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.


 
 

 

President proclaims Memorial Day as ‘Day of Prayer’

President Barack Obama May 22 saluted the service and sacrifices of America’s military members–past and present–and proclaimed Memorial Day, May 25, 2015, “as a day of prayer for permanent peace, and I designate the hour beginning in each locality at 11 a.m. of that day as a time during which people may unite in prayer....
 
 

Air Force leaders’ Memorial Day message

Secretary of the Air Force Deborah Lee James and Air Force Chief of Staff Gen. Mark A. Welsh III send the following Memorial Day message to the Airmen of the Air Force and their families: To the Airmen of the United States Air Force and their Families: On Memorial Day, Americans pause in solemn remembrance...
 
 

Headlines May 22, 2015

News: Second Marine killed in Hawaii Osprey crash identified - Marine Corps officials have identified the second Marine to die as a result of the May 17 MV-22B Osprey crash as Lance Cpl. Matthew J. Determan of Maricopa, Ariz.   Business: Israel defense exports plunge to seven-year low - Israeli defense sales last year plunged to their...
 

 

News Briefs May 22, 2015

Ukrainian officer hit with third charge in Russia A third charge has been filed against a Ukrainian military officer who has been behind bars in Moscow for nearly a year over the deaths of two Russian journalists in Ukraine. Nadezhda Savchenko, who worked as a spotter for Ukrainian troops fighting separatist rebels in eastern Ukraine,...
 
 
Army photograph by C. Todd Lopez

Smart-mortar will help Soldiers more effectively hit targets

Army photograph by C. Todd Lopez Nick Baldwin and Evan Young, researchers with the Armament Research Development and Engineering Center at Picatinny Arsenal, Pennsylvania, discuss the 120mm Guided Enhanced Fragmentation Mortar ...
 
 

Air Force assigns new chief scientist

The Air Force announced the service’s new chief scientist to serve as a science and technology adviser to the secretary of the Air Force and the chief of staff of the Air Force, May 21. Dr. Greg Zacharias will be the 35th chief scientist and is ready to “dive in” to his new role. “I...
 




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>