Posts Tagged ‘Stars’
Music of the stars‘ now louder
Distant star makes music
First stellar ‘heartbeat’ heard
Mission guide: Corot
The Kepler space telescope measures the sizes and ages of stars five times better than any other means – when it “listens” to the sounds they make.
Bill Chaplin, speaking at the AAAS conference in Washington, said that Kepler was an exquisite tool for what is called “astroseismology“.
The technique measures minuscule variations in a star’s brightness that occur as soundwaves bounce within it.
The Kepler team has now measured some 500 far-flung stars using the method.
Bill Chaplin of the University of Birmingham told the annual meeting of the American Association for the Advancement of Science that astroseismology was, in essence, listening to the “music of the stars”.
But it is not sound that Kepler measures. Its primary job is spotting exoplanets, by measuring the tiny dip in the amount of light that it sees whan a planet passes in front of a distant star.
Such precision light-level measurements also work for astroseismology, because as sound waves resonate within a star, they slightly change both the brightness and the colour of light that is emitted.
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I could literally spend the rest of my research career working on these data”
University of Birmingham
Researchers can deduce the acoustic oscillations that gave rise to the ripples on the light that Kepler sees.
Like a musical instrument, the lower the pitch, the bigger the star. That means that the sounds are thousands of times lower than we can hear.
But there are also overtones – multiples of those low frequencies – just like instruments, and these give an indication of the depth at which the sound waves originate, and the amount of hydrogen or helium they are passing through.
Since stars fuse more and more hydrogen into helium as they grow older, these amounts give astroseismologists a five-fold increase in the precision of their age estimates for stars.
“With conventional astronomy, when we look at stars we’re seeing the radiation emitted at their surfaces; we can’t actually see what’s happening inside.”
“Using the resonances, we can literally build up a picture of what the inside of a star looks like – there’s no other way of doing that. It’s not easy to do, but we’re now getting there, thanks to Kepler.”
But just the first few months of observations by Kepler has provided scientists with data on hundreds of stars, whereas Dr Chaplin said that only about 20 have been studied in detail before.
“Suddenly we have this huge database to mine,” he said.
“I could literally spend the rest of my research career working on these data – we’re just starting to mine them.”
The detection technique the scientists used allows them to probe the outer layers of stars, to compare observational data with theoretical models to show how the stars should behave and develop.
The technique is the same one that has been used in the past decade to find more than 70 planets circling other stars.
Until now, the main suspects for what made these supermassive black holes into active galactic nuclei were galactic mergers. The crashes were thought to be what drove matter into the black holes, ramping up their activity. [Gallery: Black Holes of the Universe]
But after looking at telltale signs of galactic mergers among 140 active galaxies, as well as more than 1,200 comparable inactive galaxies, over the last 8 billion years, a team of astronomers found no significant link between the galaxy crashes and black hole outbursts.
“The implication is that the universe is not evolving in such a violent way as previously thought, at least for the last 8 billion years,” research team leader Mauricio Cisternas, an astronomer at the Max Planck Institute for Astronomy in Heidelberg, Germany, told SPACE.com. The universe is thought to be about 13.7 billion years old.
Chance of ET increases.
Two massive Jupiter-like planets were recently discovered orbiting around two extremely close sister stars – an unexpected find, given the disturbing gravitational effects within most binary star systems that usually disrupt planets from forming.