Images by Date
Images by Category
Solar System
White Dwarfs
Neutron Stars
Black Holes
Milky Way Galaxy
Normal Galaxies
Galaxy Clusters
Cosmology/Deep Field
Images by Interest
Space Scoop for Kids
Sky Map
Photo Blog
Top Rated Images
Image Handouts
Fits Files
Image Tutorials
Photo Album Tutorial
False Color
Cosmic Distance
Look-Back Time
Scale & Distance
Angular Measurement
Images & Processing
Image Use Policy
Web Shortcuts
Chandra Blog
RSS Feed
Email Newsletter
News & Noteworthy
Image Use Policy
Questions & Answers
Glossary of Terms
Download Guide
Get Adobe Reader
NGC 6240: Colossal Hot Cloud Envelops Colliding Galaxies
NGC 6240
NGC 6240

  • An enormous cloud of hot gas is surrounding two merging spiral galaxies.

  • This gas reservoir contains the mass of 10 billion Suns, spans 300,000 light years, and radiates at more than 7 million degrees.

  • X-rays from Chandra (purple) have been combined with optical data from Hubble to make this composite image.

  • A burst of star formation that lasted for at least 200 million years may be responsible for this extra large cloud of hot gas.

Scientists have used Chandra to make a detailed study of an enormous cloud of hot gas enveloping two large, colliding galaxies. This unusually large reservoir of gas contains as much mass as 10 billion Suns, spans about 300,000 light years, and radiates at a temperature of more than 7 million degrees Kelvin.

This giant gas cloud, which scientists call a "halo," is located in the system called NGC 6240. Astronomers have long known that NGC 6240 is the site of the merger of two large spiral galaxies similar in size to our own Milky Way. Each galaxy contains a supermassive black hole at its center. The black holes are spiraling toward one another, and may eventually merge to form a larger black hole.

Another consequence of the collision between the galaxies is that the gas contained in each individual galaxy has been violently stirred up. This caused a baby boom of new stars that has lasted for at least 200 million years. During this burst of stellar birth, some of the most massive stars raced through their evolution and exploded relatively quickly as supernovas.

The scientists involved with this study argue that this rush of supernova explosions dispersed relatively high amounts of important elements such as oxygen, neon, magnesium, and silicon into the hot gas of the newly combined galaxies. According to the researchers, the data suggest that this enriched gas has slowly expanded into and mixed with cooler gas that was already there.

During the extended baby boom, shorter bursts of star formation have occurred. For example, the most recent burst of star formation lasted for about five million years and occurred about 20 million years ago in Earth's timeframe. However, the authors do not think that the hot gas was produced just by this shorter burst.

What does the future hold for observations of NGC 6240? Most likely the two spiral galaxies will form one young elliptical galaxy galaxy over the course of millions of years. It is unclear, however, how much of the hot gas can be retained by this newly formed galaxy, rather than lost to surrounding space. Regardless, the collision offers the opportunity to witness a relatively nearby version of an event that was common in the early Universe when galaxies were much closer together and merged more often.

In this new composite image of NGC 6240, the X-rays from Chandra that reveal the hot gas cloud are colored purple. These data have been combined with optical data from the Hubble Space Telescope, which shows long tidal tails from the merging galaxies, extending to the right and bottom of the image.

A paper describing these new results on NGC 6240 is available online and appeared in the March 10, 2013 issue of The Astrophysical Journal. The authors in this study were Emanuele Nardini (Harvard-Smithsonian Center for Astrophysics, or CfA, Cambridge, MA and currently at Keele University, UK), Junfeng Wang (CfA and currently at Northwestern University, Evanston, IL), Pepi Fabbiano (CfA), Martin Elvis (CfA), Silvia Pellegrini (University of Bologna, Italy), Guido Risalti (INAF-Osservatorio Astrofisico di Arcetri, Italy and CfA), Margarita Karovska (CfA), and Andreas Zezas (University of Crete, Greece and CfA).

NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.


Fast Facts for NGC 6240:
Credit  X-ray (NASA/CXC/SAO/E.Nardini et al); Optical (NASA/STScI)
Release Date  April 30, 2013
Scale  Image is 3 arcmin across (About 290,000 light years)
Category  Black Holes, Normal Galaxies & Starburst Galaxies
Coordinates (J2000)  RA 16h 52m 59s | Dec 02° 24´ 01.70"
Constellation  Ophiuchus
Observation Date  4 pointings between July 2001 and May 2011
Observation Time  136 hours 6 min (5 days 16 hours 6 min)
Obs. ID  1590, 6908, 6909, 12713
Instrument  ACIS
References Nardini, E et al, 2012, ApJ 765, 141; arXiv:1301.5907
Color Code  X-ray (Purple); Optical (Red, Green, Blue)
Distance Estimate  About 330 million light years (redshift = 0.0245)
distance arrow
Visitor Comments (6)

This is awesome that you'll keep those of us who actually care about this stuff, up to date. Thank you for being informative.

Posted by Evie Arrona on Monday, 08.31.15 @ 23:18pm

This is really really awesome. You guys are the best, I wish I could go up there to compliment you all for working or trying so hard to show us this. I would really want to see other galaxies and planets with my telescope, so please keep up with the good work -

Posted by keven on Wednesday, 02.12.14 @ 21:42pm

Thank you for sharing education.

Posted by Felipe Cervantes on Wednesday, 10.2.13 @ 10:42am

Great job.

Posted by kaiser on Tuesday, 10.1.13 @ 08:20am

it is amazingly beautiful, it shows how small we are!
I hope there will be more projects like Chandra to help us understand and appreciate our elegant universe!

Posted by amrfadeel on Friday, 06.7.13 @ 04:46am

Thanks NASA, Chandra, window of universe so many things watch sitting in home, god bless you guys

Posted by kulwinder singh grewal on Thursday, 05.9.13 @ 22:52pm

Rate This Image

Rating: 3.8/5
(1377 votes cast)
Download & Share


1024x768 - 694.3 kb
1280x1024 - 1.1 MB
1680x1050 - 1.6 MB
More Information
More Images
X-ray Image of NGC 6240
Jpg, Tif

More Images
Animation & Video
Tour of NGC 6240

I Can See Your Halo
Click for high-resolution animation

More Animations
More Releases
NGC 6240
NGC 6240
(06 Oct 09)

NGC 6240
NGC 6240
(19 Nov 02)

Related Images
(13 Jan 11)
(5 Aug 10)

Related Information
Related Podcast
Top Rated Images
Chandra Releases 3D Instagram Experiences

Brightest Cluster Galaxies

Timelapses: Crab Nebula and Cassiopeia A