Planetary Bullies Make Astronomers Rethink the Habitable Zone

Exoplanet orbits that seem just right for life could be bent out of shape by pushy neighbors. New simulations of extrasolar planetary systems may mean the definition of "habitable" planets needs to be completely overhauled.

When astronomers talk about the "habitable zone," they mean the shell around a star where the temperatures are right for liquid water. Any closer, and oceans will boil. Any farther, and the planet will freeze. But this definition assumes that most planets have roughly circular orbits, like the Earth and most other planets in the solar system.

"What we know from studying exoplanets is that that is definitely not the rule," said Rory Barnes of the University of Washington at the meeting of the American Astronomical Society in Miami. Many of the 454 exoplanets discovered to date have highly elliptical orbits, meaning the planets are not always the same distance from their parent star. Thanks to this uneven geometry, the planet spends more time closer to its star, which tends to make for warmer planets.

Adding another planet, especially a bullying Jupiter-sized planet, can mess with orbits and make a once-hospitable planet move in and out of the habitable zone over time. Using computer simulations of several hypothetical planetary systems, Barnes showed that a giant neighbor can pull an Earth-like planet’s orbit like a rubber band, shifting it from circular to elliptical and back to circular again in as little as a few thousand years.

"It’s a very stable, repetitive process," Barnes said.

The Earth’s orbit actually does feel similar nudges from Jupiter, known as Milankovitch Cycles. But luckily for us, these orbital shape shifts are subtle.

Barnes’ simulations predicted more-dire consequences for extrasolar planets near the edge of their habitable zones, though. If the planet is on the cooler edge of the habitable zone, it could go through cycles of freezing and thawing. If it’s on the warmer side, the temperature could fluctuate from comfy to boiling from one millennium to the next.

"The inner edge is much more dangerous," Barnes said. All the water could boil off and be lost forever, or the warming planet could experience a "runaway greenhouse" effect and end up a scorched wasteland like Venus.

But it’s not all bad news. Barnes suggests that some planets we might dismiss as snowballs could just be going through an eccentric phase.

"Our own Earth has gone through stages of glaciation — we call them snowball Earth phases — and we managed to pull out of it," he said. "On a planet like that, on the outer edge, you will have reservoirs of life, and there will be habitats that will persist."

For planets around dim, low-mass stars, which have to be especially close to be in the habitable zones, neighboring giant planets could wreak havoc with the length of the day, and the gravitational pull could cause cycles of volcanic activity and earthquakes interspersed with relative calm.

"These are fascinating worlds to think about," Barnes said. "It will do lots of interesting things as far as how climates might evolve and how evolution might happen on such a planet."

The results suggest that the current definition of "habitable zone" may be too simplistic. Astronomers may have to consider the whole family of exoplanets in a system before determining if one is habitable or not.

"One of the things that this new work is emphasizing is that one needs to be very careful about defining habitability," commented Phil Armitage of the University of Colorado, Boulder. "Those ideas about terrestrial planet formation and habitability of terrestrial planets will need to be re-evaluated from scratch."


Fuente: Wired Science

WISE Telescope Captures Heart Nebula

WISE, NASA’s newest infrared observatory, has heart. This new mosaic captures the Heart and Soul nebulas, so named because of their resemblance to hearts–both the Hallmark card and the blood-pumping variety.

"One is a Valentine’s Day heart, and the other is a surgical heart that you have in your body," said Ned Wright of the University of California, Los Angeles, who presented the image May 24 at a meeting of the American Astronomical Society.

Since its launch on December 14, 2009, the Wide-Field Infrared Survey Explorer has been circling the Earth in a polar orbit and snapping images every 11 seconds. As of yesterday, it has captured 953,880 frames and mapped about 75 percent of the sky, Wright said.

The new image is stitched together from 1,147 individual frames. The exposure took a total of 3 and a half hours spread over 11 days in February to complete. The nebulas are located in the constellation Cassiopeia, about 6,000 light years away from Earth.

The image is color-coded to make sense to human eyes, which are blind in the infrared. Blue and cyan represent the shortest wavelengths WISE is sensitive to, 3.4 and 4.6 micrometers, and highlight places where stars are being born. Green light shows small grains of dust that have been heated by starlight and glow at the 12 micrometer band. The longest wavelength, 22 micrometers, is shown in red, capturing larger dust grains.

The bright spot at the top right of the image is an active star-forming region called W3, which Wright studied with a four-pixel balloon-borne telescope for his PhD thesis in the 1970s. Wright marveled at the difference between the sketched-out contour map he made then and the glowing portrait captured by WISE.

"It’s been an amazing progress in IR astronomy, with cameras growing by a factor of a million in power in just a few decades," he said.


Fuente: Wired Science

Una hora de Gatwick en un minuto

Una hora de operaciones en el aeropuerto de Gatwick, el segundo más activo del Reino Unido, resumido en un timelapse de un minuto por Jordi Blumberg, conocido como GatwickSpotting en YouTube.

Fuente: Avion, Microsiervos

White-Light Solar Flares Finally Explained

 
The flashes of white light accompanying some solar flares are caused by the sun’s acceleration of electrons to speeds greater than half the speed of light.

The phenomenon’s new explanation derives from data recorded from a 2006 solar flare. The presence of high-energy X-rays in the same spot that scientists saw visible light tipped them off that some kind of non-thermal process was generating the light.

“These explosions are particle accelerators,” said Säm Krucker, of the Space Science Laboratories at the University of California, Berkeley. “The whole surprising thing with these flares’ light is that it could simply be heat. But that’s not the case.”

Solar flares occur when the sun’s magnetic field lines rearrange and reconnect, releasing tremendous amounts of energy. There are different types of flares, which can generate geomagnetic storms of Earth, and only some of them are accompanied by the white light flares. These were first observed in 1859 by astronomer Richard Carrington, but no one really knew how they were produced until the new observations by the Japanese satellite Hinode and the NASA SMEX mission RHESSI.

Now, it looks as if the extremely powerful electromagnetic fields somehow deliver enormous amounts of energy into particles in the sun’s photosphere. It’s not unlike what humans do at a much, much smaller scale in particle accelerators like the Large Hadron Collider.

“As opposed to the LHC where you accelerate a few particles, it would be like accelerating the whole building basically,” said Hugh Hudson, also of Berkeley’s Space Science Laboratories, who worked with Krucker.

Astronomers haven’t figured out how exactly the sun works as a particle accelerator just yet. “It’s being done by electromagnetic effects that are not really understood,” Hudson admitted.

It’s possible that as the sun eases into a more active state over the next year, scientists will have more opportunities to study the flares.

A paper on the new work, with Kyoko Watanabe of Japan Aerospace Exploration Agency as lead author, appeared May 20 in The Astrophysical Journal.

Fuente: Wired Science

Hubble Watches as Star Slowly Devours Planet

Six hundred light-years from Earth, a huge exoplanet circling close to its home star is slowly, inexorably being devoured.

WASP 12B orbits just 2 million miles from its star, which means the surface of the planet reaches temperatures over 2,800 Fahrenheit. The sun’s gravitational pull is stronger on the front surface of the planet than on the back, so the planet has been pulled into a football shape. If you were floating on the gaseous planet, and looking heavenwards, the sun would take up nearly the entire sky.

And in the next 10 million years, the star that so dominates the planet will be destroy it, according to a paper published in May in The Astrophysical Journal Letters.

It’s not exactly the kind of solar system that human beings anticipated finding in the great beyond.

"All sorts of things that we would never expected to find we’re finding,” said Carole Haswell, an astronomer at The Open University in Great Britain and the lead author on the new paper. “Our preconceptions about what planetary systems might look like were shaped by what our own solar system looked like, particularly Star Trek," she joked.

She and her team used the Hubble Space Telescope’s Cosmic Origins Spectrograph to investigate the planet by looking in the ultraviolet part of the spectrum.

"The near ultraviolet is a very sensitive probe to the presence of stuff and that allows you to deduce an effective radius for the planet," she said.

WASP 12B has a puffed up atmosphere that its star is siphoning off. That observation happily matches theoretical predictions made just a few months ago by astronomer Shu-lin Li at Peking University, Beijing. The confirmation shows yet again that exoplanetology, particularly the study of other solar systems not just individual planets, is advancing at a breakneck pace.

"It is a really nice example of theorists predicting something and we’d already observed something close to what they predicted," Haswell said.

To date, 455 exoplanets have been discovered.

Fuente: Wired Science

Stephen Hawking afirma que los viajes en el tiempo son posibles, pero sólo al futuro

Si primero fue el contacto con los extraterrestres, Stephen Hawking sigue por la vía de la ciencia ficción y le da por hablar sobre los viajes en el tiempo. En esta ocasión, el científico estadounidense británico afirma que este tipo de viajes sí serían posibles, pero únicamente hacia el futuro.

Hawking menciona que, una vez que se construyan naves espaciales que sean capaces de desplazarse al 98% de la velocidad de la luz, un día transcurrido abordo equivaldría a un año en la Tierra. De acuerdo a los cálculos del físico, se tardarían cerca de seis años para alcanzar esta velocidad. Aunque la afirmación suena un poco descabellada, Brian Cox, físico de partículas de la Universidad de Manchester, apoya la teoría basado en algunas observaciones hechas en el Gran Colisionador de Hadrones: “Cuando aceleramos partículas diminutas al 99.99% de la velocidad de la luz en el LHC de Ginebra, el tiempo transcurrido para ellas es un sietemilésima más lento del que medimos con nuestros relojes”.

¿Tiene esta teoría alguna aplicación práctica? Para Hawking, podría suponer la salvación de la Humanidad, ya que los viajeros en el tiempo podrían llegar una Tierra post-apocalíptica a repoblar (claro, si consiguen resolver el problema de cómo aterrizar y todo lo demás). Claro, al buen Stephen ya no le importa mucho lo que hablen de él, por lo que esperamos que este tipo de declaraciones suyas sean más recurrentes. En fin, no sé ustedes, pero yo ya puedo respirar más tranquilo ahora que la paradoja del viaje del tiempo ha quedado descartada.

Fuente:

Algunas curiosidades sobre el SR-71 Blackbird

Me crucé con esta anotación de Matt de 37Signals hablando del «avión más destacado del siglo XX» donde comenta algunas curiosidades sobre el SR-71 Blackbird que encontró por ahí.


Fuente: Microsiervos

La primera fotografía de la Materia Oscura

La misteriosa materia que compondría el 23 % (se especula) de toda la materia del universo es tan esquiva que jamás ha sido observada por nadie. Así que sólo podíamos sospechar que quizá existía. La materia oscura emite, absorbe e interactúa con radiación electromagnética de manera tan débil que no puede ser observada por medios técnicos ordinarios, no refleja la luz para ser observada.

Sin embargo, un equipo internacional de astrónomos de Japón, Gran Bretaña y Taiwan acaba de conseguir, por primera vez, imágenes que reflejan la distribución de materia oscura alrededor de 20 grandes cúmulos de galaxias. Los resultados se publicarán en la revista mensual de la Royal Astronomical Society. Las pruebas aún no son concluyentes, pero sí muy esperanzadoras.

Ni en el infrarrojo, ni en los rayos X ni en el ultravioleta la materia oscura había revelado aún su auténtica naturaleza. Pero utilizando lentes gravitacionales los científicos han sido capaces de mostrar las primeras imágenes en las que se “aprecia” la misteriosa materia oscura.

Utilizando el telescopio Subaru, los astrónomos observaron veinte cúmulos masivos de galaxias, los científicos han medido la distorsión de la luz desde estas galaxias hasta la Tierra, inferiendo la presencia, la cantidad y la distribución de materia oscura.

Analizando el efecto de lente gravitacional en estas imágenes, los investigadores comprobaron que, en general, la distribución de la materia oscura alrededor de esas veinte grandes agrupaciones galácticas no tiene un contorno esférico, sino plano y alargado.

Para que os hagáis una idea de qué se compone el universo, se conjetura que estos son los tantos por ciento de materia normal, materia oscura y, una más esquiva aún, energía oscura del universo: una forma hipotética de materia que estaría presente en todo el espacio, produciendo una presión negativa y que tiende a incrementar la aceleración de la expansión del Universo, resultando en una fuerza gravitacional repulsiva.

4% de la masa total del universo. La materia oscura, el 23%. Energía oscura, el 74%.


Fuente: Genciencia