A promise made is a debt unpaid. Robert Service
Chance favors the prepared mind. Louis Pasteur

Not long ago a request came down from above for a list of Chandra’s achievements that have “completely transformed the way we have viewed our world, solar system, sun, or universe."

In other words, how many discoveries of the century have you made this year?

In a bow to David Letterman, or the decimal system, or other lists of ten that you can easily summon up, Chandra Project Scientist Martin Weisskopf submitted a list of Chandra’s top ten which would probably fall beyond the event horizo, never to be seen again. Not really, because it appears below, and being an environmentally conscious group, we will likely recycle the list several times before the next request requires generation of a new list which will be similar, but not identical to previous lists because real progress is being made.

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.



The list, which could have easily been expanded to fifteen or more by including insight into the nature of stellar black holes (event horizon, rotation rate), the accretion process near black holes, the studies of the Galactic center region, starburst galaxies, etc., got me to wondering how well the promise of Chandra has been met, and whether we can possibly guess what the future holds. This led me to my personal archive to dig out copies of old proposals. The oldest was the proposal for a Large Orbiting X-ray Telescope (LOXT), which was submitted to NASA in May of 1970.

Read the full article: Chandra: Promises Made and Kept

-Wallace Tucker, CXC

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