StarDate

One of America’s first astronauts never flew in a NASA spacecraft, and never became a household name. Yet he was the first person to reach outer space more than once.

Joseph Walker poses with the X-15

In 1958, after the Soviet Union launched the first satellite, the Air Force launched a program to send the first person into space. It was called Man in Space Soonest. The service picked nine astronauts to fly it, including Walker.

Soon after that, though, NASA was created, and it was given the job of sending men into space. It picked its own astronauts. And only one of the Air Force group joined NASA’s astronaut corps: Neil Armstrong, the first person to walk on the Moon.

Walker became chief test pilot for the X-15 rocket plane. In 1963, he flew higher than 50 miles three times — an altitude that met the Air Force definition of “space.” And two of those flights passed 100 kilometers — the international definition of space.

Walker died in 1966. He was flying in formation with an experimental bomber for a photo session. His fighter jet clipped the bomber’s wing, flipped over, and exploded — a tragic ending for one of America’s first astronauts.

Script by Damond Benningfield

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It’s a bit hard to believe when you look at it, but we’re not seeing the star Aldebaran at its best.

Aldebaran stands to the lower right of the Moon this evening. It shines brightly even through the lunar glare. In fact, it’s the 14th-brightest star system in the night sky, so it’s always easy to spot.

At visible wavelengths, Aldebaran shines about 150 times brighter than the Sun. That’s mainly because the star is much bigger than the Sun, so there’s a lot more surface area to radiate light into space.

When you add up all wavelengths of light, though, Aldebaran is about 450 times brighter than the Sun. Most of that energy is in the infrared, which is invisible to the human eye.

That, too, is a result of Aldebaran’s great size. The star is nearing the end of its life, causing its outer layers to puff up to giant proportions. As those layers expanded, they also got cooler — much cooler than the Sun. That lower temperature gives Aldebaran its orange color — cooler stars are orange or red, while hotter ones are blue or white.

Cooler stars radiate most of their energy at wavelengths beyond the red end of the visible spectrum — the infrared. And that’s the case with Aldebaran. Earth’s atmosphere absorbs most infrared energy from stars. But from outside the atmosphere, if our eyes were tuned to the infrared, Aldebaran would look even brighter than it does now. Only then would we see this bright star at its absolute best.

Script by Damond Benningfield

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Mercury, Saturn, and Jupiter form a tight triangle in the dawn sky for the next few days. Unfortunately, they’re quite low, so they’re tough to see. The view is better as you go farther south.

The planets are in the east-southeast as the sky brightens. Mercury and Saturn stand highest. They’re almost side by side, with Mercury on the left. Jupiter is below them, and is brighter than its two siblings.

Mercury is the Sun’s closest and smallest planet. It’s a bare ball of rock and metal that’s about half again as big as the Moon. Jupiter and Saturn are the largest planets — giant balls of gas wrapped around heavy cores. They’re hundreds of millions of miles from the Sun.

Mercury is barely peeking into the dawn sky. Soon, it’ll drop back toward the Sun. It’ll leave Saturn behind, then pass by Jupiter. Not long after that, it’ll disappear in the solar glare. But Saturn and Jupiter are climbing away from the Sun. They’ll rise earlier and stand farther from the Sun each day.

Unfortunately, the trail the planets follow is tilted at a low angle, so the planets move low along the horizon as they climb into view. From high latitudes, in fact, all three planets will be immersed in the glare of twilight, so they’ll be quite hard to see. The angle is better from southerly latitudes — especially Hawaii and southern Florida and Texas. But even there, you’ll need a clear horizon to see this tight trio in the dawn sky.

Script by Damond Benningfield

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Big pollywogs wiggle across parts of Mars. But they’re not like pollywogs on Earth. Instead of small tadpoles, they’re craters with channels cut through their rims. They’re called pollywogs because that’s what the outline of the crater and channel resemble.

Present-day Mars is drier than any desert on Earth. Its atmosphere is too thin to allow liquid water to stand on the surface. In the distant past, though, it was much wetter. And some of the pollywogs could have been filled with water billions of years ago.

The craters that form pollywogs range from a few hundred yards to about 10 miles in diameter. At some point, such a crater was filled with water, perhaps topped with ice. When the water filled the crater, it began flowing over the lowest part of the rim. The flowing water carved a notch in the rim. And as it left the crater behind, it carved a channel, like a riverbed.

The channel in the rim didn’t cut all the way to the crater floor, though — one way that scientists know that water was flowing out of the crater, not in.

The water that filled the craters could have fallen as rain or snow any time after about three billion years ago. Or it could have bubbled up from below ground, which seems more likely. Either way, it created some of the most distinctive features on the Red Planet.

And Mars teams up with the Moon tonight. The planet looks like a bright orange star. It stands to the upper right of the Moon at nightfall.

Script by Damond Benningfield

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The proper names of most stars date back hundreds or even thousands of years. They were bestowed by the skywatchers of the ancient Mediterranean. But the brightest star of one prominent star picture was bestowed only about half a century ago.

Navi is the middle star in the letter M or W that marks Cassiopeia the queen. It’s the brightest of the letter’s five stars. Until the late 1960s, though, it was known only by catalog or scientific names — mainly Gamma Cassiopeia.

The star is 550 light-years away. And it’s a stunner: 17 times the mass of the Sun, and about 35 thousand times the Sun’s brightness. It’s only about eight million years old, but it’s already nearing the end of its life — an explosion that will blast the star to bits.

Astronaut Gus Grissom noticed the star’s lack of a proper name, so he gave it one. Grissom and crewmates Ed White and Roger Chaffee were training for Apollo 1, the first flight of the new moonship. As part of the training, they were learning to navigate by the stars. As a joke, they gave new names to three stars. All three names were parts of the astronauts\' names spelled backwards. Grissom’s middle name was Ivan, so his star became Navi.

The names probably would have faded away. But the three astronauts died when a fire broke out aboard their spacecraft during a test on the launch pad. So the names stuck — names with their own stories.

Script by Damond Benningfield

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The Sun is more than a hundred times wider than Earth, and more than 300 thousand times heavier. But imagine cramming three Suns into a ball about the size of Colorado Springs, Tulsa, or Lubbock. That would give you a black hole the size of one recently discovered in Auriga — the smallest black hole yet seen — or not seen.

The black hole itself produces no energy, so there’s no way to see it directly. But it has a companion star. The system is known by a catalog number, which we’ll shorten to 2MASS J0521.

Most black holes are found because they’re pulling gas off the surface of a companion. The gas forms a swirling disk around the black hole. It’s extremely hot, which makes it bright — and fairly easy to find.

In this case, though, that’s not happening. Instead, astronomers discovered the black hole through its gravitational pull on the companion. The motions of the two bodies allowed the astronomers to measure the masses of both. They found that the companion is about three times heavier than the Sun, but much bigger and brighter. And the dark companion is a little more than three times the Sun’s mass. At that heft, it almost has to be a black hole. If so, it’s only about a dozen miles across — the size of a small city.

2MASS J0521 appears near Capella, the brightest star of Auriga. It’s high overhead at nightfall. Capella is one of the brighter stars in the night sky, so it’s easy to spot.

Script by Damond Benningfield

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Once upon a time, Jezero Crater would have been prime real estate on Mars. The crater held a lake about as big as Lake Tahoe. And water flowed both in and out, keeping it fresh. The crater’s rim would have been a great spot for a summer home.

The lake vanished by three and a half billion years ago. But Jezero is set to once again become prime real estate. An American rover is scheduled to land there on Thursday. It’ll trundle across the landscape for years, digging into the sediments on the lakebed in search of evidence of ancient life. It’ll even stash some samples for a future mission to pick up and bring back to Earth.

Perseverance is based on the Curiosity rover, which has been working on Mars since 2012. Perseverance’s instruments will analyze the Martian rocks and dirt, look for ice buried below the surface, and track the weather.

Perseverance also carries a small helicopter, which will make several short hops across the landscape.

Jezero Crater formed when a giant asteroid slammed into Mars more than four billion years ago. Mars was much warmer and wetter then, so there was water on the surface. Rivers cut through the crater rim. That created deltas that are still visible today. The deltas could preserve evidence of ancient microbes.

The crater lake was at least 800 feet deep. It flowed over the lowest part of the rim, emptying into the plains below — adding to the appeal of this intriguing Martian crater.

Script by Damond Benningfield

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The night sky is like a quilt with 88 patches. Each “patch” is a constellation. In ancient times, though, the quilt had a lot of blank spaces. The blanks were patches of sky with no bright stars. No one bothered to create pictures or stories for them.

Astronomers began to fill in those patches in the 17th century. In 1687, for example, Johannes Hevelius created ten new constellations. Seven of them are still in use today.

That includes Leo Minor, the little lion. It represents a cub of Leo, the lion.

Its brightest star is 46 Leonis Minoris. The star is actually quite impressive. But it’s almost a hundred light-years away, so it looks faint.

The star is 1.7 times the mass of the Sun, and about eight times wider than the Sun. It’s passed the end of its normal lifetime, so it’s puffed up to several times its original size. That’s made its surface much cooler, so it shines yellow-orange.

If you lined up the Sun and 46 Leonis Minoris at the same distance, the other star would look about 20 times brighter. Because it’s much cooler, though, a lot of its light is in the infrared. So if you add up all forms of energy, 46 Leonis Minoris would shine almost 35 times brighter than the Sun — a bright beacon in a faint constellation.

Leo Minor is near Leo, which is low in the eastern sky in early evening. Leo Minor stands to the upper left of Leo’s head and mane, which form a hook, with the bright star Regulus at the bottom.

Script by Damond Benningfield

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Hercules was fighting a nine-headed serpent when another critter decided to join the fray. The crab was sent by the goddess Hera, who didn’t exactly get along with Hercules. The crab latched on to the strongman’s toe and wouldn’t let go. This fight didn’t last long, though — Hercules crushed the crab with his foot. But as a reward for its sacrifice, Hera placed the crab in the stars — as the constellation Cancer.

The crab is about a third of the way up the eastern sky at nightfall. But it isn’t much to look at — even its brightest stars probably are too faint to see from a light-polluted city. You can find its location, though. It’s about halfway between the bright star Regulus, which is low in the east at that hour, and the twins of Gemini, which are high above Regulus.

Like the constellation, the disease known as cancer was named for the crab. About 2400 years ago, Hippocrates, the father of modern medicine, was examining tumors in cancer patients. He called the tumors “karkinos” — the Greek word for “crab.” No one is sure just why; perhaps it was because the tumors were hard, like a crab shell.

A few centuries later, a Roman writer picked up the term, using the Latin word for crab: cancer. And later still, another doctor noted that the network of veins around a tumor resembled a crab’s legs. That solidified the name for this terrible disease — a name it shares with the faintest constellation of the zodiac.
 

Script by Damond Benningfield

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The profile of the star Cursa reads like this: It’s about twice as heavy as the Sun, two-and-a-half times as wide, and 50 times brighter. But every one of those numbers depends on one more: the star’s distance of 89 light-years.

Astronomers use a technique known as parallax to measure the distance to a nearby star. They compare its position to the background of stars when Earth is on opposite sides of the Sun. The star moves a little against that background between measurements. The amount it moves reveals its distance.

You can see how it works by holding a finger in front of your face. Look at it with one eye, then the other. Objects in the background shift position as you blink back and forth. And the closer the finger is to your face, the bigger the shift.

Cursa is quite close as stars go, so the shift is fairly large. Even so, the angle is tiny, so it takes really good measurements to work out the distance. The best view comes from spacecraft, above Earth’s blurring atmosphere.

The distance is critical for understanding a star. If Cursa was a little closer to us, then it would be smaller and fainter than calculated. And a greater distance would make it bigger and brighter — changing the star’s profile.

Cursa is easy to find right now. It represents the “footstool” of Orion, the hunter. During the evening hours it stands a little above Rigel, Orion’s brightest star, which is to the lower right of the hunter’s three-star belt.

Script by Damond Benningfield

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