StarDate

The American space program is gearing up to send astronauts back to the Moon. A test flight of their new capsule and booster is scheduled for later this year. A series of robotic missions will begin this year as well. Many of those missions will look for frozen water and other resources to sustain human expeditions.

A half-century ago, NASA was winding down its first wave of lunar exploration. The final Apollo missions were scheduled for launch in 1972, and the space agency was planning its next step. And 50 years today, it got the okay to go ahead. President Richard Nixon approved the space shuttle — a reusable rocket ship to carry astronauts to Earth orbit quickly, reliably, and often.

It took almost a decade to get the shuttle ready to fly, though. And it never performed the way NASA said it would. It cost more, flew less, and proved to be tricky to operate. Two of the shuttles were destroyed in flight, killing 14 astronauts.

Yet the shuttle did ferry satellites to space, including Hubble Space Telescope and a mission to Venus. Astronauts conducted scientific research, and assembled the International Space Station. The shuttle was retired a decade ago — 40 years after it was given a “go” to proceed.

The destination for the next generation of spaceships — the Moon — has a brilliant companion tonight: the planet Jupiter. It’s close to the upper right of the Moon as night falls. They drop from view about 8:30 or 9.
 

Script by Damond Benningfield

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Saturn’s rings are beautiful to look at. For scientists, they’re also valuable instruments — they provide a glimpse deep inside the giant planet.

The main rings span about three-quarters of the distance from Earth to the Moon. They consist mainly of ice — from tiny grains to big boulders — with a smattering of dust and rock.

The Cassini spacecraft studied the rings as it orbited Saturn for more than a decade. It found that the rings are constantly changing. And some of those changes are caused by what’s happening inside Saturn. Motions deep within the planet cause subtle changes in Saturn’s gravitational and magnetic fields.

A few years ago, scientists used those changes to measure the length of Saturn’s day. That had been hard to pin down because Saturn doesn’t have a solid surface. But Cassini revealed waves rippling through the rings. The waves told scientists that a day on Saturn lasts a little more than 10 and a half hours.

And this year, scientists used a wave pattern seen in one of the rings to suggest that Saturn’s core is mushy. It contains a lot of rock and metal, but it’s mixed with hydrogen and helium, which make up most of the planet. That would make the core gooey and poorly defined, like a ball of melting cheese — a discovery made possible by Saturn’s rings.

And Saturn is easy to find early this evening. It looks like a bright star quite close to the Moon. Its rings are visible through just about any telescope.
 

Script by Damond Benningfield

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Earth is huddling close to the Sun for the next couple of days — it’s closest for the whole year, in fact. It’s at a point in its orbit called perihelion, and it happens every January.

There are a couple of ways to measure the separation between Earth and the Sun. There’s the way astronomers measure it, which is from the center of Earth to the center of the Sun — 91.4 million miles at perihelion. Or you can measure it from the surfaces of the two bodies, which puts the Sun almost half a million miles closer.

The distance between Earth and the Sun changes because Earth’s orbit is an ellipse — like a slightly flattened circle. Over the course of an orbit, the distance varies by about three million miles.

When the Sun is closest, as it is now, we receive about seven percent more total solar energy than when it’s farthest, in early July. But that has nothing to do with the seasons. They’re controlled by Earth’s tilt on its axis. Right now, the north pole is tilted away from the Sun, so it’s winter in the northern hemisphere, and summer in the southern hemisphere.

The changing distance does have one important impact on the seasons. When Earth is close to the Sun, it moves faster in its orbit than when it’s farther away. So that makes the length of the seasons uneven. Here in the northern hemisphere, winter is only about 89 days long, compared to 93 days of summer — extra sunlight thanks to our lopsided path around the Sun.
 

Script by Damond Benningfield

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The stars are eternal — by human standards, anyway. But the constellations are not. That’s because the constellations were drawn by people. And what one person draws, another can erase.

Consider Quadrans Muralis. It’s the namesake for the year’s first meteor shower, the Quadrantids, because the meteors all appear to “rain” into Earth’s atmosphere from that direction. But you won’t find Quadrans Muralis on any modern starchart.

French astronomer Joseph Lalande drew the constellation in 1795. He named it for the wall quadrant — an astronomical instrument that was used to plot the positions of stars. He carved the constellation out of a mostly barren patch of sky that’s bounded by Boötes, Draco, and Hercules.

Although several of Lalande’s constellations caught on, this one didn’t. Yet the meteor shower still bears the name of the extinct constellation.

The shower itself should be at its best tomorrow night, with a peak rate of dozens of meteors per hour. If you trace the paths of the meteors across the sky, they all appear to originate in Hercules. But they can streak across any part of the sky, so you don’t need to look toward Hercules to see them.

The Moon is new today, so it’s completely out of view — it won’t dampen the fireworks. To give the Quadrantids a try, find a safe, dark viewing spot, away from city lights. Then bundle up and enjoy the show — a reminder of the changing landscape of the night sky.
 

Script by Damond Benningfield

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Four of the five planets that are easily visible to the unaided eye line up in the southwest as night falls the next few evenings. But one of them won’t stick around for long. A couple of weeks from now, it will have pulled into view in the morning sky.

That one is Venus, which has reigned as the “evening star” for months. It’s quite low as the Sun sets, so you need a clear horizon to spot it — any trees or buildings will block it out. But it’s quite bright, so it’s not hard to find.

Venus is about to cross between Earth and the Sun. As it does so, it’ll move from the sky to the morning sky. It’ll become visible there in a couple of weeks, and be an easy target by the end of the month.

The planet Mercury stands close to the upper left of Venus. It’s moving higher into the evening sky, so it’ll be a little easier to see over the next few days. It will vanish in the twilight in a couple of weeks.

Mercury is climbing toward Saturn, which is to the upper left. They’ll draw quite close next week, but they won’t quite catch up to each other. Saturn will quickly follow Mercury into the twilight.

The final planet is Jupiter, the giant of the solar system. It’s to the upper left of Saturn, and shines brilliantly — second only to Venus. Jupiter will linger in the evening twilight for a while. It’ll drop from view in mid to late February — then return to view in the morning sky in April.
 

Script by Damond Benningfield

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The sky offers up some beautiful options for seeing the old year out and the new year in tonight.

Shortly after the year’s final sunset, look toward the southwest for a lineup of four bright planets — an array that includes the second- and third-brightest objects in the night sky.

The brightest member of the quartet is Venus, the “evening star.” It’s quite low in the sky, so you need a clear horizon to spot it — any clutter will block it from view. If you do see it, look close to the left for the fainter planet Mercury. Golden Saturn stands to their upper left. And brilliant Jupiter — the solar system’s largest planet — is about the same distance to the upper left of Saturn.

The planets are all gone from view by midnight. But some especially bright stars take their place. Orion the hunter is high in the south. Look for a rectangle of four bright stars with a short line of three stars at its center — Orion’s Belt. Follow the belt to the lower left and you’ll come to the Dog Star, Sirius, the brightest star in the night sky. And if you have dark skies, look for the Milky Way arcing high overhead.

If you plan to watch the dawn of the new year, look low in the southeast for a pair of orange “eyes.” The one on the left is Mars, while the other is Antares, the star that marks the heart of the scorpion. And as twilight brightens, a fingernail crescent Moon rises below them — a tough target for the dawn of the new year.

Script by Damond Benningfield

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The Moon looks down on a couple of ancient “rivals” before and during dawn tomorrow — the planet Mars and the star Antares. They’re quite low in the southeast at first light. Mars is close to the lower left of the Moon, with Antares about the same distance to the lower right.

Mars is one of the reddest objects in the night sky, which has always drawn attention. Long ago, that color reminded skywatchers around the Mediterranean of blood, so they named the planet for the god of war.

In Rome, the god was called Mars. But in Greece, he was Ares. And that’s where the star Antares got its name. The star is bright and orange, like Mars, so it was named “Ant-Ares” — the rival of Ares.

The comparison was easy to make because Mars passes by the star every couple of years or so. When they’re close together, they really can look a lot alike — but not always. Antares always looks the same — it doesn’t change. But as Mars orbits the Sun, it gets a lot brighter or fainter depending on its distance from Earth. At times, it’s a good bit fainter than Antares. At others, it’s many times brighter.

Mars is just emerging from behind the Sun now, so it’s a long way away, which makes it fainter than Antares. But by next December, Mars will line up opposite the Sun, so it’ll be closest to us for the year. It will shine about 20 times brighter than it is now — truly outshining its colorful rival.

Tomorrow: seeing in the new year with the stars.

Script by Damond Benningfield

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The Sun’s closest planets are crossing paths in the southwest in early evening. There’s a limited viewing window because they set by the time twilight fades away.

The brighter planet is Venus. It’s the “evening star,” quite low in the sky at sunset. It’s so bright that you might mistake it for an airplane with its landing lights turned on. But it’s so low that you need a clear horizon to pick it out — any trees or buildings will block it from view.

Mercury stands a little to the lower left of Venus this evening, but it’s moving upward. It’ll be roughly even with Venus tomorrow evening, then will move up and away from it. It’ll stand a little higher in the sky at sunset for several days.

Mercury is the closest planet to the Sun, while Venus is the next one out. Yet Venus is much hotter. That’s because it has a thick atmosphere, made mainly of carbon dioxide. As we know from our changing climate here on Earth, C-O-2 is a potent greenhouse gas — it traps heat. It’s warmed the surface of Venus to more than 850 degrees Fahrenheit.

By comparison, peak temperatures on Mercury — which has no atmosphere to speak of — are about a hundred degrees lower. And most of the time, across most of the planet, it’s not nearly as hot. It can reach hundreds of degrees below zero on the nightside and at the poles — frigid conditions close to the Sun.

Keep an eye on these close, hot worlds as they cross paths in the early evening sky.

Script by Damond Benningfield

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Earth is in a danger zone. Asteroids could smack into our planet, causing massive destruction. To protect ourselves, we need to know about them well in advance. So NASA and others are scanning the skies to locate these potential killers.

Some of those efforts are based in space. NeoWise, for example, has discovered hundreds of asteroids that come close to Earth’s orbit — including more than 60 that are listed as especially threatening.

NeoWise was launched in 2009 to study the infrared universe. It shut down when it used up its coolant. But it was revived a couple of years later to look for asteroids, and it’s been working ever since. And this summer, it got a two-year extension.

NASA’s already planning its successor. Near-Earth Object Surveyor would also scan the sky in the infrared. Asteroids are dark, but they produce a lot of infrared energy, so that’s the best way to find and track them. The new craft is targeted for launch in 2026.

Scientists also are working on a plan to send a craft to tag along with Apophis, an asteroid that will pass less than 20,000 miles from Earth in 2029. The craft spent a couple of years orbiting another asteroid, and is bringing samples to Earth. After dropping them off, in 2023, it could take aim at Apophis. It could reveal details about the asteroid and how its orbit is affected by Earth and the Sun — critical details that could help track all dangerous asteroids.

Script by Damond Benningfield

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What you know and what you can prove aren’t always the same. More than four centuries ago, for example, many astronomers knew that Earth wasn’t the center of the universe — that Earth and the “planets” revolved around the Sun. But proof was elusive. Until Johannes Kepler came along.

Kepler was born 450 years ago today, to a family of modest means in present-day Germany. As a student, he studied theology, astrology, and science. All three of them shaped his view of the cosmos — as a divine creation that could reveal its secrets while guiding the future.

In 1600, Kepler became an assistant to Tycho Brahe, perhaps the best naked-eye skywatcher ever. When Tycho died the following year, Kepler inherited Tycho’s job — and his decades of meticulous observations of the night sky.

It took him several years to work it all out, but Kepler used those records to formulate new ideas about the universe. Those ideas are known today as Kepler’s laws of planetary motion. Among other things, they describe how Earth and the other planets orbit the Sun, and how the Moon orbits Earth.

Later in the century, Isaac Newton used Kepler’s laws to form his own laws about the universe — especially the laws of gravity.

Kepler contributed to science in many other ways. He explained how vision works in the human eye and in the telescope, for example. But his greatest work remains his laws of planetary motion — laws that proved what others only “knew.”

Script by Damond Benningfield

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