Embedded Files
The Bhaskaracharya Observatory for the Search of Exoplanets (BOSE) mission, named in the memory of the great 7th-century Indian astronomer, Shri Bhaskaracharya, will be the first of its kind discovery-legacy space mission from India, proposed by the Physical Research Laboratory, led by Prof. Abhijit Chakraborty (PI), with the primary aim of detecting Earth-size planets and possibly Earth-twins using the method of transit photometry. It is proposed to fly before 2035.
Artistic impression of the BOSE telescope flight model
Since the breakthrough discovery of the first exoplanet by Michel Mayor and Didier Queloz in 1995, almost 6000 exoplanets have been discovered to date. Even then, we have not found an Earth-twin capable of sustaining life as we know of. An Earth-twin here is referred to as a planet of size 0.9–1.25 R⊕ orbiting around a Sun-like star (early G type) at a distance of 0.9–1.5 Astronomical Units (AU)(Goldilocks zone). It is extremely difficult to detect the signals of an Earth-twin in transit, as the planet would only transit once in a year with a transit depth of mere ~80 parts per million (ppm), as is the case with the Sun-Earth system.
This mission aims at finding Earth-twins using the transit method of exoplanet detection with an unprecedented photometric and spatial accuracy to date. BOSE will have two 500mm clear aperture refractive optical telescopes (working in 500–1000 nm wavelength range) on a single platform at the Sun-Earth L2 point for continuous staring at a particular field with an effective Field of View (FoV) of ~400 deg2 to detect transiting exoplanets. Each telescope will be equipped with a 2x2 mosaic array of 14K×14K sCMOS detectors, 8 such detectors in total, with minimal intrinsic noise. BOSE is expected to achieve an unprecedented photometric precision of ~30 ppm on an 11th magnitude star and ~40 ppm on a 12th magnitude star in 1 hour of effective exposure. This sensitivity is expected to yield the discovery of ~2000 Earth-size planets by surveying a total of ~800,000 stars in two fields. Each of the BOSE fields will be surveyed for a period of 3 years, amounting to a minimum mission lifetime of 6 years.
The spatial resolution of BOSE is expected to be 2.65 arcsec/pixel, which is better than any similar missions, such as the Kepler (or K2), TESS, and PLATO. This combination of fine spatial resolution, large FoV, and continuous staring for longer duration over a specific field makes BOSE unique from other space-based missions. These features make BOSE suitable to discover Earth-twins/Earth-size planets, along with targeting other sciences such as asteroseismology and time-domain sciences.
Though the Earth-twin is not discovered yet, we remain hopeful about the abundance of such exoplanets. The figure shown below highlights the current landscape of exoplanetary population and how the discovery space of BOSE is going to look into a regime where no exoplanets have been detected till date.
The Mass-Period distribution of known exoplanets along with the discovery space (indicated by the arrow in teal) of the BOSE mission
(Data Credits : NASA Exoplanet Archive).
In addition to its primary aim of detecting Earth-size planets, BOSE will focus on detecting multi-planetary systems and less-discovered long orbital period exoplanets as well. It will also target exploring a wider range of exoplanet sizes, masses, and orbits, leading to a more comprehensive understanding of planetary systems, their evolution and developing a catalogue of potential Earth-twin candidates which will be pivotal for dedicated future ground-based follow-ups and space-based planet hunting missions.
H-R diagram of proposed BOSE Field 1
H-R diagram of proposed BOSE Field 1
H-R diagram of proposed BOSE Field 2
H-R diagram of proposed BOSE Field 2
The BOSE mission currently projects a 6-year mission timeline for continuous staring at 2 fields (namely the BOSE Field 1 and Field 2) for a course of 3 years each, with both the fields located in the Galactic plane, thanks to its unprecedented spatial resolution, giving the chance of looking into a completely uncharted region of the Galaxy that may potentially host a completely distinct exoplanet population than what’s previously been known. The cumulative source count for the two fields is ~800,000 (GAIA Gmag 9-14), and the optimum fields are selected after a comprehensive procedure of optimisation and selection using the GAIA DR3 dataset. The distribution of sources in the two fields can be observed from the Hertzsprung-Russell (H-R) diagrams shown in the above figures, wherein the location of the Sun in the H-R diagram is shown by the yellow marker. It is worthwhile to highlight that a substantial fraction of both fields comprises main-sequence stars, in alignment with the projected science goals of the mission.
Cumulative (approximate) planetary yield estimates for the BOSE fields (obtained with a generic transit probability of 2% and the planetary classifications and their occurrence rates are considered as per Fressin et. al (2013) scheme).
The cumulative planetary yield estimates (considering only the main sequence stars) for the BOSE mission are highlighted in the table above where the strength of the BOSE mission is evident from the projected number of detectable Earths and Super-Earths.
Page updated
Google Sites
Report abuse