GeminiFocus January 2018 - Page 18

An important goal of exoplanet science is to precisely measure masses and radii for a large enough sample of low-mass planets so that robust statistics emerge . Data from the original Kepler mission have been used to identify thousands of planet candidates , but the masses of most of these planets cannot be measured with existing spectrographs because the expected radial velocity signals are too small or the host stars are too faint , or a combination of both .
Many new transiting planet finder missions ( designed specifically to exploit the synergy between radial velocity and transit techniques ) have recently been approved : the Kepler spacecraft has been repurposed for the K2 mission ; NASA ’ s Transiting Exoplanet Survey Satellite ( TESS ) mission is scheduled for launch in March 2018 ; ESA ’ s CHaracterising EXOPlanet Satellite ( CHEOPS ) mission is planned for the end of 2018 ; and ESA ’ s PLAnetary Transits and Oscillations of stars ( PLATO ) mission is now set for 2026 . Therefore , many new small transiting planets will be identified over the next decade . This presents an enormous opportunity to expand the study of planetary statistics into the regime of planet bulk compositions — if we can measure the masses of these objects using the radial velocity method .
The Radial Velocity Method
The techniques for Doppler spectroscopy have currently progressed to the point that precisions of 1-2 meters / second ( m / s ) are routinely obtained on bright stars ( e . g ., Howard et al ., 2011 ; Lovis et al ., 2011 ), and precisions of 60-80 centimeters / second ( cm / s ) have been obtained in a few select cases ( e . g ., Pepe et al ., 2011 ). However , existing radial velocity instruments become very inefficient around V = 12th magnitude and objects with V > 13th magnitude are unattainable for all but the most intense campaigns . Therefore , 85 % of the nearly 5,000 planet candidates from the Kepler mission that have Kepler magnitudes greater than 13 are essentially out of reach of existing instruments .
In addition to having substantially improved precision and reach , the next generation of radial velocity spectrographs should also cover longer wavelengths for efficient observations of very low-mass M dwarfs . One pathway for studying habitable planets is focused on the opportunity offered by M dwarfs ; in particular the very lowest-mass M dwarfs ( those with M star
< 0.3 M B
). In contrast to solar-type stars , the habitable zones of M dwarfs are close-in enough so that planets in this region have a significant chance of transiting , making them feasible targets for transit spectroscopy observations to characterize their atmospheres . The James Webb Space Telescope ( JWST ) will be able to make measurements of the transmission spectra for such planets ( Deming et al ., 2009 ), but we first have to identify good targets .
Improved reach to fainter stars is important for the M dwarf science case . The lowestmass M dwarfs are intrinsically very faint , and current instruments can achieve 1 m / s precision only for the handful of these stars within a few parsecs ( e . g ., Proxima Centauri and Barnard ’ s Star ). To take advantage of the opportunities offered by transiting lowmass planets around low-mass M dwarfs , we need high-precision radial velocity measurements for these stars out to 20 parsecs ( Deming et al ., 2009 ). Only a few percent of planets in the habitable zones of low-mass M dwarfs will have the right orbital geometry to transit . So a large volume of space has to be probed to be assured of finding some that would be ideal targets for atmospheric studies with JWST . With these conditions in mind , MAROON-X was conceived and born .
16 GeminiFocus January 2018
An important goal of exoplanet science is to precisely measure masses and radii for a large enough sample of low-mass planets so that robust statistics emerge. Data from the original Kepler mission have been used to identify thousands of planet candidates, but the masses of most of these planets cannot be measured with existing spectrographs because the expected radial velocity signals are too small or the host stars are too faint, or a combination of both. Many new transiting planet finder missions (designed specifically to exploit the synergy between radial velocity and transit tech- niques) have recently been approved: the Kepler spacecraft has been repurposed for the K2 mission; NASA’s Transiting Exoplanet Survey Satellite (TESS) mission is scheduled for launch in March 2018; ESA’s CHaracter- ising EXOPlanet Satellite (CHEOPS) mission is planned for the end of 2018; and ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission is now set for 2026. There- fore, many new small transiting planets will be identified over the next decade. This presents an enormous opportunity to ex- pand the study of planetary statistics into the regime of planet bulk compositions — if we can measure the masses of these objects using the radial velocity method. The Radial Velocity Method The techniques for Doppler spectroscopy have currently progressed to the point that precisions of 1-2 meters/second (m/s) are routinely obtained on bright stars (e.g., Howard et al., 2011; Lovis et al., 2011), and precisions of 60-80 centimeters/second 62fR&VV'FVBfWr6VV7@66W2RrWRWB#vWfW"WЦ7Fr&FfV6G7G'VVG2&V6PfW'Vff6VB&VBn(c(c'FvGVFPB&V7G2vFn(c(c7FvGVFR&PVGF&Rf"'WBFR7BFV6P`vV֖f7W06v2FW&Vf&RRRbFRV&ǐRWB6FFFW2g&FRWW ֗76FBfRWW"vGVFW2w&VBЦW"F2&RW76VFǒWBb&V6bWЦ7Fr7G'VVG2खFFFFfr7V'7FFǒ&fV@&V66B&V6FRWBvVW&F`&FfV6G7V7G&w&26VB66fW"vW"vfVVwF2f"Vff6VB"Ч6W'fF2bfW'r72Gv&g2PFvf"7GVGr&F&RWG20f7W6VBFR'GVGffW&VB'ЦGv&g3'F7V"FRfW'vW7B72ЦGv&g2F6RvF7F"(c2"6G&7@F6"GR7F'2FR&F&RW2bЦGv&g2&R66R֖VVv6FBWG0F2&VvfR6vf6B66R`G&6FrrFVfV6&RF&vWG2f G&6B7V7G&66'6W'fF2F6&2ЧFW&RFV"F7W&W2FRW2vV& 76RFVW66Ru5Bv&R&RFPV7W&VVG2bFRG&6֗767V7G&f"7V6WG2FV֖rWB#'WBvPf'7BfRFFVFgvBF&vWG2ख&fVB&V6FfFW"7F'22'F@f"FRGv&b66V6R66RFRvW7BЦ72Gv&g2&RG&66ǒfW'fBB7W'&VB7G'VVG266WfR0&V66ǒf"FRFgVbFW6R7F'0vFfWr'6V72Rr&6VFW&B&&&N( 27F"FFRGfFvR`FR'GVFW2ffW&VB'G&6FrrЦ72WG2&VBr72Gv&g2vRVVBv&V66&FfV6GVЧ7W&VVG2f"FW6R7F'2WBF#'6V70FV֖rWB#ǒfWrW&6VB`WG2FR&F&RW2br70Gv&g2vfRFR&vB&&FvVRЧG'FG&6B6&vRfVRb76R0F&R&&VBF&R77W&VBbfFr6PFBvVB&RFVF&vWG2f"F7W&07GVFW2vFu5BvFFW6R6FF2֖B$Ղv266VfVBB&&दV'#