Authors: Andy Tzanidakis, James Davenport Date: 01.17.2022 For general questions or inquiries, please reach out to Andy ([email protected])

Intro & Motivation:

In this homework, you are asked to explore the beautiful M67 open cluster. Before starting with the solutions, let’s take a moment to realize how important open-clusters are, and why understanding stellar populations are so important.

Open clusters in many ways are perfect laboratories for us to test our understanding of stellar evolution and stellar populations. That’s because we can make two very powerful assumptions:

  1. All the stars are the same age (i.e were born all around the same time)
  2. We assume that the metallicity between each star does not differ by a lot (i.e metallicity remains roughly the same across the cluster since all the stars are born roughly in the same region)

This means that we can directly study and understand how well our current understanding of stellar theory applies to the empirical data observed!

Remember that when looking at your HR diagrams that we are looking at a snapshot in time and are able to probe a rich diversity of stellar theory. With that, let’s begin and understand a little about this fascinating cluster.

P.S For your final projects, it would be a pretty cool idea to possibly look at more stellar clusters observed with Gaia and explore the various stellar populations found!

TL;DR Solutions:

Let’s begin with importing our favorite modules in Python

import matplotlib.pyplot as plt
from astropy.io import ascii
import numpy as np
%matplotlib inline

I usually like to read my tabular data using astropy.io.ascii.read

# Read the Gaia EDR3 Gao et al. 2018 data (M67 cluster)
table = ascii.read("<https://jradavenport.github.io/astr421src/Gao2018_GaiaEDR3.csv>")

# Read the MIST stellar Isochrone table
mist = ascii.read("../data/MIS_iso.cmd", guess=True)

Let’s print the total number of stars in the Gao et al. 2018 cluster:

# How many stars are in the Gao et al. 2018 catalog?
print (f"There are {len(table)} stars in the M67 cluster!")

>>> There are 1502 stars in the M67 cluster!

Okay, cool! Before moving on, I will plot the the color-magnitude diagram (CMD):