Astronomy 110 Final Exam
What happens to a low mass star after spending most of its life on the main sequence?
- ANS-It evolves to the red giant region of the H-R diagram.
Which two ways can a star generate energy? - ANS-Fusion reactions in the core of the
star and gravitational contraction.
How does a main sequence star become a red giant? - ANS-When H in the core is
exhausted, there is no more energy generation and gravity takes over, so the He core
and the surrounding H shell contract. This leads to H-fusion due to the heat created,
which releases energy at a higher rate than the core H-burning did, and the resulting
pressure lifts up the outer layers of the star so that the outer atmosphere balloons out to
a radius more than 100x larger, therefore decreasing the surface temperature.
What is the helium flash? - ANS-When a red giant is evolving, the point at which
He-fusion begins is called the "Helium Flash" because it is so rapid that it is actually
explosive.
What is required for He-fusion? - ANS-A higher core temperature
Stars in which phase occupy the Horizontal Branch on an H-R diagram? - ANS-Red
giants going into Helium Flash
How does a star evolve to a red supergiant? - ANS-When the 4He is used up, the star is
left with a C core, which will contract and get hotter, leading to He shell-fusion. The star
then expands again to become a Red Supergiant.
How can you measure the age of clusters? - ANS-If you know the Main Sequence
lifetimes of stars, you can estimate the age of the cluster by noting the masses of the
stars that are just evolving off the M-S.
What are planetary nebulas? - ANS-When a star is going through the triple-alpha
process, the burning rate becomes unstable and makes the stellar atmosphere expand
and contract (pulsate). With each pulsation, the outer part of the stellar atmosphere is
blown by radiation out into space, which results in a planetary nebula.
For high-mass stars, what provides energy generation? - ANS-CNO cycle
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller Hkane. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £6.52. You're not tied to anything after your purchase.
