Mi lista de blogs

lunes, 2 de mayo de 2016

NASA : Promising Worlds Found Around Nearby Ultra-cool Dwarf Star .- Palabras prometedores: Encontrado una Estrella Enana Alrededor y Cercaa una Ultrarefrescante

Hola amigos: A VUELO DE UN QUINDE EL BLOG., hemos recibido información de la Agencia Espacial NASA, sobre el descubrimiento por ESO de la estrella: "Dr. Susan Lederer se encuentra junto al Telescopio UKIRT ubicado en Mauna Kea en la isla de Hawai, que se utilizó para confirmar la existencia de los exoplanetas recientemente descubiertos y restringir sus periodos orbitales. Lederer dice, "Para un pequeño, fresco, estrella tan desprendiendo gran parte de su luz en el, el telescopio infrarrojo UKIRT, diseñado exclusivamente para observaciones en el infrarrojo, era ideal para la confirmación de la existencia de estos planetas del tamaño."
More information............

Artist’s impression of three planets orbiting an ultra-cool dwarf star
This artist’s impression shows an imagined view of the three planets orbiting an ultra-cool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO’s La Silla Observatory. In this view, one of the inner planets is seen in transit across the disc of its tiny and dim parent star.
Credits: ESO/M. Kornmesser/N. Risinger (skysurvey.org)
Dr. Susan Lederer and TRAPPIST telescope
Dr. Susan Lederer stands next to the UKIRT Telescope located on Mauna Kea on the island of Hawai’i, which was used to confirm the existence of the newly discovered exoplanets and constrain their orbital periods. Says Lederer, "For such a small, cool, star giving off so much of its light in the infrared, the UKIRT telescope, designed solely for infrared observations, was ideally suited for confirming the existence of these Earth-sized planets.”
Astronomers using the TRAPPIST telescope at ESO’s La Silla Observatory have discovered three planets with sizes and temperatures similar to those of Venus and Earth, orbiting an ultra-cool dwarf star just 40 light-years from Earth.

Michaël Gillon of the University of Liège in Belgium, leading a team of astronomers including Susan M. Lederer of NASA Johnson Space Center, have used the TRAPPIST telescope to observe the star 2MASS J23062928-0502285, now also known as TRAPPIST-1. They found that this dim and cool star faded slightly at regular intervals, indicating that several objects were passing between the star and the Earth. Detailed analysis showed that three planets are present around the star.

TRAPPIST-1 is an ultra-cool dwarf star — it is much cooler and redder than the Sun and barely larger than Jupiter. Despite being so close to the Earth, this star is too dim and too red to be seen with the naked eye or even visually with a large amateur telescope. It lies in the constellation of Aquarius (The Water Carrier).

Follow-up observations with larger telescopes, including the HAWK-I instrument on ESO’s 8-metre Very Large Telescope in Chile, have shown that the planets orbiting TRAPPIST-1 have sizes very similar to that of Earth. Two of the planets have orbital periods of about 1.5 days and 2.4 days respectively, and the third planet has a less well-determined orbital period in the range 4.5 to 73 days.

"With such short orbital periods, the planets are between 20 and 100 times closer to their star than the Earth to the Sun. The structure of this planetary system is much more similar in scale to the system of Jupiter’s moons than to that of the Solar System," explains Michaël Gillon.

Although they orbit very close to their host dwarf star, the inner two planets only receive four times and twice, respectively, the amount of radiation received by the Earth, because their star is much fainter than the Sun. That puts them closer to the star than the so-called habitable zone for this system, defined as having surface temperatures where liquid water can exist, although it is still possible that they possess potentially habitable regions on their surfaces. The third, outer, planet’s orbit is not yet well known, but it probably receives less radiation than the Earth does, but maybe still enough to lie within the habitable zone. The new results will be published in the journal Nature on 2 May 2016.

NASA’s Hubble Space Telescope and K2, the Kepler spacecraft's second mission, will be observing TRAPPIST-1 and its planets later this year.

Fortuitously, two of these planets are transiting the star on May 4, an event that happens only once every two years as seen from Earth. Astronomers hope to make measurements of the atmospheres of both of these planets and look for evidence of water vapor. The Hubble Space Telescope can characterize the atmospheres of the planets in the TRAPPIST-1 system by observing them as they pass in front of, or transit, their parent star. Hubble astronomers will use spectroscopy to measure starlight as it filters through a planet’s atmosphere.

K2 will observe TRAPPIST-1 as part of their Campaign 12, which is scheduled to take place from Dec. 15 to March 4, 2017. The data are expected to be available at the public archive the end of May 2017.  

K2 will observe tens of transits of the two close-in Earth-sized exoplanets during the approximately 80-day campaign. The continuous and multiple observations will allow for measurements of predicted transit timing variations – the gravitational interaction between planets that cause transits to occur slightly earlier or slightly later than predicted. This will provide estimates of the masses of these exoplanets. Using K2’s mass measurements and TRAPPIST's ground-based size measurements, astronomers can calculate or constrain the density of the exoplanets to determine if they could be rocky worlds.

K2’s observations will also help scientists determine the orbital period of the third planet, and help find any additional small transiting objects in the system.

The TRAPPIST-1 system is an ideal target for NASA’s James Webb Space Telescope. Webb’s infrared sensitivity will be able to detect carbon dioxide, methane, water vapor, and other molecules common in the atmospheres of the rocky planets in our own solar system.

"Thanks to several giant telescopes currently under construction, including ESO’s E-ELT and the NASA/ESA/CSA James Webb Space Telescope due to launch for 2018, we will soon be able to study the atmospheric composition of these planets and to explore them first for water, then for traces of biological activity. That's a giant step in the search for life in the Universe," says Julien de Wit, a co-author from the Massachusetts Institute of Technology (MIT) in the USA.

The TRAPPIST survey is a prototype for a more ambitious project called SPECULOOS that will be installed at ESO’s Paranal Observatory.
For more information, please go to:http://www.eso.org/public/news/eso1615/
Last Updated: May 2, 2016
Editor: Mark Garcia
Free-floating exoplanet
April 7, 2016

Searching for Far Out and Wandering Worlds

Astronomers have made great strides in discovering planets outside of our solar system, termed “exoplanets.” In fact, over the past 20 years more than 5,000 exoplanets have been detected beyond the eight planets that call our solar system home.
K2 and gravitational microlensing
As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases results in a brief brightening of the background star as seen by a telescope. The artistic concept illustrates this effect. This phenomenon of gravitational microlensing enables scientists to search for exoplanets that are too distant and dark to detect any other way.
Credits: NASA Ames/JPL-Caltech/T. Pyle
The majority of these exoplanets have been found snuggled up to their host star completing an orbit (or year) in hours, days or weeks, while some have been found orbiting as far as Earth is to the sun, taking one-Earth-year to circle. But, what about those worlds that orbit much farther out, such as Jupiter and Saturn, or, in some cases, free-floating exoplanets that are on their own and have no star to call home? In fact, some studies suggest that there may be more free-floating exoplanets than stars in our galaxy.

This week, NASA's K2 mission, the repurposed mission of the Kepler space telescope, and other ground-based observatories have teamed up to kick-off a global experiment in exoplanet observation. Their mission: survey millions of stars toward the center of our Milky Way galaxy in search of distant stars' planetary outposts and exoplanets wandering between the stars.

While today's planet-hunting techniques have favored finding exoplanets near their sun, the outer regions of a planetary system have gone largely unexplored. In the exoplanet detection toolkit, scientists have a technique well suited to search these farthest outreaches and the space in between the stars. This technique is called gravitational microlensing.


Gravitational Microlensing

For this experiment, astronomers rely on the effect of a familiar fundamental force of nature to help detect the presence of these far out worlds— gravity. The gravity of massive objects such as stars and planets produces a noticeable effect on other nearby objects.

But gravity also influences light, deflecting or warping, the direction of light that passes close to massive objects. This bending effect can make gravity act as a lens, concentrating light from a distant object, just as a magnifying glass can focus the light from the sun. Scientists can take advantage of the warping effect by measuring the light of distant stars, looking for a brightening that might be caused by a massive object, such as a planet, that passes between a telescope and a distant background star. Such a detection could reveal an otherwise hidden exoplanet.
"The chance for the K2 mission to use gravity to help us explore exoplanets is one of the most fantastic astronomical experiments of the decade," said Steve Howell, project scientist for NASA's Kepler and K2 missions at NASA’s Ames Research Center in California's Silicon Valley. "I am happy to be a part of this K2 campaign and look forward to the many discoveries that will be made."
K2's Microlensing Search Area - zoom
In a global experiment in exoplanet observation, the K2 mission and Earth-based observatories on six continents will survey millions of stars toward the center of our Milky Way galaxy. Using a technique called gravitational microlensing, scientists will hunt for exoplanets that orbit far from their host star, such as Jupiter is to our sun, and for free-floating exoplanets that wander between the stars. The method allow exoplanets to be found that are up to 10 times more distant than those found by the original Kepler mission, which used the transit technique. The artistic concept illustrates the relative locations of the search areas for NASA's K2 and Kepler missions.
Credits: NASA Ames/W. Stenzel and JPL-Caltech/R. Hurt
 
This phenomenon of gravitational microlensing – “micro” because the angle by which the light is deflected is small – is the effect for which scientists will be looking during the next three months. As an exoplanet passes in front of a more distant star, its gravity causes the trajectory of the starlight to bend, and in some cases results in a brief brightening of the background star as seen by the observatory.
The lensing events caused by a free-floating exoplanet last on the order of a day or two, making the continuous gaze of the Kepler spacecraft an invaluable asset for this technique.
"We are seizing the opportunity to use Kepler's uniquely sensitive camera to sniff for planets in a different way," said Geert Barentsen, research scientist at Ames.

The ground-based observatories will record simultaneous measurements of these brief events. From their different vantage points, space and Earth, the measurements can determine the location of the lensing foreground object through a technique called parallax.
“This is a unique opportunity for the K2 mission and ground-based observatories to conduct a dedicated wide-field microlensing survey near the center of our galaxy," said Paul Hertz, director of the astrophysics division in NASA’s Science Mission Directorate at the agency’s headquarters in Washington. "This first-of-its-kind survey serves as a proof of concept for NASA’s Wide-Field Infrared Survey Telescope (WFIRST), which will launch in the 2020s to conduct a larger and deeper microlensing survey. In addition, because the Kepler spacecraft is about 100 million miles from Earth, simultaneous space- and ground-based measurements will use the parallax technique to better characterize the systems producing these light amplifications."
To understand parallax, extend your arm and hold up your thumb. Close one eye and focus on your thumb and then do the same with the other eye. Your thumb appears to move depending on the vantage point. For humans to determine distance and gain depth perception, the vantage points, our eyes, use parallax.

Flipping the Spacecraft

The Kepler spacecraft trails Earth as it orbits the sun and is normally pointed away from Earth during the K2 mission. But this orientation means that the part of the sky being observed by the spacecraft cannot generally be observed from Earth at the same time, since it is mostly in the daytime sky.

To allow simultaneous ground-based observations, flight operations engineers at Ball Aerospace and the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder will perform a maneuver turning the spacecraft around to point the telescope in the forward velocity vector. So, instead of looking towards where it’s been, the spacecraft will look in the direction of where it’s going.

This alignment will yield a viewing opportunity of Earth and the moon as they cross the spacecraft's field of view. On April 14 at 11:50 a.m. PDT (18:50 UT), Kepler will record a full frame image. The result of that image will be released to the public archive in June once the data has been downloaded and processed. Kepler measures the change in brightness of objects and does not resolve color or physical characteristics of an observed object.

Observing from Earth

To achieve the objectives of this important path-finding research and community exercise in anticipation of WFIRST, approximately two-dozen ground-based observatories on six continents will observe in concert with K2. Each will contribute to various aspects of the experiment and will help explore the distribution of exoplanets across a range of stellar systems and distances.

These results will aid in our understanding of both planetary system architectures as well as the frequency of exoplanets throughout our galaxy.

For a complete list of participating observatories, reference the paper that defines the experiment: Campaign 9 of the K2 mission.

During the roughly 80-day observing period or campaign, astronomers hope to discover over 100 lensing events, ten or more of which may have signatures of exoplanets occupying relatively unexplored regimes of parameter space.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

For more information about the Kepler and K2 missions, visit:

NASA
Guillermo Gonzalo Sánchez Achutegui