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#+title: M13 Globular Cluster
#+filetags: :celestial_objects:
#+STARTUP: latexpreview



Messier 13 is one of the best-known globular clusters in the night sky.


Messier number: 13
New General Catalogue (NGC) number: 6205
Constellation: Hercules
Distance from Earth: 25,100 ly
Discovered by: Edmond Halley in 1714


* Physical Characteristics

- M13 contains several hundred thousand stars.
- The stars are metal-poor and densely packed in the center.
- Stars have low-,etallicity, which means they wre likely formed in environments which fewer heavy metals.


* Notable Features

- M13 has a diameter of about 145 ly.
- M13 contains many blue-stragglers, which are stars that appear hotter and younger than all the other stars.
- Contains many variable stars, especially RR Lyrae variables, useful for determining distance and properties of globular clusters.
- There is onginog research into whether or not M13 contains a central medium-sized black hole.


* Observation and Viewing

- Viewed best in Summer and early Fall.
- Seen in the nothern hemisphere
- Spans 22 arcminutes of the sky. For comparison, the Moon only spans 30 arcseconds of sky.
- Diameter of 145 ly calculated using distance, angular size, and simplifying using the small-angle approximation.