StarDate

The stars are quite literally desirable. That’s because the roots that make up the word desirable mean “to long for a star, heavenly body, or constellation.”

Astronomy has a rich vocabulary: star, planet, galaxy, and many other words. Many of them also have non-astronomical meanings. A “galaxy of stars,” for example, might refer to an auditorium full of actors – though how many of them can be considered “stars” is a matter of opinion.

Some words with heavenly connections seem obvious. “Lunatic” refers to the Moon. It comes from an ancient belief that the Moon’s influence could make people behave strangely. And “jovial” – to be full of good cheer – means “of Jupiter;” in ancient astrology, the planet was thought to exert a happy influence.

Other words have more surprising connections to the stars. Consider “consider.” Its roots mean “to observe the stars.” “Sider” is from a Latin word that means “star, heavenly body, or constellation.” In fact, many words with some version of the root have a link to the stars – including desire.

Disaster also comes from ancient astrology. It meant an unfavorable position for a star or planet. “Aster” was a Latin word for star.

The word “influence” appeared in the 14th century. Dictionaries say it meant “streaming ethereal power from the stars when in certain positions, acting upon the character or destiny of men” – a good description of modern-day “influencers.”

Script by Damond Benningfield

To the eye alone, Spica is one of the 15 brightest stars in the night sky. And it really is brilliant. At visible wavelengths, it’s about 2,000 times brighter than the Sun. It looks white with a hint of blue.

When you look at Spica with special instruments, though, it’s even more impressive. It consists of two stars, not one. Both are much bigger and heavier than the Sun. And when you add up all wavelengths of light, they shine about 20 thousand times brighter than the Sun.

Most of that energy is in the ultraviolet – wavelengths that are too short for the human eye. Spica’s two stars produce so much of it because their surfaces are tens of thousands of degrees hotter than the Sun’s.

In fact, the type of energy a star emits depends almost entirely on its surface temperature. And so does the star’s color. To the eye alone, the hottest stars look blue. But they emit huge amounts of ultraviolet. The coolest stars look orange or red. They emit huge amounts of infrared light – wavelengths that are too long for the human eye.

Stars in the middle are white or yellow. They emit most of their light at visible wavelengths. So with a star like the Sun, we see most of the energy it produces – light that’s just right for the human eye.

Spica is quite close to the Moon as darkness falls this evening. The Moon will slide away from the star during the night, but they’ll still be close as they set, around dawn.

Script by Damond Benningfield

Aldebaran is like a reverse time capsule. Instead of preserving mementos from the past, the star shows us what we can expect in the distant future – the far, far distant future. It’s in a phase of life that the Sun will pass through in several billion years.

Aldebaran marks the eye of Taurus, the bull. It’s low in the western sky as evening twilight fades. It’s a little to the left of Venus, the brilliant “evening star.”

The Sun is in the prime phase of life. It’s steadily “fusing” the hydrogen atoms in its core to make helium. That produces the energy that makes our star shine.

Aldebaran has already completed that phase. Its core has converted the hydrogen to helium. Now, the star is fusing the hydrogen in a thin layer around the core. This layer is especially hot. Its radiation pushes outward on the surrounding layers of gas. That’s caused Aldebaran to swell to about 45 times the Sun’s diameter. And that’s made the star more than 400 times brighter than the Sun.

Over many millions of years, Aldebaran will use up that shell of hydrogen. Nuclear fusion will then fire up in the helium core, briefly making the star even bigger and brighter. After that, fusion in the core will begin to shut down. Aldebaran’s outer layers will blow away, briefly forming a colorful bubble. As the bubble dissipates, only the star’s now-dead core will remain – a final memento of a once impressive star.

Script by Damond Benningfield

A giant star in a galaxy more than a billion light-years from Earth died a spectacular death. Then it might have died again – an event that was even more spectacular than the first. The double demise earned it a doubly impressive title: a superkilonova – two powerful explosions from a single star.

The system was discovered last August. It produced a huge outburst of gravitational waves – ripples in spacetime. Astronomers first thought it was a kilonova – the violent merger of two super-dense corpses known as neutron stars. Such mergers produce huge amounts of the heaviest elements in the universe, including gold, platinum, and uranium.

After a few days, though, the event began to look more like a type of supernova – the explosion of a star much heavier than the Sun. But as astronomers followed the outburst with a dozen telescopes on the ground, one team suggested that it might have been both.

The supernova came first. The massive star’s core collapsed to make a neutron star. Its outer layers then blasted into space.

But the collapsing core might have split apart to make two neutron stars, not one. Or the second neutron star might have come together from debris around the first one. Either way, the tiny but massive neutron stars quickly spiraled together. That set off the second blast – a kilonova.

There are other possible explanations for the object. But for now, a superkilonova tops the list.

Script by Damond Benningfield

A pair of ancient but faint constellations flows across the southern evening sky at this time of year. The two of them share a common story, which also involves a third constellation.

Corvus and Crater have been around for more than two millennia. Their story, in fact, comes from ancient Greece.

According to the myth, the god Apollo sent Corvus, the crow, to fill a cup – known as a crater – with water from a nearby spring. On the way, the crow saw a tree filled with unripe figs. Instead of fetching the water and coming straight back, he waited for the figs to ripen. When they did, he gorged on them.

Corvus knew that Apollo wouldn’t be happy with him. So he filled the cup with water, then grabbed a water snake in his talons. He brought both back to Apollo, and blamed the snake for blocking his way. But Apollo wasn’t fooled. Instead, he was angry and vengeful. He cast crow, cup, and snake into the heavens, forming three constellations. As extra punishment, he decreed that the crow would suffer from thirst – with the water-filled cup forever just out of reach.

The constellations are in the southeast at nightfall now. Corvus contains four moderately bright stars that outline the shape of a sail. Crater, to the upper right, looks like a goblet – but you need really dark skies to see it.

Both of them sit on the back of poor Hydra, the water snake – an innocent victim of the wrath of the gods.

Script by Damond Benningfield