Unveiling the Mysteries of the Milky Way and Searching for Earth-sized Exoplanets with JASMINE

Jan. 22, 2025 | Aerospace Project Research Associate, ISAS people

KASAGI Yui / Dept. of Space Astronomy and Astrophysics, ISAS

Research Summary

Fig.1
Fig.1 Image of JASMINE

JASMINE (Japan Astrometry Satellite Mission for INfrared Exploration) is a Japanese satellite designed to conduct astrometry*1 of the Galactic center and search for exoplanets through precision photometry. It is scheduled for launch in 2031 (Fig. 1). A defining feature of JASMINE is its role as the world’s first astrometric and photometric satellite using infrared observations. Infrared capabilities enable precise measurements of the positions and motions of stars in the Galactic center’s nuclear region, which is obscured by dust and challenging to observe in visible light. Investigating the poorly understood structure of the Milky Way's core holds the key to uncovering how our Galaxy formed and evolved.
Additionally, during summer and winter, when observing the Galactic center becomes difficult, JASMINE utilize the transit method*2 to search for exoplanets within their habitable zones around M-type stars, which are less massive than the Sun. M-type stars are brighter in infrared than in visible light, making them ideal targets for JASMINE's infrared observations. Moreover, small planets are more likely to form around M-type stars, and their smaller stellar radii make it easier to detect brightness variations caused by planetary transits. Therefore, JASMINE's precise photometric observations are expected to discover Earth-sized planets.

To achieve JASMINE’s scientific objectives, it is necessary to determine stellar positions with an accuracy of 0.000040 arcseconds (1/90 millionth of a degree) and detect brightness variations caused by transiting planets with a precision of 0.3% (Fig. 2). These goals depend not only by developing temporally stable observational instruments but also by appropriately analyzing the obtained data. My previous research has primarily focused on analyzing data from M-type stars and brown dwarfs observed with ground-based high-dispersion spectrographs. These studies aim to discover Earth-mass planets around M-type stars using the radial velocity method*3 and characterize the atmospheres of brown dwarfs with properties similar to gas giant planets.
Challenges in such analyses include contamination by terrestrial atmospheric absorption lines and noise sensitivity due to the faintness of these objects. By leveraging machine learning and other techniques, I have worked to efficiently analyze high-precision data. Building on this experience, I am interested in applying data science techniques to JASMINE data. As a project researcher, I am developing analytical methods to achieve JASMINE’s precision goals.
The advancement of the JASMINE project involves a broad range of elements, including data analysis, detector testing, and the development of telescope and satellite systems. Being part of JAXA’s Institute of Space and Astronautical Science provides a valuable opportunity to closely observe how each component contributes to the project and how it progresses through collaboration with domestic and international organizations.

Fig.2
Fig. 2 (Left) Simulated image of JASMINE observation (Right) Brightness variations of a star obtained through photometric analysis of simulated images. This process detects a phenomenon where the star dims by a few percent as a planet transits in front of it, leading to the discovery of the planet.

Detector testing within the institute, for example, measures detector properties, which are then incorporated into simulation settings for accuracy validation under realistic observation conditions. Simulations also provide feedback on the calibration accuracy required for the detectors, enabling effective verification. In this environment, I aim to steadily develop analytical methods that will allow JASMINE to maximize its scientific achievements in preparation for its launch.
These data science methods are not limited to JASMINE; they can also be applied to data analysis from other space telescopes and large ground-based telescopes, potentially benefiting future space science missions. I hope to use the experience and skills gained through this project to contribute to upcoming space science endeavors.

Terminologies

  • *1 Astrometry : A foundational field of observational astronomy that involves measuring the positions of stars on the celestial sphere to determine their distances and motions.
  • *2 Transit Method : An indirect method for detecting planets by measuring the slight dimming of a star's brightness when a planet crosses the line of sight between the star and the observer.
  • *3 Radial Velocity Method : An indirect method for detecting planets by measuring the Doppler shifts in spectral lines caused by the wobble of a star induced by an orbiting planet.

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