Exoplanet caught speeding

摘要

The masses of exoplanets have so far been inferred from the tiny gravitational pull they exert on the host stars. It is now possible to measure them from shifts in spectral lines arising from the planets' atmospheres.rnBinary stars are gravitationally bound pairs of stars that orbit a common centre of mass. They are valuable systems. For more than a century, they have enabled astronomers to measure the masses of stars directly. All that was needed was to interlace Newton's law of gravitation with measurements of the stars' Doppler shift - the change in the wavelength of their light spectrum that is caused by their motion towards or away from Earth.