Aarhus University

Stars’ twinkle reveals their character.

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In 1806, English poet Jane Taylor famously lamented that a little star’s twinkle left her wondering what it was.

Fast-forward 207 years and a new analysis of starlight collected by NASA’s Kepler space telescope shows patterns in the flicker that are directly tied to the amount of boiling taking place on a star’s surface, a key indicator of its size, mass and evolutionary state.

That information, in turn, reveals volumes about any orbiting planets, including those fortuitously positioned from their parent stars for liquid surface water, apparently a key ingredient for life.

“Everything you know about planets is tied to what you know about the host star,” says Fabienne Bastien, an astronomy graduate student at Vanderbilt University.

“We don’t observe the planets directly. We observe the stars and the influence that the planets have on their stars. So in order to make any conclusions about the size of the planet or the mass of the planet as it’s pulling on the star when it’s moving, you need to know the size and the mass of the star very well.”

“That directly impacts whether or not you can claim that you have an Earth-like planet,” she says.

Bastien, who is working on a doctoral dissertation, was analysing archived Kepler data for a totally different reason when she and colleagues chanced upon strange patterns in the data that they didn’t understand.

“It was a complete surprise,” says Bastien.

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Boiling surfaces

It turns out the pattern provides a quick and relatively reliable way to determine a star’s evolutionary state.

Stars like the Sun, which is about 4.6 billion years old, eventually will evolve into red giants as they run out of fuel for nuclear fusion. The new study shows the surfaces of younger dwarf stars boiling more vigorously than older giants.

“What we are looking at here is the gravitational acceleration in the stellar outer layers, what we often call the atmosphere,” says astronomer Joergen Christensen-Dalsgaard, with Aarhus University in Denmark.

“The typical methods used have uncertainties up to 150 per cent. That very imprecise method is the easiest to do, and especially if you’re dealing with 150,000 stars and you need to characterise them all, that’s what you go to because it takes the least amount of resources. Our technique lets us beat that down to 25 per cent, which is very, very good for this field,” added Bastien.

Kepler, which collected data from about 120,000 target stars between May 2009 and May 2013, was designed to search for Earth-like planets in stars’ habitable zones,

For Bastien’s study, which appears in this week’s edition of Nature, astronomers analysed a few thousand stars in the Kepler data archive.

“If you have a large enough sample, then you start to pick out patterns in the way stars of different evolutionary states behave,” she says.

While the study is based on eight-hour flicker patterns in the visible light coming from target stars, scientists translated the data into corresponding audio wavelengths, a poignant conceptualisation that no doubt would have intrigued, and delighted, poet Taylor.

Source: http://www.abc.net.au

Apes Capable of ‘Mental Time Travel’.

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A single cue—the taste of a madeleine, a small cake, dipped in lime tea—was all Marcel Proust needed to be transported down memory lane. He had what scientists term an autobiographical memory of the events, a type of memory that many researchers consider unique to humans. Now, a new study argues that at least two species of great apes, chimpanzees and orangutans, have a similar ability; in zoo experiments, the animals drew on 3-year-old memories to solve a problem. Their findings are the first report of such a long-lasting memory in nonhuman animals. The work supports the idea that autobiographical memory may have evolved as a problem-solving aid, but researchers caution that the type of memory system the apes used remains an open question.

Elephants can remember, they say, but many scientists think that animals have a very different kind of memory than our own. Many can recall details about their environment and routes they’ve traveled. But having explicit autobiographical memories of things “I” did, or remembering events that occurred in the past, or imagining those in the future—so-called mental time travel—are considered by many psychologists to be uniquely human skills.

Until recently, scientists argued that animals are stuck in time, meaning that they have no sense of the past or future and that they aren’t able to recall specific events from their lives—that is, they don’t have episodic memories, the what-where-when of an event that happened.

Yet, several studies have shown that even jays have something like episodic memory, remembering when and where they’ve hidden food, and that rats recall their journeys through mazes, and use these to imagine future maze-travels. “There is good evidence challenging the idea that nonhuman animals are stuck in time,” says Gema Martin-Ordas, a comparative psychologist at Aarhus University in Denmark and the lead author of the new study. But trying to show that apes also have a conscious recollection of autobiographical events is “the tricky part,” Martin-Ordas admits.

To see if chimpanzees and orangutans have autobiographical memories that can later be triggered with a cue (as were Proust’s by eating the pastry), Martin-Ordas and two other researchers devised a memorable event for the apes at the Leipzig Zoo. In 2009, eight chimps and four orangutans individually watched Martin-Ordas place a piece of a banana on a platform attached to the outside of a caged testing room. The apes could get the treat only by reaching through a slot with a long stick. The researcher then hid two sticks, only one of which was long enough to reach the banana. The animals watched as she hid each tool in a box in two different rooms. The chimp or orangutan observing her actions was then released into the area with the hidden tools. They had to find the correct tool, return to the room with the tempting banana, and use the tool to retrieve the treat.

Each ape took the test four times. “We set it up to see if cues—like Proust’s madeleine—would trigger a memory event for them,” Martin-Ordas says. But instead of using a single cue like a scent or a taste, the researchers offered the apes “a constellation of cues: me, the room, and the specific problem,” Martin-Ordas says. They hoped that this combination would act as a trigger—that whenever the chimpanzees encountered this specific task with Ordas-Martin again, they would remember that they needed to search for the correct tool.

Source: sciencemag.org