StarDate

Rock hunters have been known to visit some tough environments to collect their treasures. But for the next few weeks, a group of scientists will be hunting rocks in perhaps the most extreme environment on the planet: the Antarctic ice. The researchers are hunting meteorites — chips of rock from asteroids and other solar system bodies.

A project known as ANSMET has been visiting Antarctica every southern summer since the 1970s. It’s collected more than 22,000 space rocks.

The scientists journey to McMurdo Station, the largest settlement on the continent. They survey their planned hunting grounds from the air to confirm that the areas are safe and productive. Then they’re ferried to the ice by small aircraft. They spend weeks on the ice, living in tents.

When the weather conditions are good, they traverse the ice on snowmobiles. When they find a likely meteorite, they give it an ID number, log its position with GPS, and take its picture. They then grab the specimen with a Teflon bag, making sure not to touch it with their fingers or tools — a precaution against possible contamination.

At the end of the season, the rocks are shipped to a lab at Johnson Space Center for cataloging and preliminary analysis. Samples are then sent to scientists around the world. Eventually, all the samples are sent to the Smithsonian for permanent storage and curation — rocks from beyond Earth found in one of the most extreme environments on Earth.

Script by Damond Benningfield

Mount Cecily and Mount Raymond are two fairly unremarkable peaks in the Grosvenor Mountains of Antarctica. But something remarkable litters the ice at their bases: rocks from outer space. In fact, a team of scientists will be spending the next couple of months there, gathering up the meteorites for later study. At the same time, another group will be looking for meteorites on an ice field a few hundred miles away.

The scientists are part of ANSMET — the Antarctic Search for Meteorites. It’s been sending teams to the Antarctic for more than 40 years. They’ve gathered more than 22,000 meteorites. Most are chips off the surfaces of asteroids. But many are pieces of the Moon and the planet Mars.

Antarctica is a good site to hunt for these rocks for a couple of reasons. First, out on the open ice there are very few Earth rocks. That means there’s a good chance that any rocks sitting on the surface came from space.

And second, the bases of mountains can expose meteorites that have been on Earth for a long time. As glaciers flow toward the edge of the continent, they ram into mountain ranges. Layers of ice that have been buried for thousands of years can be pushed to the surface. Strong, dry winds vaporize much of the ice, exposing rocks that had been entombed in the ice — including a high concentration of meteorites. In fact, that’s what makes the Grosvenor Mountains a good spot for hunting for rocks from beyond Earth.

More about the search tomorrow.

Script by Damond Benningfield

A tiger is headed for the skies above Antarctica. Make that a super tiger. If everything goes as planned, it’ll float 25 miles above the continent for weeks, hunting for mysterious particles from beyond our solar system.

Super-Tiger is a set of instruments that’ll be lifted by a giant balloon. It flew once before, five years ago, and set a record by remaining aloft for 55 days.

Its mission is to catch and analyze the heaviest cosmic rays — the nuclei of atoms heavier than iron blasted into space by exploding stars. Studying these elements can help astronomers understand what’s happening in the cores of stars that explode as supernovae.

The balloon will launch from McMurdo Station, the largest settlement in Antarctica. The launch window opens in early December, when the weather generally becomes calm and clear.

Southern-summer air currents form a vortex around Antarctica. A balloon launched into that vortex circles the continent. When its mission is done, its payload parachutes onto the Antarctic ice for recovery and refurbishment for future flights.

Another advantage is Antarctica’s 24-hour daylight. It provides a steady supply of solar power for the payload, and it allows the balloon to maintain a steady altitude.

NASA generally launches two or three balloons from Antarctica every southern summer. This year, though, Super-Tiger is the only one ready for flight — a tiger ready to circle around the bottom of the world.

Script by Damond Benningfield

The Sun isn’t a very good clock. The time it takes to move from one “noon” to the next can vary by as much as half a minute per day. That doesn’t have much impact on our daily lives. But it does create some interesting effects. One example is that the year’s earliest sunset comes several days before the shortest day of the year.

The solar clock varies for several reasons. The main one is that Earth’s orbit around the Sun isn’t a perfect circle, so our distance from the Sun varies by a few million miles. And that means that our orbital speed varies, too.

Right now, we’re fairly close to the Sun, so we’re moving faster than average in our orbit. So as Earth turns on its axis, it catches up to the “noontime” Sun a little earlier each day — up to about 30 seconds. Over a period of days or weeks, that can add up to several minutes.

Because of that, sunrise and sunset occur a little earlier, too. In fact, for those at the latitudes of the United States, the earliest sunsets of the year come a few days or weeks before the shortest day of the year — the winter solstice, which is coming up on December 21st.

The exact date of earliest sunset varies by latitude. For those in the south, it happens about now. From the latitude of Denver or Philadelphia, it happens in a few days. And from Minneapolis or Seattle, it comes closer to the solstice.

The date of the latest sunrise comes about the same gap after the solstice — the result of the imperfect solar clock.

Script by Damond Benningfield

Two pairs of bright objects highlight the sky at first light tomorrow. One pair is low in the west, while the other is a bit higher in the southeast. The one in the west is the most prominent one, though, because it includes the full Moon.

Actually, the Moon and its companion will be in view all night. They’ll be low in the east at nightfall, with the star Aldebaran to the lower left of the Moon. As the night progresses, though, the Moon will slide eastward against the background of stars, so it’ll move closer to Aldebaran, the ruddy eye of the bull.

For most of the United States, Aldebaran will stand above the Moon at first light. For those in the Pacific Northwest and Alaska, though, the two will get even closer about that time: The Moon will pass in front of Aldebaran, blocking it from view. The star will remain hidden for about 35 minutes for skywatchers in Seattle, and almost an hour for those in Anchorage.

By dawn, the second pair will have climbed into good view as well: the planet Mars and the star Spica. They’ll stand side by side, with Mars on the left and brighter Spica on the right. Mars looks orange, while contrasting Spica will look white or blue-white.

Over the next few weeks, Mars will stand at just about the same altitude at the same hour of each day. Spica, on the other hand, will be a little higher in the sky each day. So Spica will quickly pull away from Mars, splitting up this bright pairing in tomorrow’s morning sky.

Script by Damond Benningfield

A couple of years ago, astronomers announced the discovery of a pair of neutron stars in the widest orbit yet seen in such a system. The discovery wasn’t made by the pros, though. Instead, it was made by two high school students.

The students found the binary by studying old observations of a pulsar — a neutron star that spins rapidly, emitting “pulses” of radio waves. Changes in the timing of the pulses revealed the companion star.

Over the past decade, students from around the country have helped in the hunt for pulsars. College students from Texas to Wisconsin, for example, have remotely controlled the Arecibo telescope in Puerto Rico — one of the world’s largest radio dishes. Their observations have resulted in the discoveries of dozens of pulsars, which are the crushed corpses of once-massive stars.

Such discoveries can help astronomers learn about the stars that become pulsars, and how pulsars affect their stellar neighborhoods. And they can help in the efforts to use pulsars to detect gravitational waves.

High school students are helping in the search for pulsars as well. The Pulsar Search Collaboratory trains them to search through old radio-telescope observations for the pulses from these dead stars. That project has also produced quite a few discoveries, including the binary system announced in 2015.

These projects help advance our understanding of the universe — while training future generations of astronomers.

Script by Damond Benningfield

Pulsars are some of the most accurate clocks in the entire universe. Except, apparently, when they’re not.

A pulsar is the rapidly spinning corpse of a once-mighty star. It’s up to a couple of times the mass of the Sun, but only as wide as a city. It can spin anywhere from about once a second to hundreds of times a second. It emits beams of energy, usually in the form of radio waves, that can sweep across Earth with each spin. That makes it look like a cosmic lighthouse, flashing on and off.

Those flashes pulse on and off with an extremely consistent beat. As a result, pulsars are the most accurate clocks in the universe — better than the best atomic clocks here on Earth.

But astronomers have discovered that some pulsars periodically turn off and on — the clock suddenly stops ticking, then starts again. Some of them spend most of their time switched on, then go quiet for a while. Others are just the opposite.

Only a few of these on-again, off-again pulsars have been found. But a recent study suggested they could be common — perhaps more common than constant pulsars.

The study also suggested that the pulsars switch off because something stops the beams of energy, which are created by charged particles trapped in the pulsar’s magnetic field. So far, though, scientists haven’t determined what’s interfering with the beams — stopping the ticking of some of nature’s most accurate clocks.

More about pulsars tomorrow.

Script by Damond Benningfield

Scientists made big news last year when they announced the first detection of gravitational waves — ripples in space and time caused by the motions of massive objects. Even before the first discovery though, scientists had good evidence for the existence of the waves: measurements of the mutual orbit of two dead stars.

In 1974, two astronomers found a pair of neutron stars in orbit around each other. Neutron stars are the crushed cores of exploded stars. One of them in this binary system spins rapidly, emitting pulses of radio waves with each spin, so it’s known as a pulsar.

Precise timing of those pulses over the years revealed that the two stars are spiraling closer to each other by about 10 feet per year. That matches predictions in Albert Einstein’s theory of gravity. The theory says that massive objects should lose energy by emitting gravitational waves, causing them to get closer.

Today, astronomers are using pulsars to try to detect much longer waves — produced by supermassive black holes. Such black holes may spiral toward each other when two galaxies merge.

The gravitational waves from such an encounter would take years to pass through Earth. Each wave would compress and stretch space by a tiny amount. That would change the timing of the radio signals of pulsars. So by precisely measuring the “ticking” of many pulsars, it should be possible to catch the gravitational waves from black-hole monsters.

More about pulsars tomorrow.

Script by Damond Benningfield

Those are the sounds of the undead — radio waves from the corpses of once-mighty stars. They’re known as pulsars, because they emit pulses of energy as they spin — from about one turn per second to hundreds of turns.

A massive star ends its life with a bang — it explodes as a supernova. The star’s outer layers are blasted into space, while its core is crushed to form an ultra-dense ball known as a neutron star. It’s up to a couple of times the mass of the Sun, but only as wide as a small city. It’s so dense that a teaspoonful of its material would weigh as much as tens of millions of elephants.

The core’s collapse concentrates its original magnetic field into a tiny volume, so the neutron star is highly magnetized. Charged particles caught in the magnetic field emit energy, most often in the form of radio waves, which is beamed out into space.

The neutron star also spins fast, so the beams of energy rotate like a lighthouse beacon. If one of those beams happens to sweep past Earth, then radio telescopes see the neutron star blink on and off — it pulses, so it’s known as a pulsar.

The fastest pulsars “steal” gas from a companion star. As the gas crashes onto the neutron star, the star spins faster — up to hundreds of times per second. So recordings of the radio waves from these stars sound like electric blenders, whipping up the space around them. More about that tomorrow.

Script by Damond Benningfield

In the fall of 1967, Jocelyn Bell was looking for a “scruffy” source of radio waves in the constellation Vulpecula. Bell was working on her PhD at Cambridge University in England. She’d been using a new radio telescope to study quasars — brilliant objects billions of light-years away.

The telescope’s observations were recorded on chart paper. And one day that summer, the chart showed what Bell later called “a bit of scruff” — an odd signal that had never been seen before.

Bell continued her quasar work. But when she was done, she decided to check out the odd signal. She used a faster recorder, which spread out the signal, allowing her to see its details. And 50 years ago this week, she got a clear result — a series of pulses that were one-and-a-third seconds apart.

Bell and her adviser, Anthony Hewish, ruled out satellites and other forms of interference. And a colleague determined the source was far outside the solar system.

For a while, the astronomers considered that the pulses might have come from another civilization. But in December and January, Bell found similar signals from three other sources — suggesting that they were natural objects.

When the discovery was announced, another astronomer suggested the sources were the dead cores of mighty stars — something that had been predicted, but never seen. Those objects were soon called pulsars — bizarre stellar corpses discovered half a century ago.

More about pulsars tomorrow.

Script by Damond Benningfield