StarDate

A 1991 postage stamp has boldly gone where no stamp had gone before — to the edge of the solar system and beyond. The stamp was part of a set that depicted all nine of the solar system’s official planets. American spacecraft had explored eight of those worlds, but Pluto hadn’t yet received a visit. So the stamp featured a painting of a spacecraft flying past the remote planet, with a simple legend below: “Not yet explored.”

Pluto — now known as a dwarf planet — got its first visitor last July. In addition to cameras and other scientific instruments, New Horizons carried several small trinkets from Earth — including the 1991 stamp.

With Pluto finally explored, supporters petitioned the U.S. Postal Service to produce an updated Pluto stamp to celebrate the encounter. The Post Office has gone them one better. At a conference that begins tomorrow, it’ll debut two Pluto-themed stamps, presented under a title that proclaims “Pluto — Explored!” One of the stamps shows New Horizons, while the other features one of its pictures of Pluto.

Those aren’t the only space-related stamps to debut this year. Back in February, the postal service issued a round stamp that shows the Moon. At the upcoming conference, it’ll introduce a set of eight stamps featuring colorful images of the solar system’s major planets. And later, it’ll beam down a block of four stamps to honor the final frontier — commemorating the 50th anniversary of Star Trek.

Script by Damond Benningfield

The Juno spacecraft is just weeks away from the planet Jupiter. The craft carries several instruments that will help scientists peer into the giant planet’s interior. It also carries a few trinkets: a plaque honoring Galileo Galilei, the first person to study Jupiter through a telescope, as well as three aluminum Legos. One depicts Galileo, another is the god Jupiter, and the third is his wife, Juno, who could peer through hubby’s veil of clouds to see what he was up to.

Spacecraft have been launching with messages, trinkets, and other goodies for decades. The Voyager missions carried gold phonograph records with pictures, sounds, and video clips. Today, as the Voyagers escape the solar system, those messages are heading for the stars.

Many spacecraft carry the names of well-wishers. That began with the Cassini mission to Saturn, which launched in 1997. The signatures of would-be Saturnians were scanned and stored on a DVD — more than 600,000 of them, all of which will continue to orbit Saturn until the mission ends next year.

In addition to names, the Mars-orbiting MAVEN mission carries thousands of haiku. And a DVD aboard Phoenix, a Mars lander, was packed with 80 novels and short stories about Mars, along with a gallery of more than 60 works of art.

And New Horizons, which flew past Pluto last year, carried some of the ashes of Clyde Tombaugh, who discovered the little world, as well as other objects. More about that tomorrow.

Script by Damond Benningfield

Late spring is a good time to look for the constellation Centaurus, the mythological half-man, half-horse. His head and shoulders are visible from most of the United States. They stand due south, quite low above the horizon, about three hours after sunset, and set in the wee hours of the morning.

But the constellation’s two brightest stars, Alpha and Beta Centauri, are visible only from Hawaii and far South Texas and Florida. Alpha Centauri is to the left, and is the brighter of the two.

Skywatchers in the southern hemisphere have a gorgeous view of the entire centaur as it passes high overhead. And one South American culture — the descendants of the Inca — sees some of these stars as part of a llama. Alpha and Beta Centauri represent the llama’s eyes.

Alpha Centauri actually consists of three separate stars that are bound to each other by their mutual gravitational pull. They’re the closest stars to Earth, at a distance of about four-and-a-third light-years. But they’re still so far away that their light blurs together into a single pinpoint. Only a telescope reveals the true nature of the llama’s eye.

Beta Centauri is also a triple-star system. Its two most impressive stars are locked in a close orbit. Both stars are more than 10 times as massive as the Sun, and thousands of times brighter. They make the system easily visible from Earth even though it’s almost 400 light-years away — a hundred times farther than the llama’s other bright eye.

Script by Damond Benningfield

A perfect spiral galaxy would include a bright, round “bulge” of stars in the middle; glittering spiral arms wrapping all the way around it; dark lanes of dust swirling through the arms; and bright star clusters sprinkled about like lights on a Christmas tree.

In other words, it would look just like M81, one of the best examples of what’s called a “grand design” spiral galaxy. It’s about 12 million light-years away, and appears close to the bowl of the Big Dipper. It’s a bit smaller and less massive than our home galaxy, the Milky Way.

M81’s “bulge,” though, is much larger and brighter than the bulge in the center of the Milky Way. And the black hole in the galaxy’s heart is almost 20 times as massive as the Milky Way’s.

Its spiral arms are outlined by the galaxy’s youngest, hottest, brightest stars. Over the last billion years or so, at least two bouts of intense starbirth have brightened the arms. They’re the result of gravitational interactions between M81 and two companion galaxies. The encounters compress big clouds of gas and dust. The clouds break into small clumps, which collapse under their own gravity to form stars — stars that help make M81 one of the most beautiful galaxies of all.

Under clear, dark skies, you can spot M81 with binoculars. Find the Big Dipper, which is high in the north at nightfall right now. M81 stands below the bowl at that hour. It looks like an oval smudge of light that’s almost as wide as the Moon.

Script by Damond Benningfield

There’s a time and place for everything — especially for the stars. Each star has its own season — a time of year when it’s especially well placed for observing. And for several of the brightest stars in the night sky, that season is coming to an end. The stars are in the west and northwest as night falls, and dropping closer to the horizon by the day.

As the last blush of twilight fades away, look almost due west for Procyon, the little dog star. It’s not all that high in the sky, but if you have a clear horizon, it’ll stand out.

Procyon is best known as a winter star. As the season begins, it leads the way for the Dog Star, Sirius, the brightest star in the night sky. By now, though, Sirius has vanished from the evening sky. But because of Procyon’s more northerly position in the sky, it hangs on for a bit longer.

Two other bright stars stand to the upper right of Procyon: Pollux and Castor, the twins of Gemini. They stand side by side, parallel to the horizon, like a pair of eyes staring back at you. Pollux is the brighter of the two.

And well to the lower right of the twins, look for an even brighter marker of winter skies: golden Capella, the leading light of the charioteer.

These and all the other stars rise and set about four minutes earlier each day. So these bright stars are running out of time. They’ll fade from view in the evening twilight within weeks, bringing their season to an end — until next year.

Script by Damond Benningfield

The Moon and three bright companions arc low across the south tonight. The planet Saturn is close to the right of the Moon as night falls, with the star Antares farther to the right. And orange Mars stands above them all, shining brightest for the year.

Mars is at its peak because it’s lining up opposite the Sun in our sky, so it reflects the most sunlight directly toward Earth.

The planet is also passing closest to us. But because of its lopsided orbit, it won’t be at its absolute closest until May 30th. On that date, it’ll pass less than 47 million miles from Earth — its closest approach in a decade.

Because it’s so close, Mars is an especially big target when viewed through a telescope. Even small amateur models reveal the planet’s white polar ice caps, as well as patterns of brighter and darker markings on its surface.

When astronomers first looked at Mars through telescopes, many thought the dark regions were broad patches of vegetation — an idea that lingered well into the 20th century. That led to the idea that the planet might be inhabited by intelligent life.

The idea reached its zenith with the work of Percival Lowell, who sketched a network of “canals” cutting across the entire world. He surmised that the canals were carrying water from the ice caps, helping life survive on the Red Planet.

Alas, the dark regions on Mars are simply patches of dark rock. And the canals never existed — leaving Mars cold, dry, and barren.

Script by Damond Benningfield

Mars is earning its fearsome reputation this month. The planet named for the ancient god of war lines up opposite the Sun tomorrow. As a result, it shines brightest not only for this year, but for the next two years. It looks like a brilliant orange star. It stands close to the right of the full Moon as darkness falls tonight, with the planet Saturn and the star Antares below them.

Mars reaches “opposition” once every 26 months or so, as Earth overtakes the planet in our smaller, faster orbit around the Sun. Mars and Earth are closest around opposition, so Mars presents a bigger target than at any other time. That accounts for much of its brightness. The planet also reflects more sunlight directly toward Earth at opposition, just as the full Moon does, which intensifies its brightness.

Not all Mars oppositions are alike. The planet’s orbit is more lopsided than Earth’s orbit, so the distance from Mars to the Sun varies by more than 26 million miles. The best oppositions occur when Mars is closest to the Sun, as it will be in 2018. The worst occur when Mars is farthest from the Sun.

This year’s opposition is roughly half way between the two extremes, so Mars is putting on a good show. It’s in view all night, and outshines everything in the night sky except the Moon and the planet Jupiter.

Again, look for bright orange Mars quite close to the right of the Moon this evening. We’ll have more about Mars and its companions tomorrow.

Script by Damond Benningfield

Despite the sand and abundant sunshine, the surface of Mars isn’t exactly South Beach. The planet’s thin atmosphere is made almost entirely of carbon dioxide, and the average temperature is colder than Antarctica. Even so, the right kind of organisms might be able to survive there. In fact, they sort of have.

European scientists sent several types of tiny organisms to the International Space Station. That includes a fungus that lives inside rocks in Antarctica. Half of the organisms were placed outside the station, in a box that simulated conditions on Mars — the same atmosphere, temperature, and radiation. The others were exposed directly to space.

After a year and a half, the organisms were returned to Earth. In the lab, the researchers found that about 60 percent of the Antarctic fungi exposed to Mars-like conditions were still alive. What’s more, their DNA had been unharmed by the experience. Lichens from two European mountain ranges also fared pretty well in the Mars-like environment.

The experiment doesn’t reveal anything about whether there’s ever been life on Mars. But it does tell us that if microscopic life ever did develop on the Red Planet, it just might find today’s conditions there highly tolerable.

And Mars is in the southeast as darkness falls tonight, below the Moon. The Moon will move closer to the bright orange planet as they arc across the south during the night. And they’ll be even closer tomorrow night.

Script by Damond Benningfield

If you walk through a field of mature dandelions on a windy afternoon, you’ll see thousands of little seed pods wafting on the breeze. And a stronger wind carries away more seeds.

In a way, the same thing is happening on Mars. The solar wind is blowing away particles of the planet’s atmosphere, with gustier winds carrying off more particles. Over the eons, that process has blown away most of the atmosphere.

Today, Mars is cold and dry, and its air is quite thin. But the planet was much warmer and wetter in the distant past, with a thicker atmosphere. Scientists are trying to understand where the air and water went.

Their latest tool is MAVEN, a spacecraft that’s been orbiting Mars for a year and a half. It’s monitoring the planet’s upper atmosphere and its interaction with the solar wind.

Its observations show that, on average, the solar wind carries away about 15 pounds of charged atoms from the upper atmosphere every minute. But during solar storms, the rate goes up dramatically. And since the young Sun was more active than it is today, it generated stronger winds, which must have carried away much more of the Martian atmosphere. Over time, that depleted most of the atmosphere — leaving Mars cold and dry.

Look for bright orange Mars in the southeast as night falls. It arcs across the south during the night, and sets around sunrise.

We’ll have more about Mars tomorrow.

Script by Damond Benningfield

Mars just wasn’t comfortable in its own skin. So it shifted the skin around. That moved many of its features — like shifting your nose down to your chin.

Researchers in France outlined that scenario earlier this year. They say it explains the odd locations of underground ice and some ancient riverbeds.

The slippage took place about three-and-a-half billion years ago, after the formation of a region of giant volcanoes north of the Martian equator. Known as Tharsis, the region is tall, wide, and heavy. In fact, it’s so heavy that it began to slip southward, pulling the planet’s entire crust along with it. Eventually, it settled around the equator — about 20 degrees south of where it formed.

By that time, vast amounts of ice had been deposited beneath the planet’s poles, and riverbeds had been carved all along the surface. But the shifting crust moved those features as well. So the ice features are found well away from the present-day poles, and some of the riverbeds are found in regions that make sense only if they’ve been displaced as well.

Of course, it’s likely to take a while to confirm this picture of Martian history — and let us know if Mars really did make its own skin crawl.

And Mars is putting in its best appearance of the year right now. It rises around sunset, remains in view all night, and is at its brightest. Look for it low in the southeast as night falls, shining brilliant orange.

More about Mars tomorrow.

Script by Damond Benningfield