1D1 Universe, Galaxies & Stars Flashcards
Learn the characteristics and lifecycle stages of stars, and the formation of galaxies.
What is the Universe?
All of space, matter, energy, time, and its contents, including planets, stars, galaxies, and all other forms of matter and energy.
The Universe is the totality of all that exists, the entire cosmos.
What is a Galaxy?
A huge collection of gas, dust, and billions of stars and their solar systems, all held together by gravity.
Galaxies can take various shapes, from spiral to elliptical or irregular.
What is the Solar System?
Consists of the Sun, and everything bound to it by gravity: planets, moons, asteroids, comets, and meteoroids.
The Solar System formed about 4.5 billion years ago from a dense interstellar cloud of gas and dust.
What type of matter makes up a large fraction of the Universe?
Dark matter (it makes up 26% of the universe).
Dark matter can be detected by its gravitational effects on visible matter in the Universe.
When did our solar system form?
About 4.5 billion years ago.
From a dense interstellar cloud of gas and dust.
How many galaxies are estimated to exist in the Universe?
It is estimated that there are between 200 billion and 2 trillion galaxies in the Universe.
What are the different shapes galaxies can take?
- Spiral
- Elliptical
- Irregular
What is larger, the Universe or the Solar System?
The Universe.
The Solar System is the smallest.
What tool allows scientists to observe distant galaxies?
Hubble Space Telescope
In which galaxy do we live?
Milky Way galaxy
Our sun is just one of at least 200 billion stars in the Milky Way galaxy.
What shape is the Milky Way galaxy?
A spiral galaxy.
Consists of the Solar System and billions of other stars and their solar systems.
What is the definition of a star in Astronomy?
An incandescent ball of gas (mostly hydrogen & helium) in space producing light and heat through nuclear fusion.
What process occurs in the core of a star to produce light and heat?
Nuclear fusion.
Nuclear fusion is a process where hydrogen atoms fuse to form helium, releasing energy as light and heat.
What is the name of the graph that organizes stars according to their brightness and temperature?
Hertzsprung-Russell diagram
What is the name of the group of stars held together by a gravitational force?
Galaxy
List the five main branches of astronomy.
- Astrophysics
- Observational Astronomy
- Theoretical Astronomy
- Planetary Science
- Cosmology
What percentage of helium do stars on average contain?
Approximately 25%.
What type of stars have the lowest temperatures?
Red dwarf stars.
What is the region of the Hertzsprung-Russell diagram where most stars are located?
Main sequence.
What are constellations?
Groups of stars forming recognizable patterns in the sky.
Where do stars form?
Stars form in molecular clouds, also known as stellar nurseries, where gas and dust collapse under gravity to initiate nuclear fusion.
The gases and dust inside these clouds start to accumulate by gravity collapsing into dense balls of gas that later will begin to shine forming new stars.
What are the three types of stellar remnants?
- White dwarfs
- Neutron stars
- Black holes
White dwarfs are remnants of low to medium-mass stars, neutron stars are incredibly dense remnants of massive stars after a supernova, and black holes are formed from the remnants of the most massive stars, where gravity is so strong that not even light can escape.
What is the most common kind of stars in the Universe?
Red dwarf stars
What is the closest star to Earth after the Sun?
Proxima Centauri
What is a supernova?
A powerful and luminous explosion of a star (which marks the death of the star).
