A New Type of Spectrometer for Finding Nearby Earth-like Planets




Project Summary

Since astronomers discovered the first exoplanets around 20 years ago, various methods to detect exoplanets using modern technology have emerged. One in particular that has yielded great success is the radial-velocity method. This method relies on the measurement of the small velocities of a star due to gravitational tugs of an orbiting planet, which is derived from Doppler shifts in a high-resolution spectrum. Traditional spectrometers used for radial velocity measurements rely on charge-coupled device (CCD) detectors that cover optical wavelengths. One of the major drawbacks of the radial velocity method using traditional spectroscopy is that it is most likely to find exoplanets that are unlikely to be hosts to life. Exoplanets with close proximity to their stars and short periods produce relatively large Doppler shifts and are most easily detected. However, such planets are often very large and composed mostly of gas, making them uninhabitable. On the other hand, cooler, more Earth-like planets orbiting further away from their stars produce smaller Doppler shifts and are harder to detect.

My research seeks to improve the state of the art in radial velocity measurement using a new type of photon-counting detector known as kinetic inductance detectors (KIDs). KIDs consist of small superconducting resonant circuits patterned out of thin metal films and rely on the superconducting phenomenon of kinetic inductance, which arises from the kinetic energy of Cooper pairs moving through the material. Each detector pixel absorbs incident photons, which breaks Cooper pairs into individual quasiparticles. This causes an increase in kinetic inductance and therefore a change in resonance that is read out as a signal.  When many detector pixels are combined to form a large array, they can be used to count individual photons and operate at infrared wavelengths. This could lead to a high-resolution spectrometer capable of observing low-mass stars with Earth-like planets within 100 light-years of the sun, allowing further follow-up to determine the planets’ habitability.

In order to evaluate the feasibility of a KID-based spectrometer, I have developed a script in Python to compute the resolution of radial velocity measurements that could be obtained using such a spectrometer. Currently, I am working on adjusting the script to account for the specifications of KID arrays, spectrometer instrumentation, and optics based on existing literature. The next step is to use the program to perform simulations with existing stellar spectra data to determine if a radial velocity resolution of at least 1 m/s can be achieved. This is a useful benchmark because a 1 m/s radial velocity resolution enables exoplanets with relatively Earth-like masses and periods to be detected after one year of observations.

Over the course of my research, I have acquired data analysis and computational skills in Python. Furthermore, I have reaffirmed my interest in astrophysics. I am excited to continue working with Dr. James Aguirre and further pursue my research.