UNIVERSE - Un nuevo tipo de estrellas sorprende a los astrónomos - WORLD

Durante siete años un grupo de astrónomos centró su atención en estrellas de la constelación de Centauro, en los extremos de la Vía Láctea. Ahora descubrieron que para su sorpresa, estos soles lejanos tienen una forma de variar su brillo que no está considerado en las teorías a cerca del tema.

 

 

La paciente observación durante siete años de más de 3.000 estrellas de la constelación del Centauro, en el extremo norte de la Vía Láctea, proporcionó una buena sorpresa: 36 de ellas varían su brillo con un patrón totalmente inesperado.

De acuerdo a lo que publicó El País de Madrid, el hallazgo desafía las teorías estelares y los científicos no saben aún qué mecanismo produce ese cambio minúsculo de brillo (0,1% del brillo normal de la estrella) que han observado y que se produce en períodos que van de dos a 20 horas.

Se trata de estrellas más calientes y brillantes que el Sol, pero, aparentemente, no tienen nada de especial que las haga comportarse diferente de otras de sus pares.

"La  existencia de esta nueva clase de estrellas variables es un reto para los astrofísicos", señala Sophie Seasen, una de las científicas del equipo, del Observatorio de Ginebra al diario madrileño.

Los modelos teóricos actuales predicen que su luz no varía periódicamente, así que ahora los científicos se abocan a buscar más datos del comportamiento de este extraño nuevo tipo de estrellas.

Ya tienen alguna pista: algunas parece que giran a muchísima  velocidad, explicó el Observatorio Europeo Austral (ESO). Rotan a velocidades que superan la mitad de la que sería la velocidad crítica, es decir, el umbral a partir del cual la estrella es inestable y lanza su material al espacio. En esas condiciones, la rápida rotación tendrá un impacto importante en las propiedades internas del astro.

El hallazgo de estas peculiares estrellas fue posible gracias al trabajo continuado con un telescopio situado en el Observatorio de La Silla (Chile), del ESO.

Los investigadores del Observatorio de Ginebra presentaron su descubrimiento en la revista Astronomy and Astrophysics. "Hemos logrado este nivel de sensibilidad gracias a la gran calidad de las observaciones, combinado con un análisis muy cuidadoso de los datos", declara la líder de la investigación, Nami Mowlavi, en un comunicado del ESO. Los análisis de las imágenes continúan.

 

NOT ALONE? - Our galaxy contains 100 billion planets: Study - INDIA

 

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	Contrary to previous belief, the latest research by astronomers suggests star systems with planets are actually the norm across the cosmos. WASHINGTON: Our galaxy contains at least 100 billion planets - approximately one for every star - and many of them could harbour life, a new study claims. Contrary to previous belief, the latest research by astronomers suggests star systems with planets are actually the norm across the cosmos. Astronomers at the California Institute of Technology made their estimate while analysing planets orbiting a star called Kepler-32 - planets that are representative of the vast majority of planets in our galaxy, NASA said. "There are at least 100 billion planets in the galaxy, just our galaxy," said John Johnson, assistant professor of planetary astronomy at Caltech and co-author of the study. "That's mind-boggling," said Johnson in a statement. "It's a staggering number, if you think about it. Basically, there's one of these planets per star," added Jonathan Swift, lead author of the study. One of the fundamental questions regarding the origin of planets is how many of them there are. Like the Caltech group, other teams of astronomers have estimated that there is roughly one planet per star, but this is the first time researchers have made such an estimate by studying M-dwarf systems, the most numerous population of planets known. The planetary system in question, which was detected by NASA's Kepler space telescope, contains five planets. Two of the planets orbiting Kepler-32 had previously been discovered by other astronomers. The Caltech team confirmed the remaining three, then analysed the five-planet system and compared it to other systems found by Kepler. M-dwarf systems like Kepler-32's are quite different from our own solar system. For one, M dwarfs are cooler and much smaller than the Sun. Kepler-32, for example, has half the mass of the sun and half its radius. The radii of its five planets range from 0.8 to 2.7 times that of Earth, and those planets orbit extremely close to their star. The whole Kepler-32 system fits within just over a tenth of an astronomical unit (the average distance between Earth and the Sun) - a distance that is about a third of the radius of Mercury's orbit around the Sun. The fact that M-dwarf systems vastly outnumber other kinds of systems carries a profound implication, according to Johnson, which is that our solar system is extremely rare.

 

 

 

 

UK - SCIENCE

'No signal' from targeted ET hunt

Very long baseline interferometry results in an effective antenna of many kilometres in size

The hunt for other intelligent civilisations has a new technique in its arsenal, but its first use has turned up no signs of alien broadcasts.

Australian astronomers used "very long baseline interferometry" to examine Gliese 581, a star known to host planets in its "habitable zone".

The hunt for aliens is fundamentally a vast numbers game, so the team's result should come as no surprise.

Their report, posted online, (http://arxiv.org/abs/1205.6466) will  be published in the Astronomical Journal.

In recent years, interest in such targeted searches has begun to surge as the hunt for planets outside the Solar System continues to find them at every turn.

Astronomers currently estimate that every star in the night sky hosts, on average, 1.6 planets - implying that there are billions of planets out there yet to be confirmed.

But a number of stars have already been identified as playing host to rocky planets at a distance not too hot and not too cold for liquid water - the first proxy for amenability to life.

ET or AT&T?

Gliese 581, a red dwarf star about 20 light-years away, is a particularly interesting candidate for the Search for Extraterrestrial Intelligence, or Seti.

It has six planets, two of which are "super-Earths" likely to be in this habitable zone.

So astronomers at Curtin University's International Centre for Radio Astronomy Research in Australia, put one of radio astronomy's highest-resolution techniques to work, listening in to the star system.

Seti and the hunt for alien life

 

 

Very long baseline interferometry (VLBI) is the process of using several or many telescopes that are distant from one another, carefully combining their signals to make them effectively act as one large telescope, peering intently at a tiny portion of the sky.

The team trained the Australian Long Baseline Array onto Gliese 581 for eight hours, listening in on a range of radio frequencies.

The result was radio silence - but the team used their experience to validate VLBI as a technique particularly suited to this kind of targeted search.

Seth Shostak, principal astronomer at the Seti Institute in the US, said that the approach's strength lies in the fraction of the sky it examines.

"It's like they're looking at the sky through a 6-foot-long cocktail straw - a tiny bit of the sky, so they're only sensitive to signals that are coming from right around that star system," he told BBC News.

That is useful not only for getting a high-resolution view, but for excluding the signals from Earthly technologies that plague Seti efforts.

"Figuring out 'is this ET or AT&T?' isn't always easy, and VLBI gives you a good way of discriminating, because if you find something from that tiny, tiny dot on the sky you can say that's not one of our satellites," Dr Shostak said.

He added that the team's negative result was not disheartening, because the odds have it that the hunt for aliens, if it is ever to find them, will require thousands or millions of observations of this kind.

"Consider the fact that you could've looked at the Earth for four billion years with radio antennas - here was a planet that's clearly in the habitable zone, has liquid oceans, and has an atmosphere - and yet unless you had looked in the last 70 years and were close enough, you wouldn't have found any intelligent life," he said.

"The fact that we look at one star system and don't find a signal doesn't tell you that there's no intelligent life."