. Wells, Edgar Allen Poe, and others. The story titles included “The Man from the Atom” and “The Thing from – Beyond.”

The magazine was an instant hit. Within a year, monthly circulation was at 150,000. Other publishers quickly caught on, and began publishing many more sci-fi magazines. Over the decades, they included such titles as Fantastic, Astonishing, and Astounding. They featured many of the major figures of science fiction’s “golden age.”

Their inventive stories and eye-catching covers caught the attention of lots of youngsters. The magazines inspired many of them to pursue careers in astronomy, physics, engineering, and related fields. They also inspired future filmmakers, who expanded “scientifiction” far beyond the printed page.

Few science-fiction magazines have survived. But their influence is still felt today – on Earth – and beyond.

Script by Damond Benningfield

A future super-giant “onion” perches close to the Moon at dawn tomorrow. It’s the star Antares, the bright heart of the scorpion – one of the most impressive stars in the galaxy.

Antares is a supergiant. It’s roughly a dozen times as massive as the Sun, and hundreds of times wider. Because it’s so heavy, gravity squeezes its core tightly. That revs up the nuclear fusion in the core.

Like all stars, those reactions initially fused hydrogen to make helium. In the Sun, hydrogen fusion will last about 10 billion years. In Antares, though, it lasted a little more than 10 million years.

When the hydrogen in the core was gone, the core shrank, making it hotter – hot enough for the helium to fuse to make carbon and oxygen. That process will last about one million years. Then the carbon will fuse to make heavier elements, and so on. Each step takes less time than the one before. In the final step, silicon will fuse to make iron – a step that takes just a few days.

The lighter elements won’t all go away, though. Instead, the “ash” from each step will form layers around the core – like an onion. But that structure won’t last. The core can’t get hot enough to fuse the iron. Gravity will win out, and the core will collapse – forming an ultra-dense neutron star.

Everything outside the core will blast outward at a few percent of the speed of light. Supergiant Antares will explode as a supernova – an impressive end for an impressive star.

Script by Damond Benningfield

Canopus would be a terrible neighbor. The star is big, bright, and hot, so it might blow away any planet-making materials around nearby stars. Even worse, it may be destined to explode. That would zap any existing planets with radiation – perhaps endangering any life in nearby star systems.

Canopus is the second-brightest star in the night sky. At this time of year, it’s visible from the southern third of the United States in early evening. It’s low in the south, well below Sirius, the brightest star.

Canopus is at least eight times the mass of the Sun. So even though it’s billions of years younger than the Sun, it’s already completed the main phase of life. Within a few million years, its core will collapse, perhaps forming an ultra-dense neutron star. If so, then its outer layers will blast into space as a supernova.

Such an outburst would produce enormous amounts of X-rays and gamma rays – the most powerful forms of energy. That could strip away the ozone layer of any planet within a few dozen light-years, subjecting the surface to high levels of radiation.

So far, we know of only one planet within that range where conditions are most suitable for life. The planet itself isn’t likely to host life. But any big moons might be more comfortable homes – at least until the demise of Canopus.

Luckily for us, Canopus is 300 light-years away. So Earth is well outside the “danger zone” of this not-so-neighborly neighbor.

Script by Damond Benningfield