Scientists weigh an alien world using new telescope technique
Researchers used advanced infrared spectroscopy to precisely measure the mass of a distant planet orbiting a nearby star, confirming it's rocky like Earth. The breakthrough method could accelerate the search for potentially habitable worlds and help space agencies prioritize which exoplanets warrant further investigation.
Originaltitel: Mass determination of the ultra-short-period planet LHS 3844 b First K-band radial velocity measurements with CRIRES+
<p>We present the first planet mass measurement obtained with CRIRES+ radial velocity (RV) observations using the K-band gas cell. Our target, LHS 3844 b (TOI-136), is a transiting super-Earth with radius R-b = 1.286(-0.044)(+0.043)R(circle plus) and an orbital period of P-b = 0.462929709(-0.000000042)(+0.000000044) d, placing it in the class of ultra-short-period (USP) planets. The host star LHS 3844 is an old (7.8 +/- 1.6 Gyr), slowly rotating (P-rot = 130.0(-13.4)(+16.9)) M5.0 dwarf with M-star = 0.151 +/- 0.014 M-circle dot at a distance of 15 pc (V = 15.2 mag, K = 9.2 mag). Combining our CRIRES+ RVs with archival ESPRESSO spectra, and confirming the signal in each dataset independently, we detected periodic RV variations with a semi-amplitude K-b = 6.95(-0.60)(+0.55) m s(-1), implying a planetary mass of m(b) = 2.37 +/- 0.25 M-circle plus and a bulk density of rho(b) = 6.15(-0.61)(+0.60) g cm(-3) cm(-3), consistent with a predominantly rocky composition. We further found excess RV variability that may be attributed to stellar jitter or to an additional planetary signal, for which we identified a tentative super-Earth candidate with a period of approximate to 6.88 d. Owing to its proximity to its M-dwarf host, LHS 3844 b experiences intense irradiation and is unlikely to retain a substantial H/He envelope. Interior modeling places an upper limit on the iron-core mass fraction, which is consistent with an Earth-like rocky composition. With an emission spectroscopy metric (ESM) of 28, LHS 3844 b is a prime JWST target for atmospheric and surface characterization and the most promising surface-characterization target known. Phase-curve spectroscopy may reveal its surface mineralogy and enable the first robust detection of exoplanet surface spectral features. Our results demonstrate that near-infrared RVs obtained with CRIRES+ enable robust mass measurements of super-Earths orbiting late M dwarfs.</p>