StarDate

The stars at night, are big and bright, deep in the heart of Texas — or at least in West Texas. A new “dark skies reserve” encompasses about 15,000 square miles of western Texas and northern Mexico. It acknowledges that the night sky is already dark, and can help keep it dark in the years ahead.

Proper nighttime lighting provides a lot of advantages. It’s good for the ecosystem, because too much light can interfere with the migrations of birds and other animals. It’s good for public safety because light is directed where it’s needed — on the ground. It’s good for astronomy because extra light can spoil the view of stars and galaxies. And it’s good for astro-tourism because dark skies attract stargazers from the world over.

McDonald Observatory and other groups in West Texas and northern Mexico have helped keep the night sky dark. They’ve worked with governments to enact rules that require good nighttime lighting, and with the oil industry and others to change the way they light their operations.

That led to the creation of the Greater Big Bend International Dark Sky Reserve. It was certified by the International Dark-Sky Association, which works to preserve dark night skies around the world. It’s the largest dark sky reserve in the world. It recognizes the work done to keep the night sky dark. And it provides a model for other regions of the world — keeping the night skies dark well beyond the heart of West Texas.
 

Script by Damond Benningfield

Support McDonald Observatory

Every couple of decades, the star system V2487 Ophiuchi produces a massive explosion. Gas that’s piled up on one of its stars is blasted into space, making the system shine thousands of times brighter than average. The last such outburst was seen 24 years ago today, in fact.

But you don’t have to wait that long to see fireworks from the system. About once a day, it produces a “superflare” — a deadly outburst of radiation that dwarfs anything seen from the Sun.

The system consists of two stars. One is similar to the Sun, while the other is a white dwarf — the dead core of a once normal star. They’re so close together that the white dwarf “steals” gas from the other star. The gas forms a disk around the white dwarf.

Because the stars are so close, the companion spins rapidly. That generates a powerful magnetic field. And according to a study by astronomers at LSU, that’s the source of the superflares. Magnetic field lines extend into the disk around the white dwarf — or even to the white dwarf itself. The lines quickly become twisted and tangled. Then they snap, releasing huge amounts of energy — a superflare.

The largest one yet seen was 20 million times more powerful than the largest flare ever seen on the Sun. And a typical flare is about 10 times larger than those seen from any other star. The flares would strip away the atmospheres of orbiting planets, and destroy any life — making V2487 Ophiuchi a place to avoid.
 

Script by Damond Benningfield

Support McDonald Observatory

Getting to know an exoplanet takes time. As an example, consider a planet in the constellation Ophiuchus. Astronomers have compiled quite the dossier on the planet. But they still have a lot to learn.

Gliese 1214b orbits a red dwarf — a cool, faint cosmic ember. The system is about 48 light-years away. That’s close by astronomical standards, which is one reason the planet has attracted so much attention.

It was discovered in 2009. It passes in front of its star once every 1.6 days, blocking some of the star’s light. That’s allowed astronomers to measure its size: a little less than three times the diameter of Earth. And they’ve used another technique to figure out the planet’s mass: a bit more than eight times Earth’s mass.

As the planet passes in front of its star, some of the starlight filters through its atmosphere. That’s provided some hints about the atmosphere’s composition. But the atmosphere is topped by a thick haze, so astronomers can’t see what’s underneath.

One recent study posited that the planet itself is dense and heavy, like Earth, with a big iron core. It’s topped by an atmosphere of hydrogen and helium that’s thousands of miles thick, and could have changed little since the planet was born.

But other scientists have proposed other models — including some in which the planet has a lot of water. So it’s going to take a lot more time to really get to know Gliese 1214b.
 

Script by Damond Benningfield

Support McDonald Observatory

Mercury is the closest planet to the Sun, so its surface can be scorching — hot enough to melt lead. But Mercury doesn’t have an atmosphere, so the heat isn’t carried around the entire planet. So regions that never see the Sun can be extremely cold — cold enough for slabs of ice at or near the surface.

The cold spots are found at the poles. The bottoms of some craters there never see the light of day, so they stay cold all the time. And a few spots between the craters stay in the shadows as well.

Astronomers discovered the ice decades ago by bouncing radar beams off Mercury’s surface. The echo of ice is different from that of rock and dirt. A spacecraft in orbit around Mercury confirmed the radar findings.

A recent study revealed more details about the ice. Astronomers had used the giant Arecibo radio telescope in Puerto Rico, which collapsed in 2020. They found that some of the ice in craters at the north pole was almost pure water. And they found possible new deposits in regions where no ice was expected. But some of the pure ice was surrounded by ice that was mixed with dirt. That could change ideas about how and when this hot planet got its cold spots.

Mercury is just peeking into view now. It’s low in the eastern sky as twilight brightens. It’s well to the lower left of Venus, the “morning star.” It’ll climb a bit higher over the next few days. The view is better from the southern parts of the country than the northern.
 

Script by Damond Benningfield

Support McDonald Observatory

The Moon takes aim at the heart of the scorpion tonight — the bright star Antares. It’s below the Moon at nightfall, but closer to the left of the Moon as they set, in the wee hours of the morning.

The region around Antares is filled with young stars. Many of them, like Antares, are big and bright. And the region also may be filled with planets. A recent study reported dozens of possible “rogue” planets — worlds that don’t orbit a star.

Because they’re far away from any stars, the free-floating planets reflect almost no starlight, making them faint. But the planets are young, so they’re still warm. That means they produce a glow of their own, mainly at red and infrared wavelengths. Astronomers discovered the possible planets by analyzing 20 years of observations by telescopes on the ground and in space.

It took some careful work to pick out the planets. But the astronomers reported finding about 70 planets that were roughly as massive as Jupiter, the giant of our own solar system. And they found as many as a hundred more objects that could also be planets.

The planets could have formed as a cloud of gas and dust that was too small to make stars collapsed to form smaller bodies. On the other hand, the planets could have been born around stars, then kicked away by encounters with other planets. Or perhaps there’s some other explanation for the wayward planets in that busy region of the galaxy.

Script by Damond Benningfield

Support McDonald Observatory

Aquila, the eagle, spreads its wings across the evening sky as we head into summer. Right now, it’s low in the east a couple of hours after sunset. Its brightest star, Altair, is at the bottom right point of the wide-spread Summer Triangle. Altair represents the eagle’s breast, with its wings above and below.

A pair of stars at one of the wingtips faces a spectacular future. The two stars will ram together, then explode as a supernova — in about 700 million years.

The system is known as Henize 2-428. It consists of two white dwarfs — the dead cores of once-normal stars like the Sun. They’re only a few hundred thousand miles apart — so close that they orbit each other once every four hours. As they orbit, though, they radiate gravitational waves — a process that causes them to spiral closer and closer.

Each of the stars is a bit less massive than the Sun. So when they merge, they’ll be almost twice as massive as the Sun. And for a white dwarf, that’s a bad thing. With that much mass, the white dwarf can’t hold itself together. It undergoes a runaway nuclear reaction that blows the star to bits.

Such an explosion is known as a supernova, and it’s extremely bright. For a few hours, the explosion may shine as brightly as the rest of the stars in the galaxy combined. The exploded stars will leave behind an expanding cloud of debris that will glow for thousands of years — the last hurrah of a pair of doomed stars.
 

Script by Damond Benningfield

Support McDonald Observatory

A mismatched pair of planets huddles close together the next few mornings. One of them is brilliant but small; the other is faint but giant.

Venus and Uranus are low in the east at dawn. Venus is the “morning star” — the brightest object in the night sky other than the Moon — so you can’t miss it. Tomorrow, Uranus is less than two degrees to its upper left — about the width of your finger held at arm’s length. But Uranus is so faint that you need binoculars to pick it out. It looks like a faint star.

The difference in brightness is mainly the result of the different distances of the two planets. Uranus is more than 15 times farther from Earth right now. It’s also 25 times farther from the Sun, so it receives a lot less sunlight. Yet Uranus is more than four times wider than Venus. So if you lined them up side by side, Uranus would far outshine Venus.

Seen through a telescope, Uranus looks blue green. That’s the result of methane in its upper atmosphere. It absorbs red light, allowing only bluer wavelengths to reflect out into space. Hazes of methane and other compounds also block the view of cloud features in the atmosphere, so Uranus generally looks like a smooth, bland marble.

Venus and Uranus will be about the same distance apart on Sunday morning. After that, though, the gap between them will get bigger, as Venus slides to the lower left — leaving its giant but faint companion behind.
 

Script by Damond Benningfield

Support McDonald Observatory

An impressive star system snuggles close to the Moon tonight. Spica, the brightest star of Virgo, is to the lower left of the Moon as night falls, and they move even closer later on.

Although it looks like a single point of light, Spica is really two stars. They’re separated by just a few million miles. Each of them is much bigger, heavier, and hotter than the Sun, and thousands of times brighter.

There’s no evidence of planets around the stars. If any exist, they probably orbit both stars, not a single star.

To have conditions that are comfortable for life, the planets would have to be billions of miles out — a hundred times farther than Earth is from the Sun.

Even if such worlds had life, it might not look familiar. That’s because the stars emit huge amounts of ultraviolet radiation — the form of energy that causes sunburn and skin cancers. Earth is protected from the Sun’s ultraviolet energy by ozone in the atmosphere. But it’s unlikely that a planet could have enough ozone to protect it from the intense ultraviolet from the stars of Spica. So if there were life, it would have to adapt to the radiation, so it probably would be very different from anything on Earth.

One other complication is that Spica’s stars are much younger than the Sun is. So even if they have planets, it’s unlikely that there’s been enough time for life to evolve around these bright stars.

Tomorrow: mismatched planets at dawn.
 

Script by Damond Benningfield

Support McDonald Observatory

The Cat’s Eye Nebula isn’t just nice to look at, it’s nice to listen to as well. Scientists have converted images of the nebula to sound, providing a new way to appreciate its beauty.

The nebula is the final gasp of a dying star. The nuclear reactions in the star’s core are shutting down, so it’s pumping its outer layers of gas out into space. That’s formed a complicated series of bubbles and shells. The central bubbles are bright and colorful, and resemble the eye of a cat.

It’s surrounded by more bubbles, nested one inside the other. They may have formed at intervals of about 1500 years, as the star blew them into space. If so, then the first one began forming about 15,000 years ago as seen from Earth. The bright central bubbles began forming just one thousand years ago, and signal the star’s demise. Eventually, only its hot but dead core will remain: a white dwarf.

Astronomers converted images of the nebula to sound. The sounds represent different wavelengths, and the intensity of the different parts of the image. They scan from the center of the nebula like a radar beam — providing a new way to appreciate this beautiful dying star.

The Cat’s Eye Nebula is in Draco, the dragon, which coils around Polaris, the North Star. The nebula is off to the upper right of Polaris at nightfall, and is a popular target for small telescopes.
 

Script by Damond Benningfield

Support McDonald Observatory

Asteroids hit Earth all the time. Most of them are so small that they burn up in the atmosphere. But a few either explode in the air or slam into the surface. That can cause damage ranging from broken windows to extinction of most of Earth’s life.

So scientists have been working on ways to protect us from potential impacts. If an asteroid or comet is far enough out, we might be able to nudge it into a safe orbit. If it’s closer, we might have to nuke it. And a new idea is designed to save us from impacts that are weeks or even hours away.

The concept is headed by Philip Lubin of the University of California-Santa Barbara. It would deploy “kill vehicles” in Earth orbit or on the Moon. If an asteroid or comet was detected on a collision course with Earth, a vehicle would intercept it. It would blast out thousands of tiny bits of shrapnel. They’d tear into the object, ripping it apart. The fragments would either miss Earth or enter the atmosphere and burn up.

NASA has funded a study of the concept. The team says it could potentially destroy an asteroid or a comet up to a kilometer in diameter with as little as 60 days warning. Smaller but still hazardous targets could be intercepted in as little as days or even hours.

Such a system would take years to develop and deploy. And it might face challenges from space treaties. Yet it’s one more possible weapon in the fight to protect Earth from deadly cosmic missiles.
 

Script by Damond Benningfield

Support McDonald Observatory