The Goldilocks Zone of Habitable Planets

TITLE OF FORUM DISCUSSION: THE CIRCUM-STELLAR HABITABLE ZONE:

by

lim ju boo

Student in Astronomy

University of Oxford


CEd Cert (Evolution / Mystery of  Life) May, 2019
University of Cambridge 

The Goldilocks Zone is a zone from a star where water could exist on the surface of an Earth-like planet outside our Solar System, and where the existence of life maybe possible?

Calculations on the Goldilocks Zone:

Given the relative sizes of the Habitable Zones around stars which are relatively 0.25, 0.5, 5 and 10 times the luminosity of the Sun

Applying the equations for the given luminosity of the Sun

R _i = √ (L _star / 1.1)

R ₀ = √ (L _star / 0.53)

R _i = the inner boundary of the habitable zone in astronomical units (AU)

R _o = the outer boundary of the habitable zone in astronomical units (AU)

L star is the absolute luminosity of the star

1.1 is a constant value representing stellar flux at the inner radius (Kasting et al., 1993), (Whitmire et al., 1996)

0.53 is a constant value representing stellar flux at the outer radius (Kasting et al., 1993), (Whitmire et al., 1996)


Examples of Habitable Radius around a star:

0.25 x the luminosity of the Sun, it would 0.47 AU (inner radius), and 0.68 AU (outer radius)

0.5 x the luminosity of the Sun, it would 0.67 AU (inner radius), and 0.97 AU (outer radius)

5.0 x the luminosity of the Sun, it would be 2.13 AU (inner radius) and 0.3.0 AU (outer radius)

10 x the luminosity of the Sun, it would be 3.0 AU (inner radius) and 4.34 AU (outer radius)

AU = Astronomical Unit is Earth-Sun distance

 = 1.495 978 707×1011 metres, or about 150 million kilometres (93 million miles).

However in my personal thinking this may just be a theoretical mathematical-physical concept, because for life to be possible in another planet it is not just the physical Earth-like environment like heat, light and water that are just right, but I think we also need to consider the presence of complex organic compounds in their correct constituents and configurations to start jump life.

Not just the presence of carbon, nitrogen, hydrogen and oxygen to form amino-acids and other organic compounds as in Miller and Harold Urey experiment, but much more complex than that, which is the ability for organic molecules to form DNA which is still not life, but merely the chemical foot-prints of life.

What I strongly believe than just the synthesis of nucleic acids and DNA, is the presence of “the spark of life” (whatever that is residing inside a living body) to “ignite” these chemical substances into life itself in order for any exoplanet or even planets in our own Solar System (other than our own Earth) to give rise to life itself, and continue to support it as on Earth.

Although I don’t mean to show disrespect to these mathematical formulas given by researchers and astronomers, I am only expressing the freedom of my own (scientific) thinking that the Goldilocks Zone is only a zone that may mimic Earth-like physical environments on an (exo)planet such as the presence of water if it is not too near or too far away from a parent star, but does not mean there are life there on these extra-solar planets

I hope I will not be penalized as a student for my independent thinking

Thank you.

References: 

1. Kasting, James; Whitmire, Daniel; and Reynolds, Ray (1993). Habitable zones around main sequence stars. Icarus 101: 108 - 128

2. Kasting, James F. (1996). Habitable zones around stars: An update. In: Doyle, Laurence (ed.). Circumstellar Habitable Zones, 117 - 142. Travis House Publications, Menio Park