Brought to you by Dr. Roy Gretton, Journal Editor of The Nottingham Astronomical Society.
Please note, the NAS new permanent venue for our main meetings on the first Thursday in the month. Nottingham Emmanuel School, Gresham Park Road, West Bridgford, Nottingham, NG2 7YF.
The path that the Sun appears to take around our sky in the course of a year is called the ecliptic, and is so named because eclipses of the Sun and Moon always take place along this line. Viewed another way, the ecliptic marks out the plane of the Earthโs orbit around the Sun and, because our planetโs
axis is inclined at an angle of 23.5 degrees to the equator, the ecliptic is inclined at this same angle to the celestial equator. As all the planets orbit the Sun in roughly the same plane as the Earth, the planets themselves never seem to stray far from the ecliptic. At some times of the year the planets appear high in the sky, and at other times low down. Generally the planets appear high in the evening in spring because, if we look toward the sunset on a spring evening, the ecliptic makes a steep angle with the horizon, with the result that any planet in that part of the sky tends to be high up and easy to spot. Conversely, if we look in the same direction on an autumn evening, the ecliptic makes a shallow angle with the horizon, so that an evening planet tends to be low down and less easy to observe in the autumn.
These remarks also apply to the Moon.
On a spring evening the crescent Moon is high in the west (and almost looks to be lying โon its backโ) whereas on an autumn evening the crescent Moon is low down (so low that you might not even notice it) and appears to be standing on one of its ends. The angle of the ecliptic explains why Venus has been so prominent in the evening sky this spring (as it was in the spring of 2020, during the first Covid lockdown). But now, as May turns into June, although Venus is still getting brighter and further from the Sun, it may be a little less prominent because the ecliptic will be making a less steep angle with the horizon.
Because Venus is closer to the Sun than we are, it displays phases similar to those of the Moon. A small telescope (say, threeยญinch aperture) will show the phases of Venus as spring turns into summer this year.
The Other Planets
Mercury is unobservable in May and June this year. Mars is visible all evening, though continuing to fade, and in June will be about the same brightness as Castor, the dimmer of the Heavenly Twins, and will be setting around midnight. Of the gas giants, Saturn will be creeping over the eastern horizon at 2am as May gives way to June, to be followed by the much brighter Jupiter an hourยญ-andยญ-aยญ-half later, although by then the sky will be brightening ahead of sunrise, which will occur well before 5am.
From late May until late July at our latitude the sky is never fully dark. Itโs a favourite time of year for amateur astronomers to do maintenance on their equipment in readiness for the return of darker nights. The main planetary event we shall be looking forward to this year will be the autumn opposition of Jupiter, when the giant planet will be higher in our sky than it has been for years.
Phases of the Moon
| MAY | JUNE | |
| Full Moon | 5th | 4th |
| Last Quarter | 12th | 10th |
| New Moon | 19th | 18th |
| First Quarter | 27th | 25th |
