Mysterious centaurs orbiting sun may be comets: Nasa
PTI | Jul 27, 2013, 11.29 AM IST
The true identity of centaurs is one of the enduring mysteries of astrophysics.
Observations from Nasa’s Wide-field Infrared Survey Explorer (WISE) find that most centaurs are comets.
Until now, astronomers were not certain whether centaurs are asteroids flung out from the inner solar system or comets travelling in toward the Sun from afar.
“Our data point to a cometary origin for most of the objects, suggesting they are coming from deeper out in the solar system," said James Bauer of Nasa’s Jet Propulsion Laboratory in Pasadena, California.
“Cometary origin" means an object likely is made from the same material as a comet, may have been an active comet in the past, and may be active again in the future, researchers said.
The findings come from the largest infrared survey to date of centaurs and their more distant cousins, called scattered disk objects.
NEOWISE, the asteroid-hunting portion of the WISE mission, gathered infrared images of 52 centaurs and scattered disk objects.
Fifteen of the 52 are new discoveries. Centaurs and scattered disk objects orbit in an unstable belt. Ultimately, gravity from the giant planets will fling them either closer to the sun or farther away from their current locations.
Infrared data from NEOWISE provided information on the objects’ albedos, or reflectivity, to help astronomers sort the population.
NEOWISE can tell whether a centaur has a matte and dark surface or a shiny one that reflects more light.
The puzzle pieces fell into place when astronomers combined the albedo information with what was already known about the colours of the objects.
Visible-light observations have shown centaurs generally to be either blue-grey or reddish in hue. A blue-grey object could be an asteroid or comet. NEOWISE showed that most of the blue-grey objects are dark, a telltale sign of comets. A reddish object is more likely to be an asteroid.
“Comets have a dark, soot-like coating on their icy surfaces, making them darker than most asteroids," said the study’s co-author, Tommy Grav of the Planetary Science Institute in Tucson, Ariz.
“Comet surfaces tend to be more like charcoal, while asteroids are usually shinier like the moon," said Grav.
The results indicate that roughly two-thirds of the centaur population are comets, which come from the frigid outer reaches of our solar system.
It is not clear whether the rest are asteroids. The centaur bodies have not lost their mystique entirely, but future research from NEOWISE may reveal their secrets further.
The study was published in The Astrophysical Journal.
NASA Satellite Reveals New View Of Sun
IRIS satellite captures never-before-seen details of the sun, enabling scientists to better understand its effect on Earth.
NASA’s Interface Region Imaging Spectrograph (IRIS), launched into space last month, has returned its first images of the sun. While scientists have yet to study and understand the data, NASA said this is the most detail about the sun’s processes that a spacecraft has ever captured.
NASA revealed the images during a media teleconference on Thursday. IRIS, a 400-pound, seven-foot-long satellite, was able to take images that are 10 times higher in resolution and 20 times faster than previously possible.
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The satellite consists of a single instrument: an ultraviolet telescope combined with an imaging spectrograph. The telescope is capable of capturing high-resolution images and spectra, a kind of data. The spectra are used to determine velocities and temperatures of gas emissions from the surface of the sun to several thousand kilometers above the sun’s surface. IRIS collects data about one percent of the sun at a time, enabling scientists to see details as small as 150 miles across.
[ NASA is looking to private enterprise to help create products for space exploration. Read NASA Seeks Public-Private Project Partnerships. ]
The goal of the two-year mission is to help scientists learn how the sun creates such intense energy. The satellite will study in detail the lowest layers of the sun’s atmosphere, called the interface region. That particular part of the sun affects many aspects of near-Earth space, including particles that fill the solar system. The sun’s behavior also influences the Earth’s climate and weather patterns. But the mission goes beyond making scientific discoveries. The findings would allow spacecraft designers to create instruments and electronics that are better protected from solar flares, for instance.
“The [interface] region provides diagnostics for all the regions of the sun. They’re small events in the sun that are dynamic and energetic," said Bart DePontieu, IRIS science lead of Lockheed Martin’s Advanced Technology Center.
Science teams at Lockheed Martin and the University of Oslo in Norway have created numerical simulations of the sun that show similarities to the spectra returned by IRIS. But there are also striking differences. “The discrepancies are telling us that something is missing in our model. This is crucial to understanding how the sun affects Earth and understanding global problems like climate change," DePontieu said.
Lockheed Martin designed IRIS and also manages the mission. NASA’s Ames Research Center is using 3-D numerical modeling on supercomputers to interpret the data. The IRIS Mission Operations Center, located within the Ames Research Center, sends commands to IRIS and monitors telemetry.
IRIS achieved a milestone on July 17, when its telescope door opened in space. Within the first 21 hours of the door opening, the satellite began capturing its first images. They revealed multiple thin, fiber-like structures that have never been seen before, as well as contrasts in density and temperature throughout the interface region. Scientists plan to combine the information taken by IRIS with the findings of NASA’s Solar Dynamics Observatory, which studies the whole sun.
The solar observatory lifted off aboard a Pegasus XL rocket from California’s Vandenberg Air Force Base on June 27. Although delayed by a day due to a massive power outage at the launch site, the satellite successfully entered its destination, low-Earth orbit. During the first 30 days, ending July 27, the IRIS team has been conducting tests and spacecraft system checks. The mission is scheduled to begin full science operations by Aug. 26.
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NASA satellite offers stunning view of Sun’s mysterious atmosphere
The IRIS was launched on June 27 as a NASA Small Explorer mission.
|Photo credit: NASA/SDO/IRIS|
Thanks to NASA’s Interface Region Imaging Spectrograph (IRIS), researchers have had their first glimpse of the hitherto unexplored region of the lowest layers of the Sun’s atmosphere.
The images from IRIS reveal this interface region in extraordinary detail, revealing dynamic magnetic structures and material flows in the atmosphere. Such insights hint at the tremendous amount of energy transfer occurring throughout the region. These features may help power the Sun’s million-degree atmosphere, driving the solar wind that flows out to fill the expanse of the solar system.
“These beautiful images from IRIS are going to help us understand how the Sun’s lower atmosphere might power a host of events around the Sun,” said Adrian Daw, the mission scientist for IRIS at NASA’s Goddard Space Flight Center, in a news release. “Anytime you look at something in more detail than has ever been seen before, it opens up new doors to understanding. There’s always that potential element of surprise.”
According to John Grunsfeld, associate administrator of the Science Mission Directorate at NASA, these first observations have opened a new window into the Sun’s energetics. The mission itself has been a successful science partnership between government, industry, academia, and international institutions.
The IRIS was tailored to allow scientists to observe the interface region in exquisite detail. Understanding this region is important as it drives the solar wind and forms ultraviolet emission, which impact near-Earth space and Earth’s climate.
On July 17, the telescope became operational, and the imaging spectrograph began its first observations of the Sun. Within its first images, a previously unseen multitude of thin, fiber-like structures were revealed, showing enormous contrasts in density and temperature throughout the region. The images also show spots that rapidly brighten and dim, giving an indication of how energy is transported and absorbed.
The quality of the images is just what scientists were hoping for, according to Alan Title, the project’s principal investigator at Lockheed Martin. Though there is much work ahead of the team to fully grasp what is being shown, the quality of the data will enable this.
The IRIS was launched on June 27 as a NASA Small Explorer mission. Before its successful launch, however, NASA’s mission to examine the lowest layers of the Sun’s atmosphere was delayed by a large power outage on Earth. The power outage occurred at California’s Vandenberg Air Force Base. Fortunately, NASA engineers were able to quickly restore power to launch facilities impacted by the power outage.
IRIS’ instrumentation is made up of a combination of an ultraviolet telescope and a spectrograph. The telescope can provide high-resolution images resolved to features as small as 150 miles across, while the spectrograph splits the Sun’s rays into its various wavelengths, measuring the amount of any given wavelength. Analysis of these spectral lines provides information on velocity, temperature and density, which is essential to track how energy and heat moves.
In the coming weeks and months, scientists will scrutinize the incoming data provided by the IRIS on this interface region, which will be collected at least an order of magnitude faster than any previous solar observatory.
Ultimately, NASA hopes to answer the following questions using data collected by IRIS:
1) Which types of non-thermal energy rule in the chromosphere and beyond?
2) How does the chromosphere control mass and energy supply to the coronas and heliosphere?
3) How do magnetic flux and matter climb through the lower atmosphere and what role does flux manifestation have in solar flares and coronal mass ejections?
IRIS’s resolution, wide temperature coverage and state of the art computer modeling will help scientists to map plumes of solar materials as the travel through the Sun’s mysterious atmosphere.