Calculate a star's evolution

Compute a star's rotation and activity evolution tracks, then plot a quantity, query values at specific ages, and save the result for reuse.

Prerequisites

Make sure the package and stellar evolution data are installed:

pip install fwl-mors
mors download all

Units

Throughout MORS, Age is in Myr, Prot is in days, and Omega is in units of the current solar rotation rate (\(\Omega_\odot = 2.67 \times 10^{-6}\) rad s\(^{-1}\)).

Step 1: Create a `Star`

Pick one of the following ways to specify the initial rotation:

A) Set initial rotation rate \(\Omega\) (at ~1 Myr)

import mors
star = mors.Star(Mstar=1.0, Omega=10.0)

B) Set initial rotation period in days

import mors
star = mors.Star(Mstar=1.0, Prot=2.7)

C) Set rotation percentile in the 1 Myr distribution

import mors
star = mors.Star(Mstar=1.0, percentile=50.0)  # median rotator
# string shortcuts are also accepted:
star = mors.Star(Mstar=1.0, percentile='slow')    # 5th percentile
star = mors.Star(Mstar=1.0, percentile='medium')  # 50th percentile
star = mors.Star(Mstar=1.0, percentile='fast')    # 95th percentile

D) Fit a track through a known rotation at a known age

import mors
star = mors.Star(Mstar=1.0, Age=100.0, Omega=50.0)

Warning

Option D will raise an exception if the requested rotation rate is outside the range achievable for that mass and age (below the slowest or above the fastest possible track). See Troubleshooting for the specific error messages.

Step 2: Inspect available quantities and units

star.PrintAvailableTracks()  # requires logging to be configured
print(star.Units['Lx'])      # prints the units string for Lx

To configure logging first:

from mors.logs import setup_logger
setup_logger("INFO")
star.PrintAvailableTracks()

Step 3: Plot an evolutionary track

Tracks are stored in star.Tracks and also exposed as star.<Quantity>Track arrays:

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.plot(star.AgeTrack, star.LxTrack)
ax.set_xlabel(f"Age [{star.Units['Age']}]")
ax.set_ylabel(f"Lx [{star.Units['Lx']}]")
ax.set_xscale('log')
ax.set_yscale('log')
plt.show()

Step 4: Query a value at a specific age

# Using the generic Value method
lx = star.Value(Age=150.0, Quantity='Lx')

# Using the quantity accessor (preferred)
lx = star.Lx(Age=150.0)

Both return a linearly interpolated scalar at the requested age. The age must be within the range of the evolutionary track.

Step 5: Save and reload

import mors

star.Save(filename="star.pickle")

# Always use mors.Load rather than pickle.load directly,
# as it re-attaches the quantity accessor functions
star2 = mors.Load("star.pickle")
print(star2.Lx(Age=4500.0))

Common pitfalls

Age is always in Myr, not years or Gyr.
Omega is in units of \(\Omega_\odot\), not rad s\(^{-1}\).
Do not use pickle.load directly to reload a saved star — use mors.Load instead.
PrintAvailableTracks uses the logging system and produces no output unless logging is configured.