December 27 – Discovery of Messier 92 (1777)

The small, densely packed globular cluster Messier 92 was discovered on this day in 1777, not by Charles Messier, but by Johann Elert Bode. Messier didn’t spot it until 1781.

M92 (Photo credit: the Isaac Newton Group of Telescopes, La Palma)

M92 is a barely-naked eye object of magnitude 6.4, located in the constellation of Hercules. It is one of the oldest and brightest globular clusters, though not as bright as its neighbour in Hercules, M13, and is about 27,000 light years from Earth.

Some of the stars in M92 are about 14 billion years old, making them roughly the same age as the Universe. This established age probably led to lively debate among astronomers when the Hubble Constant was first used to put the age of the Universe at 12 billion years.

December 27 – Birth of Johannes Kepler (1571)

Today is Johannes Kepler’s birthday.

Kepler was born in Weil der Stadt, a small town near Stuttgart, on December 27th 1571, and was introduced to astronomy from an early age, whether he liked it or not, by being taken outside to witness the Great Comet of 1577, C/1577 V1, at age 6. The comet was also seen, incidentally, by Tycho Brahe, with whom Kepler would later spend some time studying at the site of Brahe’s new observatory near Prague.

Johannes Kepler

Kepler’s works included many revolutionary (and I mean that in several ways) publications on the behaviour of planets. His Astronomia Nova, published in 1609, contained arguments in favour of a heliocentric ‘universe’, and Harmonia Mundi (“The Harmony of the World”, 1619) was the setting for his third law of planetary motion.

As well as being an influential astronomer, Kepler was also a major influence in the field of optics (possibly because his own eyesight wasn’t the best). He was the first person to explain how a telescope works; worked out how our eyes perceive depth; investigated how a pin hole camera might be used to produce pictures, and discovered total internal reflection.

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1968 – Splashdown, south of Hawaii, of Apollo 8, following a 6 day flight that included the first Earthrise seen by humans, and the first Christmas broadcast from a craft orbiting the Moon.

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