Exoplanet Research Makes Giant Leap Forward: First Direct Light Signal Received
Exoplanet science has advanced immeasurably since the first speculative discovery of Gamma Cephei Ab (GCAb – 1988). Since then more than 1900 exoplanets, residing in over 1200 separate planetary systems, have been officially confirmed.
Adopted detection methods have been incredibly successful, although slightly limited. Since the discovery of GCAb, various indirect techniques have been developed that mainly involve measuring stellar light variations caused by planetary transits (Transit method), and/or subtle oscillatory movements in a star’s observed position (Radial velocity/Doppler method).
Advancing these methods, a team from Instituto de Astrofísica e Ciências do Espaço (IA) and Universidade do Porto, Portugal, have obtained, for the first time, a spectroscopic light signal from the exoplanet 51 Pegasi b—a Jupiter like planet orbiting a main sequence star, 50 light years from Earth in the constellation of Pegasus—using a newly devised, direct, method. The method works by filtering reflected planetary light from the host star’s spectrum, which acts as a control source for any observations. The team point out, extracting faint planetary signals from a star’s dominant glare is an extremely difficult task; however, the advantages of the technique are self-evident as planetary transits are not required. This breakthrough characteristic should increase detection rates, as well as revealing planetary information otherwise unobtainable using indirect methods.
As lead researcher, Jorge Martins, highlights: “This type of detection technique is of great scientific importance, as it allows us to measure the planet’s real mass and orbital inclination, which is essential to more fully understand the system. It also allows us to estimate the planet’s reflectivity, or albedo, which can be used to infer the composition of both the planet’s surface and atmosphere.”
Martins’ discovery was obtained using the increasingly dated ‘HARPS’ instrument (3.6m telescope, La Silla Observatory, Chile), which is highly encouraging. The new technique promises exciting times ahead for exoplanet science when more advanced, next generation, ESO instruments, such as ESPRESSO (VLT) and E-ELT, become operational.
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