Space

April 24, 2012

NASA’s Spitzer finds galaxy with split personality

While some galaxies are rotund and others are slender disks like our spiral Milky Way, new observations from NASA’s Spitzer Space Telescope show that the Sombrero galaxy is both.

The galaxy, which is a round, elliptical with a thin disk embedded inside, is one of the first known to exhibit characteristics of the two different types. The findings will lead to a better understanding of galaxy evolution, a topic still poorly understood.

“The Sombrero is more complex than previously thought,” said Dimitri Gadotti of the European Southern Observatory in Chile and lead author of a new paper on the findings appearing in the Monthly Notices of the Royal Astronomical Society. “The only way to understand all we know about this galaxy is to think of it as two galaxies, one inside the other.”

The Sombrero galaxy, also known as NGC 4594, is located 28 million light-years away in the constellation Virgo. From our viewpoint on Earth, we can see the thin edge of its flat disk and a central bulge of stars, making it resemble a wide-brimmed hat. Astronomers do not know whether the Sombrero’s disk is shaped like a ring or a spiral, but agree it belongs to the disk class.

“Spitzer is helping to unravel secrets behind an object that has been imaged thousands of times,” said Sean Carey of NASA’s Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. “It is intriguing Spitzer can read the fossil record of events that occurred billions of years ago within this beautiful and archetypal galaxy.”

Spitzer captures a different view of the galaxy than visible-light telescopes. In visible views, the galaxy appears to be immersed in a glowing halo, which scientists had thought was relatively light and small. With Spitzer’s infrared vision, a different view emerges. Spitzer sees old stars through the dust and reveals the halo has the right size and mass to be a giant elliptical galaxy.

While it is tempting to think the giant elliptical swallowed a spiral disk, astronomers say this is highly unlikely because that process would have destroyed the disk structure. Instead, one scenario they propose is that a giant elliptical galaxy was inundated with gas more than nine billion years ago. Early in our universe, networks of gas clouds were common, and they sometimes fed growing galaxies, causing them to bulk up. The gas would have been pulled into the galaxy by gravity, falling into orbit around the center and spinning out into a flat disk. Stars would have formed from the gas in the disk.

“This poses all sorts of questions,” said Ruben Sanchez-Janssen from the European Southern Observatory, co-author of the study. “How did such a large disk take shape and survive inside such a massive elliptical? How unusual is such a formation process?”

Researchers say the answers could help them piece together how other galaxies evolve. Another galaxy, called Centaurus A, appears also to be an elliptical galaxy with a disk inside it. But its disk does not contain many stars. Astronomers speculate that Centaurus A could be at an earlier stage of evolution than the Sombrero and might eventually look similar.

The findings also answer a mystery about the number of globular clusters in the Sombrero galaxy. Globular clusters are spherical nuggets of old stars. Ellipticals typically have a few thousand, while spirals contain a few hundred. The Sombrero has almost 2,000, a number that makes sense now but had puzzled astronomers when they thought it was only a disk galaxy.

 




All of this week's top headlines to your email every Friday.


 
 

 

Headlines April 23, 2014

News: U.S. conducts spy flights over Russia - After a tit-for-tat series of delays, the United States conducted an Open Skies Treaty intelligence flight over Russian territory April 21, a State Department official said.  Army paratroopers heading to Poland after Russian annexation of Crimea - U.S. Army paratroopers are arriving in Poland to begin a series of...
 
 

News Briefs April 23, 2014

U.S. military deaths in Afghanistan at 2,177 As of April 22, 2014, at least 2,177 members of the U.S. military had died in Afghanistan as a result of the U.S.-led invasion of Afghanistan in late 2001, according to an Associated Press count. The AP count is one less than the Defense Department’s tally. At least...
 
 

Northrop Grumman sets new greenhouse gas emission reduction goal of 30 percent by 2020

Northrop Grumman announced April 22 its commitment to reduce greenhouse gas emissions by 30 percent from 2010 levels by 2020, as part of its commemoration of Earth Day.   “Northrop Grumman is dedicated to top performance in environmental sustainability,” said Wes Bush, chairman, chief executive officer and president. “This new goal sets the bar significantly...
 

 

Lockheed Martin demonstrates enhanced ground control system, software for small UAV

Lockheed Martin’s Group 1 family of unmanned aircraft systems is migrating to enhanced automation capabilities using its Kestrelô “Fly Light” flight control systems and industry-leading mobile Ground Control Station software. The increased automation allows operators to focus on executing the mission, rather than flying various aircraft. Earlier this year, Lockheed MartinR...
 
 

U.S. Navy awards General Dynamics $33 million to operate, maintain military sealift ships

The U.S. Navy has awarded General Dynamics American Overseas Marine LLC a $32.7 million contract modification to operate and maintain seven large, medium-speed, roll-on / roll-off ships for the Military Sealift Command. AMSEA is a wholly owned subsidiary of General Dynamics. Under the terms of the modification, AMSEA will provide services including crewing, engineering, maintenance,...
 
 

US Navy deploys Standard Missile-3 Block IB for first time

In partnership with the Missile Defense Agency, the U.S. Navy deployed the second-generation Standard Missile-3 Block IB made by Raytheon for the first time, initiating the second phase of the Phased Adaptive Approach. “The SM-3 Block IB’s completion of initial operational testing last year set the stage for a rapid deployment to theater,” said Dr....
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>