November 2020

by Roger Davies

A s October turns to November the clocks have gone back and the nights are lengthening. By 6pm it is dark and in November and December you can spot four planets through the night.

Jupiter and Saturn are visible together low in the southern sky in the early evening before setting in the south-west at about 8pm. Watch them night after night through November & December — they get closer together in the sky and by December 21st, when you’ll catch them low in the early evening western twilight, they'll be only 0.1 degrees apart — just 1/5 of the diameter of the full Moon. This is the closest conjunction of Jupiter and Saturn since 1623! The next conjunction between these gas giant planets is October 31, 2040 — so let’s hope for clear skies!

Mars, despite being passed opposition, is still splendid, bright and orange-red, seen in the constellation of Pisces rising in the early evening and in the sky almost the whole night.

Venus, the brightest planet, can be seen in the eastern sky an hour before sunrise which, in early November is about 7am. Early risers viewing Venus can ponder whether the discovery, reported in September, of phosphene molecules in the atmosphere of Venus, in quantities vastly greater than expected, is evidence of bacterial life; an indication that we have much to learn about atmospheric chemistry, or just a mistake in the data-handling as has recently been reported. See also here.

In mid-November the Earth passes through the debris left by Comet Tempel-Tuttle which gives rise to the Leonid meteor shower. The comet has a period of 32 years, we expect it to re-appear in 2031. Meteors are grain-of-sand sized specks of debris that burn up in the Earth's atmosphere producing long trails that persist for just a second or two. We expect a maximum of about 10 meteors per hour at the peak of the shower in the hours after midnight on the 17th November, although meteors from the shower will be seen for a few days around the 17th.

The Leonid meteors appear to come from the direction of the Lion's head (or sickle) part of the constellation of Leo that will rise at midnight on November 17th.
The meteors will appear to be coming from the sickle part of the constellation Leo, as shown in the figure. Leo rises at midnight on Nov 17th when the Moon is just two days old so the sky will be dark which, weather permitting, will make for a good display of the Leonids this year.

The 2020 Nobel Prize in Physics

Winners of the Nobel Prize in 2020

Earlier in October astronomers celebrated the award of the 2020 Nobel Prize for Physics for work on black holes to Sir Roger Penrose, Professor Reinhard Genzel & Professor Andrea Ghez. It was particularly exciting for Oxford University scientists to see our colleague in mathematics, Roger Penrose, recognised for demonstrating that Einstein's general theory of relativity predicted the formation of black holes. That work was a carried out in the 1960s shortly after the discovery of enormously luminous radio galaxies and quasars. The greatest puzzle surrounding quasars was how they are able to generate prodigious amounts of energy (1040 Watts) from within a volume as small as the Solar System. The prime candidate for how to do this turned out to be the energy released as material falls onto a black hole.

After decades of work using the Hubble Space Telescope and the largest telescopes on the ground, astronomers deduced that almost all galaxies contain a 'supermassive' black hole between one million and ten billion times the mass of the Sun at their centre. These are essentially dead quasars. By monitoring the positions and motions of the stars orbiting around the centre of our Milky Way over more than two decades Genzel & Ghez showed that there is indeed such a beast; a black hole with mass four million times that of the Sun, at the heart of our own galaxy. It was for this work that they were awarded the other half of the Nobel Prize. When Penrose's paper was published in 1965 the measurements made by Genzel & Ghez were completely impossible. Two developments in technology made their discovery possible. First imaging infrared detectors, now used in heat sensing cameras, made it possible to see through the obscuring dust that keeps the Galactic Centre hidden from us at visible wavelengths. The second technology involves sharpening the images of stars which are blurred as the light rays from them pass through the atmosphere — this is what gives rise to stars twinkling but it distorts all the pictures we take from the ground. Without this image sharpening technology, the stars in the centre of the Milky Way would be blurred together and it would not be possible to measure their individual positions and speeds — essential to measure the mass of the black hole. As is the case in many areas of science, new discoveries follow the application of new technologies and methods to old problems.

In 2019 an international team of radio astronomers led by Professor Heino Falcke at Radbaud University in Nijmegen in the Netherlands used a global array of radio telescopes, 'The Event Horizon Telescope', to make this image of the shadow of a black hole in the centre of one of nearest radio galaxies. Credit: EHT.

Happy stargazing!

SEE ALSO by Roger Davies:
Stargazing • February 2021
Stargazing • November 2020
Stargazing • September 2020
Comet Neowise • July 2020
Stargazing • July & August 2020
Stargazing • June 2020
Stargazing • May 2020
Stargazing • April 2020

Roger Davies is a resident of the village of Kidlington, Oxfordshire.

Roger is the Philip Wetton Professor of Astrophysics and Director of the Hintze Centre for Astrophysical Surveys at the Department of Physics, University of Oxford,

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