StarDate

On summer days, we sometimes complain that it’s hot enough to fry eggs on the sidewalk, the car, or any other exposed surface. On some planets in other star systems, though, it’s hot enough to vaporize the eggs, the sidewalk, and even the car. In fact, astronomers have discovered vaporized iron, nickel, and other metals in the atmospheres of several exoplanets.

All of these planets are giants — at least as big as Jupiter, the giant of our own solar system. That means they’re big balls of gas. And the planets are all quite close to their parent stars — no more than a few percent of the distance from Earth to the Sun.

At such close range, the atmospheres of these planets are heated to thousands of degrees. That means their daytime skies are free of clouds or hazes. On some of them, though, clouds may form on the nightside, where it’s cooler.

One planet where it’s too hot for clouds even at night is KELT-9b. It’s the hottest planet yet seen, with temperatures of more than 7,000 degrees. That causes the atmosphere to puff up, making KELT-9b about three times wider than Jupiter.

By watching as the planet passes in front of its star, allowing starlight to filter through the atmosphere, astronomers have measured what’s in the atmosphere. The list of elements includes iron, titanium, and chromium. It also includes a couple of “rare-earth” elements — scandium and yttrium — more metals for a blazing-hot planet.

Script by Damond Benningfield

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Like many rare-earth elements, vanadium could see a surge in demand in the coming years. It’s used in a type of battery at some wind- and solar-power stations. Such batteries aren’t all that common today. But they could become more common in the future.

Vanadium is the 20th-most-common element in Earth’s crust — found in minerals and in deposits of oil and gas. And astronomers have found another source — in a super-hot planet about 850 light-years away.

Metals have been seen in the atmospheres of several exoplanets. Such worlds are giants. And they’re so close to their parent stars that they’re extremely hot.

Astronomers measure what’s in the atmosphere by watching as a planet passes in front of the star. Starlight filters through the atmosphere, which adds the “fingerprint” of its own chemical elements. For WASP-121b, the list includes iron, nickel, magnesium — and vanadium.

The planet is just a couple of million miles from its star, so its atmosphere is heated to more than 4500 degrees. And the star acts as a blowtorch, blasting away some of the atmosphere — creating a fountain of hot metal.

WASP-121b and its star, WASP-121, are in the constellation Puppis, which is quite low in the south this evening. About 10 p.m., the system stands directly below Sirius, the brightest star in the night sky. But WASP-121 is so faint that you need a telescope to see it.

We’ll have more about metallic skies tomorrow.

Script by Damond Benningfield

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A lot of water is frozen in the Martian ice caps. And there may be a lot of liquid water below them. Such locations might be good places to look for signs of microscopic life.

Scientists discovered the first evidence of water below the south polar ice cap a couple of years ago. They used radar aboard a Mars-orbiting spacecraft to peer through the ice. It showed a possible pool of water almost 20 miles wide. It could be as little as a few inches deep, but it could be much deeper.

A more recent study, using several more years of observations, strengthened the evidence for that pool. And it found three more possible pools nearby — each of them a few miles wide.

The Martian atmosphere is too thin to allow liquid water to exist at the surface — it would quickly boil away. Below the ice caps, though, it’s a different story. The combination of high pressure and high levels of salinity may allow water to exist in liquid form for a long time — perhaps millions of years.

And as long as the levels of minerals in the water aren’t too high, it’s possible that the pools could support microscopic life — making them prime targets for future studies.

And Mars is in great view tonight. The planet is high in the south as night falls, above the Moon. It looks like a bright orange star. It’s a little closer to the upper right of the Moon as they set in the wee hours of the morning.

Tomorrow: rare metals in distant skies.

Script by Damond Benningfield

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One popular theme of 1950s sci-fi movies was rejuvenation. A woman would stay youthful by stealing various bodily fluids from others. And some stars do the same thing.

Blue stragglers are found mainly in globular clusters — densely packed families of stars. The clusters are old — more than 10 billion years. Blue stars, though, are hot and vigorous, so they burn out quickly. The only stars in these clusters today should be more sedate, so they should be fairly red. Any blue stars in the clusters, then, are oddballs.

Blue stragglers most likely have been rejuvenated — they’ve gained a youthful look by stealing the lifeblood of other stars.

Some of them probably have done so gradually. They have close companion stars. If the companion is more massive, it dies earlier. As it does, it puffs up, allowing the other star to take some of its gas. The recipient gets bigger and hotter. The higher temperature makes it look blue.

Others have gained the youthful look more dramatically — by merging with another star. The combined star is also bigger, hotter, and bluer — a single star rejuvenated by another.

The first blue stragglers were found in the cluster Messier 3 — a family of half a million stars about 34,000 light-years away. It’s in the constellation Canes Venatici, the hunting dogs, and is easily visible through binoculars. It climbs into good view in the east-northeast by midnight, and stands high overhead at dawn.

Script by Damond Benningfield

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The planet Mercury will lurk low in the evening sky over the next couple of weeks. It’ll lose a little bit of its brilliance each night. But it’ll also climb a little higher in the sky for the next few nights, making it a bit easier to find.

Mercury is the closest planet to the Sun. Since Earth is the third planet, Mercury always huddles close to the Sun in our sky. At best, it’s visible for a little while after sunset or before sunrise. And it spends most of the time in those viewing windows in the twilight.

It takes Mercury just 88 Earth days to orbit the Sun, so it moves across the sky in a hurry. That means you don’t have to look all that carefully to notice that it changes position from day to day.

This week, for example, if you look for it at the same time each evening, in the south-southwest not long after sunset, you’ll see it stairstep up the sky. The planet looks like a bright star, but it can be tough to find in the glow of evening twilight.

By early next week, though, Mercury will be dropping back toward the horizon — and the Sun. And it’ll be getting fainter from night to night, making it tougher to find. It’ll be gone from view by the end of January.

Mercury will cross between Earth and the Sun on February 8th, moving from the evening sky to the morning sky as it does so. And it’ll pull into view by late in the month — cycling across the sky in a hurry.

Tomorrow: rejuvenation for old stars.

Script by Damond Benningfield

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A star like the Sun is born as a big ball of hot gas. It then spends most of its life getting rid of much of that gas — either in a trickle, or in one giant gasp. The star system known as Procyon contains one star that’s completed that final gasp, and another that’s about to start.

Procyon is the eighth-brightest star in the night sky. Right now, it’s low in the east not long after nightfall. It’s well to the left or upper left of Sirius, the brightest star in the night sky.

The star we see is known as Procyon A. It’s about half-again as massive as the Sun, about twice as wide, and about seven times as bright. Like all stars, it blows a “wind” of hot gas off its surface. Right now, the wind is thin — there’s not a lot to it.

But Procyon A is about to end its “normal” lifetime and enter the next phase — as a giant. Its wind will become much thicker, surrounding the star in a thin cloud. And in a hundred million years or so, it’ll move into the final phase. It’ll expel all of its outer layers of gas over just a few thousand years. That will leave only the star’s dead core — a white dwarf.

That’s already happened to the other star in the system, Procyon B. It was born much heavier than Procyon A, so it aged more quickly. It blew away its outer layers more than a billion years ago. That left Procyon A with a dead companion — and a glimpse into its own future.

Tomorrow: A planet that sprints across the sky.

Script by Damond Benningfield

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The Sun can feel cold and remote at this time of year. But that’s not the case for a NASA spacecraft. It’s scheduled to fly less than nine million miles from the Sun tomorrow. That’s far closer than any other spacecraft has ever been.

Parker Solar Probe is designed to study the Sun’s magnetic field, plus the solar wind — a flow of charged particles that blows past Earth and the other planets. It recorded the interactions between the magnetic field and the solar wind during an earlier pass. It’s trying to find out how the wind is created.

It’s also trying to find out what heats the Sun’s outer atmosphere, the corona. It’s recorded “waves” produced as particles escape from the corona and join the solar wind.

Parker Solar Probe will accomplish those goals by getting closer and closer to the Sun. At its closest, in 2025, it’ll pass just 4.3 million miles from the Sun.

Reaching that point won’t be easy, though. The probe will fly past Venus several times, using the planet’s gravity to sculpt its orbit.

Parker carries a thick shield to protect it from the Sun’s heat. But it’s not exposed to the most intense radiation for long. When it’s close to the Sun it travels fast. Tomorrow, it’ll reach almost 300,000 miles per hour — fast enough to zip from coast to coast in about half a minute. Even so, it’ll be close to the Sun long enough to enhance our knowledge of our amazing star.

Script by Damond Benningfield

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Two “number threes” are swinging past each other in the evening sky. One of them is Mars, which looks like a bright orange star high in the south at nightfall. And the other is Uranus. It’s just a few degrees from Mars, but you need binoculars to pick it out.

The planets of the solar system are split into two groups of four — one group close to the Sun, the other farther out.

The close group comprises the small, rocky planets, including Earth. Mars is the third-largest planet in the group — a bit more than half the diameter of Earth. The far group consists of giant planets made of gas or ices. And Uranus is the third-largest planet in that group, at four times Earth’s diameter.

Mars and Uranus are so different because they formed in different regions. Mars was born close to the Sun, where conditions were hotter. Radiation and winds from the young Sun cleared out most of the lighter elements, leaving only heavier ones. So Mars and the other inner planets are made of rock and metal.

Uranus formed far from the Sun, where it was much colder. The Sun couldn’t clear away the lighter elements in that region, so many of them glommed on to the newly forming planets — helping them grow to giant proportions.

Tonight, look for Uranus to the left of Mars by a bit more than the width of your finger held at arm’s length. Mars will move closer to Uranus over the next few days, and pass over the top of it a week from tonight.

Script by Damond Benningfield

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A couple of planets lead the Moon down the sky after sunset. Both planets are bright. But they’re quite low in the sky, so they’ll be hard to see. You need a clear horizon — no trees or buildings to block the view. And binoculars can help you pick them out.

Start looking soon after sunset. First find the Moon, which is the barest of crescents. The Sun lights up only a sliver of the side of the Moon that faces our way. As the sky darkens, though, you should easily make out the rest of the lunar disk. That’s because it’s illuminated by earthshine — sunlight reflected from a nearly full Earth.

Scan to the lower right of the Moon for Mercury. It’s the closest planet to the Sun, so it never moves far from the Sun in our sky. It’s putting in a pretty good evening appearance, though. It’ll climb higher above the horizon for several nights before it heads back toward the Sun. So if you don’t spot Mercury this evening, you’ve still got some time.

That’s not the case for Jupiter, which stands to the lower right of Mercury. It’s the largest planet in the solar system, and it shines brightly. But you won’t see it unless you have a clear horizon. And it won’t be around much longer — it’ll vanish any day now.

The view of this challenging lineup will be a little better from more southerly locations, where the Moon and planets align at a better angle. Even so, the planets will be tough to spot through the evening twilight.

Script by Damond Benningfield

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A huge star in Canis Major, the big dog, is getting ready to flood the interstellar market with huge supplies of chemical elements — everything from carbon and oxygen to silicon and iron. In fact, it’ll dump enough material to make several stars as massive as the Sun.

Wezen is Canis Major’s third-brightest star. It rises directly below the top dog, Sirius — the brightest star in the night sky. They’re in good view in the southeast by 8 or 8:30.

Wezen is a supergiant. It’s so large that if it took the Sun’s place in our own solar system, it would extend all the way out to Earth. It’s also more than 15 times as massive as the Sun. That extra weight squeezes the star’s core, heating it and revving up its nuclear “engine.”

And that’s what makes Wezen such a busy chemical factory. Stars fuse together lightweight elements in their cores to make heavier ones. They do so in stages. In the first, they fuse hydrogen to make helium. Next, they fuse the helium to make carbon, oxygen, and nitrogen. Stars like the Sun stop there. But heavy stars make even heavier elements — all the way up to iron.

When the core is converted to iron, it takes more energy to make heavier elements than the star can produce. So fusion stops and the core collapses. The outer layers then explode as a supernova. That expels many of the elements created inside the star into space — which is just what will happen with Wezen in a few million years.

Script by Damond Benningfield

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