Archive

Archive for October 17, 2011

Dark Matter Mystery Deepens

October 17, 2011 Leave a comment

Credit: David A. Aguilar (CfA)

Credit: David A. Aguilar (CfA)

Like all galaxies, our Milky Way is home to a strange substance called dark matter. Dark matter is invisible, betraying its presence only through its gravitational pull. Without dark matter holding them together, our galaxy’s speedy stars would fly off in all directions. The nature of dark matter is a mystery — a mystery that a new study has only deepened.

“After completing this study, we know less about dark matter than we did before,” said lead author Matt Walker, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.

The standard cosmological model describes a universe dominated by dark energy and dark matter. Most astronomers assume that dark matter consists of “cold” (i.e. slow-moving) exotic particles that clump together gravitationally. Over time these dark matter clumps grow and attract normal matter, forming the galaxies we see today.

Cosmologists use powerful computers to simulate this process. Their simulations show that dark matter should be densely packed in the centers of galaxies. Instead, new measurements of two dwarf galaxies show that they contain a smooth distribution of dark matter. This suggests that the standard cosmological model may be wrong.

Full Story: http://www.cfa.harvard.edu/news/2011/pr201129.html

ROSAT Satellite Set to Re-enter Earth’s Atmosphere

October 17, 2011 Leave a comment

During its mission, the ROentgen SATellite (ROSAT) performed its observations in an elliptical orbit at distances of between 585 and 565 kilometres above the surface of the Earth. Since its decommissioning, atmospheric drag has caused the satellite to lose altitude. In June 2011, it was at a distance of only about 327 kilometres above the ground. Due to the fact that ROSAT does not have a propulsion system on board, it was not possible to manoeuvre the satellite to perform a controlled re-entry at the end of its mission in 1999. When the spacecraft re-enters the atmosphere at a speed of approximately 28,000 kilometres per hour, the X-ray observatory will break up into fragments, some of which will burn up by the extreme heat. The latest studies reveal that it is possible that up to 30 individual pieces weighing a total of 1.7 tons may reach the surface of the Earth. The largest single fragment will probably be the telescope’s mirror, which is very heat resistant and may weigh up to 1.7 tons.

Full Story: http://www.dlr.de/dlr/en/desktopdefault.aspx/tabid-10432/620_read-830/

Cassini Significant Events 10/04/11 – 10/11/11

October 17, 2011 Leave a comment

The most recent spacecraft telemetry was acquired on Oct. 11 from the Deep Space Network tracking complex at Canberra, Australia. The Cassini spacecraft is in an excellent state of health and with the exception of the CAPS instrument being powered off, all subsystems are operating normally. Information on the present position and speed of the Cassini spacecraft may be found on the “Present Position” page at: http://saturn.jpl.nasa.gov/mission/presentposition/.

Full Story: http://saturn.jpl.nasa.gov/news/significantevents/significantevents20111013/

UChicago Launches Search for Distant Worlds

October 17, 2011 Leave a comment

Courtesy of NASA/JPL-Caltech/T. Pyle

Courtesy of NASA/JPL-Caltech/T. Pyle

Since 1995, scientists have discovered approximately 600 planets around other stars, including 50 planets last month alone, and one that orbits two stars, like Tatooine in Star Wars. Detection of the first Earthlike planet remains elusive, however, and now the University of Chicago joins the search with the addition of Jacob Bean and Daniel Fabrycky to the faculty.

“I can’t imagine a more profound impact on humanity than the discovery that there are other Earthlike worlds or that we are not alone,” said Rocky Kolb, the Arthur Holly Compton Distinguished Service Professor in Astronomy & Astrophysics and department chairman.

Bean joins the faculty as an assistant professor in astronomy & astrophysics this autumn quarter. Fabrycky, who was a member of the team that discovered the Tatooine-like planet, will join the department next fall. Bean and Fabrycky were hired following a joint search conducted by the Department of Astronomy & Astrophysics and the Department of Geophysical Sciences.

The new faculty additions come as the University as a whole is engaged in a significant expansion of its faculty. The departments of geophysical sciences and astronomy & astrophysics had identified the study of exoplanetary systems as one priority for their faculty, noting that discoveries in this arena “could have intellectual, cultural, and societal impacts comparable to those of Copernicus, Galileo and Darwin.”

Full Story: https://news.uchicago.edu/article/2011/10/13/uchicago-launches-search-distant-worlds

Galaxy Mergers Don’t Trigger Most Black Hole Feeding Frenzies

October 17, 2011 Leave a comment

A survey of distant galaxies using the Hubble Space Telescope has put another nail in the coffin of the theory that galaxy mergers are the main trigger for turning quiescent supermassive black holes into radiation-blasting active galactic nuclei.

Led by astronomers at the University of California, Santa Cruz, the new study examined the morphology and structure of distant galaxies hosting active central black holes. The researchers found that these galaxies were no more likely to be involved in an ongoing merger than non-active galaxies of similar mass.

“Theoretical models show that a merger is a great way to trigger an active galactic nucleus, because it funnels a lot of gas to the center of the galaxy. But we found that most of the host galaxies did not look disturbed. They look like disk galaxies, and a disk would be destroyed by a merger,” said Dale Kocevski, a postdoctoral researcher at UC Santa Cruz and first author of a paper on the findings to be published in the Astrophysical Journal.

Full Story: http://news.ucsc.edu/2011/10/agn-distant-galaxies.html

Seeking a New Name for Transformed Scientific Icon

October 17, 2011 Leave a comment

The most famous radio telescope in the world is about to get a new name. The Very Large Array, known around the world, isn’t what it used to be. The iconic radio telescope, known around the world through movies, documentaries, music videos, newspaper and magazine articles, advertisements, textbooks, and thousands of scientific papers, is nearing the completion of an amazing transformation. More than a decade of effort has replaced the VLA’s original, 1970s-vintage electronics with modern, state-of-the-art equipment.

The result is a completely new scientific facility.

“The VLA Expansion Project, begun in 2000, has increased the VLA’s technical capabilities by factors of as much as 8,000, and the new system allows scientists to do things they never could do before,” said Fred K.Y. Lo, Director of the National Radio Astronomy Observatory. “After more than three decades on the frontiers of science, the VLA now is poised for a new era as one of the world’s premier tools for meeting the challenges of 21st-Century astrophysics,” he added.

And so it’s time, the Observatory has decided, to give this transformed scientific facility a new name to reflect its new capabilities.

The Observatory is seeking ideas for a new name from the public and the scientific community.

Full Story: http://www.nrao.edu/pr/2011/rename/