Stars And The Universe Continued
Aperçu
Our Sun is one star among hundreds of billions in the Milky Way, which is itself one galaxy among billions in the Universe. The light from those distant galaxies carries a startling message: stretched towards the red, it tells us the whole Universe is expanding.
In this lesson you will learn the scale of the Milky Way and the Universe, what redshift is and why it is evidence for an expanding Universe and the Big Bang, and how cosmic microwave background radiation supports the same theory. You will use the Hubble constant to estimate the age of the Universe.
Objectifs
- [Core] Know that the force that keeps an object in orbit around the Sun is due to the gravitational attraction of the Sun
- [Core] Know that the Sun is a star of medium size, consisting mostly of hydrogen and helium, and that it radiates most of its energy in the infrared, visible and ultraviolet regions of the electromagnetic spectrum
- [Core] Know that stable stars are formed as protostars from interstellar clouds of gas and dust due to gravitational attraction
- [Core] Know that the next stages of the life cycle of a star depend on its mass: (a) a small mass star (about the same mass as the Sun): red giant → white dwarf + planetary nebula (b) a large mass star: red supergiant → supernova → neutron star (c) a very large mass star: red supergiant → supernova → black hole
- [Core] Know that: (a) galaxies are each made up of many billions of stars (b) the Sun is a star in the galaxy known as the Milky Way (c) other stars that make up the Milky Way are much further away from the Earth than the Sun is from the Earth
- [Core] Know that the Milky Way is one of many billions of galaxies making up the Universe and that the diameter of the Milky Way is approximately 100 000 light-years
- [Supplement] Know that the strength of the Sun’s gravitational field decreases and that the orbital speeds of the planets decrease as the distance from the Sun increases
- [Supplement] Know that stars are powered by nuclear reactions that release energy and that in stable stars the nuclear reactions involve the fusion of hydrogen into helium
- [Supplement] Know that the nebula from a supernova may form new stars with orbiting planets
- [Supplement] Know that the Big Bang Theory is supported by many astronomical observations and states that: (a) the Universe expanded from a single point of high density and temperature (b) the Universe is still expanding (c) the Universe is approximately 13.8 billion years old
Note de cours
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Évaluation de la leçon
Félicitations, vous avez terminé la leçon sur Stars And The Universe Continued. Maintenant que vous avez exploré le concepts et idées clés, il est temps de mettre vos connaissances à lépreuve. Cette section propose une variété de pratiques des questions conçues pour renforcer votre compréhension et vous aider à évaluer votre compréhension de la matière.
Vous rencontrerez un mélange de types de questions, y compris des questions à choix multiple, des questions à réponse courte et des questions de rédaction. Chaque question est soigneusement conçue pour évaluer différents aspects de vos connaissances et de vos compétences en pensée critique.
Utilisez cette section d'évaluation comme une occasion de renforcer votre compréhension du sujet et d'identifier les domaines où vous pourriez avoir besoin d'étudier davantage. Ne soyez pas découragé par les défis que vous rencontrez ; considérez-les plutôt comme des opportunités de croissance et d'amélioration.
- The diameter of the Milky Way is approximately: A. 100 light-years B. 100 000 light-years C. 1 light-year D. 100 million km Answer: B
- Redshift in the light from a distant galaxy means its observed wavelength is: A. shorter B. longer C. unchanged D. zero Answer: B
- Redshift of distant galaxies is evidence that the Universe is: A. contracting B. expanding C. static D. rotating Answer: B
- Cosmic microwave background radiation is observed: A. only from one direction B. from all directions in space C. only from the Sun D. only from the Milky Way Answer: B
- The Hubble constant H0 is defined as: A. v x d B. v / d C. d / v D. d x t Answer: B
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