A compact multi-planet system around a bright nearby star from the Dispersed Matter Planet Project

To put the Solar System's terrestrial planets in context, the detection and characterization of low-mass exoplanets is important but challenging. The Dispersed Matter Planet Project targets stars with anomalously low Ca uc(ii) H and K chromospheric emission, indicative of circumstellar absorbing gas. Here we report high-precision, high-cadence radial-velocity measurements of the F8V star DMPP-1 (HD 38677). These were motivated by depressed Ca uc(ii) H and K line cores indicative of short-period, ablating planets producing circumstellar gas. We find a compact planetary system with orbital periods of about 2.9-19 days, comprising three super-Earth-mass planets (about 3-10 M_⊕) and one Neptune-mass planet (about 24 M_⊕). The irradiated super-Earths may be remnant cores of giant planets after mass loss while crossing the Neptune desert. A priori inferences about the presence of short-period planets enabled the efficient discovery of the DMPP-1 planets. We anticipate informative follow-up characterization studies.