The best spectrographs are limited in stability by their calibration light source. Laser frequency combs are the ideal calibrators for astronomical spectrographs. They emit a spectrum of lines that are equally spaced in frequency and that are as accurate and stable as the atomic clock relative to which the comb is stabilized. Absolute calibration provides the radial velocity of an astronomical object relative to the observer (on Earth). For the detection of Earth-mass exoplanets in Earth-like orbits around solar-type stars, or of cosmic acceleration, the observable is a tiny velocity change of less than 10 cm s-1, where the repeatability of the calibration – the variation in stability across observations – is important. Hitherto, only laboratory systems or spectrograph calibrations of limited performance have been demonstrated. Here we report the calibration of an astronomical spectrograph with a short-term Doppler shift repeatability of 2.5 cm s-1, and use it to monitor the star HD75289 and recompute the orbit of its planet. This repeatability should make it possible to detect Earth-like planets in the habitable zone of star or even to measure the cosmic acceleration directly.
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The TESS (Transiting Exoplanet Survey Satellite) mission has discovered many exoplanet candidates that need to be confirmed and characterized from the ground. One of them orbits Ross 176, a K-type dwarf star, where we have identified a promising hot “water-world” candidate. Using spectroscopic observations with the CARMENES instrument, we confirmed the planetary nature of the signal detected by TESS and estimated the planet’s mass. To improve the analysis, we applied an advanced statistical method called Gaussian Process, which allowed us to separate the star’s own variability (quite strongAdvertised on -
Type 2 quasars (QSO2s) are active galactic nuclei (AGN) seen through a significant amount of dust and gas that obscures the central supermassive black hole and the broad-line region. Here, we present new mid-infrared spectra of the central kiloparsec of five optically selected QSO2s at redshift z ∼ 0.1 obtained with the Medium Resolution Spectrometer module of the Mid-Infrared Instrument (MIRI) aboard the James Webb Space Telescope (JWST). These QSO2s belong to the Quasar Feedback (QSOFEED) sample, and they have bolometric luminosities of log L bol = 45.5 to 46.0 erg s −1 , global starAdvertised on -
Observations made with the James Webb Space Telescope (JWST) have revealed a larger-than-expected number of massive galaxies when the Universe was still young. The focus of this study is precisely one of these galaxies, ZF-UDS-7329. It is a very compact object, and its spectrum suggests that it formed at a very early stage, when the Universe was around 2 billion years old. According to theoretical predictions, these objects first formed a generation of stars at the center of their dark matter halos and subsequently grew by merging with other halos. However, due to the random nature of theseAdvertised on