P2 - Life Cycle of Stars & Galileo and Copernicus Flashcards
What is the first stage of the life cycle of a star?
Stars initially form from clouds of dust and gas.
What is the second stage of the life cycle of a star?
The force of gravity makes the gas and dust spiral in together to form a protostar, Gravitational energy has been converted in heat energy so the temperature rises.
What is the third stage of the life cycle of a star?
When the temperature gets high, hydrogen nuclei undergo thermonuclear fusion to form helium nuclei and give out massive amounts of heat and light. A star is born, it immediately enters a long stable period where the heat created by the nuclear fusion provides an outward pressure to balance the force of gravity pulling everything inwards. In this stable period its called a main sequence star and it typically lasts several billion years.
What is the fourth stage of the life cycle of a star?
Eventually the hydrogen begins to run out and the star then swells into a red giant, it will appear red because the surface cools.
What is the fifth stage of the life cycle of a star?
A small to medium sized star like the sun then becomes unstable and ejects in outer layer of dust and gas as a planetary nebula.
What is the sixth step of the life cycle of a star?
The planetary nebula leaves behind a hot dense solid core, a white dwarf, this would eventually fade away.
What is the sixth step of the life cycle of a star ( big stars) ?
Big stars however form red super-giants, they start to glow brightly again as they undergo more fusion and and contract several times, forming heavier elements in various nuclear reactions eventually they explode in a supernova.
What is the seventh step of the life cycle of a star ( big stars ) ?
The exploding supernova throws the outer layers of dust and gas into space leaving a very dense core called a neutron star. If the star wars big enough it will become a black whole.
What did most ancient Greeks believe about the Earth?
Most ancient Greek astronomers believed that the sun, moon, planets and stars all orbited the Earth in perfect circles - This is known as the geocentric model or Ptolemaic model.
What happened to the Ptolemaic model?
The Ptolemaic model was the accepted model of the universe from the time of the ancient Greeks until the 1500s, it was only in the 1600s that it began to be replaced by the Copernican model?
What was the Copernican model?
The Copernican model states that the Earth and planets all orbit the sun, which is at the center of the Universe in perfect circles.
The idea had been around for 2000 years, but the model was first introduced in a book by Copernicus in 1543.
This book showed astronomical observations could be explained without having the Earth at the center of the Universe.
What is a heliocentric model?
A heliocentric model is a model with the sun at the center.
The Copernican Model uses this.
What evidence did Galileo find to support this theory?
Around 1610 Galileo was observing Jupiter using a telescope, when he saw some stars in a line near the planet, when he looked again he saw these stars never moved away form Jupiter and seemed to be carried along with the planet which suggested they weren’t stars but moons orbiting Jupiter, this showed not everything was in orbit around the Earth, also evidence that the Ptolemaic model was wrong.
What else did Galileo notice about Jupiter besides its moons?
In the Autumn of 1610, Galileo noticed that nevus has phases were the amount of the planet that’s lit by the Sun seems to change over time.
- If the Ptolemaic model was right then these changes would be very small because Venus would always be in front of the sun.
- But if the Copernican model was right, Venus move in front of and behind the Sun and so the changes in the amount of Venus was lit would be really big, Just like Galileo saw.
What happened to Galileo due to his accumulated evidence of the Copernican model being better?
Copernicus’ ideas weren’t very popular at the time because the current models had been around for a long time.
- The models was also condemned by the church, they claimed that the model went against the Bible, which said the Earth was at the center of the Universe
Gradually evidence for the Copernican model increased thanks to more technological advances.
