Question

part 2: exploring stars with different masses
observe the life cycle of each of the stars below. observe where they
begin on the hertzsprung - russell diagram and the stages they go
through during their life. fill in the chart and then answer the questions
below.

mass of star	number of stages	total lifespan	final state
4
10
30
40

1. where on the main sequence do the lower mass stars start?
2. where on the main sequence do higher mass stars start?
3. there are three possible outcomes for the final stage of a stars life

depending on the stars initial mass. name the 3 possible final stages.

★ deneb and betelgeuse are both 20x the mass of the sun. deneb has
100 times the radius of the sun and its temperature is about 8000k.
betelgeuse has 1,000 times the radius of the sun and its temperature
is about 3,500k. select a star with 20x the mass of the sun and run the
animation. use this to find what stage both deneb and betelgeuse
are in. hint: you may have to use your mouse to click on a spot on
the path of the star.

how much longer goes deneb have to live? betelgeuse? use your
mouse to point and click on a spot.

Explanation:

To answer these questions, we rely on stellar evolution concepts (part of Astronomy, a subfield of Natural Science - Physics or Astronomy).

1. Lower - mass stars start on the main sequence at the lower - right (cooler, less luminous) region. This is because lower - mass stars have lower core temperatures and pressures, so they fuse hydrogen at a slower rate, resulting in lower luminosity and cooler surface temperatures.
2. Higher - mass stars start on the main sequence at the upper - left (hotter, more luminous) region. Higher - mass stars have more massive cores, leading to higher core temperatures and pressures. This allows them to fuse hydrogen at a much faster rate, making them more luminous and hotter.
3. The three possible final stages of a star's life, depending on its initial mass, are:

• White Dwarf: For stars with initial mass less than about 8 times the mass of the Sun (after going through planetary nebula ejection).
• Neutron Star: For stars with initial mass between about 8 and 20 - 30 times the mass of the Sun (after a supernova explosion, the core collapses to form a neutron star).
• Black Hole: For stars with initial mass greater than about 20 - 30 times the mass of the Sun (after a supernova explosion, the core collapses further to form a black hole as the mass is too great for even neutron degeneracy pressure to support it).

For the Deneb and Betelgeuse part, since they are 20 times the mass of the Sun, they are in the red supergiant stage (Deneb and Betelgeuse are known red supergiants). To find how much longer they have to live, we know that high - mass stars like them (20 solar masses) have relatively short remaining lifespans. Typically, a 20 - solar - mass star in the red supergiant stage has only a few million years left (Deneb and Betelgeuse are estimated to have a few million years remaining, with Betelgeuse perhaps a bit less than 100,000 years in some estimates, but more accurately, a few million years for stars of this mass in the red supergiant phase). However, to get precise values, one would use the interactive animation (as hinted) to click on the star's path and read the remaining lifespan.

Answer:

1. Lower - mass stars start at the lower - right of the main sequence.
2. Higher - mass stars start at the upper - left of the main sequence.
3. The three possible final stages are White Dwarf, Neutron Star, Black Hole.

(For Deneb and Betelgeuse: They are in the red supergiant stage. The remaining lifespan of Deneb and Betelgeuse is a few million years (precise value from animation), with Betelgeuse often estimated to have less than 100,000 years in some popular accounts, but more accurately, a few million years for 20 - solar - mass red supergiants.)