A new space science satellite "Einstein Probe" (Einstein Probe, EP) developed by the Space Science Pilot Project of the Chinese Academy of Sciences was successfully launched at the Xichang Satellite Launch Center on the afternoon of January 9. The scientific research team of the National Astronomical Observatories of the Chinese Academy of Sciences, which is responsible for the development and construction of the "Einstein Probe" satellite scientific application system, explained that the scientific objectives of the satellite mainly include the discovery of X-ray transient celestial bodies in the universe, the exploration of black hole flares and the mapping of black hole distribution, and the exploration of X-ray signals from gravitational wave sources.
Schematic diagram of the "Einstein Probe" satellite in orbit. Courtesy of the National Astronomical Observatories of the Chinese Academy of Sciences.
One of the main scientific objectives of the Einstein Probe satellite is to discover X-ray transient objects in the universe and to monitor the activity of known celestial bodies, the nature of these phenomena and the associated physical mechanisms. Yuan Weimin, chief scientist of the "Einstein Probe" satellite and researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, said that the changes in celestial radiation are mainly manifested in two categories: one is the temporary and burst sources, which are not suitable in time and space, such as supernova shock bursts, high redshift gamma bursts, special gamma bursts and X-ray flashes, magnetars, neutron star binary stars, white dwarfs (cataclysmic variable stars), etc.;The other type is the continuous radiation change of celestial bodies, such as various types of active galactic nuclei massive black holes, black holes and neutron stars X-ray binary, cataclysmic variable stars (stellar mass black holes, other compact objects), extremely bright X-ray sources, etc.
He said that the large field of view of the "Einstein Probe" satellite can monitor transient and erupting objects at higher sampling frequencies, and can obtain the change in X-ray flow intensity (light curve) of the time scalar scale from second to month for large sample objects. For bright X-ray sources, the soft X-ray energy spectrum and its long-term variation over time can also be obtained, which can improve the understanding of the law and radiation mechanism of X-ray radiation changes of celestial bodies. These results can be used to measure the physical parameters of celestial bodies, discover new time-varying phenomena and laws, and further understand the nature, physical processes and evolution of celestial bodies.
Zhang Chen, assistant to the chief scientist of the "Einstein Probe" satellite, head of the optical system of the wide-field X-ray telescope, and researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, said that discovering and exploring the flare of silent black holes in the universe, mapping the distribution of black holes, and further understanding their origin, evolution and material accretion processes are another major scientific goal of the "Einstein Probe" satellite.
As the most mysterious celestial body in the universe, the detection and study of black holes has always been the focus of astronomy, and it is also one of the directions of most interest to the public. According to the difference in mass, black holes can be divided into stellar black holes, intermediate-mass black holes and massive black holes, these black holes do not emit light by themselves, but can produce electromagnetic radiation by accretion of surrounding materials to release gravitational energy, and are mainly observed as active galactic nuclei and black holes X-ray binary stars. The idea that there is a massive or even supermassive black hole at the center of galaxies is now widely accepted, but only about 10% of galaxies are active, and the remaining 90% are quietly inactive, and tidal disintegration events (TDE) provide unique probes for studying silent black holes.
These stealthy black holes can only be discovered by large fields of view or telescopes that survey the sky quickly when they erupt, and the "Einstein Probe" satellite, which has both a large field of view and high sensitivity, is a powerful tool for discovering these silent black holes, which will expand the existing samples by magnitude, and provide conditions for mapping the distribution of black holes, as well as further understanding of their origin, evolution and material accretion processes.
Another scientific goal of the Einstein Probe satellite is to explore X-ray signals from gravitational wave sources in order to improve understanding of extremely compact objects and their merger processes. Liu Yuan, chief engineer of the "Einstein Probe" satellite scientific application system and researcher at the National Astronomical Observatories of the Chinese Academy of Sciences, said that the satellite will use its large field of view, high sensitivity, and fast response performance advantages to carry out search, follow-up observation, and research of X-ray counterparts of gravitational wave sources.
Through the detection of the electromagnetic counterpart of the gravitational wave source, the precise positioning of the gravitational wave source is providedThrough the measurement and study of electromagnetic radiation energy, spectrum and light variation, it helps to identify the nature of gravitational wave sources and the physical process of gravitational wave generation, and provides clues for the study of the nature of its predecessor stars. Gravitational wave measurements can directly give the luminosic distance of the source, and the detection of its electromagnetic wave counterpart can measure the redshift, so the gravitational wave cosmology can be studied by studying the redshift-distance relationship measurement of a sample case to test the cosmological model.
In addition, the "Einstein Probe" satellite is expected to detect the temporary source of X-rays driven by magnetars as theoretically predicted as the products of binary neutron star merger, which will play an important role in limiting the identification of binary neutron star merger products and neutron star equations, and provide an important observation basis for the study of astrophysical problems such as the mass distribution of binary neutron stars, the new celestial bodies formed by merger and their evolution laws, and the properties of merger projectiles. (ENDS).