¿Cómo disfrutar al máximo desde Colombia la lluvia de estrellas que caerá este domingo?

ORIGINAL: Caracol Radio

Caracol

Agosto 11 de 2013

Foto: ocio.uncomo.com

Caracol Radio habló con el geofísico Gonzalo Duque, profesor de astronomía de la Universidad Nacional, quien dio algunas instrucciones y explicó en qué consiste la lluvia de estrellas.

Expertos de la Universidad Nacional sede Manizales, recomendaron observar el fenómeno de lluvia de estrellas sin equipos especiales y desde zonas despejadas, en especial sectores rurales, procurando estar en áreas poco iluminadas.

El geofísico Gonzalo Duque, docente del centro educativo y profesor de astronomía, indicó que es un fenómeno que se extenderá hasta el 24 de agosto y que se observará en su plenitud y esplendor este domingo y lunes, por lo cual recomendó escoger las áreas de las ciudades y poblaciones en las que hay menos contaminación visual, en las que es reducido el número de edificios y se ve más despejado el firmamento.

Explicó el experto que desde el 16 de julio la tierra entró a un nube de polvo y de gas asociada a un cometa que tiene un periodo de retorno de unos 133 años, ese cometa pasa y deja el camino sucio, de ahí la lluvia de meteoritos o de estrellas que va hasta finales de agosto y que se puede observar sin gafas o binóculos al no implicar riesgo alguno.

Indicó que todo consiste en una línea similar a un cabello delgado con una señal luminosa que se desprende de un satélite en el cielo pero de manera muy rápida, una especie de estrella fugaz. Dijo que el paso de las estrellas genera entre 10 y 40 toneladas de polvo que caen totalmente incineradas en toda la atmósfera a 100 kilómetros por hora.

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Watch 3 years of solar activity in a 3-minute video

ORIGINAL: LA Times

By Deborah Netburn

April 24, 2013, 4:27 p.m.

Thanks to NASA, you can now stare at the sun for three minutes straight.

No, don't run outside and look up. Instead, check out the clip above that condenses three years of sun images into a hypnotic three-minute video that shows our closest star rotating on its axis, radiating energy and light.

The images in the video were taken by the Solar Dynamics Observatory, a NASA satellite that launched three years ago in 2010, with the express purpose of helping scientists better understand the sun and how its magnetic fields shift and change. 

To that end, the Solar Dynamics Observatory is constantly monitoring the sun, including snapping an image of it every 12 seconds in 10 different wavelengths.

The video above was created by stitching together two of those images per day over a three-year period. The images in the video were taken in the extreme ultraviolet range and represent solar material at temperatures of about 600,000 Kelvin. Each image is displayed for two frames. 

That spinning motion you see is the sun's 25-day rotation, and over the course of the video, you should be able to see solar activity grow as the sun nears the pinnacle of its 11-year solar cycle.

At the 00:30 mark and at 2:28 you can spot a partial eclipse of the sun by the moon,
at 1:11 you will see the Aug. 9, 2011, X6.9 Flare, which was the largest solar flare of this solar cycle, and at 1:51 you will see the transit of Venus.

The sun does appear to subtly increase and decrease in size over the course of the video, but that's because the distance between the Solar Dynamics Observatory and the sun has changed a bit over time. 

Admittedly, the video may seem repetitive to some viewers, but if you can stick it out till the end, you are treated to a four-wavelength view, which shows how different the sun appears depending on what wavelengths you are measuring.

Off-Peek: Radio Telescopes Edge In on Plasma Jet Spewing from Massive Black Hole

ORIGINAL: Scientific American

By John Matson

Zooming in on Galaxy M87 reveals answers about the turbulent environment surrounding the invisible black hole at its center

JET ENGINE: Astronomers have now zoomed in on the base of the jet emanating from Galaxy M87.Image: NASA and The Hubble Heritage Team (STScI/AURA)

Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...

Black holes, by definition, emit no light. They are unseeable.

But astronomers would like to get as close as they can by zooming in on the region immediately surrounding a black hole. That is the objective of the Event Horizon Telescope (EHT), a network of linked radio telescopes around the globe.

An actual event horizon—the point beyond which light and matter alike become hopelessly lost to a black hole's pull—remains out of sight, but the telescope has now succeeded in piercing the veil of a nearby supermassive black hole to peer into unprecedented depths of its turbulent surroundings.

Researchers trained EHT radio dishes in Hawaii, Arizona and California on the giant elliptical galaxy M87, some 54.5 million light-years away. The galaxy features a dramatic jet, thousands of light-years long, emanating from its center and thus, presumably, from the galaxy's black hole. In a study published online September 27 in Science, Sheperd Doeleman of the Massachusetts Institute of Technology's Haystack Observatory in Westford, Mass., and his colleagues report that the dish network has resolved the base of M87's jet. The size of the jet at that position, close to its origin, in turn allowed the researchers to deduce some of the most fundamental attributes of both the galaxy's behemoth black hole, which weighs in at a mass of 6.6 billion suns, and the swirling disk of matter surrounding it.

Outside the event horizon of a black hole orbits a disk of material pulled in but not yet consumed by the gravitational pull of the black hole. That accretion disk grows quite dense and hot as infalling material collides and compresses, emitting copious amounts of radiation in the process. Accretion disks can also accelerate particles into a jet of plasma that propagates outward at a substantial fraction of light speed.

Doeleman and his colleagues measured the base of the jet in M87 to ascertain the inner edge of stability within the black hole's accretion disk, beyond which matter quickly falls inward to its doom. That edge, the densest and fastest-moving part of the accretion disk, can fling particles outward with ease. "The jets that we see from M87 are likely launched from right around this region," Doeleman says.

The EHT, with its superior resolving power from the long baselines separating its individual sites, allowed the researchers to measure a size for the jet's footprint of just 5.5 times the black hole's Schwarzschild radius. (The Schwarzschild radius is the size below which a given mass cannot be compressed without collapsing into a black hole.) "We saw something that was just impossibly small, startlingly small," Doeleman says.

The size of the jet—and, by inference, the size of the innermost stable orbit within the accretion disk—implies that the black hole is spinning, and that the accretion disk is rotating in the same direction. A nonrotating black hole would feature a much wider jet, and an accretion disk spinning counter to the black hole's rotation would launch a fountain that was broader still.

In measuring the jet's footprint the researchers had to account for distortions, caused by the warped spacetime of Einstein's general theory of relativity, inherent to observations of such massive objects. Because of the distortion, a particle jet measured by Earth-based tools can appear larger than it actually is. "The black hole acts as its own lens," Doeleman says. "That's just because the black hole is bending the light rays like taffy."

Simply visualizing the event horizon is not the only goal of the project. A central aim is to peer into an astrophysical environment dominated by supermassive objects to see if gravity works as predicted. "If Einstein's theory is going to break down, it's probably going to be near a black hole," Doeleman says, before acknowledging that the reigning theory of gravity has survived countless challenges before. "It is never wise to bet against Einstein," he adds. "I think the bookies in Vegas give you very long odds. But you have to try."

[VIDEO] Why Are Astronauts Weightless?

ORIGINAL: Veritasium

Why astronauts in the space station are weightless?

The most common answer is because there is no gravity in space. But of course there is gravity in space, especially where the space station is located (only about 400km from Earth's surface).

What is the right answer?