Universe & Stars Flashcards
How do we calculate things that are far away from us?
Parallax, Star Brightness, Cephids
What is a Parallax?
In reality stars are really far away so the parallax angles will be really small so instead we use arc seconds as the angle units.
1 arc second = 1/3600 of a degree
A parsec is the distance of our sun and an object with a parallax angle of 1 arc second.
This method is only useful for stars within 400 light years of us.
What is Star Brightness?
For the thousands of stars that are within 400 light years there appears to be a correlation between brightness and the colour of a star. For stars >400 light years away we can measure the colour.
We can infer the brightness of a star at its origin. We then compare with the brightness we receive on Earth. By seeing how much brightness is lost we can guess how far the star is away from us.
What are Cephids?
Cepheids are stars that change their apparent brightness.
Henrietta Swan Leavitt measured the periodicities by measuring the ‘ups’ and ‘downs’ of Cepheids.
Leavitt discovered that brighter stars had longer periodicities. By knowing their brightness we can guess their distance by using
method 2.
What is a telescope?
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light).
How has technology improved understanding of the universe?
Improvements in observational technology have enabled more detailed information to be obtained regarding the large-scale structure of the universe.
How are stars distributed?
Stars are clustered together in galaxies and these galaxies are clustered into groups.
How are galaxies distributed?
A galactic cluster is a cluster of roughly a few hundred young stars in a loose distribution. This is also called an open cluster.
A galactic supercluster is a large group of smaller galaxy groups and clusters, and are among the largest structures of the cosmos.
What determines the shape of galaxies?
1) Gravity
2) Angular momentum
3) Collisions
What is the HR diagram?
Scientists like classifying stars based on their colour, brightness of light and their sizes. They have made a picture called the Hertzsprung Russel (HR) diagram which mirrors the life cycle of stars.
Where are heavy elements made?
Heavy elements are made in the intense explosion seen in supernovas.
What is nucleosynthesis?
Formation of elements by fusion.
What was the evidence to show the earth is not flat?
Position change of stars at différent latitudes
What is the geometric model?
Sun and planets orbit the earth
How did Ptolemy explain retrograde movements of the planets?
Planets have epicycles
What did Copernicus propose?
Heliocentric model. Earth and planets orbit the sun.
How did Galileo confirm the Copernicus model?
Observing phases of venus
What is the paradigm shift that Copernicus caused?
Movement in the belief from geocentric to heliocentric model
What is Occam’s razor?
The principle of simplicity that states ‘when there are two competing theories, the simpler theory is preferred.’
How do computer based models work?
Computer-based models are used to make testable predictions, which can be especially useful when experimentation is not possible.
What is a paradigm shift?
Radical, abrupt and fundamental changes in scientific understanding.
Johannes Kepler
- Used Brahe’s Equipment to refine the Copernican heliocentric model
- Refined Copernicus’ model by showing planets move in elliptical orbits
- Produced laws that could accurately predict movements of the planets (Kepler’s laws of planetary motion)
Why are computers used?
Computer-based models are used to make testable predictions, which can be especially useful when experimentation is not possible.
What are asteroids?
Rocky debris ranging in size, mostly found in Jupiter belts between Mars and Jupiter
What are comets?
A mixture of ice (methane water and nitrogen) and dust/rock
What is the Kuiper belt?
Remnants of the solar system formation found on the outer region of the solar system. Objects on the Kuiper belt are either rock and/or icy and includes the dwarf planets Pluto, Haumea and Makemake.
What are meteorites?
Meteorites are objects that survive impact with the earth. They are typically asteroid fragments (rocky and metallic) but can contain water (e.g. from comets) and organic compounds.
