Chapter 8: Space physics Flashcards
(36 cards)
How do stars produce their energy?
Nuclear fusion, in which 2 smaller nuclei join to make a larger one, releasing energy. Example: 11H + 21H = 32He
What is acceleration?
Acceleration is when either the magnitude or direction of an object change. For example, a car switching from moving at 30 mph to moving at 60 mph, or a car changing direction. The earth, as it orbits the sun, is constantly accelerating, since it is constantly changing direction, but that does not mean it is gaining speed
How long ago was the sun formed?
4.6 billion years ago
What is a protostar?
Sometimes, clouds made of cold hydrogen and dust collapse due to the force of gravity. This makes the atoms and molecules within the cloud move extremely fast, giving them large amounts of kinetic energy. When they crash into each other, their kinetic energy is turned into heat, increasing the internal energy of the gas, making the temperature rise to millions of degrees
How does fusion begin?
The temperate inside the cloud gets so high that the hydrogen nuclei begin to collide, forming helium and releasing energy. This starts a chain reaction
What holds a star together?
The outward force of fusion trying to expand a star balances the inward force of gravity trying to collapse a star
What is a main sequence star?
One that releases energy by fusing hydrogen to form helium. Our sun is a main sequence star.
What is a red giant?
A very large star that fuses helium into heavier elements
What are the life paths a low-mass star (such as our sun) can take?
Protostar, Small star, Red giant, white dwarf, black dwarf
What are the life paths a high-mass star can take?
Protostar, Large star, Red supergiant, Supernova, and then either a neutron star or a black hole
What happens when a star collapses?
When a star begins to run out of hydrogen, it begins to collapse inwards because the force of gravity is no longer balanced out by the force of fusion, heating up the core, making it produce even heavier elements than helium. This makes the star expand into a red giant, where it continues to fuse helium
What is velocity?
A vector quantity taking into account both direction and speed
How do we know that our earth was once part of another star?
It has elements heavier than iron on it
What happens when a small star collapses (from red giant phase)?
When the star runs out of helium, it collapses into a white dwarf, eventually cooling down into a black dwarf, a cold, dark, dead star
What happens when a large star collapses (from red supergiant phase)?
When the star runs out of helium, it blows up in a runaway nuclear reaction known as a supernova (in which elements heavier than iron are fused). If the star’s mass is below a certain threshold, it becomes a neutron star. If not, it becomes a black hole
Describe a circular orbit
The direction of the object’s velocity is at a tangent to the orbit path. The object accelerates towards whatever it’s orbiting, but doesn’t get any closer to it. Gravity provides the force to accelerate the planet
What happens as the planet gets closer to the star it’s orbiting?
It speeds up, since gravity is what provides the force that keeps the object moving
What is redshift?
When EM waves coming from a far away object are stretched due to the Doppler effect. We can tell that redshift has occurred because the lines on an emission spectrum are shifted to one end. Redshift was discovered by Edwin Hubble in the 1920s
What does redshift tell us about the universe?
It tells us that the universe is expanding
What is the Big Bang Theory?
The theory that 13.8 billion years ago, the universe expanded outwards from a singularity and has been expanding ever since. Things further away from the solar system move away faster. The universe expanding is a lot like a balloon being blown up
What is CMBR?
CMBR (or cosmic microwave background radiation) is radiation that was released shortly after the creation of the universe
How does CMBR support the Big Bang Theory?
Because the Big Bang theory states that at the beginning, a large amount of EM waves were produced (whose wavelengths increased over time, making them microwaves right now). This is supported by the 1960s discovery of CMBR
When and why did the Big Bang Theory become widely accepted?
The Big Bang Theory became widely accepted in the 1960s after the discovery of CMBR by 2 scientists
Explain the models for the future of the universe?
Up until the 1990s, we believed that the universe would one day stop expanding and collapse again in a “Big Crunch”. With the discovery of dark energy (which is said to be suppressing gravity, we now believe that the rate at which the universe expands is increasing