The distance $D$ to an exoplanet system with imaging and spectral measurement can be obtained by using the orbit as a ruler. The measurement of the Distance to a typical exoplanet system with imaging and spectral measurement can be accurate to $\delta D/D\sim 0.2$, if the orbital velocity of the ...
In observational astronomy, we essentially measure the location, flux density (at certain frequency and certain time), distance and angular size of the sources. A parameter space of observational astronomy can be constructed with the parameters such as the sample size of sources, frequency ...
We propose to use the rotation period to constrain the average density of an object with gravitationally confined surface. The average density is inverse proportional to the square of the rotation period, while independent of the size of the object. The lower limit of the average density can ...
Five-hundred-meter Aperture Spherical radio Telescope (Nan et al. 2011) is the largest single-dish radio telescope in the world, starting to achieve in the studies of pulsars and fast radio bursts (Qian et al. 2020). The ITRF coordinates of a fixed point of an observatory is required for pulsar se ...