Promoting Transdisciplinary and Transeultural Cooperation In Space Science in Face of COVID-19-Interview with Prof.Wing-Huen Ip,Executive Director of ISSI-BJ

Prof.Wing-Huen Ip,a world-renown scientist in cometary physics,planetary science,solar system evolution and exoplanets,took the post of the Executive Director of the International Space Science Institute一Beijing(ISSI-BJ)in June.As the only partner of the well-known International Space Science Institute(ISSI)in Bern outside Switzerland,ISSI-BJ has adopted the same tools as ISSI to facilitate international cooperation and academic exchanges:workshops,forums,and others that rely on in-person communications.

A study of the global magnetic activity of the star Kepler-17 using light curve inversion with bipartite regularization

A new method of light curve inversion with bipartite regularization(LIBR),which is complementary to the previous treatments by Bonomo and Lanza and Estrela and Valio,is used to reconstruct the physical properties of star spots on the solar-type star Kepler-17 by using the full Q1-Q17 data set.The Markov Chain Monte Carlo(MCMC)method was applied to find the best profile of the reconstructed surface.The known value of the rotation inclination of Kepler-17 allows the generation of a star spot model in a sequence of stellar rotation with a period of 12.26 d.Because of the nature of the light curve inversion,the spot model is limited to the equatorial region.We also investigated the starspot lifetimes of Kepler-17 utilizing the MCMC method.Combined with the LIBR inversion results,it was found that the star spots typically last from one to several stellar rotations.From the time evolution of the spot size,a magnetic cycle period of 437 d can be derived.This value is comparatively shorter than the solar cycle which might be a consequence of the younger age(~1.78 Gyr)of Kepler-17.The light curve of Kepler-17 is characterized by the presence of large-amplitude variation caused by star spots but no superflare activity.An interesting possibility is that the magnetic energy stored in the star spot regions could have been constantly dissipated by electrodynamic interaction between the central star and the hot Jupiter,Kepler-17 b,via a lower-level energy release process.

Preface: Frontiers in Astrophysics(Ⅱ)——A special issue dedicated to the 20th anniversary of RAA(2001–2020)

On the arrival of the 20 th anniversary of the journal,Research in Astronomy and Astrophysics(RAA),we see rapid progress in the frontiers of astronomy and astrophysics.To celebrate the birth and growth of RAA,a special issue consisting of 11 invited reviews from more than 30 authors,mainly from China,has been organized.This is the second volume of the special issues entitled Frontiers in Astrophysics published in RAA.The publication aims at evaluating the current status and key progress in some frontier areas of astronomy and astrophysics with a spirit of guiding future studies.

Preface: The Chang'e-3 lander and rover mission to the Moon

The Chang＇e-3 （CE-3） lander and rover mission to the Moon was an in- termediate step in China＇s lunar exploration program, which will be followed by a sample return mission. The lander was equipped with a number of remote-sensing instruments including a pair of cameras （Landing Camera and Terrain Camera） for recording the landing process and surveying terrain, an extreme ultraviolet camera for monitoring activities in the Earth＇s plasmasphere, and a first-ever Moon-based ultravi- olet telescope for astronomical observations. The Yutu rover successfully carried out close-up observations with the Panoramic Camera, mineralogical investigations with the VIS-NIR Imaging Spectrometer, study of elemental abundances with the Active Particle-induced X-ray Spectrometer, and pioneering measurements of the lunar sub- surface with Lunar Penetrating Radar. This special issue provides a collection of key information on the instrumental designs, calibration methods and data processing pro- cedures used by these experiments with a perspective of facilitating further analyses of scientific data from CE-3 in preparation for future missions.

Surface thermophysical properties on the potentially hazardous asteroid (99942) Apophis

We investigate the surface thermophysical properties（thermal emissivity, thermal inertia,roughness fraction and geometric albedo） of asteroid（99942） Apophis, using the currently available mid-infrared observations from CanariC am on Gran Telescopio CANARIAS and far-infrared data from PACS on Herschel, based on the Advanced Thermophysical Model. We show that the thermal emissivity of Apophis should be wavelength dependent from 8.70 μm to 160 μm, and the maximum emissivity may appear around 20 μm, similar to that of Vesta. Moreover, we further derive the thermal inertia,roughness fraction, geometric albedo and effective diameter of Apophis within a possible 1σ scale of Γ = 100（-52）^（＋100）＋Jm^（-2）s^-0.5K^-1, fr = 0.78~1.0, pv = 0.286（-0.026）^（＋0.030） and D（eff） = 378（-25）^（＋19）m, and 3σscale of Γ = 100（-100）^（＋240）Jm^（-2）s^-0.5 K^-1, fr = 0.2~1.0, pv = 0.286（-0.029）^（＋0.039） and D（eff） = 378（-29）^（＋27） m. The derived low thermal inertia but high roughness fraction may imply that Apophis could have regolith on its surface, where stronger space weathering but weaker regolith migration has happened in comparison with asteroid Itokawa. Our results show that small-size asteroids could also have fine regolith on the surface, and further infer that Apophis may have been delivered from the Main Belt by the Yarkovsky effect.

A Revisit of the Phobos Events

The magnetic field disturbances detected by the Phobos-2 spacecraft in 1989 have been suggested to be caused by a ring of dust and/or gas emitted from the Martian moon,Phobos.The physical nature of these"Phobos events"is examined using results from related investigations over the last twenty years.It is concluded that there is no clear evidence at present to support the association of magnetic field disturbances in the solar wind with Phobos.The situation will be further clarified taking advantage of the multi-spacecraft observations of the Yinghuo-1(YH-1),Mars Express and MAVEN missions beginning in 2012.It is expected that many novel features of solar wind interaction with Phobos(and possibly also Deimos) itself will also be revealed.

Discovery of 13 New Variable Stars in the Field of the Open Cluster NGC 2168 (M35)

A wide-field time-series CCD photometric survey of variable stars in the field of the open cluster NGC 2168 was carried out using the BATC Schmidt telescope. In total 13 new variable stars are discovered with three W UMa systems,one EA type and two EB type eclipsing binaries （one of them could be a W UMa system）, and seven pulsating stars including three candidates of δ Scuti stars.

Detection of large color variation in the potentially hazardous asteroid(297274) 1996 SK

Low-inclination near-earth asteroid （NEA） （297274） 1996 SK, which isalso classified as a potentially hazardous asteroid, has a highly eccentric orbit. Itwas studied by multi-wavelength photometry within the framework of an NEA colorsurvey at Lulin Observatory. Here, we report the finding of large color variationacross the surface of （297274） 1996 SK within one asteroidal rotation period of4.656 ± 0.122 hours and classify it as an S-type asteroid according to its averagecolors ofB - V = 0.767 ± 0.033, V - R = 0.482 ± 0.021, V - I = 0.801 ± 0.025and the corresponding relative reflectance spectrum. These results might be indica-tive of differential space weathering or compositional inhomogeneity in the surfacematerials.