Lecture 1 Flashcards
(19 cards)
What is the visibility of stars on a clear, dark night?
A few thousand stars are visible to the naked eye
Many more stars are visible through binoculars and telescopes
From what do stars form?
Giant clouds of interstellar gas
What are star clusters?
Groups of stars that formed from the same interstellar cloud
Why are star clusters useful to astronomers?
They allow comparison of properties of stars with similar ages and distances
All stars in a cluster lie at about the same distance and formed at about the same time
What are the two main types of star clusters?
- Open clusters
- Globular clusters
What are the characteristics of open clusters?
Contain up to several thousand stars and are found in the disk of the galaxy
What are the characteristics of globular clusters?
Contain hundreds of thousands of stars, closely packed, found mainly in the halo of the galaxy
What are associations in astronomy?
Loose groupings of stars of spectral type O and B, not gravitationally bound
How can we measure the age of a star cluster?
By finding the main-sequence turnoff point on an H-R diagram
What is the age of globular clusters compared to open clusters?
Globular clusters can be as old as about 13 billion years, while open clusters are much younger
What is required to plot an H-R diagram?
Knowledge of absolute luminosity and distance to the star
What is the relationship between apparent magnitude and distance in star clusters?
In the same cluster, apparent magnitude is a measure of absolute magnitude
What is the main sequence fitting method?
A technique to plot H-R diagrams using relative brightness instead of absolute luminosity
What is the mass-luminosity relation?
L is approximately proportional to the cube of the mass, L = M^3 (more exactly L = M^3.5)
Where are the most massive stars located on the H-R diagram?
At the top left of the H-R diagram
What is the outcome of studying associations and clusters of stars?
Associations are newly formed stars, open clusters are gravitationally bound, and globular clusters are much older
What generation of stars do globular clusters belong to?
Population II
Fill in the blank: Stars shine brilliantly by _______.
nuclear fusion
True or False: All stars in a cluster have different ages.
False
