Download Shashanka R. Gurumath1, Hiremath KM2, and

Shashanka R.
1
Gurumath ,
Hiremath K.
2
M. ,
and Ramasubramanian
1
V.
1. School of Advanced Sciences, VIT University, Vellore – 632014
2. Indian Institute of Astrophysics, Bengaluru-560034
Email: [email protected]
Abstract
Humans' quest is to understand how the universe is originated and has been evolved; how the stars, planets and finally life is
emerged on the Earth? Solar system still not revealed most of its mysteries despite of many theories were proposed on its formation
and evolution. In addition, humans’ are exploring the distant universe with powerful telescopes and sophisticated instruments in
search of Earth’s twin. The detection of first exoplanet (Mayor and Queloz 1995) provides a hope for searching Earth’s twin outside
the Solar system. Till date around 2900 exoplanets are discovered with different physical and orbital characteristics (Winn and
Fabrycky 2015). Question arises as to, why the nearby planets around other stars are massive when compared to the terrestrial
planets of Solar system? Where we should look in the distance universe in order to find the Earth’s twin? In order to unfold these
mysteries, exoplanetary data of Sun-like G stars is analyzed. With reasonable constraints on the orbital characteristics of exoplanets
and by making correction for the stellar mass loss, a non-linear relationship between exoplanetary masses and stellar masses is
obtained that suggests, massive stars harbor massive planets. With this empirical mass relationship, typical stellar mass that can
harbor an Earth mass planet is estimated to be ~ 0.2 times the Sun's mass. According to astronomical standard, this estimated mass
of a star belongs to spectral type of M stars. It is to be noted that, nearly 70% of stars in our galaxy are belongs to M stars. Hence,
this study suggests that, M stars are more likely to harbor an Earth’s twin.
Introduction:
Sun is the only star which we can understand better compared to other.
Sun have four terrestrial planets and four Jovian planets.
The planets around other stars are known as Exoplanets
Exoplanets have different physical and orbital characteristics than the solar system planets
In solar system, all planets nearer to sun have negligible mass and solid surface, which is not a similar case in
exoplanets
• Hence we need to have a relation which relates Stars mass and respective planetary mass
• With the help of this relationship, we may get an idea about the stellar mass which harbor earth like planets.
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𝑡2
𝑀𝑖𝑛𝑖 = Mpre +
𝑡1
𝑑𝑀
𝑑𝑡
𝑑𝑡
Mini – initial mass of star
Mpre – present mass of star
t1 – initial time
t2 – present time (age of star)
Fig. 1. Illustrates the dependence of stellar
mass with its age. The exponential law fit is
indicated by the red continuous line with a
law.
Table 1. Represents the different rate of mass loss of host stars and
estimated initial mass of sun.
Fig. 2. Above figures illustrates the dependence of present mass of the
exoplanets with the initial mass of star. The blue triangular cross marks indicate
the absolute exoplanetary masses. The red and blue continuous line in left
figure indicates the power law fit of planetary mass versus stellar initial mass
with a power law of the form of equations obtained from C. de Jager and
Cranmer mass loss respectively. Similarly right figure indicates the power law fit
of planetary mass versus stellar initial mass with a power law obtained from
host star mass loss.
Table 2. Represent the relationship between the planetary mass versus initial
host star mass and estimated missing mass in the vicinity of sun.
Conclusions:
Acknowledgment:
• From the Figures 2, one can say that the massive
host stars harbor massive planets in their vicinity.
• From the relationships between host star mass and
planetary mass, host star mass for the earth like
planets is estimated ~0.2 Mʘ
• Chance of detection of earth like planets are more
around the M type stars.
• There is missing mass in the vicinity of Sun.
Reference:
First author is thankful to organizers of BINA
workshop for providing the local hospitality during
the period of conference.
Mayor M. and Queloz D. (1995), Nature, 378,
355
• Winn, J.N. and Fabrycky, D.C. (2015),
ARA&A, 53, 409
•