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viernes, 11 de marzo de 2016

NASA | 2016 Science - Seeing the Inner Corona . Eclipse Total


Scientists from NASA Goddard explain the experiment they will perform in Indonesia during the March 2016 total solar eclipse. During the brief period of totality, the team will use a new instrument to measure polarized light from the sun’s faint atmosphere, the corona, in order to study the temperature and speed of electrons.
Credits: NASA’s Goddard Space Flight Center/Duberstein

A Moment in the Sun’s Atmosphere: NASA’s Science During the March 2016 Total Solar Eclipse


As the moon slowly covers the face of the sun on the morning of March 9, 2016, in Indonesia, a team of NASA scientists will be anxiously awaiting the start of totality – because at that moment, their countdown clock begins. They plan to take 59 several-second exposures of the sun in just over three minutes, capturing data on the innermost parts of the sun’s volatile, superhot atmosphere – a region we can only observe during total solar eclipses when the sun’s overwhelmingly bright face is completely blocked by the moon.

“The sun’s atmosphere is where the interesting physics is,” said Nelson Reginald, one of several space scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who will conduct an experiment in Indonesia during March 2016’s total solar eclipse. “A total solar eclipse gives us the opportunity to see very close to the solar limb.”
The lower part of the sun’s atmosphere, the corona, is one of the most scientifically interesting areas of the sun. It’s thought to hold the keys to several solar mysteries, from the acceleration of the solar wind, to the birth of explosive clouds of solar material called coronal mass ejections, to the mysterious heating of the corona as a whole. Using a new instrument, the NASA science team will observe aspects of polarized light that carry information about the temperature and velocity of electrons in the lower corona.

Though it’s about as bright as the full moon, the corona is ordinarily drowned out by the sun’s much brighter face, except during total solar eclipses. To study the corona outside of total solar eclipses, scientists use instruments called coronagraphs, which create artificial eclipses by using solid disks to block sun’s bright face and reveal the comparatively faint corona. But because light bends around sharp edges – a phenomenon known as diffraction – coronagraph disks obscure the inner corona, as well as the solar surface, to combat this effect.

“You can’t see the corona that close to the surface with a coronagraph. You cut off a large portion of the innermost corona,” said Nat Gopalswamy, principal investigator of the eclipse experiment at Goddard. “The main advantage of the total solar eclipse is seeing much closer to the sun’s surface.”
 
SOHO image of the sun
Outside of total solar eclipses, scientists use an instrument called a coronagraph to see the sun’s tenuous atmosphere. Because of how light bends around sharp edges coronagraphs block this extra light by blocking part of the inner corona. In this coronagraph image, the white circle outlines the extent of the solar surface, showing how much of the sun's atmosphere is blocked by the coronagraph’s disk.
 
Credits: NASA/SOHO
 
The team will use their three minutes of totality to examine the polarized light coming from the sun’s inner corona, light that contains information about the temperature and velocity of the electrons there. Light is polarized when its electric field oscillates along one axis, for instance, up-and-down or side-to-side. Unlike dust, electrons mainly scatter polarized light, meaning that isolating the polarized light can give information about the temperature and flow speed of coronal electrons. Polarized light scattered by these electrons dominates in the regions of the corona closest to the solar surface – so total solar eclipses are our best chance to gather this information. 

“We first used this instrument during the 1999 total solar eclipse in Turkey,” said Reginald.

The minutes-long timeframe of total solar eclipses limits the amount of data we can collect during our occasional glimpses at the inner corona, so the team rebuilt their instrument over the last year to make it even faster.

“Before, we would have had use a polarizer that would turn through three angles for each wavelength filter,” said Reginald. “The new polarization camera eliminates the need for a polarization wheel.”

Rather than using a hand-turned polarization wheel to take three separate images in each polarized direction, the new camera uses thousands of tiny polarization filters to read light polarized in different directions simultaneously. Each pixel in the new camera is made of four subpixels with differently-oriented polarization filters, which provides the team with four separate but simultaneous images of the corona and cuts out the need to change polarization filters between exposures.

“We’ve cut down the length of time required for our experiment by more than 50 percent,” said Gopalswamy. “The polarization camera is faster and less risky, because it’s one less moving part.”

Though the team will be performing the experiment for the first time in the province of North Maluku, Indonesia – chosen for its accessibility and high chances of clear skies during the eclipse – they’ve already given their updated instrument a test run.  

“The brightness of the full moon is about equal to the brightness of the total solar eclipse,” said Reginald. “So we set up our telescope in the parking lot for practice.”

In partnership with Exploratorium, NASA TV will be showing a live stream of the eclipse on March 8, 2016, from 8-9 pm ET. 

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Last Updated: March 3, 2016
Editor: Rob Garner

March 9, 2016
 

Solar Eclipse Over the South Pacific Ocean

Clouds over the ocean gradually shaded darker at right as solar eclipse begins to move across
During the afternoon of March 9, 2016, a total solar eclipse was visible in parts of southeast Asia and a partial eclipse was visible in parts of Alaska, Hawaii, Guam, and America Samoa. An eclipse occurs when the moon passes directly between Earth and the sun. When the moon's shadow falls on Earth, observers within that shadow see the moon block a portion of the sun's light.
The MODIS instrument on NASA's Aqua satellite captured this image of the total solar eclipse moving across the south Pacific Ocean at 03:05 UTC on March 9, 2016.
on the morning of March 9 at 01:40 UTC.
Image Credit: NASA Goddard MODIS Rapid Response Team
Last Updated: March 9, 2016
Editor: Sarah Loff

March 9, 2016
2016 Solar Eclipse
solar eclipse of March 2016 seen from Indonesia
This photo shows the March 2016 solar eclipse as seen from South Tangerang, Indonesia.
Credit: Photo copyright Ridwan Arifiandi; Creative Commons license CC BY-NC 2.0
Last Updated: March 9, 2016
Editor: Rob Garner
 
Feb. 26, 2016

NASA’s IBEX Observations Pin Down Interstellar Magnetic Field

Immediately after its 2008 launch, NASA’s Interstellar Boundary Explorer, or IBEX, spotted a curiosity in a thin slice of space: More particles streamed in through a long, skinny swath in the sky than anywhere else. The origin of the so-called IBEX ribbon was unknown – but its very existence opened doors to observing what lies outside our solar system, the way drops of rain on a window tell you more about the weather outside.

Now, a new study uses IBEX data and simulations of the interstellar boundary – which lies at the very edge of the giant magnetic bubble surrounding our solar system called the heliosphere – to better describe space in our galactic neighborhood. The paper, published Feb. 8, 2016, in The Astrophysical Journal Letters, precisely determines the strength and direction of the magnetic field outside the heliosphere. Such information gives us a peek into the magnetic forces that dominate the galaxy beyond, teaching us more about our home in space.
artist concept of boundary region of our solar system
(Artist concept) Far beyond the orbit of Neptune, the solar wind and the interstellar medium interact to create a region known as the inner heliosheath, bounded on the inside by the termination shock, and on the outside by the heliopause.
Credits: NASA/IBEX/Adler Planetarium

The new paper is based on one particular theory of the origin of the IBEX ribbon, in which the particles streaming in from the ribbon are actually solar material reflected back at us after a long journey to the edges of the sun’s magnetic boundaries. A giant bubble, known as the heliosphere, exists around the sun and is filled with what’s called solar wind, the sun’s constant outflow of ionized gas, known as plasma. When these particles reach the edges of the heliosphere, their motion becomes more complicated.  

simulation illustrating IBEX ribbon
This simulation shows the origin of ribbon particles of different energies or speeds outside the heliopause (labeled HP). The IBEX ribbon particles interact with the interstellar magnetic field (labeled ISMF) and travel inwards toward Earth, collectively giving the impression of a ribbon spanning across the sky.
Credits: SwRI/Zirnstein
 
“The theory says that some solar wind protons are sent flying back towards the sun as neutral atoms after a complex series of charge exchanges, creating the IBEX ribbon,” said Eric Zirnstein, a space scientist at the Southwest Research Institute in San Antonio, Texas, and lead author on the study. “Simulations and IBEX observations pinpoint this process – which takes anywhere from three to six years on average – as the most likely origin of the IBEX ribbon.”

Outside the heliosphere lies the interstellar medium, with plasma that has different speed, density, and temperature than solar wind plasma, as well as neutral gases. These materials interact at the heliosphere’s edge to create a region known as the inner heliosheath, bounded on the inside by the termination shock – which is more than twice as far from us as the orbit of Pluto – and on the outside by the heliopause, the boundary between the solar wind and the comparatively dense interstellar medium.

Some solar wind protons that flow out from the sun to this boundary region will gain an electron, making them neutral and allowing them to cross the heliopause. Once in the interstellar medium, they can lose that electron again, making them gyrate around the interstellar magnetic field. If those particles pick up another electron at the right place and time, they can be fired back into the heliosphere, travel all the way back toward Earth, and collide with IBEX’s detector. The particles carry information about all that interaction with the interstellar magnetic field, and as they  hit the detector they can give us unprecedented insight into the characteristics of that region of space.

“Only Voyager 1 has ever made direct observations of the interstellar magnetic field, and those are close to the heliopause, where it’s distorted,” said Zirnstein. “But this analysis provides a nice determination of its strength and direction farther out.”

The directions of different ribbon particles shooting back toward Earth are determined by the characteristics of the interstellar magnetic field. For instance, simulations show that the most energetic particles come from a different region of space than the least energetic particles, which gives clues as to how the interstellar magnetic field interacts with the heliosphere.

For the recent study, such observations were used to seed simulations of the ribbon’s origin. Not only do these simulations correctly predict the locations of neutral ribbon particles at different energies, but the deduced interstellar magnetic field agrees with Voyager 1 measurements, the deflection of interstellar neutral gases, and observations of distant polarized starlight.

However, some early simulations of the interstellar magnetic field don’t quite line up. Those pre-IBEX estimates were based largely on two data points – the distances at which Voyagers 1 and 2 crossed the termination shock.  

“Voyager 1 crossed the termination shock at 94 astronomical units, or AU, from the sun, and Voyager 2 at 84 AU,” said Zirnstein. One AU is equal to about 93 million miles, the average distance between Earth and the sun. “That difference of almost 930 million miles was mostly explained by a strong, very tilted interstellar magnetic field pushing on the heliosphere.” 

But that difference may be accounted for by considering a stronger influence from the solar cycle, which can lead to changes in the strength of the solar wind and thus change the distance to the termination shock in the directions of Voyager 1 and 2. The two Voyager spacecraft made their measurements almost three years apart, giving plenty of time for the variable solar wind to change the distance of the termination shock.

“Scientists in the field are developing more sophisticated models of the time-dependent solar wind,” said Zirnstein.

The simulations generally jibe well with the Voyager data.
measurements of "IBEX ribbon"
The IBEX ribbon is a relatively narrow strip of particles flying in towards the sun from outside the heliosphere. A new study corroborates the idea that particles from outside the heliosphere that form the IBEX ribbon actually originate at the sun – and reveals information about the distant interstellar magnetic field.
Credits: SwRI

“The new findings can be used to better understand how our space environment interacts with the interstellar environment beyond the heliopause,” said Eric Christian, IBEX program scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in this study. “In turn, understanding that interaction could help explain the mystery of what causes the IBEX ribbon once and for all.”

The Southwest Research Institute leads IBEX with teams of national and international partners. NASA Goddard manages the Explorers Program for the agency’s Heliophysics Division within the Science Mission Directorate in Washington.
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Last Updated: Feb. 26, 2016
Editor: Rob Garner
 

El 8 de Marzo se Producirá un Eclipse Total de Sol

 
06.03.16.- La gente de parte del sudeste asiático verá el Sol en una nueva luz el 8 de Marzo de 2016, (9 de Marzo, hora local) durante un eclipse total de Sol que va a durar más de un minuto en todos los puntos de su trayectoria.
A medida que la Luna pase exactamente entre el Sol y la Tierra - una ocurrencia relativamente rara que ocurre sólo una vez al año a causa del hecho de que la Luna y el Sol no orbitan en el mismo plano exacto - bloqueará la cara brillante del Sol, revelando la atmósfera solar tenue y relativamente débil, la corona.
"Se nota algo fuera de la luz del Sol cuando llega a la totalidad," dijo Sarah Jaeggli, científico espacial en el Centro de Vuelo Espacial Goddard de la NASA en Greenbelt, Maryland, que ha visto dos eclipses solares totales. "Su entorno adquieren un elenco de crepúsculo, a pesar de que es de día y el cielo sigue siendo azul."
 
 
El fenómeno durará entre uno y medio a poco más de cuatro minutos en cada lugar, aunque pasarán más de tres horas entre el momento en el que el lugar más occidental comience a ver el eclipse y hasta que la ubicación más oriental vea el final del eclipse. La gente a lo largo de la trayectoria de la totalidad - que abarca más de 14.162 kilómetros de largo, pero sólo 156 kilómetros de ancho en su punto más ancho - tendrá la oportunidad de ver la corona solar solamente mientras la cara del Sol está totalmente cubierta por la Luna.
Los eclipses totales de este tipo son posibles debido a que la geometría planetaria es muy precisa: El Sol es 400 veces más ancho que la Luna, pero también está un poco más de 400 veces más lejos de la Tierra que la Luna durante los eclipses solares totales, por lo que nuestros ojos apreciarán el mismo tamaño en el cielo. Esto significa que la Luna puede bloquear la totalidad de la cara del Sol, mientras que oscurece solamente una pequeña porción de la corona interior.
 
 
Aunque sólo las personas a lo largo del camino estrecho de la totalidad verán el eclipse total, millones de personas más verán el eclipse solar de manera parcial en Asia y el Pacífico, incluyendo Hawai, Guam y partes de Alaska. También se verá el eclipse de manera parcial a lo largo de la trayectoria de la totalidad durante más de una hora antes y después del eclipse total.
Si tienes la suerte de poder observar este acontecimiento, debes tener mucho cuidado: nunca se debe mirar directamente al Sol, ya que si no se utiliza una protección adecuada, se pueden causar graves daños oculares. Existen varias maneras de observar el evento, bien a través de gafas especiales, o telescopios con filtros adecuados. Pero recuerde, NUNCA se debe de mirar directamente al Sol.

Spooky lightning

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  • Title Spooky lightning
  • Released 09/03/2016 10:07 am
  • Copyright ESA/NASA
  • Description ESA astronaut Tim Peake took this image circling Earth 400 km up in the International Space Station. He commented: “Sometimes looking down on Earth at night can be kinda spooky.”
    The image shows lightning strikes illuminating clouds over Western Australia during a thunderstorm. The Space Station travels at 28 800 km/h so it takes only 90 minutes to complete an orbit of Earth. Astronauts often spot thunderstorms and are impressed by how much lightning they observe.
    Although this picture was taken in Tim’s free time, the Station is used for research into elusive phenomena in the upper atmosphere during thunderstorms – red sprites, blue jets and elves. Some of the most violent electric discharges are very difficult to capture from the ground because of the atmosphere’s blocking effect. From space, astronauts can judge for themselves where to aim the camera, where to zoom in and follow interesting regions for researchers.
  • Id 356086
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Guillermo Gonzalo Sánchez Achutegui