47 episodes

Part 14: 14. Stellar classification, distribution, evolution, and observation.

These short videos were created in August 2007 by Dr. Christopher D. Impey, Professor of Astronomy at the University of Arizona, for his students. They cover a broad range of terms, concepts, and princples in astronomy and astrobiology. Dr. Impey is a University Distinguished Professor and Deputy Head of the Astonomy Department. All videos are intended solely for educational purposes and are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. The full list of collections follows below:

01. Fundamentals of Science and Astronomy
02. Ancient Astronomy and Celestial Phenomena
03. Concepts and History of Astronomy and Physics
04. Chemistry and Physics
05. Quantum Theory and Radiation
06. Optics and Quantum Theory
07. Geology and Physics
08. Solar Neighborhood and Space Exploration
09. Outer Planets and Planetary Atmospheres
10. The Solar System
11. Interplanetary Bodies
12. Formation and Nature of Planetary Systems
13. Particle Physics and the Sun
14. Stars 1
15. Stars 2
16. Stars 3
17. Galactic Mass Distribtuion and Galaxy Structure
18. Galaxies
19. Galaxies 2
20. Galaxy Interaction and Motion
21. Deep Space and High-Energy Phenomena
22. The Big Bang, Inflation, and General Cosmology
23. The Big Bang, Inflation, and General Cosmology 2
24. Chemistry and Context for Life
25. Early Earth and Life Processes
26. Life on Earth
27. Life in the Universe
28. Interstellar Travel, SETI, and the Rarity of Life
29. Prospects of Nonhuman Intelligences

14. Stars 1 University of Arizona

    • Science

Part 14: 14. Stellar classification, distribution, evolution, and observation.

These short videos were created in August 2007 by Dr. Christopher D. Impey, Professor of Astronomy at the University of Arizona, for his students. They cover a broad range of terms, concepts, and princples in astronomy and astrobiology. Dr. Impey is a University Distinguished Professor and Deputy Head of the Astonomy Department. All videos are intended solely for educational purposes and are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. The full list of collections follows below:

01. Fundamentals of Science and Astronomy
02. Ancient Astronomy and Celestial Phenomena
03. Concepts and History of Astronomy and Physics
04. Chemistry and Physics
05. Quantum Theory and Radiation
06. Optics and Quantum Theory
07. Geology and Physics
08. Solar Neighborhood and Space Exploration
09. Outer Planets and Planetary Atmospheres
10. The Solar System
11. Interplanetary Bodies
12. Formation and Nature of Planetary Systems
13. Particle Physics and the Sun
14. Stars 1
15. Stars 2
16. Stars 3
17. Galactic Mass Distribtuion and Galaxy Structure
18. Galaxies
19. Galaxies 2
20. Galaxy Interaction and Motion
21. Deep Space and High-Energy Phenomena
22. The Big Bang, Inflation, and General Cosmology
23. The Big Bang, Inflation, and General Cosmology 2
24. Chemistry and Context for Life
25. Early Earth and Life Processes
26. Life on Earth
27. Life in the Universe
28. Interstellar Travel, SETI, and the Rarity of Life
29. Prospects of Nonhuman Intelligences

    • video
    Sun and Climate Change

    Sun and Climate Change

    Transcript: The Sun is the source of all the Earth’s energy, and life could not exist without the Sun. In addition, there’s growing evidence that long term variations in the Sun’s output profoundly affect the Earth’s climate. For example, in the period from 1645 to 1715 sunspots were at a generic minimum called the Maunder Minimum. And in Europe an ice age was experienced with cold temperatures, and this is confirmed by tree rings from the time. From 1540 to the present day there have been many droughts in Africa. Statistical analysis shows that they correlate very well with sunspot minima. Thus, on a period of the solar cycle there’s evidence that the Sun affects the Earth’s climate. In addition, there is less secure evidence that variation in the Sun’s output affects the Earth’s climate on a timescale of hundreds or thousands of years. Earth, for example, experiences mini ice ages every several thousand years. This evidence is less good because evidence of the Sun’s output is indirect over those timescales, as is evidence of the Earth’s temperature.

    • 1 min
    • video
    Solar Constant

    Solar Constant

    Transcript: The solar constant is the amount of Sun’s radiation that reaches the Earth. Assuming the atmosphere to be perfectly transparent, 1,370 joules reach every square meter of the Earth surface every second. Variations in the solar constant are subtle, only about 0.1 percent per year. However, they can be larger in percentage terms at regions beyond the visible spectrum in ultraviolet rays or x-rays. In particular, in the ultraviolet ozone in the upper atmosphere can affect the amount of radiation that reaches the Earth surface. Small changes in the energy budget from the Sun’s radiation can affect the weather and climate of the Earth in serious and systematic ways. Thirteen hundred and seventy watts is a lot of energy; the average family home intercepts 50 to 100 kilowatts. Even accounting for a relatively low efficiency of a solar cell, and only half to a third of the time of a twenty-four hour day when the Sun is out, solar energy is clearly an abundant energy source.

    • 1 min
    • video
    Cosmic Energy Sources

    Cosmic Energy Sources

    Transcript: Almost all of the world’s energy comes from non-renewable sources or fossil fuels. These energy sources took 300 million years to aggregate on the Earth, originating with solar energy and living organisms. We have significantly depleted them in only one hundred years. Modern energy usage is very inefficient; the United States wastes energy equivalent to $300 billion a year. The standard modes of energy use are also inefficient. An incandescent light is only five percent efficient, the internal combustion engine only ten percent efficient. However, clean and efficient energy sources do exist. They are cosmic fuels. The first is solar energy itself. Solar cell technology has now improved to the point where solar cells are about fifty percent efficient which is ten times more efficient than an incandescent light bulb. Fuel cells is the other possible technology. Fuel cells create energy from hydrogen, the ultimate cosmic fuel, the most abundant element in the universe and a clean energy source. Fuel cells are also approaching fifty percent in their efficiency.

    • 1 min
    • video
    Stars

    Stars

    Transcript: Nearly 2,000 years ago Ptolemy's Almagest, a compendium of astronomical information, contained catalogs of star names. Ancient knowledge was brought to Europe by Arab astronomers who gave names to many of the brightest stars in the sky. The Arab article is al and so we have Algol, Aldebaran, Altair, Alcor, and others. Other stars were named from myths and legends and are often given names associated with the constellation in which they reside. Thus, Alpha Centauri is the first star named in the Centaur constellation; Delta Scuti is the fourth star named in the shield constellation. Other catalogs exist too; T Tauri is the twentieth variable star in the constellation the bull. Astronomers name fainter stars by their coordinates and are given numbers rather than names, and despite what you may read in some parts of the popular press, it’s not possible to exclusively buy a star name. Star names are given by the International Astronomical Union.

    • 1 min
    • video
    Star Names

    Star Names

    Transcript: Nearly 2,000 years ago Ptolemy's Almagest, a compendium of astronomical information, contained catalogs of star names. Ancient knowledge was brought to Europe by Arab astronomers who gave names to many of the brightest stars in the sky. The Arab article is al and so we have Algol, Aldebaran, Altair, Alcor, and others. Other stars were named from myths and legends and are often given names associated with the constellation in which they reside. Thus, Alpha Centauri is the first star named in the Centaur constellation; Delta Scuti is the fourth star named in the shield constellation. Other catalogs exist too; T Tauri is the twentieth variable star in the constellation the bull. Astronomers name fainter stars by their coordinates and are given numbers rather than names, and despite what you may read in some parts of the popular press, it’s not possible to exclusively buy a star name. Star names are given by the International Astronomical Union.

    • 1 min
    • video
    Light Year

    Light Year

    Transcript: The vast distances to the nearest stars encourage astronomers to use a new unit of distance. Whereas meters and kilometers work well on the Earth, and the astronomical unit is the appropriate unit for scales within the solar system, the distance scale to the stars is given as a lightyear. A lightyear is the distance that light travels in one year. It’s equal to about 6-million-million miles or 1016 meters. It’s defined as the speed of light, three hundred thousand kilometers per second, times the number of seconds in a year. Notice two things. The lightyear is not a metric unit. Occasionally astronomers use none metric units when they are convenient for the scales they’re dealing with, and also a lightyear is a unit of distance, not a unit of time.

    • 56 sec

Top Podcasts In Science

Listeners Also Subscribed To

More by University of Arizona