24/7 Space News  





. GBT Reveals Satellite Of Milky Way In Retrograde Orbit

Artist's rendition of the path of satellite galaxy Complex H (in red) in relation to the orbit of the Sun (in yellow) about the center of the Milky Way Galaxy. The outer layers of Complex H are being stripped away by its interaction with the Milky Way. The hydrogen atmosphere (in blue) is shown surrounding the visible portion (in white) of the Galaxy. CREDIT: Lockman, Smiley, Saxton; NRAO/AUI

Green Bank - May 26, 2003
New observations with National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) suggest that what was once believed to be an intergalactic cloud of unknown distance and significance, is actually a previously unrecognized satellite galaxy of the Milky Way orbiting backward around the Galactic center.

Jay Lockman of the National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia, discovered that this object, known as "Complex H," is crashing through the outermost parts of the Milky Way from an inclined, retrograde orbit. Lockman's findings will be published in the July 1 issue of the Astrophysical Journal Letters.

"Many astronomers assumed that Complex H was probably a distant neighbor of the Milky Way with some unusual velocity that defied explanation," said Lockman.

"Since its motion appeared completely unrelated to Galactic rotation, astronomers simply lumped it in with other high velocity clouds that had strange and unpredictable trajectories."

High velocity clouds are essentially what their name implies, fast-moving clouds of predominately neutral atomic hydrogen. They are often found at great distances from the disk of the Milky Way, and may be left over material from the formation of our Galaxy and other galaxies in our Local Group.

Over time, these objects can become incorporated into larger galaxies, just as small asteroids left over from the formation of the solar system sometimes collide with the Earth.

Earlier studies of Complex H were hindered because the cloud currently is passing almost exactly behind the outer disk of the Galaxy. The intervening dust and gas that reside within the sweeping spiral arms of the Milky Way block any visible light from this object from reaching the Earth.

Radio waves, however, which have a much longer wavelength than visible light, are able to pass through the intervening dust and gas.

The extreme sensitivity of the recently commissioned GBT allowed Lockman to clearly map the structure of Complex H, revealing a dense core moving on an orbit at a 45-degree angle to the plane of the Milky Way.

Additionally, the scientist detected a more diffuse region surrounding the central core. This comparatively rarefied region looks like a tail that is trailing behind the central mass, and is being decelerated by its interaction with the Milky Way.

"The GBT was able to show that this object had a diffuse 'tail' trailing behind, with properties quite different from its main body," said Lockman. "The new data are consistent with a model in which this object is a satellite of the Milky Way in an inclined, retrograde orbit, whose outermost layers are currently being stripped away in its encounter with the Galaxy."

These results place Complex H in a small club of Galactic satellites whose orbits do not follow the rotation of the rest of the Milky Way. Among the most prominent of these objects are the Magellanic Clouds, which also are being affected by their interaction with the Milky Way, and are shedding their gas in a long stream.

Since large galaxies, like the Milky Way, form by devouring smaller galaxies, clusters of stars, and massive clouds of hydrogen, it is not unusual for objects to be pulled into orbit around the Galaxy from directions other than that of Galactic rotation.

"Astronomers have seen evidence that this accreting material can come in from wild orbits," said Butler Burton, an astronomer with the NRAO in Charlottesville, Virginia.

"The Magellanic clouds are being torn apart from their interaction with the Milky Way, and there are globular clusters rotating the wrong way. There is evidence that stuff was going every-which-way at the beginning of the Galaxy, and Complex H is probably left over from that chaotic period."

The new observations place Complex H at approximately 108,000 light-years from the Galactic center, and indicate that it is nearly 33,000 light-years across, containing approximately 6 million solar masses of hydrogen.

Radio telescopes, like the GBT, are able to observe these cold, dark clouds of hydrogen because of the natural electromagnetic radiation emitted by neutral atomic hydrogen at radio wavelengths (21 centimeters).

Globular clusters, and certain other objects in the extended Galactic halo, can be studied with optical telescopes because the material in them has collapsed to form hot, bright stars.

The GBT is the world's largest fully steerable radio telescope. It was commissioned in August of 2000, and continues to be outfitted with the sensitive receivers and components that will allow it to make observations at much higher frequencies.

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

Related Links
National Radio Astronomy Observatory
SpaceDaily
Search SpaceDaily
Subscribe To SpaceDaily Express




Tempur-Pedic Mattress Comparison

Newsletters :: SpaceDaily Express :: SpaceWar Express :: TerraDaily Express :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News


hello world
Newly-Discovered Star May Be Third-Closest
Pasadena - May 26, 2003
The local celestial neighborhood just got more crowded with a discovery of a star that may be the third closest to the Sun. The star, "SO25300.5+165258," is a faint red dwarf star estimated to be about 7.8 light-years from Earth in the direction of the constellation Aries.

---------------------------------------------------------
New from Telescopes.com!

It's new. And it's downright terrific!

Celestron's CPC Schmidt-Cassegrain telescope is the scope you've been waiting for! It offers new alignment technology, advanced engineering, and bold new design at a new, low price!

In fact, Celestron's Professional Computerized (CPC) scope with revolutionary SkyAlign Alignment Technology redefines everything that amateur astronomers are looking for. It offers quick and simple alignment, GPS technology, unsurpassed optical quality, ease of use, advanced ergonomics, enhanced computerization and, most important, affordability.

Want to view M-31 tonight? One button takes you there!

Shop for telescopes online at Telescopes.com! today!
------------------------------------------------------------

.
Get Our Free Newsletters Via Email
  



  • A Deep Space Exploration Extravaganza Set To Unfold
  • Moon Society and Artemis Society Endorse Space Settlement Initiative
  • No Sweat With Personal Aircon
  • Iowa-based Company Takes Soyfoods to Space

  • MARS Rovers Get Bio Scrub Ahead Of Launch
  • Mars Express Will Put Europe About And On Mars
  • MARS-1 Humvee Rover Reaches Devon Island After Crossing Frozen Sea
  • A New Way To Explore The Surface Of Mars

  • Atlas 5 Launches Hellas-Sat
  • Air Products Wins Delta IV Supply Contract
  • Successful Liftoff For Ariane-5
  • AsiaSat 4 In Orbit Makes It 64 Consecutive Launch Successes For Atlas

  • Foundation Hails White House Remote Sensing Policy
  • All That Glitters: The First ERS/Envisat Interferogram
  • AeroAstro Teams With Dutch Firm To Develop Remote Sensing Stations
  • Veridian To Study Adapting Commercial Satellite Imagery for Military Use

  • Brighter Neptune Suggests A Planetary Change Of Seasons
  • Pluto-Kuiper Belt Mission Moves Ahead
  • Having Pups Over Pluto And The Planetary Misfits Of The Kuipers
  • Pork For All

  • GBT Reveals Satellite Of Milky Way In Retrograde Orbit
  • Newly-Discovered Star May Be Third-Closest
  • Technion-CERN Scientists Predict Supernova
  • Science Begins For LIGO In Quest To Detect Gravitational Waves

  • Moon's Early History May Have Been Interrupted By Big Burp
  • Memories Of Orange Rock From The Lunar Age
  • Taos Goes Lunar With International Talkfest
  • Moon and Earth Formed out of Identical Material

  • Lockheed Martin and Spectrum Astro Team For GPS III Bid
  • AeroAstro Initiates SENS Remote Data Monitoring Service in North America
  • Communication Satellites Telling Us Where They Are
  • Upgraded GPS satellite Shipped To Cape for July Launch

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement