Saturday, May 11, 2013

Greetings from Carpinteria/UCSB - Astronomy

I am in Carpinteria, CA; soon to be headed back home (vacation goes by soooooooo fast!)

Last night was a sight to see. Unfortunately I did not catch the young moon, but I did manage to see Jupiter, and the constellations Ursa Major, Leo, Gemini, and Virgo. I can thank Google Sky for the immense help. Who knew the stars of Cancer were so faint?

My trip to the UCSB Library (Davidson Library) completed a circle for me. It was there where I got the itch to visit the mathematics section of as many libraries I can get to. I first visited the UCSB library last September.

This visit I concentrated more on astronomy than mathematics. Learning about the structure of the Milky Way has become an interest for me.

Thanks to Tycho Brahe, comets are a major part of astronomy. He also brought all the astronomical almanacs to date around 1600, all without a telescope. Telescopes were first used by Galileo Galilei. Brahe's data was eventually inherited by Johannes Kepler, who was both an astrologer and astronomer.

Kepler showed how proportional the orbits of Jupiter (inscribed circle) and Saturn (circumscribed circle) were (well, in general) by drawing two circles around an equilateral triangle. My attempt at drawing is shown above. (Freehand art was never my strength).

Unlike what astronomers believed before, Galileo showed, among other things:
1. Planets are not self-moving.
2. Stars are not close to the Earth, instead they are distant suns.

The Milky Way

Harlow Shapley was the first to locate the Earth's place in the Milky Way Galaxy (around 1919): in the galactic disc two thirds out from the center. Today, astronomers estimate that we are about 24,500 to 27,000 light years away from the center; which could be a good thing. The center of our galaxy is said to be a massive black hole.

During the time of World War II, H.C. van de Hurst suggested trying to detect radio waves emitted by hydrogen atoms. This opened the door to a more detailed map of our celestial sky.

Source: Charles A. Whitney. "The Discovery of our Galaxy" Alfred A. Knoff: New York. 1971

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Currently, the center of our Milky Way lies in the constellation Sagittarius (♐). The biggest identifier is a radio source named Sagittarius A*, which can't be seen by the naked eye. It lies near the boarder of Scorpio (Scorpius) and Ophiuchus.

Coordinates of Sagittarius A* (approximately)
RA (α) 17hr 45min 40.04sec (266.416833°)
Dec (δ) -29°00'28.1" (-29.007806°)

I am curious: with the precision of the equinoxes, will Sagittarius A* "move" to Scorpio and/or Ophiuchus in the far future? It stands to reason, since the point (0hr, 0°), the vernal equinox once lied in the constellation Aries 2,000 years ago, now lies in Pisces on its way to Aquarius.

It is also an explanation why the star Polaris in Ursa Minor and the star Vega in Lyra trade the honor of being the North Star approximately every 12,857 years. (Close to 13,000) Source: http://csep10.phys.utk.edu/astr161/lect/time/precession.html

Hipparchus determined that the stars rotated approximately 50 arc seconds (50".3 to 50".4) around the ecliptic pole. Hence, it takes about 25,714 2/7 years for the stars to complete one cycle. (≈ 360°/50".4 = 360°/0.014°)

Until next time, cheers!


Eddie



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