Relationship Between Planetary System Architecture And Stellar Spectral Type

Astronomy is an observation-based science.Before 1990s,our research about the relationship between planetary systems and host stars was limited to our Solar System.Is the planetary system architecture of the Solar System Special?Or is it ubiquitous in the Milky Way?We couldn' t give an answer.In 1995,the first exoplanet 51 Peg b was discovered,and our research on planet entered a new chapter.With the advancement of science,the improvement of instruments,and the increasing number of people who are engaged in the field of exoplanets,many exoplanets have been discovered.After the launch of NASA's Kepler telescope,the number of known exoplanets increased exponentially.Today,we have discovered about 4,000 exoplanets.The large quantities of exoplanet data provide us a good opportunity to study exoplanets statistically.For the class of Jupiter-size and terrestrial planets,the relationship between their occurrence rate and host star,has been studied by many previous works.This paper will use Kepler data to explore the relationship between stellar spectral type and planetary system architecture.After that,we use N-body numerical simulation to explore the effects of stellar mass and metallicity on planetary formation and evolution.In the first chapter,we briefly introduce the existing methods of detecting exoplanets and the statistical analysis of exoplanets.The most commonly used methods for detecting exoplanets are the Radial Velocity method and the Transit method,beside which their are Direct imaging,Astrometry,and Micro-lensing methods.Before the launch of the Kepler space telescope in 2009,the total number of exoplanets was less than 600,most of which were discovered using the Radial Velocity method.Later,Kepler used the Transit method to detect exoplanets,which was more efficient.During its service period,about 7,000 exoplanets and candidates were discovered,which greatly changed human perception of the universe.With a comprehensive library of planetary samples,scientists have conducted statistical analysis of exoplanets,including analysis of planetary types,planetary occurrence rates,planetary orbital and physical parameters,host star spectral types,and metallicity.And a joint analysis of stellar-planetary parameter characteristics.Such statistical analysis can deepen understanding of the formation and evolution of planets,inspire thinking about the origin of life,which has important scientific significance.In the second chapter,we analyze the influence of stellar spectral type on the architecture of the planetary system from the planetary data observed by the Kepler telescope.We analyzed planets around different spectral stars in the Kepler telescope's field of view and found that the occurrence rate of exoplanets gradually decreases from M-type stars to F-type stars.We want to explore whether this result is real or because of observational selection effects.So we used numerical simulation to generate a large number of planetary systems and calculated the probability that these systems were discovered.By comparing the simulated planets with the real observed planets,we find that from the M-type stars to the F-type stars,as the mass of the star increases,or equivalently the surface effective temperature increases,then the fraction of stars with Kepler-like planets decreases and the average number of planets with period less than 400 days per planetary system drops from 3 to 2.Based on our results,we give empirical formulas for planet occurrence rate as a function of stellar mass or surface temperature.In particular,we found that the dispersion of the orbital inclination of planetary system suddenly increases around 6000 K,which is consistent with the temperature where the observed obliquities of planetary systems rise.The patterns that planetary system changes with stellar spectral type provide us a lot of inspiration about the process of planet formation.In the third chapter,we use N-body method to simulate the formation and evolution of planets in protoplanetary disks.We explored the effects of star mass,metallicity,and protoplanetary disk mass on this process.Through simulations,we found that for stars with low mass and low metallicity,it is easier to form terrestrial planets around them;for stars with high mass and high metallicity,the planetary embryos grow fast,and it is easier to start accretion of gas,leading to a higher occurrence rate of Jupiter-size planets.The effect of disk mass is similar.The greater the mass of the disk,the greater the probability of occurrence of Jupiter-size planets.In particular,we found that hot Jupiters only form in disks with mass about 0.1 solar mass.By comparing the simulated planets with the observed data,we derive the initial state of the protoplanetary disk.We believe that for systems with Jupiter-size planets,the average mass of the protoplanetary disk should be about four times that of Minimum Mass Solar Nebula.In the last chapter we summarize the entire content and look forward to new observations in the future.Thanks to the on-going and up-coming new telescopes,we are not only finding more planetary systems,but obtaining information such as the composition of the exoplanet atmosphere.More and more detailed information can help us further explore the evolution of exoplanets and learn more about the role of the solar system in the universe.