24 Questions
What is the force that attracts two nuclei to fuse?
Strong nuclear force
What is the equation that describes the conversion of mass into energy?
E=mc^2
How many Jupiter masses is a low mass or average star equivalent to?
13 Jupiter masses
What is the process that occurs in the core of a star when hydrogen runs out?
The core begins to shrink and gets hotter
What are the two light elements that were primarily present in the clouds from which the first stars formed?
Hydrogen and helium
What is the process by which a gas cloud collapses under gravity?
Contraction
What is the stage of a star's life cycle when the outer layers are pushed away from the core?
Red giant phase
How long does the hydrogen fuel last in the core of a star like the sun?
9 billion years
What occurs during a supernova event?
Elements with an atomic number greater than 26 are fused
What is the mass limit of a white dwarf?
Less than 1.4 solar masses
What happens to the electrons in a white dwarf?
They push against each other to prevent collapse
What is the result of a star's remnant with a mass greater than 1.4 solar masses?
A neutron star is formed
What is the process that occurs during the formation of a neutron star?
Electrons fuse with protons to make neutrons
What is the approximate mass of a teaspoon of white dwarf material?
15 tons
What is the origin of heavy elements in the universe?
During a supernova event
What is the characteristic of the Crab Nebula?
A supernova remnant
What is the primary process by which chemical elements are formed?
Nucleosynthesis
Which of the following cosmological events is responsible for the formation of elements with an atomic number greater than 26?
Supernova Nucleosynthesis
During the first few minutes after the Big Bang, what were the primary particles formed?
Quarks and Leptons
What is the process by which hydrogen atoms combine to form molecules?
Clumping of Hydrogen Atoms
What is the primary factor that determines the classification of stars in the Harvard system?
Temperature
What is the approximate surface temperature of M stars in Kelvin?
3,500 K
What is the mnemonic device used to remember the order of star classification in the Harvard system?
Oh Be A Fine Girl Kiss Me
What is the primary location where nucleosynthesis occurs in stars?
Core
Study Notes
Nucleosynthesis
- Nucleosynthesis is a theory that explains the formation of chemical elements
- Three cosmological events where nucleosynthesis occurs:
- Big Bang
- Stars
- Supernova
Big Bang Nucleosynthesis
- Occurred in the first few minutes after the Big Bang
- Quarks and leptons were created
- Universe was very hot, then cooled down, allowing particles to form protons and neutrons
- Eventually formed elements, including:
- Helium formation
- Hydrogen formation: protons and electrons bound together to form hydrogen atoms
Stellar Nucleosynthesis
- Occurs in stars
- Elements up to iron are formed
- Stars are classified by temperature, not color
- Surface temperatures of stars range from 3.5k Kelvin (M stars) to 25k Kelvin (O stars)
Nuclear Fusion
- Positively charged nuclei repel each other, but high-energy collisions can overcome this repulsion
- Strong nuclear force: attraction of two nuclei to fuse, resulting in a lighter nucleus and energy release
- Energy release is used to counteract gravitational pull
Stellar Evolution
- Low mass or average stars:
- Equivalent to 13 Jupiter masses or approximately one solar mass
- Formed from gas clouds of hydrogen and helium
- Gravity causes contraction, triggering fusion
- Hydrogen fusion continues for around 9 billion years
- When hydrogen runs out, the core shrinks and gets hotter, causing the outer layers to expand and form a red giant
- Red giant phase:
- Produces heavier elements, such as carbon and oxygen
- Eventually leads to a supernova explosion
Supernova
- All heavy elements are synthesized during this event
- Elements with an atomic number greater than 26 (Iron) are formed
- Brighter than the galaxy that contains it
- Visible with the naked eye if it occurs in our galaxy
White Dwarfs
- Interior is like a big metallic solid
- Electrons push against each other to prevent collapse
- Mass is limited to less than 1.4 solar masses (Chandrasekhar limit)
- Gravity is not enough to collapse itself
- One teaspoon of a white dwarf would weigh around 15 tons
Neutron Stars
- Formed from remnants of massive stars
- Electrons fuse with protons to make neutrons, triggering a supernova
- Result is a gigantic atomic nucleus
This quiz covers the theory of nucleosynthesis, which explains the formation of chemical elements. It includes the three cosmological events where nucleosynthesis occurs: the Big Bang, Stars, and supernovae.
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