StarDate

We live on a cosmic dust bunny – a planet built from grains of dust made of elements forged in the stars.

A star “fuses” lightweight elements in its core to make heavier ones. The process begins with hydrogen, the lightest and simplest element, followed by helium, the next element.

Near the end of its life, a star like the Sun makes carbon, oxygen, and nitrogen. When the star dies, it expels some of these elements into space. Stars that are more massive than the Sun make even heavier elements, all the way up to iron. These stars die in titanic explosions that build even heavier elements.

And collisions between massive stellar corpses forge some of the heaviest elements of all – things like gold and uranium. All of these elements blow out into space, where they can be incorporated into new stars and planets.

As these elements move outward, they can stick together to form solid grains, known as dust.

Our solar system was born from a giant cloud of gas and dust. Most of its material formed the Sun. But some of the leftovers formed a disk around the Sun. Dust grains in the disk stuck together to make bigger and bigger chunks.

Close to the Sun, these chunks coalesced to form Earth and the other inner planets. Farther out, they formed the cores of the planets, which then pulled in much of the leftover gas. So Earth and the other worlds of the solar system are cosmic dust bunnies – materials created by the stars.

Script by Damond Benningfield

The supergiant star Antares could use a supergiant dust mop. The star has created clumps of dust that can be more than a billion miles across. The dust can be both a help and a hindrance. It tells us something about the star itself. But it also makes it more difficult to see the “edge” of the star.

Antares is in good view early tomorrow, just a whisker away from the Moon.

The star is many times heavier than the Sun, hundreds of times wider, and tens of thousands of times brighter. But the exact details are hard to pin down. In part, that’s because it’s hard to pin down the star’s distance. One reason for the uncertainty is that Antares expels a lot of gas into space. That makes Antares look “fuzzy.” And the fuzzier a star looks, the tougher it is to measure its distance.

Sometimes, the gas is blown out in big clumps. Bubbles many times bigger than the Sun may well up from inside the star. As the blobs move farther from Antares, they get cooler. That allows atoms and molecules to stick together to make small solid grains of dust. The composition of the dust reveals some details about the star and its environment.

Astronomers have discovered several clumps of dust that are big enough to encompass most of our own solar system. They contribute to the uncertainty over the size of Antares – making it a little more difficult to pin down the details of this massive star.

We’ll have more dusty skies tomorrow.

Script by Damond Benningfield

Two bright orange stars pass high across the south this evening: Betelgeuse, at the shoulder of Orion the hunter; and Aldebaran, the eye of the bull, well to its upper right.

An even redder star perches below Orion’s feet, although you need binoculars or a telescope to see it.

Hind’s Crimson Star is one of the most remarkable stars in the galaxy. It pulses in and out like a beating heart. Each beat changes the star’s size by tens of millions of miles.

The star is quite near the end of its life. It no longer produces nuclear reactions in its core, although it does produce them in a thin shell around the core.

At a minimum, Hind’s Crimson Star is hundreds of times wider than the Sun. But the star is unstable. The energy from the shell around the core heats the star’s outer layers, causing them to puff up. As these layers expand, they cool, then fall inward again. Each cycle takes about 14 months.

The surface of the star is so cool that it shines reddish orange. But that’s not the only reason for its color. A lot of carbon has been dredged from its interior and pulled to the surface. The carbon absorbs blue light, enhancing the red.

Some of the carbon and other elements are being blown into space, forming a cloud of dust grains around the star. Eventually, the star’s outer layers will all blow away, leaving only its hot, dense core – a tiny stellar corpse known as a white dwarf.

Script by Damond Benningfield

Dying stars are among the most beautiful objects in the universe. They create colorful bubbles that can glow for thousands of years. And depending on our viewing angle, they can look like a butterfly, a cat’s eye, an hourglass, or other fanciful forms.

An example is NGC 3242. It’s known as the Eye Nebula, or the Ghost of Jupiter Nebula for its resemblance to the giant planet. In fact, because they look like planets, such objects are known as planetary nebulas.

They form when a Sun-like star reaches the end of its life. The star no longer produces nuclear reactions in its core, so the core collapses and becomes extremely hot. The radiation pushes away the surrounding layers of gas. They flow out into space, forming a nebula.

In the Ghost of Jupiter, the nebula consists of several shells of gas. They were expelled at different times, and they’re moving at different speeds. When a faster shell overtakes a slower one, the material heats up and emits X-rays. Over time, the nebula spreads out and cools, so it fades away.

The star at the center of the Ghost of Jupiter is hundreds or thousands of times brighter than the Sun. Soon, though, it will fade as well, becoming a hot but faint corpse – a white dwarf.

The Ghost of Jupiter is in Hydra, the water snake. The nebula climbs into view, in the southeast, by about 9 o’clock. Under dark skies, it’s just visible through binoculars, and an easy target for telescopes.

Script by Damond Benningfield

Whether you like your mythology impish or scary, the constellation Hydra has a story for you. It represents a serpent – a water snake or a dragon. It either got involved with a sneaky crow, or had to be destroyed by the strongman.

In one version, Hydra was a multi-headed monster that lived in a lake or a swamp. It roamed the countryside, eating livestock and causing other problems. It was so nasty that even its breath or a whiff of its blood could kill.

Heracles came to destroy the monster as one of his 12 labors. Every time he cut off one of its heads, though, two more grew in its place. Finally, his nephew brought a torch and seared each head as it was chopped off. That allowed Heracles – the Greek version of Hercules – to carry the day.

In the other version, the god Apollo sent a crow to fetch a cup of water. The crow detoured to gorge on figs. When he finally returned to Apollo, he blamed his tardiness on a water snake. Apollo wasn’t fooled, though. He hurled the crow into the sky, along with the snake and the water cup. He put the snake between the other two to prevent the lying crow from getting a cool drink of water.

Hydra is the largest and longest constellation. Its head is in the east in early evening, but its tail doesn’t clear the horizon until hours later. Only one of its stars is easily visible. You need dark skies to see any of the others.

We’ll talk about a dying star in Hydra tomorrow.

Script by Damond Benningfield

The Moon has an especially close companion at dawn tomorrow: Spica, the brightest star of Virgo. Depending on your location, they might be separated by as little as the width of a pencil held at arm’s length. And from some parts of the world, the Moon will briefly cover the star.

Spica is a binary – two stars locked in orbit around each other. They’re so close together that we can’t see them as individual stars.

If we could line up the Sun and the system’s main star, Spica A, at the same distance, Spica A would look more than 2,000 times brighter than the Sun. But that’s only part of the story. The surface of Spica A is tens of thousands of degrees hotter than the Sun. Such hot stars produce much of their light in the ultraviolet. If you add that to the equation, Spica A is about 20 thousand times the Sun’s brightness.

The star is so hot because it’s especially heavy – roughly a dozen times the mass of the Sun. Gravity squeezes the star’s core much more tightly than the Sun’s core. That makes the core extremely hot, which revs up its nuclear fusion reactions. Energy from those reactions heats the surrounding layers.

But such massive stars don’t live long. Spica A is only about 12 million years old, compared to four and a half billion years for the Sun. Yet it’s already completed the prime phase of its life. Within a few million years, it’s likely to explode as a supernova – a brilliant demise for a brilliant star.

Script by Damond Benningfield

The boldest and brightest of all constellations wheels across the south on February nights: Orion. It’s marked by the hunter’s bright belt of three stars, surrounded by a box of four bright stars.

One of the meekest and faintest constellations also wheels across the south on February nights. Caelum, the chisel, is due south in early evening. It sits directly atop the horizon for those at the middle latitudes of the United States, and a little higher for those farther south.

No matter where you are, though, it’s not much to look at – a few stars that are so faint that you need a dark sky to see them at all.

The constellation was created by Nicolaus Louis de la Caille. The French astronomer visited the southern tip of Africa in the 1700s. He made catalogs and maps of the southern stars. When he published his findings, he included 14 new constellations made from those stars. Most of them were named for scientific or artistic instruments.

La Caille named this constellation Caelum Sculptoris – “the engraver’s chisel.” Later, the name was shortened to just Caelum.

Its brightest star is actually two stars – a binary system about 65 light-years away. The main star is hotter and brighter than the Sun. Its companion is a red dwarf – a cosmic ember that’s not visible without a telescope. But even the bright star is barely visible – a pale dot in a pale constellation chiseled from the southern sky.

Script by Damond Benningfield

This might be Valentine’s Day, but some of the trappings of the day sound like they might be more suitable for Halloween. That’s because most of the gold in the universe – along with silver and platinum – may have been forged in collisions between dead stars.

Astronomers watched that process in action in 2017, when two neutron stars rammed together. That triggered a burst of gravitational waves – ripples in spacetime that were “heard” on Earth.

A neutron star is the tiny but ultra-dense corpse of a massive star. When two of them collide, they blast out huge amounts of matter. As the material cools, it builds up heavier elements – including gold.

Some of those elements are radioactive. As they decay, they glow, creating a kilonova – a fireball billions of times brighter than the Sun.

Telescopes saw the 2017 outburst less than two seconds after the gravitational waves arrived – the first time a source of the waves was seen in other forms. A recent study found that material from the blast was racing outward at almost half the speed of light.

Astronomers watched the formation of heavy elements almost minute by minute as the cloud of debris expanded. They couldn’t see the formation of gold itself, but they did see related elements. That allowed them to calculate the amount of gold that was created: enough to make 10 planets as heavy as Earth – perhaps providing the raw materials for future golden trinkets.

Script by Damond Benningfield

To nuke or not to nuke? That is the question: whether ’tis nobler to suffer the impacts of outrageous asteroids or to take arms against them, and by doing so end them. And a recent study says that, if necessary, nuke ’em.

When an asteroid a few miles wide hit Earth 66 million years ago, it wiped out the dinosaurs and most of the other life on our planet.

Such planet killers are rare, but they could still hit us. So scientists have studied ways to deflect them. With enough warning, we could pelt an asteroid with cannonballs – hunks of metal traveling at thousands of miles per hour. That could give the asteroid a big enough nudge to miss us.

If the asteroid is too big, or it’s discovered too late, the obvious solution seems to be nuclear weapons. But they have their own drawbacks – they might split an asteroid apart, pelting Earth with a bunch of big rocks instead of one giant one.

But a recent study by weapons experts found that an explosion in front of an asteroid might kick it away.

Researchers zapped some tiny simulated asteroids with X-rays in the Z Machine at Sandia National Laboratories – a device used to study nuclear weapons.

Script by Damond Benningfield

You don’t have to actually see something to know it’s there. You might feel it, hear it, or smell it. In other words, you use all your senses to suss it out.

Astronomers do that all the time. They may not see a star through their telescopes, for example, but they know it’s there because they use all their senses – special instruments that “see” what the eye cannot.

An example is Regulus, the brightest star of Leo. What we see as Regulus looks like a single point of light even through the largest telescopes. But instruments attached to those telescopes reveal a second star.

The instruments spread the light from the system into its individual wavelengths or colors – a spectrum. Each chemical element imprints a unique pattern in the spectrum. But Regulus shows two sets of those lines. And over time, the patterns move back and forth. That means Regulus has a companion just a few million miles away. The two objects orbit each other once every 40 days.

The companion is a white dwarf – the corpse of a once normal star. It’s much smaller and fainter than the system’s main star, and the two stars are quite close together. That makes it impossible to see the white dwarf through the glare. But we know it’s there – thanks to the extended senses of astronomy.

Regulus is quite close to the full Moon as night falls this evening. The Moon moves away from Regulus during the night, but they’re still close at dawn.

Script by Damond Benningfield