NRAO August Media Tip Sheet

1. GBT in the Dark Matter Detection Race: Dark matter makes up nearly 25 percent of the cosmos but it doesn't interact with light and so far has been detected only by its gravitational influence. Weakly interactive massive particles (WIMPs) are leading candidates for dark matter, but they have thwarted detection thus far. A new observing technique with the National Science Foundation's (NSF) Green Bank Telescope (GBT) may be able to provide a new line of evidence that WIMPs exist, and more importantly say something about their properties. Theory predicts that when WIMPs collide at very high energies they can produce a fleeting subatomic particle known as a pion. Certain pions, which live only for a few seconds, decay into the familiar electron and its antimatter twin, the positron. It's these latter two particles that pique the interest of radio astronomers. When electrons and positrons get entwined in powerful magnetic fields, they emit radio waves that the GBT is uniquely capable of detecting, if the conditions are right. Normally this characteristic radio signature would be obscured by emission from the churning medium between stars in a galaxy. Dwarf spheroidal galaxies, however, are unusually quiescent yet teem with dark matter, making them ideal targets for study. To further reduce background noise, the researchers used existing surveys from NRAO's Jansky Very Large Array to remove other known sources of radio waves. Four such galaxies were included in this first study: Draco, UmaII, Coma, and Will1. The observations did not reveal any telltale signals, but did put an upper limit on how often dark matter particles collide and produce pions. The researchers conclude that radio searches with the GBT are at least as capable of detecting dark matter as other indirect techniques, such as gamma-ray searches.

Publication: "A Deep Search for Extended Radio Continuum Emission from Dwarf Spheroidal Galaxies: Implications for Particle Dark Matter" is accepted for publication in the Astrophysical Journal. [http://xxx.lanl.gov/abs/1301.5306]

Authors: Kristine Spekkens, Royal Military College of Canada; Brian Mason, National Radio Astronomy Observatory; James E. Aguirre, University of Pennsylvania; and Bang Nhan, University of Colorado

2. Supernova Remnant Forging Copious Cold Molecules: Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected, for the first time, the formation of new molecules in the remains of a star that went supernova. By detecting and mapping the distribution of these molecules, the researchers also have caught a glimpse of the final internal structure of the star, which became "frozen in" to the debris when the star exploded. The astronomers discovered these new molecules in the fading embers of a star that went supernova in 1987, known, conveniently, as 1987A. Located in the Large Magellanic Cloud, a nearby satellite galaxy of the Milky Way, supernova 1987A provides a unique opportunity to study how the aftermath of a supernova evolves. Computer models that attempt to recreate the conditions just prior to a supernova suggest that there is powerful and rapid mixing inside the star. This churning, astronomers speculate, is the trigger that sets off the explosion. Since it's impossible to peer inside an actual star, astronomers study the debris of a supernova to see how material is distributed and how the remnant of the star evolves over time to infer the conditions just prior to the explosion. Earlier research with infrared telescopes detected a small amount of CO glowing hot within the first 500 days after the explosion. Twenty-five years later, the new ALMA results, which are the first of their kind, reveal a supernova environment filled with ten times the amount of CO detected by the infrared studies. The astronomers estimate that there is about 10 percent the mass of our Sun in CO and also a significant mass of silicon monoxide (SiO) currently in the supernova remnant. These molecules are forming in areas with abundant atomic carbon, silicon, and oxygen atoms, elements that only form inside the nuclear furnace of a star and get spilled into the cosmos during a supernova explosion. Over time, as they cool, the atoms are able to bond, creating the CO and SiO that is detectable by ALMA. The molecules forming in SN1987A, or at least their constituent atoms, could someday be incorporated into future planets.

Publication: "Carbon Monoxide in the Cold Debris of Supernova 1987A" is accepted for publication in the Astrophysical Journal Letters. [http://arxiv.org/abs/1307.6561]

Authors: J. Kamenetzky, Univ. of Colorado at Boulder; R. McCray, University of Colorado; R. Indebetouw, National Radio Astronomy Observatory & University of Virginia; et al.

3. Sound of a Solar Flare: Solar flares are powerful outbursts triggered by the rending of the Sun's strong magnetic fields. The shock wave from a solar flare propagates through the solar corona, producing brief but powerful bursts of radio waves. A particularly specular radio burst occurred November 15, 2005. That event was recorded by the NRAO's Green Bank Solar Radio Burst Spectrometer and combined with data from the San Vito Solar Observatory in Italy by Stephen White of the U.S. Air Force Research Lab. Tim Bastian at the NRAO in Charlottesville, Va., rendered the data from a visual representation to an audio representation using one-to-one conversion of the radio frequencies to audible sound. The resulting sound data helps illustrate the changes in frequency that occur during these events and provides unique and entertaining insights into our solar environment.

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The Robert C. Byrd Green Bank Telescopes (GBT) is the most technically advanced single-dish radio telescope in the world. Its 100-meter dish boasts more than two acres of area for collecting faint radio waves from the Universe.

ALMA, an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.