General Relativity, Quantum Chromodynamics, and Quantum Electrodynamics are the bases of modern physics. Tests of these fundamental physical laws in extreme conditions (extreme gravity, extreme density, and extreme magnetic field) may be carried out by observing black holes and compact objects. We summarize the main problems in this field as “One Singularity, Two Stars, and Three Extremes”, and are currently developing the X-ray Timing and Polarization (XTP) mission to explore these problems.
XTP is the successor of HXMT, but will use focusing optics and advanced detector technology. The main characteristics of XTP are to use an array of focusing telescopes to realize large detection area and high sensitivity simultaneously. The designed effective area of XTP is ~1 m2,about one order of magnitude larger than the previous focusing telescopes such as ESA’s XMM-Newton, and JAXA’s Astro-H in development. With such capabilities XTP can systematically study the fundamental physics laws and processes in extremely strong gravitational field, test the General Relativity theory, and measure the spin of black holes. XTP will also have hard X-ray focusing telescopes with an effective area of ~300 cm2 (@30 keV), and 2000 cm2 (@2 keV) (1-10 keV) for the soft X-ray polarization measurements. Therefore, in addition to the core sciences mentioned above, XTP can also study the equation of state of matter in neutron stars and the physics in strong magnetic field.
Illustration of the XTP satellite
XTP has been selected as a background project by the Strategic Pioneer Program (SPP) on Space Science of the Chinese Academy of Sciences. IHEP is leading this project. A major problem with XTP is that it faces strong competition of a Europeanmission LOFT. We need to solve its key technologies, make it officially approved, and then launch it as early as possible, so that it can obtain its expected core science results.