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.

 

 

 

 

THE UNIVERSE - ENIGMATIC STAR

Enigmatic disappearance around a star

Is there any magician around the TYC 8241 2652 1 star? This very young star, similar to our Sun and located at 456 light years from us, just disappear, as if by magic, almost the entirety of the huge disk of dust which surrounded it. "It is like the Tower of magic classic: move is, a blow there is more", summarizes Carl Melis, astronomer at the University of California (San Diego), and main author of the article published in Nature on 5 July, where this enigmatic disappearance is described first. Except that this time, it's not a rabbit that can slip into the bottom of a high hat of shape: "in this case, we are talking about a quantity of sufficient dust to fill an inner solar system (in the case of our system solar, it's space including the orbits of mercury, Venus, Earth, Mars and the asteroid belt)"(,_NDLR), and it is really a party ", adds Carl Melis.

TYC 8241 2652 1 is a star of about 10 million years. Next to our Sun and its almost 4.6 billion years, it is a young child. But this is not really a baby who is born. In its short existence - scale astronomical - residues of its formation (gas, ice, dust) have had the time to try agglomerate in planet (s). It is not known if this process has resulted because no companion has for the moment been detected around this star not really close, but astronomers believe that the dust disk that a few years ago, surrounded TYC 8241 2652 1 was not the original disk from which to manufacture the planets but rather a secondary diskconsisting of grain from the multiple collisions that embryos of planets (planetesimals) had suffered. Heated by the Sun, these dust fishnets in infra-red and it is in this wavelength that they had been detected as early as 1983.

That have thus been exactly astronomers?They followed the evolution in time of infra-red radiation of this drive by recovering data from four space telescopes working in this field - IRAS in 1983, Akari in 2006, WISE in 2010 and Herschel in 2011-, that they were supplemented by observations on the ground made with the telescope at Gemini South in the Chile (in 2008, 2009, 2012) and the NASA Infrared Telescope Facility of Hawaii (2011). Until 2008, the amount of light emitted by the disk is stable. When new measures are carried out in 2009, it fell close to a third party. And in 2010, this figure has again been divided by ten and what is left of the disk is at the limit of detectable. "It is as if the rings of Saturn were missing, said one of the authors of the Naturearticle, Benjamin Zuckerman, Professor in the Department of physics and Astronomy of the University of California (Los Angeles)." " Is even more surprising because this dusty debris disk was larger and much more massive than Saturn's rings."

The problem of the researchers, is that no known model is able to do away with such a quantity of matter within two years. "Nothing similar has never been observed around hundreds of stars that astronomers have studied the disks of dust, adds Benjamin Zuckerman." " The disappearance of the dust around TYC 8241 2652 1 was so weird and so fast as in the beginning, I thought that strange stuff had distorted our observations."But that was not the case. In addition, during the two years in question, the star demonstrated stability and seems to have known no violent anger to sweep the dust.

For the moment, the astronomers have in hand than two assumptions a little dysfunctional to try to understand what happened. The first imagine that the presence of gas in the disk causes accretion of dust in the direction of the star. The problem is there, to succeed such cleaning in such a short time, a mass of gas 10 times superior to that of the disk of dust and that the authors of the study are well confused to explain where such a quantity of gas could come. The latter staged a violent collision between planetesimals or even the breakup of one of them. In both cases, a large amount of small debris is ejected in the disk. Under certain conditions, they would be able to cause a snowball effect, hitting grains of dust from the disk, with chips, in turn, going to hit other grains, etc. This avalanche of collisions could lead to the disintegration and the evacuation of the majority of the grain. The scenario is pretty but, also, it faces a problem of size because the model that he resumed, conceived in 2006, refers to a process for about... one thousand years, not two.

The puzzle of the TYC 8241 2652 1 star adds yet more complexity to the poorly known phenomena that are at work in these disks of dust. Phenomena that interest astronomers because they are responsible for the formation of the planets and all systems solar, more or less exotic, that researchers discovered since 15 years.