The direct imaging of Earth-like planets in solar neighbors is challenging. Both transit and radial velocity (RV) methods suffer from noise due to stellar activity. By choosing a typical configuration of an X array interferometer, we used theoretical formulas to calculate the intrinsic Poisson noise and the noise of stellar activities. Assuming a fixed array with no rotation and ignoring other systematic and astrophysical noises, we considered a single active region on a stellar disk, including both spots and flares with different parameters, for instance, the position, size, and temperature of the active regions. Then we simulated the S/N of Earth-like planets in HZ around G dwarf stars (solar-like) and M dwarfs (Proxima-like), with different stellar activities in the mid-infrared (MIR) band ( 7-12 $μ$m). The noise attributed to stellar activity has much less influence than the Transit and RV method when detecting Earth-like planets around both G and M dwarfs. I.e. Stellar activity can hardly influence the detection of Earth-like planets around G dwarf stars. However, detecting Earth-like planets around M dwarfs, which are usually more active, can be significantly hindered. We also analyzed the uncertainty of the planet's location due to the deduced S/N. Consequently, we have determined the possibility of mistaking a planet in the HZ as being outside the HZ based on an erroneous S/N measurement. Selecting quiescent target stars or monitoring the light curves of stars would be a helpful way to get rid of contaminates associated with violent stellar activities.
Understanding exoplanet formation and finding potentially habitable exoplanets is vital to an enhanced understanding of the universe. The use of nulling interferometry to strongly attenuate the central starlight provides the opportunity to see objects closer to the star than ever before. Given that exoplanets are usually warm, the 4 microns Mid-Infrared region is advantageous for such observations. The key performance parameters for a nulling interferometer are the extinction ratio it can attain and how well that is maintained across the operational bandwidth. Both parameters depend on the des…
Tricouplers for nulling interferometry with photonic integrated circuits
California Institute of Technology（加州理工学院）；Astrophotonics Australia（天文光子学澳大利亚）；University of California, Los Angeles（加利福尼亚大学洛杉矶分校）；NASA Jet Propulsion Laboratory（美国国家航空航天局喷气推进实验室）；University of Maryland（马里兰大学）
Tri-coupler geometries for achromatic nulling interferometry in the near-infrared
Astrophotonics Australia；Department of Astronomy, California Institute of Technology（加州理工学院天文学系）；Physics & Astronomy Department, University of California, Los Angeles（加州大学洛杉矶分校物理与天文系）
Understanding the atmospheres of exoplanets is a milestone to decipher their formation history and potential habitability. High-contrast imaging and spectroscopy of exoplanets is the major pathway towards the goal. Directly imaging of an exoplanet requires high spatial resolution. Interferometry has proven to be an effective way of improving spatial resolution. However, means of combining interferometry, high-contrast imaging, and high-resolution spectroscopy have been rarely explored. To fill in the gap, we present the dual-aperture fiber nuller (FN) for current-generation 8-10 meter telescop…
Photobombing for the Large Interferometer For Exoplanets (LIFE). A new criterion for target confusion and application to a MIR rotating nulling interferometer
Proxima b is our nearest potentially rocky exoplanet and represents a formidable opportunity for exoplanet science and possibly astrobiology. With an angular separation of only 35~mas (or 0.05~AU) from its host star, Proxima b is however hardly observable with current imaging telescopes and future space-based coronagraphs. One way to separate the photons of the planet from those of its host star is to use an interferometer that can easily resolve such spatial scales. In addition, its proximity to Earth and its favorable contrast ratio compared with its host M dwarf (approximately 10$^{-5}$ at …
We address three major questions in astronomy, namely the detection of biosignatures on habitable exoplanets, the geophysics of exoplanets and cosmology. To achieve this goal, two requirements are needed. First a very large aperture to detect spectro-polarimetric and spatial features of faint objects such as exoplanets, and second a continuous monitoring to characterize the temporal behavior of exoplanets such as rotation period, meteorology and seasons. An Earth-based telescope is not suited for continuous monitoring and the atmosphere limits the ultimate angular resolution and spectro-polari…
Space interferometry is the inevitable endpoint of high angular resolution astrophysics, and a key technology that can be leveraged to analyse exoplanet formation and atmospheres with exceptional detail. However, the anticipated cost of large missions such as Darwin and TPF-I, and inadequate technology readiness levels have resulted in limited developments since the late 2000s. Here, we present a feasibility study into a small scale formation flying interferometric array in Low Earth Orbit, that will aim to prove the technical concepts involved with space interferometry while still making uniq…
Phosphine could be a key molecule in the understanding of exotic chemistry happening in (exo)planetary atmospheres. While it has been detected in the Solar System's giant planets, it has not been observed in exoplanets yet. In the exoplanetary context however it has been theorized as a potential biosignature molecule. The goal of our study is to identify which illustrative science cases for PH3 chemistry are observable with a space-based mid-infrared nulling interferometric observatory like the LIFE (Large Interferometer For Exoplanets) concept. We identified a representative set of scenarios …
We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81 - 12.41 um) emission around the nearby main-sequence star eta Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% +/- 0.35% over a field-of-view of 140 mas in radius (~2.6\,AU at the distance of eta Corvi) and shows no significant variation over 35° of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by Spitzer/IRS (~23% across the N' band), suggesting that a significant fraction of…
In recent years, a number of observations have been made of the transits of 'Hot Jupiters', such as HD 189733b, which have been modelled to derive atmospheric structure and composition. As measurement techniques improve, the transit spectra of 'Super-Earths' such as GJ 1214b are becoming better constrained, allowing model atmospheres to be fitted for this class of planet also. While it is not yet possible to constrain the atmospheric states of small planets such as the Earth or cold planets like Jupiter, this may become practical in the coming decades and if so, it is of interest to determine …
We report the discovery of a low-mass planet orbiting Gl 15 A based on radial velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab is a planet with minimum mass Msini = 5.35 $\pm$ 0.75 M$_\oplus$, orbital period P = 11.4433 $\pm$ 0.0016 days, and an orbit that is consistent with circular. We characterize the host star using a variety of techniques. Photometric observations at Fairborn Observatory show no evidence for rotational modulation of spots at the orbital period to a limit of ~0.1 mmag, thus supporting the existence of the planet. We detect a second RV signal w…
