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To help Pádraìg on his way here are a few extracts from the Astronomy section at Brian's Timelines

Astronomical Units of Distance

  • The Lunar Distance: 384,401 km (240,000 miles).
  • The Astronomical Unit: 149,597,871 kilometers (92,955,807 miles).
  • The Light Year: There are several methods for calculating the length of a light year but the conventionally adopted value is the distance travelled by light in a Julian year of 365.25 days. In terms of other units, this makes the light-year equivalent to 63,241 astronomical units, 9,461 billion kilometers (5,877 billion miles).
  • The Parsec: (The word is constructed from Parallax + second) A unit of astronomical length. It is the distance at which the mean radius the of Earth's orbit (one astronomical unit) would subtend an angle of one second of arc and equal to 3.258 light-years, 3.086 × 10¹³ kilometers (1.918 × 10¹³ miles).
  • Rounding these figures gives us the following approximations:
    1 Parsec 3 Light Years 204 thousand Astronomical Units 31 trillion kilometers.
Supernova 1987A
168,000 BC
Supernova 1987A in the Large Magellanic Cloud explodes,
seen on Earth on February 23, 1987.
(Composite of RGB + UV)

2800 BC
The construction of Stonehenge is started. The building of Stonehenge took place over many centuries and was completed around 1000 BC. Alignments of the stones at Stonehenge mark the rising and setting points of the Sun at the solstices.

En Hedu'anna 2354 BC
The astronomer, En Hedu'anna, lived in Babylon. Hers is the first female name recorded in astronomical history. She was the daughter of Sargon of Akkad, who founded the Sargonian Dynasty in Babylon some 4000 or so years ago. He appointed her the chief astronomer priestess of the moon.

Visby Lenses
800-1000 AD
Visby lenses possibly used to make a telescope. Visby lenses are lens-shaped manufactured artifacts made of quartz. They were found in a viking grave in Gotland dating from approximately the 10th century. The lenses may have been imported from the Middle-East via Viking trading routes, but there is also evidence of local manufacture of lenses.

Crab Nebula
Chinese record a supernova that was visible in the daytime, they call it the "guest star". The matter blasted outward by the supernova, in the constellation Taurus is nowadays observable as the Crab Nebula.

Gregorian Telescope 1724
Astronomer James Gregory (1638-1675), Professor of Mathematics, University of St Andrews, described his design for a telescope in his 1663 publication "The Advance of Optics" and John Hadley constructs the first working telescope to this design.



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