Transit of Venus, Sun-Earth Day 2012

National Aeronautics and Space Administration

Goddard Space Flight Center

Transit of Venus, Sun-Earth Day 2012

Eclipse Facts

  1. The longest duration for a total solar eclipse is 7.5 minutes.
  2. Eclipse shadows travel at 1,100 miles per hour at the equator and up to 5,000 miles per hour near the poles.
  3. The maximum number of solar eclipses (partial, annular, or total) is 5 per year.
  4. A total eclipse can only happen during a new moon.
  5. Nearly identical eclipses (total, annual, or partial) occur after 18 years and 11 days, or every 6,585.32 days (Saros Cycle).
  6. A total solar eclipse is not noticable until the Sun is more than 90 percent covered by the Moon. At 99 percent coverage, daytime lighting resembles local twilight.
  7. The width of the Moon's shadow is at most 170 miles wide.
  8. There are at least 2 solar eclipses per year somewhere on the Earth.
  9. Total solar eclipses happen about once every year or two.
  10. From the Earth's surface, the Sun's corona ("crown") can ONLY be seen during a total eclipse.
  11. The alignment of Sun, Venus, and Earth comes in pairs that are eight years apart but separated by over a century. For example, the last pair happened in December 1874 and December 1882. The next pair would be in June 2004 and June 2012. After 2012, subsequent pairs will be in December 2117 and December 2125.
  12. There will be 36 solar eclipses from 2001-2025, of which 15 will be total eclipses on some part of Earth's surface – a little less than the average of one a year.
  13. Transits and eclipses are rare celestial events. Transits of Venus allow astronomers to calculate more accurately the distance of Venus from the Sun, and subsequently the distances of other planets. One can see the corona or atmosphere of the Sun safely with naked eyes only during a total solar eclipse.
  14. Gemini 12 witnessed a total solar eclipse in 1966 and the International Space Station, in 2006. The Hubble Space Telescope will be aimed at the moon to detect dips in brightness during the 2012 transit of Venus. The Solar Dynamic Observatory will capture the Sun during the 2012 transit in unprecedented detail.
  15. A transit of Venus occurs when Venus passes directly between the Sun and the Earth. A solar eclipse occurs when the moon passes between the Sun and the Earth, and the moon fully or partially blocks the Sun as viewed from a location on Earth.

Space Weather Facts

  1. Solar flares can sometimes heat the solar surface to temperatures of 80 million F - far hotter that the sun's core!
  2. The fastest coronal mass ejection was recorded on August 4, 1972 and traveled from the sun to earth in 14.6 hours - a speed of nearly 10 million kilometers per hour!
  3. On April 8, 1947, the largest sunspot in modern history reached its maximum size of over 330 times Earth's area.
  4. The most powerful solar flare in the last 500 years occurred on September 2, 1859 and was sighted by two astronomers who happened to be looking at the sun at exactly the right time!
  5. Between May 10-12, 1999, the solar wind nearly vanished, causing Earth's magnetosphere to expand in volume by over 100 times!
  6. A typical CME can be millions of kilometers in size, but have the mass of only a small mountain!
  7. Some sunspots are cool enough that water vapor can form at a temperature of 1,550 C.
  8. The most powerful aurora can generate over 1 trillion watts of power.
  9. The March 13, 1989 Quebec blackout, the result of a major geomagnetic storm, caused a $6 billion loss to the Canadian economy.
  10. During intense solar flares, astronauts see bright flashing streaks of light as a result of high-energy particles zipping through their eyeballs.
  11. The largest, single, challenge for astronauts traveling to Mars will be to overcome exposure to solar storms and radiation.
  12. Space Weather Forecasting costs only $5 million a year, but supports over $500 billion in annual revenue from the satellite and electrical power industries.
  13. Over $2 billion in satellite technology was damaged or destroyed during the last sunspot cycle.
  14. A major solar 'superstorm' such as the one in 1859 could cost $30 billion a day to the US electrical power grid, and up to $70 billion to the satellite industry.
  15. The August 4, 1972 solar flare was so powerful that, by some estimates, a spacesuited astronaut would have received a lethal does of radiation.
  16. Earth's climate was seriously chilled during the Maunder Minimum (1645-1715) when no 11-year sunspot cycles were detected.
  17. During a single second, the sun converts 4 million tons of matter into pure energy.
  18. The core of the sun is nearly as dense as lead, and has a temperature of 15 million C.
  19. During a severe solar storm, Earth loses about 100 tons of its atmosphere into space.
  20. Toy 'rare-earth' magnets can be 5 times stronger than a sunspot magnetic field.

Magnetism Facts

  1. All magnetic fields are produced by moving or spinning charged particles...somewhere
  2. Lines of magnetic force do not actually exist.
  3. Magnetic poles always come in pairs.
  4. The strongest magnetic field in nature is from the magnetar star SGR 1806-20, which has been estimated as 800 trillion Gauss.
  5. A typical galaxy like the Milky Way has a magnetic field strength of about 0.000003 Gauss.
  6. A refrigerator magnet has a strength of 100 Gauss.
  7. A sunspot can have a magnetic field with a strength up to 10,000 Gauss, but they live very short lives!
  8. Most magnetic storms on Earth happen during the Equinoxes in March and September
  9. The sun's magnetic poles flip their location on the sun every 22 years, called the Hale Magnetic Cycle.
  10. Earth's magnetic poles reverse their geographic locations every 300,000 years. The last event happened 780,000 years ago.
  11. Magnetic pole 'reversals' have no effect on the rotational poles of a star or planet.
  12. The geographic location of Earth's North Magnetic Pole is currently moving nearly due-North at a speed of 100 meters per day.
  13. Earth's magnetic field is declining in strength by 5% every century.
  14. Depending on your rate and direction of motion, a pure magnetic field can be turned into an electric field and vice versa.
  15. Magnetic fields and electric fields are aspects of a more basic field in nature called the electromagnetic field.
  16. A toy magnet produces more force on a paperclip than the entire mass of Earth through its gravity.