The first decade of science with Chandra and XMM-Newton

Abstract

NASA's Chandra X-ray Observatory and the ESA's X-ray Multi-Mirror Mission (XMM-Newton) made their first observations ten years ago. The complementary capabilities of these observatories allow us to make high-resolution images and precisely measure the energy of cosmic X-rays. Less than 50 years after the first detection of an extrasolar X-ray source, these observatories have achieved an increase in sensitivity comparable to going from naked-eye observations to the most powerful optical telescopes over the past 400 years. We highlight some of the many discoveries made by Chandra and XMM-Newton that have transformed twenty-first century astronomy.T ypically, cosmic X-rays are produced in extreme conditionsfrom intense gravitational and magnetic fields around neutron stars and black holes, to intergalactic shocks in clusters of galaxies. Chandra 1 and XMM-Newton 2 have probed the space-time geometry around black holes, unveiled the importance of accreting supermassive black holes in the evolution of the most massive galaxies, demonstrated in a unique manner that dark matter exists, and confirmed the existence of dark energy. They have also tracked the production and dispersal of heavy elements by supernovae and measured the magnitude and rate of flaring of young Sun-like stars. Table 1 gives a subjectiveand by-no-means complete listof significant discoveries made using these observatories.With an order-of-magnitude or more improvement in spectral and spatial resolution and sensitivity, Chandra and XMM-Newton have shed light on known problems, as well as opened new areas of research. These observatories have clarified the nature of X-ray radiation from comets 3 , collected a wealth of data on the nature of X-ray emission from stars of all ages 4,5 , and used spectra and images of supernova shock waves to confirm the basic gas dynamical model 6,7 of these objects. They have resolved into discrete point sources the diffuse emission from the plane of the Galaxy 8 , as well as the diffuse extragalactic X-ray background 9 . They have discovered hundreds of supermassive black holes at the centres of galaxies and for many of those obtained high-resolution spectra that have Comets Established charge-exchange as mechanism for X-ray emission. Individual stars Measured densities, temperatures and composition of hot plasmas, testing models for stellar evolution, X-ray emission from stellar coronae, and stellar winds. Star formation and star-forming regions Discovered X-ray emission from gas accreting onto stellar surfaces and influenced by magnetic fields; detected giant flares from young stars, with implications for planet formation. SupernovaeEstablished that Kepler's supernova was a thermonuclear event. Supernova remnants (SNRs) Discovered a central compact object in the Cas A SNR and traced the distribution of elements indicating turbulent mixing along with an aspherical explosion. Imaged forward and reverse shock waves in several SNR, with implications for the acceleration of cosmic rays. Pulsar wind nebulaeResolved jets ...