Observaciones de las ondas gravitacionales detectadas por LIGO sugieren dos escenarios de formación de agujeros negros

Un agujero negro binario. NASA

• MADRID, 23 (EUROPA PRESS)
• Un equipo de físicos dirigido por investigadores de la Universidad de Birmingham, en Reino Unido, junto a la Universidad de Maryland, la Universidad de Chicago y el Instituto Kavli de Física Teórica, en Estados Unidos, han descrito en un artículo publicado en 'Nature' cómo las observaciones de las ondas gravitacionales --detectadas por el interferómetro LIGO en 2015 y 2017-- limitan a dos las posibles explicaciones para la formación de agujeros negros fuera de la Vía Láctea.
  Según los investigadores, o los agujeros negros de fuera de la Vía Láctea giran más lentamente que aquellos que se hallan en la Vía Láctea --donde los científicos han sido capaces de observar electromagnéticamente agujeros negros orbitados por estrellas y mapear su comportamiento, es decir, su rápido giro-- o bien giran rápidamente, pero son 'volteados' con giros aleatoriamente orientados a su órbita.
  Las ondas gravitacionales ofrecen información sobre los dramáticos orígenes del agujero negro que de otro modo no podrían obtenerse. Los físicos concluyeron que las primeras ondas gravitacionales detectadas, en septiembre de 2015, fueron producidas durante la fracción final de un segundo de la fusión de dos agujeros negros para producir un solo agujero negro giratorio más masivo. Las colisiones de dos agujeros negros habían sido predichas, pero nunca observadas.
  Como tal, las ondas gravitacionales presentan la mejor y única manera de obtener una mirada profunda a la población de agujeros negros binarios de masa-estelar más allá de la galaxia de la Vía Láctea, donde se encuentra la Tierra. Este documento afirma que los agujeros negros vistos a través de las ondas gravitacionales son diferentes a los observados anteriormente en la Vía Láctea en una de dos maneras posibles.
  LAS DOS POSIBILIDADES DE FORMACIÓN
  La primera posibilidad es que los agujeros negros estén girando lentamente. Si ese es el caso, la investigación sugiere que algo diferente sucede a las estrellas que forman estos agujeros negros a las observadas en la Vía Láctea.
  La segunda posibilidad es que los agujeros negros estén girando rápidamente, de forma muy parecida a los de la Vía Láctea, pero se han 'caído' durante la formación y, por lo tanto, ya no están alineados con la órbita. Si este es el caso, significaría que los agujeros negros están viviendo en un ambiente denso --muy probablemente dentro de los cúmulos estelares--. Esto permitiría una formación considerablemente más dinámica.
• Sin embargo, también existe la posibilidad de que ambas posibilidades sean verdaderas --que hay casos de agujeros negros que giran lentamente en el campo y ejemplos de agujeros negros que giran rápidamente en un ambiente denso--.
  Según el doctor Will Farr, de la Facultad de Física y Astronomía de la Universidad de Birmingham, al presentar estas dos explicaciones y descartar otros escenarios, se está proporcionando a aquellos que estudian y tratan de explicar la formación de los agujeros negros un objetivo al que dirigirse. "En nuestro campo, conocer la cuestión a preguntar es casi tan importante como conseguir la respuesta en sí", afirma Farr.
  Por su parte, el profesor Ilya Mandel, también de la Universidad de Birmingham, asegura que la explicación correcta se sabrá en los próximos años. "Este campo está en el periodo de la infancia, estoy seguro de que en un futuro próximo miraremos hacia atrás a estas primeras detecciones y modelos rudimentarios con nostalgia y a una mejor comprensión de cómo se forman estos exóticos sistemas binarios", vaticina el experto.

Fuente: http://www.lavanguardia.com/vida/20170823/43762035076/observaciones-de-las-ondas-gravitacionales-detectadas-por-ligo-sugieren-dos-escenarios-de-formacion-de-agujeros-negros.html

Hubble Detects Exoplanet with Glowing Water Atmosphere

This artist's concept shows hot Jupiter WASP-121b, which presents the best evidence yet of a stratosphere on an exoplanet.

Credits: Engine House VFX, At-Bristol Science Centre, University of Exeter

The top of the planet's atmosphere is heated to a blazing 4,600 degrees Fahrenheit (2,500 Celsius), hot enough to boil some metals.

Credits: NASA, ESA, and G. Bacon (STSci)

Scientists have discovered the strongest evidence to date for a stratosphere on a planet outside our solar system, or exoplanet. A stratosphere is a layer of atmosphere in which temperature increases with higher altitudes.

"This result is exciting because it shows that a common trait of most of the atmospheres in our solar system -- a warm stratosphere -- also can be found in exoplanet atmospheres," said Mark Marley, study co-author based at NASA's Ames Research Center in California's Silicon Valley. "We can now compare processes in exoplanet atmospheres with the same processes that happen under different sets of conditions in our own solar system."

Reporting in the journal Nature, scientists used data from NASA's Hubble Space Telescope to study WASP-121b, a type of exoplanet called a "hot Jupiter." Its mass is 1.2 times that of Jupiter, and its radius is about 1.9 times Jupiter's -- making it puffier. But while Jupiter revolves around our sun once every 12 years, WASP-121b has an orbital period of just 1.3 days. This exoplanet is so close to its star that if it got any closer, the star's gravity would start ripping it apart. It also means that the top of the planet's atmosphere is heated to a blazing 4,600 degrees Fahrenheit (2,500 Celsius), hot enough to boil some metals. The WASP-121 system is estimated to be about 900 light years from Earth – a long way, but close by galactic standards.

Previous research found possible signs of a stratosphere on the exoplanet WASP-33b as well as some other hot Jupiters. The new study presents the best evidence yet because of the signature of hot water molecules that researchers observed for the first time.

“Theoretical models have suggested stratospheres may define a distinct class of ultra-hot planets, with important implications for their atmospheric physics and chemistry,” said Tom Evans, lead author and research fellow at the University of Exeter, United Kingdom. “Our observations support this picture.”

This 360° animation depicts planet WASP-121b; an exoplanet with an atmosphere of glowing water. With an atmosphere hot enough to boil iron, WASP-121b is a type of exoplanet known as a 'hot Jupiter'. The planet orbits closely to it's host star, located in the constellation of 'Puppis', about 900 light years away from Earth.

To study the stratosphere of WASP-121b, scientists analyzed how different molecules in the atmosphere react to particular wavelengths of light, using Hubble's capabilities for spectroscopy.  Water vapor in the planet's atmosphere, for example, behaves in predictable ways in response to certain wavelengths of light, depending on the temperature of the water.

Starlight is able to penetrate deep into a planet's atmosphere, where it raises the temperature of the gas there. This gas then radiates its heat into space as infrared light. However, if there is cooler water vapor at the top of the atmosphere, the water molecules will prevent certain wavelengths of this light from escaping to space. But if the water molecules at the top of the atmosphere have a higher temperature, they will glow at the same wavelengths.

"The emission of light from water means the temperature is increasing with height," said Tiffany Kataria, study co-author based at NASA's Jet Propulsion Laboratory, Pasadena, California. "We're excited to explore at what longitudes this behavior persists with upcoming Hubble observations."  

The phenomenon is similar to what happens with fireworks, which get their colors from chemicals emitting light. When metallic substances are heated and vaporized, their electrons move into higher energy states. Depending on the material, these electrons will emit light at specific wavelengths as they lose energy: sodium produces orange-yellow and strontium produces red in this process, for example. The water molecules in the atmosphere of WASP-121b similarly give off radiation as they lose energy, but in the form of infrared light, which the human eye is unable to detect.

In Earth's stratosphere, ozone gas traps ultraviolet radiation from the sun, which raises the temperature of this layer of atmosphere. Other solar system bodies have stratospheres, too; methane is responsible for heating in the stratospheres of Jupiter and Saturn's moon Titan, for example.

In solar system planets, the change in temperature within a stratosphere is typically around 100 degrees Fahrenheit (about 56 degrees Celsius). On WASP-121b, the temperature in the stratosphere rises by 1,000 degrees (560 degrees Celsius). Scientists do not yet know what chemicals are causing the temperature increase in WASP-121b's atmosphere. Vanadium oxide and titanium oxide are candidates, as they are commonly seen in brown dwarfs, "failed stars" that have some commonalities with exoplanets. Such compounds are expected to be present only on the hottest of hot Jupiters, as high temperatures are needed to keep them in a gaseous state.

"This super-hot exoplanet is going to be a benchmark for our atmospheric models, and it will be a great observational target moving into the Webb era," said Hannah Wakeford, study co-author who worked on this research while at NASA's Goddard Space Flight Center, Greenbelt, Maryland.

The Hubble Space Telescope is a project of international cooperation between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, manages the telescope. The Space Telescope Science Institute (STScI) in Baltimore, Maryland, conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington. Caltech manages JPL for NASA.

For more information about Hubble, visit:

https://nasa.gov/hubble
http://hubblesite.org

For more information about exoplanets, visit:

https://exoplanets.nasa.gov

Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6425
elizabeth.landau@jpl.nasa.gov

Ray Villard
Space Telescope Science Institute, Baltimore, Maryland
410-338-4514
villard@stsci.edu

2017-204     

Last Updated: Aug. 4, 2017

Editor: Tony Greicius

Fuente: https://www.nasa.gov/feature/jpl/hubble-detects-exoplanet-with-glowing-water-atmosphere

Scientists photograph BIRTH OF TIME with astonishing new dark energy camera

SCIENTISTS have pictured the moment the lights came on in the universe – effectively the dawn of recordable time.

The cosmic dawn: Dark energy camera reveals 23 young galaxies that appeared just 800 million years after the Big Bang.

Using the powerful Dark Energy Camera in Chile, researchers have spotted 23 young galaxies as they appeared 800 million years after the Big Bang, when the universe first began to transform from the darkness of its birth

For the first 300,000 years after the Big Bang the rapidly expanding universe was dark and filled with neutral hydrogen gas doing nothing much.

But over the next half billion years the first stars and galaxies arrive through a process known as re-ionization – turning the lights on in the universe.

NASA

Let there be light: NASA pic of how the universe became illuminated

Using an amazing Dark Energy Camera which is part of the -meter Blanco Telescope, at Cerro Tololo Inter-American Observatory (CTIO), in northern Chile, scientists have captured a picture of 23 of these young galaxies – the very dawn of visual time.

Arizona State University astronomers Sangeeta Malhotra and James Rhoads, working with international teams in Chile and China, are now attempting to find when the very first light illuminated the universe.

This dramatic moment, known as re-ionization, occurred sometime in the interval between 300 million years and one billion years after the Big Bang.

NASA

Last scattering: The universe was dark for 300 million years and will remain a closed book

Mr Malhotra said: “Before re-ionization, these galaxies were very hard to see, because their light is scattered by gas between galaxies, like a car's headlights in fog.

“As enough galaxies turn on and 'burn off the fog' they become easier to see. By doing so, they help provide a diagnostic to see how much of the 'fog' remains at any time in the early universe.

"Several years ago, we carried out a similar study using a 64-megapixel camera that covers the same amount of sky as the full moon.

"The Dark Energy Camera (DECam) by comparison, is a 570-megapixel camera and covers 15 times the area of the full moon in a single image."

NASA

Light show: How re-ionisation turned the lights on in the universe

DECam was recently made even more powerful when it was equipped with a special narrowband filter, designed at ASU's School of Earth and Space Exploration (SESE), primarily by Rhoads and Zheng (who was a SESE postdoctoral fellow and is currently at the Shanghai Astronomical Observatory in China), with assistance from Alistair Walker of NOAO.

Mr Zheng said: "We spent several months refining the design of the filter profile, optimizing the design to get maximum sensitivity in our search.

The galaxy search using the ASU-designed filter and DECam is part of the ongoing "Lyman Alpha Galaxies in the Epoch of Reionization" project (LAGER). It is the largest uniformly selected sample that goes far enough back in the history of the universe to reach cosmic dawn.

"The combination of large survey size and sensitivity of this survey enables us to study galaxies that are common but faint, as well as those that are bright but rare, at this early stage in the universe," says Malhotra.

Junxian Wang, a co-author on this study and the lead of the Chinese LAGER team, adds that "our findings in this survey imply that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang."

The next steps for the team will be to build on these results. They plan to continue to search for distant star forming galaxies over a larger volume of the universe and to further investigate the nature of some of the first galaxies in the universe.

Read more: http://www.dailymail.co.uk/sciencetech/article-4747960/Dark-energy-camera-reveals-look-cosmic-dawn.html#ixzz4obIADV27 
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Fuente: http://www.express.co.uk/news/science/835116/DAWN-OF-TIME-dark-matter-camera-when-did-time-start-re-ionizaton

La primera imagen del entramado de materia oscura que conecta las galaxias

^{En un mapa de color falso, la región en que se encuentran las galaxias aparece en blanco, mientras que los filamentos de materia oscura uniendo las galaxias se presenta en rojo.} 

^{S. Epps & M. Hudson / University of Waterloo}

El universo, ese mundo infinito de oscuridad salpicado de trillones de galaxias, es, de hecho un entramado de redes intergalácticas conectadas por filamentos invisibles de materia oscura. Si es que hasta ahora se te ha hecho complicado pensar en cómo sería este escenario, un grupo de científicos ha conseguido darnos una idea. Por fin, gracias a investigadores de la Universidad de Waterloo, Canadá, hemos sido capaces de capturar la primera imagen compuesta de un “puente de materia oscura” que conecta y une las galaxias. El trabajo ha sido publicado en Monthly Notices of the Royal Astronomical Society.

La imagen compuesta, que combina un número de imágenes individuales, confirma las predicciones de que las galaxias a lo largo del universo están atadas juntas a través de una red cósmica conectada por materia oscura —hasta ahora— imposible de observar.

La materia obscura, esa misteriosa sustancia que se estima, comprende el 25% del universo, no brilla, no absorbe ni refleja luz, lo que la ha hecho largamente indetectable a no ser por la gravedad. “Esta imagen nos lleva más allá de las predicciones hacia algo que podemos ver y medir”, han indicado los autores en declaraciones que recoge Phys.org.

Como parte del trabajo, Mike Hudson y Seth Epps usaron una técnica llamada “weak gravitational lensing” (lente gravitacional débil), un efecto que hace que las imágenes de galaxias distantes se deformen ligeramente bajo la influencia de una masa invisible como un planeta, un agujero negro, o en este caso, la materia oscura. El efecto fue medido en imágenes desde una observación multianual del cielo en el Telescopio Canadá-Francia-Hawaii.

Así, combinaron imágenes de lente de más de 23.000 pares de galaxias a 4.500 millones de años luz de distancia para crear una imagen compuesta o un mapa que muestra la presencia de materia oscura entre las dos galaxias. Los resultados muestran que el puente de filamento de materia oscura es más fuerte entre sistemas a menos de 40 millones de años luz separados.

La técnica, explican los astrónomos, no solo permite ver la existencia de los filamentos de materia oscura, sino también en qué medida estos filamentos enlazan a las galaxias.

Al igual que la materia oscura, los agujeros negros son objetos misteriosos del espacio de los que cada cierto tiempo se conoce nuevos detalles: hace poco un grupo de científicos europeos reveló que las estrellas se forman dentro de los flujos de material expulsados de los agujeros negros supermasivos.

Fuente: https://nmas1.org/news/2017/04/13/imagen-materia