Author: Fraser Cain

Image credit: NASA

NASA’s Terra satellite is keeping a watchful camera pointed towards a glacier in the mountains of Peru. A large crack has appeared in the sheet of ice, and it could crumble into Lake Palcacocha, sending a wall of water and rubble into a nearby town of 60,000 people. This has been a controversial announcement, however, with several US and Peruvian geologists feel that the danger is exaggerated.

An Earth-monitoring instrument aboard NASA’s Terra satellite is keeping a close eye on a potential glacial disaster-in-the-making in Peru’s spectacular, snow-capped Cordillera Blanca (White Mountains), the highest range of the Peruvian Andes.

Data from NASA’s Advanced Spaceborne Thermal Emission and Reflection Radiometer (Aster) is assisting Peruvian government officials and geologists in monitoring a glacier that feeds Lake Palcacocha, located high above the city of Huaraz, 270 kilometers (168 miles) north of Lima. An ominous crack has developed in the glacier. Should the large glacier chunk break off and fall into the lake, the ensuing flood could hurtle down the Cojup Valley into the Rio Santa Valley below, reaching Huaraz and its population of 60,000 in less than 15 minutes.

“Remote sensing instruments like Aster can serve a vital role in mountain hazard management and disaster mapping by providing rapid access to data, even in regions not easily accessible by humans,” explained Dr. Michael Abrams, associate Aster team leader at NASA’s Jet Propulsion Laboratory, Pasadena, Calif.

“Aster’s unique vantage point from space gives scientists another tool with which to see early signs of potential glacial flood-burst events and to monitor changes in glacial behavior over time. In Huaraz, Peruvian authorities and scientists will incorporate Aster data along with data from ground-based monitoring techniques to better assess current conditions and take steps necessary to reduce risks to human lives and property,” Abrams said.

Comparison images of the area and more information are available at: http://photojournal.jpl.nasa.gov/catalog/PIA03899. Huaraz can be seen in the images’ left-center, with Lake Palcacocha in the images’ upper right corners at the head of a valley, below the snow and glacier cap. The left image was acquired on November 5, 2001; the right on April 8, 2003.

Glacial flood-bursts, known by Peruvians as “aluviones,” occur periodically when water is released abruptly from a previously ice-dammed lake alongside, within, or above a glacier. The release can be caused by various triggering events. These flood-bursts typically arrive with little or no warning, carrying liquid mud, large rock boulders and blocks of ice.

The Rio Santa Valley is no stranger to such disasters. Since 1702, floods caused by glaciological conditions have repeatedly caused death and destruction in the region. One particularly devastating event in 1941 destroyed approximately one-third of Huaraz, killing an estimated 5,000 to 7,000 people. Since then, the Peruvian government has emphasized control of the water level in Lake Palcacocha and other lakes in the region that pose similar threats. The efforts appear to have worked; since 1972, no destructive floods resulting from the breakout of glacial lakes have occurred. Nevertheless, officials are still monitoring the current situation closely.

Aster’s broad spectral coverage and high spectral resolution is ideally suited for monitoring dynamic conditions and changes in Earth’s landscape over time, including glacial advances and retreats. Its 14 spectral bands measure from the visible to the thermal infrared wavelength region, and it can “see” at a resolution of 15 to 90 meters (about 50 to 300 feet).

Aster provides scientists in numerous disciplines with critical information used for surface mapping and monitoring of dynamic conditions and changes over time. Example applications include monitoring glacial advances and retreats and potentially active volcanoes; identifying crop stress; determining cloud morphology and physical properties; evaluating wetlands; monitoring thermal pollution and coral reef degradation; mapping surface temperatures of soils and geology; and measuring surface heat balance. It can also image the same area as frequently as every other day in response to urgent priorities.

Aster is one of five Earth-observing instruments launched December 18, 1999, on NASA’s Terra satellite. Japan’s Ministry of Economy, Trade and Industry built the instrument. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products.

The Terra satellite is part of NASA’s Earth Science Enterprise, a program dedicated to understanding the Earth as an integrated system and applying Earth system science to improve prediction of climate, weather and natural hazards using the unique vantage point of space.

The California Institute of Technology in Pasadena manages JPL for NASA.

Original Source: NASA/JPL News Release

Image credit: Chandra

The latest photos released from the Chandra X-Ray Observatory show x-rays produced from a brown dwarf which is orbiting a binary star system at a distance of 2.75 times that of the Pluto Charon orbit around the Sun. The star system is 180 light-years away from Earth in the constellation of Hydra. The brown dwarf, TWA 5B, is a failed star between 15 and 40 times the size of Jupiter.

A Chandra observation revealed X-rays produced by TWA 5B, a brown dwarf star orbiting a young binary star system known as TWA 5A. The star system is 180 light years from the Earth and a member of a group of about a dozen young stars in the Hydra constellation. The brown dwarf orbits the binary star system at a distance about 2.75 times that of Pluto’s orbit around the Sun.

The sizes of the sources in the image are due to an instrumental effect that causes the spreading of pointlike sources. For a comparison of the actual size of TWA 5B to the Sun and the planet Jupiter, see the illustration below.

Brown dwarfs are often referred to as “failed stars” because they are under the mass limit (about 80 Jupiter masses, or 8 percent of the mass of the Sun) needed to spark the nuclear fusion of hydrogen to helium which supplies the energy for stars such as the Sun. Lacking any central energy source, brown dwarfs are intrinsically faint and draw their energy from a very gradual shrinkage or collapse.

Young brown dwarfs, like young stars, have turbulent interiors. When combined with rapid rotation, this turbulent motion can lead to a tangled magnetic field that can heat their upper atmospheres, or coronas, to a few million degrees Celsius. The X-rays from both TWA 5A and TWA 5B are from their hot coronas.

TWA 5B is estimated to be only between 15 and 40 times the mass of Jupiter, making it one of the least massive brown dwarfs known. Its mass is rather near the boundary (about 12 Jupiter masses) between planets and brown dwarfs, so these results could have implications for the possible X-ray detection of very massive planets around stars.

Original Source: Chandra News Release

Image credit: Subaru Telescope

The Subaru telescope, based in Japan, has detected the most distant galaxy ever recorded at 12.8 billion light-years away. The Subaru Deep Field project team uncovered 70 candidate distant objects, by using a special filter which only allows light of a very specific wavelength to pass through – one that corresponds to objects which are approximately 13 billion light-years away.

Subaru telescope has found a galaxy 12.8 billion light years away (a redshift of 6.58; see note 1), the most distant galaxy ever observed. This discovery is the first result from the Subaru Deep Field Project, a research project of the Subaru Telescope of the National Astronomical Observatory of Japan which operates the Subaru telescope. The Subaru Deep Field (SDF) project team found approximately 70 distant galaxy candidates by attaching a special filter designed to detect galaxies around 13 billion light years away on a camera with a wide field of view. Follow-up observations with a spectrograph confirmed that two out of nine of the candidates are in fact distant galaxies. One of these is the most distant galaxy ever observed. This discovery raises the expectation that the project will be able to find a large number of distant galaxies that will help unravel the early history of the universe in a statistically meaningful manner.

The SDF project is an observatory project of the National Astronomical Observatory of Japan designed to showcase the abilities of Subaru telescope and to resolve fundamental astronomical questions that are difficult to address through Subaru’s regular time allocation system. Most research programs on Subaru telescope are selected through a competitive time allocation process called Open Use, which is open to all astronomers but allows a maximum of only three observing nights every six months. By pooling together observing nights reserved for the observatory and astronomers that contributed to the establishment of Subaru Telescope, an observatory project can address questions that require greater telescope resources than the typical research proposal. The SDF project’s main goal is to detect a large number of the most distant galaxies detectable and to understand their properties and their impact on the evolution of the universe. The speed of light is the fundamental limit to how fast information can travel (see note 2). When we detect light from a galaxy 13 billion light years away, that means we are seeing the galaxy as it was 13 billion years ago. Looking for ever more distant galaxies means looking at galaxies at earlier and earlier times in the universe.

The SDF observations took advantage of the fact that light from distant galaxies have a characteristic wavelength and shape. Astronomers think that the earliest galaxies rapidly formed stars from hydrogen, the dominant form of matter in the universe. The light from these stars would have excited any hydrogen remaining around them to higher energy states and even ionize it. When excited hydrogen returns to lower energy states, it emits light at several distinct wavelengths. However, most of this light would escape the young galaxy as an emission line at 122 nanometers because “bluer” light with shorter wavelengths and higher energy can re-excite other hydrogen atoms. Since the universe is expanding, the farther away a galaxy is from us, the faster it is moving away from us. Because of this movement, light from distant galaxies are doppler shifted to longer, or redder wavelengths, and this emission line is “redshifted” to a longer wavelength that is characteristic of the galaxy’s distance and the galaxy itself appears redder. As the light travels the long distance from its origin to Earth, light at the higher energy side, or blue side of the emission line, can be absorbed by the neutral hydrogen in intergalactic space. This absorption gives the emission line a distinctive asymmetrical look. A overall red appearance and a strong emission line at a particular wavelength with a particular asymmetrical shape is the signature of a distant new born galaxy.

To detect the most distant galaxies ever observed, the SDF team developed a special filter that only passes light with the narrow wavelength range of 908 to 938 nanometers. These wavelengths correspond to the 122 nanometer emission line after travelling a distance of 13 billion light years. The team installed the special filter, and two other filters at shorter and longer wavelengths bracketing the special filter, on Subaru telescope’s Suprime-Cam, Subaru Prime Focus Camera, and carried out an extensive observing program from April through May 2002. Suprime-Cam has the capability of imaging an area of the sky as large as the full moon in one exposure, a unique capability among instruments on 8-m class and larger telescopes, and is extremely well suited for surveys of very faint objects over large areas of the sky. By observing an area of the sky the size of the moon for up to 5.8 hours in each filter, the team was able to detect over 50,000 objects, including many extremely faint galaxies. By selecting galaxies that were bright only in the special filter and preferentially red, the team found 70 candidates for galaxies at a redshift of 6.6 (or a distance of 13 billion light years; see figure 1).

In June 2002, the team used FOCAS, the Faint Object Camera and Spectrograph on Subaru telescope, to observe 9 of the 70 candidates, and confirmed the generally red appearance and an emission line with a distinctive asymmetry in 2 objects (see figure 2), and determined that their redshifts are 6.58 and 6.54. The light from these galaxies was emitted 12.8 billion years ago when the universe was only 900 million years old. The previously observed most distant galaxy, with a redshift of 6.56, was discovered by looking at a large cluster of galaxies that can amplify light from more distant galaxies with a gravitational lensing effect. (See our press release from May 2002, http://www.naoj.org/Latestnews/200205/UH/index.html.)The SDF observations is the first time multiple galaxies at such a great distance have been observed, and without the help of gravitational lensing. The galaxy with a redshift of 6.58 is the most distant galaxy ever observed.

The SDF team expects to find many more distant galaxies through continued observations. Before the first stars and galaxies formed, the universe was in a stage that Astronomers call “the dark ages of the universe”. Determining when the dark ages ended is one of the most important astronomical questions of our time. Core members of the team, Keiichi Kodaira from the Graduate University of Advanced Studies in Japan, Nobunari Kashikawa from the National Astronomical Observatory of Japan, and Yoshiaki Taniguchi from Tohoku University hope that by detecting a statistically significant number of distant galaxies, they can begin to characterize the galaxies that heralded the end of the universe’s dark ages.

Original Source: Subaru News Release