Astronomy

Most of the iron on Earth came from:

supernova explosions

Older clusters have main sequence turn-off points at what color?

Redder colors (cooler stars)

What happens when a massive star’s core becomes iron?

The core collapses rapidly

Which of the following describes main sequence stars?

They are fusing hydrogen in their cores

Open clusters are:

Young and loosely bound group of stars

How do open clusters differ from globular clusters?

Open clusters are younger and contain fewer stars

The vertical axis of the H-R diagram typically represents:

Luminosity

A star’s position on the main sequence is primarily determined by its:

Mass

After a supernova, a core greater than 3 solar masses likely becomes:

A black hole

A nova is:

A sudden brightening of a white dwarf in a binary system

What happens in a close binary system when one star becomes a white dwarf?

Material can transfer to the white dwarf, leading to novae or supernovae

The primary energy source for stars on the main sequence is:

Hydrogen fusion into helium

What happens in the core of a low-mass star when hydrogen runs out?

The core contracts and heats up, beginning helium fusion

We determine the age of a cluster using:

Main sequence turn-off point

What is the likely fate of a star with a mass greater than 25 solar masses?

It collapses into a black hole

The key factor that determines a star's evolutionary path is its:

Mass

What allows a nova to repeat over time?

Ongoing mass transfer in a binary system

In a neutron star, collapse is prevented by:

Neutron degeneracy pressure

What are the axes of the Hertzsprung-Russell (H-R) diagram?

Luminosity and temperature

An accretion disk forms when:

Material spirals into a compact object like a white dwarf or black hole

What does the B-V color index represent?

The stars temperature and color

What marks the turn-off point on a cluster's HR diagram?

The point where stars leave the main sequence

Which observational quantity is directly plotted on the Y-axis of an HR diagram made from B and V data?

Apparent or absolute V magnitude

What causes a star to leave the main sequence and enter the giant phase?

It exhausts hydrogen in its core

What is the approximate age range of most globular clusters based on HR diagrams?

Over 12 billion years

Why is B-V color index useful in plotting an HR diagram?

It estimates temperature using observable photometric data

Where are main sequence stars found on the HR diagram?

Along a diagonal from upper-left to lower-right

What distinguishes a star cluster HR diagram from a general stellar population?

All stars are at the same distance and age

What does a star’s position on the main sequence primarily depend on?

It’s mass

What is the shape of the main sequence on a B-V vs. V magnitude diagram?

Downward slope from left to right

Why are most stars in a globular cluster located near the lower-right of the HR diagram?

They are cooler and less luminous main sequence stars

Why must we filter out stars with inconsistent radial velocities in HR diagram studies of clusters?

They are likely non-cluster members

A lower B-V value indicates a star is:

Hotter and bluer

What physical properties are plotted on a Hertzsprung-Russell (HR) diagram?

Temperature vs. luminosity

If a star has a high V magnitude but low B magnitude, its B-V index will be:

Negative, indicating a blue star

How does the turn-off point help astronomers determine the age of a star cluster?

It reveals the lifespan of stars that have just left the main sequence

Compared to open clusters, globular clusters are generally:

Older and more densely packed

What is typically found above the main sequence on an HR diagram of an old cluster?

Red giants and horizontal branch stars

Which type of stars evolve off the main sequence first in a cluster?

High-mass blue stars

What is the primary fuel used by stars on the main sequence?

Hydrogen