Habitable Zone Lifetimes Calculator (Rushby et al. 2013)

Basic calculator output for Earth. The green lines show the location of the HZ at present, the solid red and solidblue lines show the location of the HZ at the beginning of the star’s lifetime, and the dashed red and blue lines show the locations of the inner and outer boundaries, respectively, at the end of the star’s main sequence lifetime. (The star is not to scale!).

L = luminosity
ZAMS = Zero age main sequence
TMS = Terminal main sequence
MSL = main sequence lifetime
e.g. 'Inner' = Inner boundary of habitable zone in AU (astronomical units)

Habitable Zone Lifetimes Calculator (Rushby et al. 2013)

This is a very simple calculator based on Rushby et al (2013), Kopparapu et al. (2013), and the earlier work of Kasting et al. (1993). It estimates the habitable zone (HZ) limits for a narrow range of stars (about 0.5 to 1.2 Solar masses), including how the boundaries (as defined by the 7 limits given in Kopparapu et al., 2013) change over time. The HZ model is coupled to a simple stellar evolution code to allow for the change in luminosity over time to be estimated (see Rushby et al., 2013). See below for some example output, for a link to the MATLAB code.

Sun:
1 M
0.71 L to 1.8 L (luminosity evolution at Earth)
10.9 Gyr main sequence lifetime
Approximately 4.5 Gyr old

Example Model Output:

Earth
Total Habitable Zone Lifetime: 4.61 Gyr
0.112 Gyr left in HZ

Mars
Total Habitable Zone Lifetime: 9.2 Gyr
In HZ for at least past 2.6 Gyr (or 4.54 Gyr?)
7.33 Gyr left in HZ
In Cold Zone for 1.8 Gyr from ZAMS? (*not supported by evidence from Mars surface)

Venus
Total Habitable Zone Lifetime: 4.04 Gyr
In Runaway Greenhouse Zone for past 0.45 Gyr.

Tau Ceti:
0.78 M
0.22 L to 0.64 L (luminosity evolution at Tau Ceti e
23.1 Gyr main sequence lifetime
Approximately 10 Gyr old

Tau Ceti e
Total Habitable Zone Lifetime: 20.28 Gyr
In HZ for 4.2 Gyr at present
16.1 Gyr left in HZ
In Cold Zone for 5.7 Gyr prior to HZ

Link to MATLAB code