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The Journal of the British Astronomical Association, 2021 December

Volume 131, Number 6

The ghost mountains of Venus feature in the final paper by the late Richard Baum, alongside the 2021 BAA Christmas Quiz, and how to get involved in observing exoplanets.

Log in or join the BAA today to view this journal online. A full list of contents is also available.

Selected highlights from this Journal:

Refereed Papers

J. H. Schröter & the ghost mountains of Venus
Since the invention of the telescope, observers of Venus have often reported irregularities in the shape of the planet’s terminator and cusps. Some of these, such as terminator undulations, might be easily ascribed to poor seeing conditions; others, such as cusp extensions near inferior conjunction, are undoubtedly real and evidence of Venus’s atmosphere. This paper considers a third category: detached points of light recorded by several observers at the cusps of the planet, explained by some as high mountain peaks catching the sunlight. Among those who argued for the existence of such mountains was Johann Schröter, a stance that brought him into conflict with the views of William Herschel. Nowadays the ‘ghost mountains of Venus’ are seen for what they are: an illusion encouraged by a growing belief in the plurality of Earth-like worlds.
Richard Baum
Observing exoplanets with the MicroObservatory: 43 new transit light curves of the hot Jupiter HAT-P-32b
Observations of 43 complete transits of the hot Jupiter exoplanet HAT-P-32b using the MicroObservatory 0.15m robotic telescope network, covering a period of seven years, are presented. Compared with the most recent ephemeris for the system, the precision of the mid-transit times yields a root-mean-square value from the predicted model of 3.0min. The estimated system parameters based on EXOFAST modelling are broadly consistent with the default parameter values listed in the NASA Exoplanet Archive. An updated orbital period of 2.15000815 ± 0.00000013d and ephemeris of 2458881.71392 ± 0.00027BJDTDB are consistent with recent studies of the system using larger telescopes. Using this updated ephemeris, the predicted mid-transit time for a notional observation of HAT-P-32b by the NASA JWST mission in mid-2021 is improved by 1.4min compared with the discovery ephemeris and is approximately eight times more precise. Likewise, the mid-transit time for an observation by the ESA ARIEL mission in 2020 is improved by 1.7m
Martin J. F. Fowler, Frank F. Sienkiewicz, Robert T. Zellem & Mary E. Dussault
Five thousand years of Jupiter–Saturn conjunctions
The recent so-called ‘Great Conjunction’ of Jupiter and Saturn, in 2020 December, was the latest in a series of conjunctions of the two planets that occur, on average, every 19.67 years. Although events between Jupiter and Saturn are visually not the most spectacular of conjunctions, they are of great historical interest due to the triple conjunction that occurred around the time of the Nativity, which authors such as Hughes (1976) have associated with the Star of Bethlehem. A total of 309 Jupiter–Saturn conjunctions are found between 1000 BC and AD 4000, which include 84 grouped in 28 triple conjunctions. The 2020 conjunction is found to be in the top five percent of closest approaches of the two planets over five millennia. The closest conjunctions show a strong preference for occurring in Cancer in July/August, or Capricornus in December.
Mark Kidger
The five greatest sunspot groups
Remarkably, the five largest recorded sunspot groups all occurred during a period of just over five years, from 1946 February to 1951 May, during Solar Cycle 18. These are the only groups known with areas greater than 4,500 millionths of the Sun’s visible hemisphere. This paper examines the white-light activity of the groups.
Peter Meadows