Dead Stars Tell Many Tales

deadstarstel.jpg

Dead Stars Tell Story of Planet Birth

Astronomers have turned to an unexpected place to study the evolution of planets — dead stars. Observations made with NASA’s Spitzer Space Telescope reveal six dead “white dwarf” stars littered with the remains of shredded asteroids. This might sound pretty bleak, but it turns out the chewed-up asteroids are teaching astronomers about the building materials of planets around other stars.

So far, the results suggest that the same materials that make up Earth and our solar system’s other rocky bodies could be common in the universe. If the materials are common, then rocky planets could be, too.

“If you ground up our asteroids and rocky planets, you would get the same type of dust we are seeing in these star systems,” said Michael Jura of the University of California, Los Angeles, who presented the results today at the American Astronomical Society meeting in Long Beach, Calif. “This tells us that the stars have asteroids like ours — and therefore could also have rocky planets.” Jura is the lead author of a paper on the findings accepted for publication in the Astronomical Journal.

Asteroids and planets form out of dusty material that swirls around young stars. The dust sticks together, forming clumps and eventually full-grown planets. Asteroids are the leftover debris. When a star like our sun nears the end of its life, it puffs up into a red giant that consumes its innermost planets, while jostling the orbits of remaining asteroids and outer planets. As the star continues to die, it blows off its outer layers and shrinks down into a skeleton of its former self — a white dwarf.

Sometimes, a jostled asteroid wanders too close to a white dwarf and meets its demise — the gravity of the white dwarf shreds the asteroid to pieces. A similar thing happened to Comet Shoemaker Levy 9 when Jupiter’s gravity tore it up, before the comet ultimately smashed into the planet in 1994.

Spitzer observed shredded asteroid pieces around white dwarfs with its infrared spectrograph, an instrument that breaks light apart into a rainbow of wavelengths, revealing imprints of chemicals. Previously, Spitzer analyzed the asteroid dust around two so-called polluted white dwarfs; the new observations bring the total to eight.

“Now, we’ve got a bigger sample of these polluted white dwarfs, so we know these types of events are not extremely rare,” said Jura.

In all eight systems observed, Spitzer found that the dust contains a glassy silicate mineral similar to olivine and commonly found on Earth. “This is one clue that the rocky material around these stars has evolved very much like our own,” said Jura.

The Spitzer data also suggest there is no carbon in the rocky debris — again like the asteroids and rocky planets in our solar system, which have relatively little carbon.

A single asteroid is thought to have broken apart within the last million years or so in each of the eight white-dwarf systems. The biggest of the bunch was once about 200 kilometers (124 miles) in diameter, a bit larger than Los Angeles County.

Jura says the real power of observing these white dwarf systems is still to come. When an asteroid “bites the dust” around a dead star, it breaks into very tiny pieces. Asteroid dust around living stars, by contrast, is made of larger particles. By continuing to use spectrographs to analyze the visible light from this fine dust, astronomers will be able to see exquisite details — including information about what elements are present and in what abundance. This will reveal much more about how other star systems sort and process their planetary materials.

“It’s as if the white dwarfs separate the dust apart for us,” said Jura.

Posted in Science | Tagged | Comments Off

Ancient Stone Circles of Mars

Mystery stone circles may point to water on Mars

STONE circles on Mars are prompting a rethink about the planet’s ancient climate.

Using cameras on NASA’s Mars Reconnaissance Orbiter, Matt Balme of the Open University in Milton Keynes, UK, and his colleagues mapped the Elysium Planitia, a region near the equator. They saw rings up to 23 metres across made up of stones sorted by size into concentric bands.

On Earth, similar structures form via repeated freezing and thawing of ice, but with the stones sorted into layers. Water in soil under stones freezes faster than in surrounding soil, and the expanding ice pushes the stones upwards. Larger stones rise faster, and so layers sorted by size form.

What sorts the material concentrically is a mystery, but if a freeze-thaw mechanism was responsible, there must have been liquid water near the surface recently. This would mean that the climate was once 40 to 60 °C warmer than conventional estimates suggest.

Peter Grindrod from University College London thinks that the circles “would be an interesting target to look for evidence of past water on Mars”.

Posted in Science | Tagged | Comments Off

Sweden De-Ices Its History

Pollen Grain Study Yields New Picture Of Ice Age

According to a new doctoral dissertation at Stockholm University in Sweden, based on analyses of deposits of pollen grains, it is possible that all of Sweden was virtually free of ice for long periods during the latest ice age. The findings show that the glaciation might have started some 20,000 later than was previously assumed.

“It’s important that we get to the bottom of when the great ice sheets covered Sweden and how warm it might have been when there was no ice. At present there are two extremely different hypotheses, which makes it difficult to study how the ice age climate relates to various parameters in the climate system, such as the earth’s relation to the sun,” says Martina Hättestrand, a doctoral candidate at the Department of Physical Geography and Quaternary Geology, Stockholm University.

In order to understand the climate system of the earth, researchers today are studying the climatic variations of ice ages. Since we have the most land forms and geological traces preserved from the latest ice age, much of the research focuses on that particular period. An important aspect of the research is to study when the huge continental ice sheets grew and when they melted away, and to study the environment and climate of the areas that were free of ice. The size and movement patterns of the ice sheets can be calculated by studying land forms and moraine deposits. The ice-free periods can be studied by pollen analysis, among other methods. Pollen analysis is a method in which scientists use pollen grains preserved in ancient sediment to create a picture of what plants once grew in the area and what the climate was like.

Martina Hättestrand’s dissertation is based on studies of pollen grains that were deposited more than 40,000 years ago in small lakes during the ice-free phases of the latest glaciation. During the warm phases of the Ice Age, high amounts of birch pollen were deposited, which indicates that summer temperatures were around 10 degrees centigrade in northern Sweden. During cold ice-free phases, mostly grass and herbal pollen was deposited.

“The findings from my dissertation indicate that the first icing up phase of the latest Ice Age may in Scandinavia have started about 95,000 years ago – which is some 20,000 years later than was previously thought,” says Martina Hättestrand.

According to the previously accepted hypothesis, Sweden was covered with ice 75,000-20,000 years ago. Martina Hättestrand’s hypothesis, on the other hand, is that Sweden may have largely been ice-free between 59,000 and 40,000 years ago. If this is true, the last ice sheet of the Ice Age formed much more rapidly than was previously believed in order to have reached all the way down to northern Germany during the maximum phase about 22,000 years ago.

The latest Ice Age is called the Weichselian glacial (glaciation) in northern Europe. It started roughly 120,000 years ago and ended about 10,000 years ago. The definition of an ice age is that it has a colder climate than an interglacial period, which is the type of climate we live in today. The climate varied a great deal during the ice ages.

Posted in History | Tagged | Comments Off

Cavemen, You Got Nothing on Comets

After all those years of human guilt thinking our primitive ancestors hunted the megafauna to extinction, now we learn it was just a comet. Damn. Can’t we do anything right?

earth_impact.jpg

Scientists say comet killed off mammoths, saber-toothed tigers

First an explosion as powerful as thousands of megatons of TNT rained meteorites down on North America. Then forest fires broke out across the continent, sending up a thick layer of soot and dust that blocked out the sun. A sudden ice age ensued, and some of the Earth’s largest animals went extinct in a blink of geological time.

t’s well known that a meteorite colliding with Earth is considered the most likely reason dinosaurs died off 65 million years ago. Now a team of scientists says it has found new evidence that a comet triggered a similar extinction much more recently: just 13,000 years ago, when humans were around to witness the event and suffer its terrible consequences.

The researchers also think that when the comet exploded above the planet’s surface – ultimately killing off mammoths, saber-toothed tigers and other large mammals that roamed North America – Chicago wasn’t too far from ground zero.

“If you’d been in Chicago back in that time, it would’ve been one very bad day,” said Allen West, an Arizona geophysicist and one of the authors of a paper appearing Friday in the journal Science.

The scientists, led by University of Oregon anthropologist Douglas Kennett, say their report offers up a “smoking bullet” – proof it was a comet that set off the sudden, thousand-year freeze and wiped out the big animals of the era.

Working at multiple sites across the continent, researchers found nanodiamonds – microscopic particles thought to be found on comets – in a 13,000-year-old layer of rich sedimentary soil called a “black mat.” Beneath the layer with the nanodiamonds, fossils of the animals are abundant. After that layer, they disappear, West said.

“It’s extraordinary that tens of millions of animals disappeared synchronously at exactly the time when the diamonds and carbon layer are laid down across the continent,” said West, whose co-authors include DePaul University chemist Wendy Wolbach.

Arrowheads and other artifacts from the Clovis culture of humans – an early hunter-gatherer society – also vanish after the black mat was laid down 13,000 years ago.

In 2007, West and a team of scientists published an analysis of black mats from several regions that found heavy metals, soot and charcoal suggestive of meteorite impacts and subsequent fires. The new report says the discovery of nanodiamonds in the same material is more evidence of a cosmic strike.

Archeologists have long speculated about whether climate change or over-hunting drove the mammoths, tigers and other “megafauna” to extinction and led to the decline of the Clovis culture.

Read also:

Diamonds suggest comets caused killer cold spell

Posted in History, Science | Tagged , | Comments Off

Going to Pompeii

Today is a smeary, cold day outside, so it’s a perfect day for a trip elsewhen in time. I’m taking the kids back to ancient Pompeii via my city’s rather awesome Discovery Place. Their latest exhibit is The last Days of Pompeii, which features the history as well as actual artifacts from the city, such as mosaics and casts of the victims buried in the ash.

pompeii.jpg

Even entire streets, beaches, and gardens full of victims have been preserved:

408px-pompeii_garden_of_the_fugitives_02.jpg

I also found this cool computer depiction of the event on Wikipedia:

290px-pompeii_the_last_day_1.jpg

But my kids have been wonderfully entertained by an erupting volcano over Pompeii exhibit billboard they had on the side of the interstate. It smoked and lit up much to the kids amusement.

Here is a sad one:

587px-pompeji_geto%cc%88teter_hund.jpg

Cast of a dog that died in Pompeii as a result of the eruption of Mt. Vesuvius. Archaeologists believe the dog was chained outside the House of Vesonius Primus, a Pompeiian fuller.

Everything passed away that day, but it is amazing to me how this entire city was preserved for all time even as it died. This is a unique and irreplaceable fragment of human history. It is also a monument.

Can’t wait to take the city back in time through these ancient Roman streets. Ciao.

Posted in History | Tagged | Comments Off

Saturn Gets Edgy

hst_saturn_ringplane.jpg

Saturn Gets Edgy

So you got a telescope for Christmas/Hanukkah/Newtonmass/whatever… or you’ve had one for awhile. Either way, you get a treat this week. Or a lack of one. Saturn’s rings are going away.

Well, kinda. Saturn, like the Earth, is tipped a bit compared to the plane of its orbit; we’re canted at a 23.5 degree tilt, and Saturn is off from being vertical by about 26.7 degrees. Saturn’s magnificent rings are aligned with its equator, so that means that roughly twice every Saturn orbit we cross the “ring plane”. In other words, from Earth we see them edge-on.

And the rings are thin. Incredibly thin. Despite being over 200,000 km across, the rings are typically at most only a few dozen meters thick. To scale, that’s far thinner than a piece of paper.

So when we pass through the plane of the rings, they practically disappear from sight. I’ve seen it once through a telescope, when we were near (but not quite at) that point, and Saturn looks pretty weird when it goes commando. We’re used to it wearing these big gaudy rings, and there it was, nearly nude. It’s maybe not the best time to show the planet off to friends and family, but it’s still pretty cool.

The Earth actually doesn’t pass through the ring plane until September 2009, but at that time Saturn will be on the other side of the Sun, and pretty much unobservable. You’d think that a month or two before then would be the best time to observe the narrowly thinning rings, but in fact the best time is right now! Due to the vagaries of our mutual orbits, the rings are actually at a minimum right now, the last week of 2008, when they are inclined just 0.8 degrees to our line of sight.

If you have a telescope, get out and take a look! Saturn will be nearly ringless for the next few months, and then the rings will start to open up once again. After that, you’ll have plenty of time to soak in the phenomenal view of the solar system’s best showpiece — the next ring plane crossing isn’t until March of 2025.

Right now, Saturn is in the constellation Leo and shines fairly brightly at about magnitude 1, about the same brightness as the star Regulus which marks the heart of the lion. It rises around midnight local time right now, and is high enough to observe a couple of hours later. You can find sky maps at Your Sky and Heavens Above, and you can read more about the ring plane crossing on the NASA news page, and on Alan Dyer’s astronomy page.

And I have to add: this isn’t merely a curiosity; there is scientific value to this event. Telescopes can focus on the planet and see things otherwise hidden in the glare of the very bright rings. Faint moons, the existence of material above and below the ring plane, features on Saturn itself: all these can be easier to see without the icy, reflective ring particles blasting out light. It’s funny. Saturn is the most beautiful planet in the solar system through a telescope because of those rings, but it may be the most scientifically interesting when we can’t see them at all.

Posted in Science | Tagged | Comments Off

Is Single White Rhino the Last Hope for the Species?

3c8643d4-0a26-40a3-9379-be443c157f9d-big.jpg

Single male rhino, 20, seeks mate to save species

KUALA LUMPUR, Malaysia (AP) — He probably hasn’t dated in two decades, but the survival of a species may depend on whether Tam can get lucky soon.

A male rhinoceros recently rescued on the edge of Borneo’s rain forest is expected to become the first participant of a Malaysian breeding program for his critically endangered ilk, a wildlife expert said Wednesday.

The roughly 20-year-old Borneo Sumatran rhino, nicknamed “Tam,” was found wandering in an oil palm plantation in August with an infected leg likely caused by a poacher trap.

Tam, whose species is known for its solitary nature, has been resettled in a wildlife reserve in Malaysia’s Sabah state, the last preserve of the Borneo Sumatran rhino – a subspecies of the bristly, snub-nosed Sumatran rhino.

Authorities hope to bring at least five male and female rhinos into the reserve over the next few years so that they can mate and produce offspring, said Junaidi Payne, the senior technical adviser for the World Wildlife Fund’s Malaysian Borneo chapter.

“Their numbers are so low that they might drift into extinction if no one does anything,” Payne told The Associated Press.

Experts cannot confirm how many Borneo Sumatran rhinos remain in the wild, but estimates range from 10 to 30 individuals, many of them isolated from others in their species.

Borneo Sumatran rhinos have rapidly vanished in recent decades as their habitat has been lost to logging, plantations and other development. Poachers have hunted them for their horns, which are used in traditional medicines.

The rhinos in Sabah’s 300,000-acre (120,000-hectare) reserve will probably be able to find each other through their scent and mate without human interference, Payne said.

“If they are not stressed out by people, the chances of success should be better,” he said.

Hope for the subspecies was boosted after Malaysian government officials and WWF experts found new evidence of them in the wild in May 2005. Rhino protection units have since launched patrols to deter poaching.

Conservationists have warned the rhinos could face extinction in the next 10 years.

© 2008 The Associated Press.

Posted in Science | Tagged , | Comments Off