Which of the following statements comparing open and globular star clusters is not true?
A) Open clusters are found only in the disk of the galaxy while globular clusters may be found both in the disk and the halo of the galaxy.
B) Stars in open clusters are relatively young while stars in globular clusters are very old.
C) Open and globular clusters each typically contain a few hundred stars.
D) For both open and globular clusters, we can assume that all the stars in a particular cluster are about the same age.
The correct answer and explanation is :
The correct answer is: C) Open and globular clusters each typically contain a few hundred stars.
Explanation:
Star clusters are groups of stars that are gravitationally bound and formed from the same molecular cloud. They come in two primary types: open clusters and globular clusters. While they share some similarities, they are very different in structure, age, and star population.
Open Clusters:
- Open clusters are loosely bound groups of stars, found primarily in the disk of the galaxy.
- They typically contain a few dozen to a few thousand stars.
- These stars are relatively young, often only a few million to a few billion years old.
- Because they are young, many of their stars are blue and hot.
- Over time, open clusters disperse as gravitational interactions with other stars and galactic forces tear them apart.
Globular Clusters:
- Globular clusters are tightly bound, spherical collections of stars.
- They are found primarily in the halo of the galaxy, but they can also be seen passing through the galactic disk.
- These clusters are very old, often around 10 to 13 billion years, making them among the oldest known objects in the universe.
- They typically contain hundreds of thousands to millions of stars, not just a few hundred.
- These stars are older, cooler, and more evolved, often red or yellow in color.
Evaluating the Choices:
- A is true: open clusters are found in the disk; globular clusters are in the halo and sometimes the disk.
- B is true: open clusters have young stars, globular clusters have old stars.
- D is also true: stars within any given cluster form from the same gas cloud and are approximately the same age.
- C is not true: open clusters may have a few hundred to a few thousand stars, but globular clusters contain far more—up to millions of stars.
Thus, statement C is false and is the correct answer to the question.