In this month: November

7th November 1631

A transit of Mercury occurs. Many astronomers set up to capture Mercury's movement in front of the Sun. However only one, a catholic priest named Pierre Gassendi, published his observations and revealed for the first time the size of a planet compared to the Sun. Thus, Pierre Gassendi became the first known person to observe a transit of Mercury.

He observed the transit in a darkened room by projecting the image of the Sun through his telescope. Initially, he thought he was seeing a sunspot because Mercury is so tiny compared to the size of the solar disc. Mercury's apparent size is about 150 times smaller than the Sun.

On average there are about 13 or 14 transits of Mercury per century. They occur either in May or November. The image left is by NASA of the Transit of Mercury 6 May, 2016.

14th November 2003

Sedna, a dwarf planet, is discovered by a team of American astronomers at Palomar Observatory. At the time of its discovery it was the most distant object in the solar system that had ever been observed at a distance of 13 billion kilometres from the Sun. Sedna has an exceptionally long and eccentric orbit that ranges between 12.9 billion kilometres and 135 billion kilometres and takes approximately 11,400 years to complete. In certain points of its orbit Sedna technically lies in interstellar space and can be considered an "interstellar object" (although that term is usually used to refer to an object in interstellar space that is not gravitationally bound to a nearby star). Its surface is one of the reddest among solar system objects with a composition comprising largely of water, methane, and nitrogen ices

The name Sedna comes from Inuit mythology. She is the goddess of the sea and marine animals.

5th November 2018

Voyager 2 becomes only the second spacecraft in history to leave the heliosphere, the boundary that marks the beginning of interstellar space. (The first spacecraft being Voyager 1 in 2012). The spacecraft is now in its extended mission of studying interstellar space. As of September 2021, Voyager 2 has been operating for 44 years reaching a distance of 19 billion kilometres from Earth.

Launched on the 20th August 1977 Voyager 2 is the only spacecraft to study all four of the solar system's giant planets at close range and the first human-made object to fly past Uranus and Neptune. Because of the direction in which it is flying out of the solar system, Voyager 2 can only receive commands from Earth via one antenna in the world, the DSS 43 dish situated at the Deep Space Network in Canberra. A round-trip communication with Voyager 2 now takes about 35 hours, 17 and a half hours each way. The image above is an artist's impression of the Voyager spacecraft, courtesy NASA.

BORN

19th November 1845

Agnes Giberne.

English amateur astronomer, although she is best remembered for her books popularising science. Her first foray into science was a book on astronomy Sun, Moon and Stars: Astronomy for Beginners, the illustration below of the Moon is from that book.

She sent the proofs to Charles Pritchard, the Savilian Professor of Astronomy, at Oxford University and he was so impressed that he wrote, without being asked, a very positive introduction.

Giberne worked on the committee setting up the British Astronomical Association and became a founder-member

in 1890.

10th November 1861

Robert Thorburn Ayton Innes. Scottish astronomer.

Best known for discovering Proxima Centauri in 1915, one of three known stars in the Alpha Centauri system. Prior to this discovery astronomers believed that Alpha Centauri was the closest star to our solar system. He was also the first astronomer to have seen the Great January Comet of 1910. Innes was the co-founder of the British Astronomical Association (NSW) now Sydney City Skywatchers.

A self-taught astronomer and despite having had no formal training in astronomy he was invited by HM Astronomer Sir David Gill to take up a post at the Royal Observatory, Cape of Good Hope in 1894. In 1903 he took up the position of Director of the new Transvaal Meteorological Observatory in Johannesburg and in 1912 was appointed first Union Astronomer at the Union Observatory. He tirelessly campaigned for South Africa's astronomy infrastructure believing that its clear skies were ideally suited for astronomical observation. The lunar crater Innes and the asteroid 1658 Innes are named after him. The image left of Innes is courtesy the South African Astronomical Observatory.

9th November 1943

Don Backer. American astrophysicist.

He discovered the first millisecond pulsar, PSR B1937+21, which rotates at a rate far beyond what was expected of pulsars before its discovery.

He was also involved in the discovery of a Jupiter-sized planet around pulsar PSR B1620-26, thought to be the oldest known extrasolar planet. He lay the groundwork to detect gravitational waves from rapidly rotating neutron stars and was a pioneer in Very Long Baseline Interferometry, a technique used in radio astronomy to achieve high angular resolution images of astronomical sources. His efforts were directed towards understanding Sagittarius A*, the supermassive black hole at the centre of the Milky Way.

Backer served in different positions in the Berkeley Astronomy Department from 1998 to 2008.

The image above shows Becker in 2007, courtesy NRAO/AUI. In 2008, he was appointed director of Berkeley's Radio Astronomy Laboratory a position he held until his death in 2010.