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
Cassiopeia A: NASA'S Chandra Finds Superfluid in Neutron Star's Core
Cassiopeia A
Cassiopeia A

  • Evidence for a bizarre state of matter - known as a superfluid - has been found in Cassiopeia A.

  • Cassiopeia A (Cas A for short) is a supernova remnant located about 11,000 light years away from Earth.

  • Chandra observations taken over a decade show significant cooling in the dense core left behind after the explosion.

This composite image shows a beautiful X-ray and optical view of Cassiopeia A (Cas A), a supernova remnant located in our Galaxy about 11,000 light years away. These are the remains of a massive star that exploded about 330 years ago, as measured in Earth's time frame. X-rays from Chandra are shown in red, green and blue along with optical data from Hubble in gold.

At the center of the image is a neutron star, an ultra-dense star created by the supernova. Ten years of observations with Chandra have revealed a 4% decline in the temperature of this neutron star, an unexpectedly rapid cooling. Two new papers by independent research teams show that this cooling is likely caused by a neutron superfluid forming in its central regions, the first direct evidence for this bizarre state of matter in the core of a neutron star.

The inset shows an artist's impression of the neutron star at the center of Cas A. The different colored layers in the cutout region show the crust (orange), the core (red), where densities are much higher, and the part of the core where the neutrons are thought to be in a superfluid state (inner red ball). The blue rays emanating from the center of the star represent the copious numbers of neutrinos -- nearly massless, weakly interacting particles -- that are created as the core temperature falls below a critical level and a neutron superfluid is formed, a process that began about 100 years ago as observed from Earth. These neutrinos escape from the star, taking energy with them and causing the star to cool much more rapidly.

This new research has allowed the teams to place the first observational constraints on a range of properties of superfluid material in neutron stars. The critical temperature was constrained to between one half a billion to just under a billion degrees Celsius. A wide region of the neutron star is expected to be forming a neutron superfluid as observed now, and to fully explain the rapid cooling, the protons in the neutron star must have formed a superfluid even earlier after the explosion. Because they are charged particles, the protons also form a superconductor.

Using a model that has been constrained by the Chandra observations, the future behavior of the neutron star has been predicted. The rapid cooling is expected to continue for a few decades and then it should slow down.

Fast Facts for Cassiopeia A:
Credit  X-ray: NASA/CXC/UNAM/Ioffe/D.Page,P.Shternin et al; Optical: NASA/STScI; Illustration: NASA/CXC/M.Weiss
Release Date  February 23, 2011
Scale  Image is 8.91 arcmin across (about 26 light years)
Category  Supernovas & Supernova Remnants
Coordinates (J2000)  RA 23h 23m 26.7s | Dec +58° 49' 03.00"
Constellation  Cassiopeia
Observation Date  Nine observations in 2004: Feb 8, Apr 14, 18, 20, 22, 25 28, May 01, 05
Observation Time  278 hours
Obs. ID  4634-4639, 5196, 5319-5320
Instrument  ACIS
Also Known As Cas A
References Page, D. et al., 2011, Phys.Rev.Lett. 106, 081101 ( Shternin, P. et al. 2011, MNRAS, L206S (
Color Code  X-ray: Red 0.5-1.5 keV; Green 1.5-2.5; Blue 4.0-6.0, Optical: Gold
Distance Estimate  About 11,000 light years
distance arrow
Visitor Comments (23)

There is another star in Cassiopeia that is expected to go super nova anytime now. In fact this star may have exploded already but the light from the star going super nova may not have reached Earth yet.

Posted by Michael A. Amato on Thursday, 09.17.15 @ 21:22pm

This is one of my favorite constellations. I love this image

Posted by Esty Clark on Tuesday, 07.22.14 @ 15:35pm

Amazing issues here. I am very glad to see your post.
Thank you so much and I am having a look ahead to touch you.

Posted by Marcus on Saturday, 02.22.14 @ 10:26am

When and will this neutron star ever affect the earth and mankind? How long will it take for it to reach us?

Posted by jett on Wednesday, 12.5.12 @ 09:24am

I like the website that you had create because you can learn any thing from it about the space.

Posted by Maryam Ayyub on Tuesday, 05.29.12 @ 23:08pm

I am in a group of enthusiasts and professional physicists and we are wondering if the superfluid state in the core and on the surface are discrete states or is there any communication between the two?

Posted by Mike Baskett on Tuesday, 03.20.12 @ 17:40pm

I am doing a science project on this star and I wanted to know if anyone knows the estimated life left in this stage of the star?

Posted by Brittany on Wednesday, 02.22.12 @ 22:01pm

Perhaps the perpendicular blue lines represent electrons chased from the helium atom balloon around the central reactor system. That would be the ponderomotive force that is mentioned in Nature 29 Oct. 2009. Because of the star's gravity, the protons of helium atoms cannot follow.
That part about electrons not neutrinos is a supposition, but giant opposed galaxy face bulges are definitely caused by the Ponderomotive force.

Posted by Ed McCarvill on Monday, 02.6.12 @ 12:52pm

It is really exciting to have such a discovery in this age. We could learn more and do more in the future.

Posted by Taylor Locksmith on Sunday, 07.24.11 @ 22:55pm

If neutrinos are emitted then a nuclear reaction has to take place Two neutrons sticking together to a pair of neutrons is no nuclear reaction so where the neutrinos come from

If the formed neutron pair is superfluid and does not interact anymore with the rest of the star then it cannot exchange thermal energy with the remaining neutrons For the thermal balance the emission of the neutrinos is then insignificant because the other neutrons cannot see that the pair has lost energy by neutrino emission So where does the cooling come from ultimately

Posted by Roland Hildebrand on Friday, 03.11.11 @ 12:30pm

Dear Stup id,
Thanks for your questions. There isn't anything special that will happen to stars when they cross the same plane as the black hole, since their strong gravity acts in all directions. Jets from black holes shoot out in two opposite directions, but this directionality is driven by the spin of material falling onto the black hole in a disk, and by the spin of the black hole itself and isn't caused by weaker gravity acting in this direction.
P.Edmonds, CXC

Posted by P. Edmonds on Wednesday, 03.9.11 @ 11:22am

Dear Paul Boland,
Thanks for your question. You are right that the light take 11,000 years to each us, but nevertheless the star's explosion would have been *observable* from Earth about 1680 (it's not actually clear whether the supernova was actually observed, unlike the case for Tycho's or Kepler's supernova). Astronomers talk about events as observed in images, ie in "Earth's time frame". Please see:
for more details.
P.Edmonds, CXC

Posted by P. Edmonds on Wednesday, 03.9.11 @ 11:19am

Dear Bill Matthew,
Thanks for your question, which is a good one because the theory here is complicated. We have posted additional information on our web-site that provides more details about this work. See in particular:

and the bottom animation (with the long caption) at:

P.Edmonds, CXC

Posted by P. Edmonds on Wednesday, 03.9.11 @ 11:14am

Bill Matthew,
The Stefan-Boltzmann law that says that the total electromagnetic radiation varies according to the area of the radiating surface and the fourth power of temperature. They assume that the surface area of the Neutron star doesn't change significantly, so a change in luminosity corresponds to a change in temperature. The temperature can be estimated from the Neutron star's spectrum. If the temperature is dropping faster than can be explained by the loss due to radiation then it must cooling by some additional means. The additional means being neutrino emission.

Posted by billy on Tuesday, 03.8.11 @ 21:08pm

Paul Boland, what the article could have said to make things a bit clearer is, the light from the explosion reached earth 330 years ago. You can think of the explosion as having actually occurred 11,000 years before that, although, of course, relativity shows the folly of any absolute time scale.

Posted by AquaRegia on Tuesday, 03.8.11 @ 08:48am

How exciting it is to observe a stellar event unfolding on a human time scale.

Posted by kerry on Saturday, 03.5.11 @ 15:16pm

From what I have read on the internet about Superfluid is most mind boggling. Now this, Superfluid found in Caseopea A. What a great discovery.
The mysteries that await us out there are always a great learning experience and mind boggling.
This is one great article, thanks so much Chandra team.
Marvin L. S.

Posted by Marvin L. S. on Thursday, 03.3.11 @ 21:02pm

Fascinating picture. I know there is a lot of knowledge that allows the analysis to take place but could someone briefly explain the leap from an image to such a detailed belief of what is being seen?

Posted by Bill Matthew on Monday, 02.28.11 @ 15:22pm

Wow, cool.

Posted by zbethel on Friday, 02.25.11 @ 15:29pm

This news article is causing me a bit of confusion. This star being 11,000 light years away, it would take 11,000 years for the light from that star to reach us. However, the image shows the exploded star which happened only 330 years ago. How can this be? Surely if the star exploded in 1681 or there about, we should not be able to see the light of that explosion, the result so to speak, until the year 12,681 that's 11,000 years later, the time it would that the light to travel the distance of 11,000 light years.

Posted by Paul Boland on Thursday, 02.24.11 @ 22:12pm

This might be a stupid question to all who visit this site on a regular basis, but have we ever tried to see what happens to stars when they cross the same plain as the black hole in the center of their galexys? also do black holes suck or have the same pull on things that are over the top, like where it shoots out if it's a quasar? and if not, why does the gravity of a black hold go out in a 3d bubble or is more like a flat disk?

Posted by Stup id on Wednesday, 02.23.11 @ 22:28pm

As a former avid amateur, and now a present avid amateur pursuing a degree, I have always wondered what a star made out of neutrons would look like. The concept just sounds bizarre, as much as I've read about it. How wonderful are these endless mysteries.

Posted by Brendan D on Wednesday, 02.23.11 @ 20:02pm

If this Neutron Star is in line with us does it give off a signal? A most fascinating subject, always something new to learn. Thanks.

Marvin L. S.

Posted by Marvin L. S. on Wednesday, 02.23.11 @ 19:58pm

Rate This Image

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


1024x768 - 1022.9 kb
1280x1024 - 1.4 MB
1680x1050 - 1.8 MB
More Information
Blog: Cassiopeia A

More Images
X-ray Image of
Cassiopeia A
Jpg, Tif

More Images
Animation & Video
Low-resolution animation
Tour of Cassiopeia A

More Animations
More Releases
Cassiopeia A
Cassiopeia A
(22 Jul 24)

Cassiopeia A
Cassiopeia A
(24 Apr 24)

Cassiopeia A
Cassiopeia A
(08 Jan 24)

Cassiopeia A
Cassiopeia A
(18 Oct 22)

Cassiopeia A
Cassiopeia A
(02 Feb 22)

Cassiopeia A
Cassiopeia A
(21 Apr 21)

Cassiopeia A
Cassiopeia A
(26 Aug 19)

Cassiopeia A
Cassiopeia A
(12 Dec 17)

Cassiopeia A
Cassiopeia A
(15 Nov 13)

Cassiopeia A
Cassiopeia A
(29 Mar 12)

Cassiopeia A
Cassiopeia A
(04 Nov 09)

Cassiopeia A
Cassiopeia A
(06 Jan 09)

Cassiopeia A
Cassiopeia A
(06 Jan 09)

Cassiopeia A
Cassiopeia A
(15 Nov 06)

Cassiopeia A
Cassiopeia A
(13 Jun 05)

Cassiopeia A
Cassiopeia A
(23 Aug 04)

Cassiopeia A
Cassiopeia A
(19 Aug 02)

Cassiopeia A
Cassiopeia A
(27 Jun 00)

Cassiopeia A
Cassiopeia A
(21 Dec 99)

Cassiopeia A
Cassiopeia A
(26 Aug 99)

Related Images
SN 1006
SN 1006
(15 Dec 05)

Tycho's SN
(18 Feb 09)

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

Brightest Cluster Galaxies

Timelapses: Crab Nebula and Cassiopeia A