Chandra's Top Ten (As of early 2011, and not necessarily in order of importance):
1. Deep field observations resolved the X-ray background and showed that it is dominated by accreting supermassive black holes including a large number of highly obscured black holes.
2. Images of clusters of galaxies established that energetic feedback by rotating supermassive black holes dramatically affects the evolution of intracluster gas and galaxies.
3. X-ray rings and jets around rotating neutron stars provide the most direct evidence of the transformation of rotational energy of these stars into jets and winds of high-energy particles.
4. X-ray and optical observations of the Bullet cluster of galaxies show the separation of dark and ordinary matter in a collision between galaxy clusters.
5. Observations of the rate at which massive galaxy clusters grow have provided confirmation that the expansion of the universe is accelerating, an effect attributed to the prevalence of dark energy, and have ruled out some alternatives to Einstein's General Theory of Relativity.
6. Observations of supernova remnants showed that supernova explosions are asymmetric and turbulent, requiring mixing of layers either during or prior to the explosions, and images of supernova shock waves provide evidence for acceleration of electrons to extremely high energies.
7. Detection of absorption by highly ionized oxygen atoms in X-ray spectra of a quasar behind the Sculptor wall of galaxies provided evidence for the Warm Hot Interstellar Medium thought to contain the missing baryons in the local universe.
8. Chandra observations of spectrally soft X-ray sources in early-type galaxies led to the conclusion that mergers, rather than accretion-driven explosions, are responsible for the Type Ia supernovas in these galaxies.
9. A number of multi wavelength studies of star clusters have provided an unprecedented look at the co-evolution of young stars and their disks in a wide variety of conditions.
10. Chandra was used to discover and/or contribute to an understanding of the X-ray emission processes from comets, the moons, of Jupiter, the Io plasma torus, the atmospheres of Venus and Mars.
