A comet is a clump of frozen gases mixed with dust. These "dirty snowballs" cast off gas and dust whenever they venture near the sun. What powers this activity is frozen water transforming from solid ice to gas, a process called sublimation. Jets powered by ice sublimation release dust, which reflects sunlight and brightens the comet. Typically, a comet's water content remains frozen until it comes within about three times Earth's distance to the sun, or 3 astronomical units (AU), so astronomers regard this as the solar system's "snow line."
"Comet Garradd was producing lots of dust and gas well before it reached the snow line, which tells us that the activity was powered by something other than water ice," said Dennis Bodewits, an assistant research scientist at the University of Maryland, College Park, and the study's lead investigator. "We plan to use Swift's unique capabilities to monitor Garradd as it moves beyond the snow line, where few comets are studied."
Comets are known to contain other frozen gases, such as carbon monoxide and dioxide (CO and CO2), which sublimate at colder temperatures and much farther from the sun. These are two of the leading candidates for driving cometary activity beyond the snow line, but phase transitions between different forms of water ice also may come into play.
C/2009 P1 was discovered by Gordon J. Garradd at Siding Spring Observatory, Australia, in August 2009. Astronomers say that the comet is "dynamically new," meaning that this is likely its first trip through the inner solar system since it arrived in the Oort cloud, the cometary cold-storage zone located thousands of AU beyond the sun.
Comet Garradd was closest to the sun on Dec. 23, 2011, and passed within 118 million miles (1.27 AU) of Earth on March 5, 2012. The comet remains observable in small telescopes this month as it moves south though the constellations Ursa Major and Lynx.
Although Swift's prime task is to detect and rapidly locate gamma-ray bursts in the distant universe, novel targets of opportunity allow the mission to show off its versatility. One of Swift's instruments, the Ultraviolet/Optical Telescope (UVOT) is ideally suited for studying comets.
The instrument includes a prism-like device called a grism, which separates incoming light by its wavelength. While Swift's UVOT cannot detect water directly, the molecule quickly breaks up into hydrogen atoms and hydroxyl (OH) molecules when exposed to ultraviolet sunlight. The UVOT detects light emitted by hydroxyl and other important molecular fragments — such as cyanide (CN), carbon monosulfide (CS) and diatomic and triatomic carbon (C2 and C3, respectively) — as well as the sunlight reflected off of cometary dust.
"Tracking the comet's water and dust production and watching its chemistry change as it moves deeper into the solar system will help us better understand how comets work and where they formed," said Stefan Immler, a researcher and Swift team member at NASA's Goddard Space Flight Center in Greenbelt, Md.
Swift last observed the comet on April 1, when it was 1.53 AU away and just past the orbit of Mars. Although detailed results are not yet available, Bodewits estimates that Comet Garradd was shedding about 400 gallons of water each second -- enough to fill an Olympic-size swimming pool in under 30 minutes.
But the water given off by the comet was only about half of the dust mass it produced. Bodewits estimates that each second, Garradd was losing about 7,500 pounds (3.5 metric tons, or about twice the typical mass of a small car) in the form of dust and icy grains.
Thanks to Garradd's brightness and the UVOT's sensitivity and resolution, researchers can monitor the comet when it is beyond the grasp of most ground-based observatories. Plans call for observations at eight different distances from the sun out to about 5.5 AU, which the comet will reach in April 2013.Francis Reddy
Francis Reddy | EurekAlert!
Studying fundamental particles in materials
17.01.2017 | Max-Planck-Institut für Struktur und Dynamik der Materie
Seeing the quantum future... literally
16.01.2017 | University of Sydney
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).
Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...
Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.
The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...
10.01.2017 | Event News
09.01.2017 | Event News
05.01.2017 | Event News
17.01.2017 | Earth Sciences
17.01.2017 | Materials Sciences
17.01.2017 | Architecture and Construction