No Arabic abstract
X-ray observatories contribute fundamental advances in Solar System studies by probing Sun-object interactions, developing planet and satellite surface composition maps, probing global magnetospheric dynamics, and tracking astrochemical reactions. Despite these crucial results, the technological limitations of current X-ray instruments hinder the overall scope and impact for broader scientific application of X-ray observations both now and in the coming decade. Implementation of modern advances in X-ray optics will provide improvements in effective area, spatial resolution, and spectral resolution for future instruments. These improvements will usher in a truly transformative era of Solar System science through the study of X-ray emission.
During the last few years our knowledge about the X-ray emission from bodies within the solar system has significantly improved. Several new solar system objects are now known to shine in X-rays at energies below 2 keV. Apart from the Sun, the known X-ray emitters now include planets (Venus, Earth, Mars, Jupiter, and Saturn), planetary satellites (Moon, Io, Europa, and Ganymede), all active comets, the Io plasma torus (IPT), the rings of Saturn, the coronae (exospheres) of Earth and Mars, and the heliosphere. The advent of higher-resolution X-ray spectroscopy with the Chandra and XMM-Newton X-ray observatories has been of great benefit in advancing the field of planetary X-ray astronomy. Progress in modeling X-ray emission, laboratory studies of X-ray production, and theoretical calculations of cross-sections, have all contributed to our understanding of processes that produce X-rays from the solar system bodies. At Jupiter and Earth, both auroral and non-auroral disk X-ray emissions have been observed. X-rays have been detected from Saturns disk, but no convincing evidence of an X-ray aurora has been observed. The first soft (0.1- 2 keV) X-ray observation of Earths aurora by Chandra shows that it is highly variable. The non-auroral X-ray emissions from Jupiter, Saturn, and Earth, those from the disk of Mars, Venus, and Moon, and from the rings of Saturn, are mainly produced by scattering of solar X-rays. The spectral characteristics of X-ray emission from comets, the heliosphere, the geocorona, and the Martian halo are quite similar, but they appear to be quite different from those of Jovian auroral X-rays. X-rays from the Galilean satellites and the IPT are mostly driven by impact of Jovian magnetospheric particles. This paper reviews studies of the soft X-ray emission from the solar system bodies, excluding the Sun.
The high resolution non-dispersive spectroscopy and unprecedented sensitivity of Athena+ will revolutionize solar system observing: the origin of the ions producing Jupiters X-ray aurorae via charge exchange will be conclusively established, as well as their dynamics, giving clues to their acceleration mechanisms. X-ray aurorae on Saturn will be searched for to a depth unattainable by current Earth-bound observatories. The X-ray Integral Field Unit of Athena+ will map Mars expanding exosphere, which has a line-rich solar wind charge exchange spectrum, under differing solar wind conditions and through the seasons; relating Mars X-ray emission to its atmospheric loss will have significant impact also on the study of exoplanet atmospheres. Spectral mapping of cometary comae, which are spectacular X-ray sources with extremely line-rich spectra, will probe solar wind composition and speed at varying distances from the Sun. Athena+ will provide unique contributions also to exoplanetary astrophysics. Athena+ will pioneer the study of ingress/eclipse/egress effects during planetary orbits of hot-Jupiters, and will confirm/improve the evidence of Star-Planet Interactions (SPI) in a wider sample of planetary systems. Finally Athena+ will drastically improve the knowledge of the X-ray incident radiation on exoplanets, a key element for understanding the effects of atmospheric mass loss and of the chemical and physical evolution of planet atmospheres, particularly relevant in the case of young systems.
Representative abundances of the chemical elements for use as a solar abundance standard in astronomical and planetary studies are summarized. Updated abundance tables for solar system abundances based on meteorites and photospheric measurements are presented.
Indian Centre for Space Physics is engaged in pioneering balloon borne experiments with typical payloads less than ~ 3.5kg. Low cost rubber balloons are used to fly them to a height of about 40km. In a double balloon system, the booster balloon lifts the orbiter balloon to its cruising altitude where data is taken for a longer period of time. In this Paper, we present our first scientific report on the variation of Cosmic Rays and muons with altitude and detection of several solar flares in X-rays between 20keV and 100keV. We found the altitude of the Pfotzer maximum at Tropic of Cancer for cosmic rays and muons and catch several solar flares in hard X-rays. We find that the hard X-ray (> 40keV) sky becomes very transparent above Pfotzer maximum. We find the flare spectrum to have a power-law distribution. From these studies, we infer that valuable scientific research could be carried out in near space using low cost balloon borne experiments. Published in Online version of Indian Journal of Physics.
The Transiting Exoplanet Survey Satellite (TESS), launched successfully on 18th of April, 2018, will observe nearly the full sky and will provide time-series imaging data in ~27-day-long campaigns. TESS is equipped with 4 cameras; each has a field-of-view of 24x24 degrees. During the first two years of the primary mission, one of these cameras, Camera #1, is going to observe fields centered at an ecliptic latitude of 18 degrees. While the ecliptic plane itself is not covered during the primary mission, the characteristic scale height of the main asteroid belt and Kuiper belt implies that a significant amount of small solar system bodies will cross the field-of-view of this camera. Based on the comparison of the expected amount of information of TESS and Kepler/K2, we can compute the cumulative etendues of the two optical setups. This comparison results in roughly comparable optical etendues, however the net etendue is significantly larger in the case of TESS since all of the imaging data provided by the 30-minute cadence frames are downlinked rather than the pre-selected stamps of Kepler/K2. In addition, many principles of the data acquisition and optical setup are clearly different, including the level of confusing background sources, full-frame integration and cadence, the field-of-view centroid with respect to the apparent position of the Sun, as well as the differences in the duration of the campaigns. As one would expect, TESS will yield time-series photometry and hence rotational properties for only brighter objects, but in terms of spatial and phase space coverage, this sample will be more homogeneous and more complete. Here we review the main analogues and differences between the Kepler/K2 mission and the TESS mission, focusing on scientific implications and possible yields related to our Solar System.