Transit of Venus, Sun-Earth Day 2012

National Aeronautics and Space Administration

Goddard Space Flight Center

Transit of Venus, Sun-Earth Day 2012

Observing Certificate Program Parallax Activity

Parallax Method 2 - Distance using Relative Orbit Speed
The four Contacts for a transit of Venus. From left to right we have Contacts 1, 2, 3 and 4.

The four Contacts for a transit of Venus. From left to right we have Contacts 1, 2, 3 and 4.

    Assumptions:
  • Diameter of the Sun - 0.5244 degrees
  • Diameter of Venus = 0.0163 degrees
  • Orbit speed of Earth = 29.8 km/s
  • Orbit speed of Venus = 35.0 km/s
  • Earth-Venus distance in Astronomical Units = 0.28

    • Enter your observations for the contact times of the transit below.
    Enter observed contact times:
  1. Enter 1st contact:
  2. Enter 2nd contact:
  3. Enter 3rd contact:
  4. Enter 4th contact:
    Duration between contacts:
  1. Contacts 2 & 1:
    1068 seconds
  2. Contacts 3 & 2:
    21854 seconds
  3. Contacts 3 & 1:
    22922 seconds
  4. Contacts 4 & 3:
    1068 seconds
  5. Contacts 4 & 2:
    22922 seconds
  6. Contacts 4 & 1:
    23990 seconds
    Speed of Venus:
  1. Contacts 2 & 1:
    0.06741 arcseconds/sec
  2. Contacts 3 & 2:
    0.06726 arcseconds/sec
  3. Contacts 3 & 1:
    0.06666 arcseconds/sec
  4. Contacts 4 & 3:
    0.06741 arcseconds/sec
  5. Contacts 4 & 2:
    0.06666 arcseconds/sec
  6. Contacts 4 & 1:
    0.06611 arcseconds/sec
    Individual Astronomical Unit Estimates:
  1. Contacts 2 & 1:
    149270000 km
  2. Contacts 3 & 2:
    149610000 km
  3. Contacts 3 & 1:
    150960000 km
  4. Contacts 4 & 3:
    149270000 km
  5. Contacts 4 & 2:
    150960000 km
  6. Contacts 4 & 1:
    152220000 km

Average Astronomical Unit:

150 million km

NASA Fact

Earth's magnetic poles reverse their geographic locations every 300,000 years. The last event happened 780,000 years ago.