StarDate

The timeframe for astronauts to visit Mars keeps on slipping. Such a trip isn’t likely to happen for decades, if at all. Yet researchers are continuing to prepare for it by studying how a crew might react during the long journey.

NASA, for example, is funding a project called HI-SEAS. Six volunteers are living on the slope of Mauna Loa, a volcanic mountain in Hawaii. The living conditions are designed to simulate a one-year stay on Mars. The volunteers live in a dome, wear spacesuits when they go outside, and get their power from sunlight. There’s a time lag for communications with a command center, and no other direct contact with anyone else.

One of the project’s goals is to understand how a crew gets along in cramped, isolated conditions. That’s also a goal of a project sponsored by the European Space Agency — one in which the conditions are even more like those on Mars.

Scientists are studying the behavior of crew members who spend a year at a research base in Antarctica. It’s almost 400 miles from the nearest outpost. And during the winter, it’s so cold that aircraft can’t fly in or out, so the crew is stranded.

This year, scientists are looking at changes in crew members’ balance and sleep patterns, as well as their hearts and bones. They’ll also look for changes in performance as crew members “pilot” a simulated spacecraft.

These experiments will help space agencies pick a crew for a real trip to Mars — whenever it may happen.

More about Mars tomorrow.

Script by Damond Benningfield

For the light from the star Spica, it’s been a long journey. It began about 250 years ago — around the year 1766. By then, the American colonists were getting angry at their rulers in England, but were still a decade away from declaring independence. Parliament repealed an unpopular tax early in the year, briefly tamping down the fires of revolution.

Since then, the light from Spica has traveled about one-and-a-half million billion miles. To put it another way, if you were flying in a jet airliner at a steady speed of 500 miles per hour, it would take you more than 300 million years to cover that distance.

Spica’s light doesn’t take nearly that long to cross the interstellar gulf because it moves at, well, the speed of light — 670 million miles per hour. According to Albert Einstein’s theories of relativity, nothing can move faster than that.

As the light races toward Earth, some of it is absorbed by gas and dust between the stars. There’s not a lot between here and Spica, though, so most of the light is uninterrupted — it just keeps on cruising.

Spica stands close to the right of the Moon as they rise in late evening, and a little farther from the Moon at first light. And if you happen to look in that direction, some of the star’s light will end its journey across the galaxy by striking your eye — a journey that began on the surface of a brilliant star, and ended on a winter’s night on a planet 250 light-years away.

Script by Damond Benningfield

The Voyager 1 spacecraft is 12-and-a-half billion miles from the Sun, and moving farther every day. Yet it continues to transmit readings from some of its instruments as it plunges into interstellar space.

The twin Voyagers are powered by plutonium generators (black tube below the body of the spacecraft) [NASA/JPL]One reason Voyager is still working is its power source: a nuclear generator powered by plutonium. It provides about 250 watts of electricity — almost four decades after the craft was launched.

In fact, a form of the element — plutonium-238, which can’t be used to make bombs — has powered quite a few missions. It charged instruments left on the Moon by Apollo astronauts, for example, along with probes to the outer planets, where the Sun is too faint to use solar power. Today, it’s powering the Curiosity Mars rover, the Cassini mission at Saturn, and New Horizons, which flew past Pluto last year.

The plutonium generates heat through radioactive decay. Special materials convert that heat to electricity. Plutonium-238 has a half-life of about 88 years, so the amount of power slowly declines over the generator’s lifetime.

NASA’s facing a shortage for future missions. It has only about 40 pounds of usable plutonium in stock. The Department of Energy stopped producing new plutonium decades ago. NASA’s paying for new production, but it’s expensive and time consuming. Eventually, the project may yield a couple of pounds per year. With the supplies on hand, that may make it possible to power several new missions to the outer solar system.

Script by Damond Benningfield

When New Horizons flew past Pluto last summer, it was already carrying a bit of "Pluto" along with it. The spacecraft is powered by plutonium — an element that was discovered 75 years ago this week, and that was later named Pluto in honor of the recently found planet.

Glenn Seaborg led the team of physicists at UC Berkeley that made the discovery. The team bombarded samples of uranium — number 92 in the periodic table of the elements — with the nuclei of a heavy form of hydrogen. That created the next-heavier element, number 93. Since uranium was named for the planet Uranus, the next element was named for the next planet out, Neptune.

Then, on the night of February 23rd, 1941, Seaborg’s team found that the neptunium underwent a type of radioactive decay, creating element 94: plutonium.

The researchers prepared a paper about the discovery for a scientific journal. They had to withdraw it, though, when they discovered that the new element could undergo nuclear fission. In other words, it could be split apart to release a huge amount of energy — making it a possible ingredient for an atomic bomb. So Seaborg’s team couldn’t tell the world about the new element until after World War II.

Plutonium was used in A-bombs — including the one that destroyed much of Nagasaki, Japan, in August of 1945.

Today, plutonium is a major power source for spacecraft exploring the outer solar system. We’ll have more about that tomorrow.

Script by Damond Benningfield

The Moon has a brilliant companion tonight. It looks like a big, fat star close to the upper left of the Moon as they climb into good view a couple of hours after sunset.

Despite that “stellar” appearance, though, Jupiter is really a planet — the biggest in the solar system. It’s about 11 times wider than Earth, and more massive than all the other planets combined.

Jupiter takes advantage of that great heft. The young solar system contained trillions of small comets and asteroids. But Jupiter’s powerful gravity hurled many of them out of the Sun’s domain. Some may have been captured by other stars, but most probably are wandering through the galaxy alone.

Jupiter continues that influence today. It alters the orbits of any comets or asteroids that pass anywhere near it. It flings many of them away from the inner solar system, to regions where they’re no threat to Earth. But it flings others toward the Sun and Earth, increasing the likelihood of a collision. So the planet can be both a protector and a nemesis to our own.

Jupiter’s gravity even has an effect on the solar system’s other planets, including Earth. Although Jupiter’s gravitational pull is tiny compared to that of the Sun, over time, its influence adds up. And when you combine that with the influences of the other planets, it means that astronomers can precisely project Earth’s orbit only a few tens of millions of years into the future — the blink of a cosmic eye.

Script by Damond Benningfield

A bright star and an even brighter planet flank the full Moon tonight. Both of them lose a bit of their luster in the bright moonlight, but both are still easy to spot.

The trio is in good view by about 8 o’clock. The star Regulus, the heart of Leo, stands above the Moon, while the giant planet Jupiter is about the same distance to the lower left of the Moon.

Jupiter is the biggest planet in the solar system, so almost everything about it is over-sized: its mass, its storms, its entourage of moons. And it has the most powerful auroras in the solar system.

Auroras are curtains of light high in the sky. On Earth, they shimmer to life as charged particles from the Sun hit atoms of nitrogen and oxygen high in the atmosphere, causing them to glow.

For the most part, the auroras on Jupiter aren’t created by the Sun. Instead, they’re energized by particles from monster volcanoes on the moon Io. Some of the particles are swept up by Jupiter’s magnetic field. They’re funneled toward the planet’s magnetic poles, where they form giant rings in the upper atmosphere.

While most of the glow from the auroras on Earth is in the form of visible light, the auroras on Jupiter glow across the entire electromagnetic spectrum, from radio waves to X-rays. And they produce enough energy to power all the cities on Earth — an abundant supply of energy from curtains of light.

More about Jupiter and the Moon tomorrow.

Script by Damond Benningfield

In most calendar systems, two astronomical objects play leading roles: the Sun and Moon. Their motions across the sky define the day, the month, and the year.

Yet some calendars have relied on other lights in the sky: the stars. The first appearance of a star in morning twilight told people that it was time to plant or reap crops, or to move to a warmer climate for the coming winter. Or a star reaching its highest point in the sky at midnight told them that it was time for important rituals.

One of those markers is Regulus, the brightest star of Leo, the lion. It’s to the lower left of the Moon as night falls this evening, and even closer to the Moon at first light tomorrow.

Regulus was one of the most important stars of the ancient world. In ancient Persia it was one of the four “guardians of heaven,” so it was a key marker in the calendar.

And today, Regulus plays a role in the calendar of the Mayan people of Central America — the descendants of the ancient Mayan civilization.

When Regulus stands highest in the sky at midnight — which happens this month — villagers begin preparing the fields for crops. And they begin planting mountain corn when the waxing Moon passes by Regulus in March — an important reminder that’s as easy as watching the stars.

And watch Regulus as it pops into view near the Moon in early evening, and stays close throughout the night. It’ll stand just above the Moon as they set during the dawn twilight.

Script by Damond Benningfield, Copyright 2015

Pollux is one of the brightest stars in the night sky — and one of the closest. The best measurement to date says the brighter of Gemini’s “twins” is less than 34 light-years away. Only a few hundred stars are closer, and few of those are especially bright. Even so, there’s a bit of uncertainty in exactly how far away Pollux really is — a matter of about 500 billion miles.

Astronomers measure the distances to nearby stars with a technique called parallax. They compare the star’s location against other stars when Earth is on opposite sides of the Sun. That tiny shift is like looking at a nearby object with first one eye, then the other — it shifts back and forth a bit against the background of more-distant objects.

The distance to Pollux was measured with an orbiting satellite. Above Earth’s blurring atmosphere, it saw the stars as crisp pinpoints instead of fuzzy blobs, improving its view. It found a distance of 33.78 light-years. But the uncertainty in that measurement is almost a tenth of a light-year — about half a trillion miles. It’ll take a much more precise measurement for future starship navigators to reach this bright stellar neighbor.

Look for Pollux high above the Moon this evening, with its “twin,” Castor, close by. Two other bright stars surround the Moon. The “little dog” star, Procyon, stands to the upper right of the Moon, with Regulus, the heart of the lion, to the lower left of the Moon. More about the Moon and Regulus tomorrow.

Script by Damond Benningfield, Copyright 2015

Some folks who played important roles in the early days of the telescope line up not far from the Moon tonight. Galileo is there — the first scientist to study the heavens through a telescope. So is Hans Lippershey, who is often credited with inventing the telescope. And, fittingly enough, they all circle around Copernicus, who demonstrated that the Sun, not Earth, is at the center of the solar system.

The names were bestowed on the members of a system known as 55 Cancri, in Cancer, the crab, which spreads out to the lower left of the Moon this evening.

The system contains five known planets. They range from a few times the mass of Earth to a few times the mass of Jupiter, the largest planet in our own solar system.

Until last year, the main designations for those planets were the name 55 Cancri followed by a letter of the alphabet. So the planets were known as 55 Cancri b, c, d, e, and f. And those names will remain.

To jazz things up a bit, though, last year the International Astronomical Union held a contest to give proper names to the planets in several star systems. For 55 Cancri, it picked the suggestion made by a group in the Netherlands, and named the planets for people associated with the invention of the telescope and its early use.

And since 55 Cancri itself didn’t have a proper name, it was given one as well. So Galileo and the system’s other planets all orbit Copernicus — a star at the center of a busy planetary system.

Script by Damond Benningfield

If you’d like to travel into the future — even the far-distant future — you don’t need a time machine. Instead, a starship will do just fine. Fire up the engines, head into space, and keep your foot on the gas.

The laws of physics seem to make it impossible — or nearly so — to travel through time in anything like the modern concept of a time machine — something that allows you to move through the centuries at will. Yet those same laws make it possible to zoom into the future.

The concept is known as time dilation. It says that as you travel faster, your clock ticks more slowly compared to those you left behind. That concept has been proven by putting atomic clocks in airplanes and aboard GPS satellites. In fact, if GPS clocks weren’t adjusted to account for time dilation, the entire system would fail.

At the orbital speed of a satellite, the difference is tiny — a few millionths of a second per day. As speed increases, though, the effect becomes more significant.

If you could travel at 90 percent of the speed of light for one year as measured by the clock on your ship, more than two-and-a-quarter years would pass back on Earth. At 99 percent of lightspeed, it’s more than seven years per ship year. And at 99.99 percent, the ratio is 70 Earth years per ship year.

Of course, there is the problem of finding a fast starship to carry you. But so far, that’s the only known way to beat Time by just a little — and travel into the future.

Script by Damond Benningfield, Copyright 2015