Is it a bird? Is it a plane? It's no Super Moon either!

Star chart

Star chart - Credit: Torbay Astronomical Society

John Stapleton writes a monthly column to inform readers of what to look for in the night sky, report anything of current interest in astronomy and to advise new stargazers how to get the best out of their new hobby:

By now all of you 'lockdown stargazers' will be looking forward to this month's 'Super Moon' however this is not the correct astronomical term for this event.

The term 'Super Moon' was first coined within astronomical circles and picked up by the press in April, 2011.

That year the Moon reached the closest possible point in its orbit to the Earth.

Because the orbits of both Earth and Moon are elliptical (not circular) about a point that is not the centre of the Earth but some two thirds of the distance from the centre towards the surface, the two bodies wobble around each other.

Along with other 'wobble factors' and tidal drag on the Moon, these cause points - the astronomical term for these is apsides - in the orbit to 'slide' so that the closest possible Moon occurs only once every 8.8 years.

Therefore, the Full Moon of April. 2019. was also a closest possible Moon but the closest Full Moon this year will not be as close or as large and, therefore, not as super.

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Astronomers already have a term for the closest approach of an object to the Earth and that is 'perigee', with the farthest point in an orbit from the Earth being the 'apogee'.

Astronomers also have a word which describes the relative positions of the Sun, Earth and Moon at Full Moon or New Moon i.e. when the three bodies are in a straight line and that is 'syzygy'.

This is an approximate straight line since a perfect - straight line - syzygy would result in an eclipse of the Sun or Moon.

So, when we see the largest Full Moon of the year in April it is, formally, an apsidal, perigee syzygy, in astronomical terms.

And this may be part of the reason why the (up to now) only astrological term 'Super Moon' was used to make it sound simpler.

In fact, the difference in size of the Moon between one Full Moon and the next is indiscernible to the naked eye, although images of the 'Super Moon' and the Full Moon six months later, the farthest from the Earth, will show the difference when compared with each other.

This distant Moon is also referred to by astrologers as a 'Mini Moon' but this does not seem to have attracted the notice of the press, yet.

The next closest possible Moon will occur in April, 2028, so that is the next Full Moon which will deserve the appellation 'Super Moon', if that is what we are going to use to name it.

Torbay Astronomical Society

Torbay Astronomical Society - Credit: Torbay Astronomical Society

The Star Chart

The sky will look like the chart on April 7 at 9pm and again on April 22 at 8pm. And four minutes earlier on each successive night e.g. 8.56 on April 8.

To use the chart hold it above your head whilst facing South so that you can look directly from the chart to the sky.

Sky notes

Please note all times given in this article are in GMT so remember to add an hour to get the time in BST which started on Sunday, March 28.

Mercury and Venus: Both of these inner planets (because they orbit the Sun closer than the Earth) are too close to the Sun in their orbits, from our point of view, to be seen this month.

Mars: The red planet is still visible but is getting fainter as it moves away from the Earth. It can be seen against the background constellation of Taurus, above the distinctive “V” that forms the head of the bull. This “V” is called the Hyades and is a cluster of associated stars. At one end of the “V” is the star Aldebaran which is reddish orange in colour. Mars is the next reddish object out from the “V” and somewhat fainter than Aldebaran. The planet will lie close to the Moon on 17th which may make it easier to find. By the end of the month Mars will be seen against the background constellation of Gemini and on the 26th will lie close to another star cluster known as M35. This would make an interesting sight or image in a digital camera. The camera is all that is needed for a one-off image.

Jupiter: The largest planet rises in the early morning (5am) and in the south-eastern sky at the end of the month when it will be seen against the background stars of Aquarius. Before that it is too low for us to see.

Saturn: The ringed planet also rises just before 5:00am very slightly higher than Jupiter and on the same horizon. Saturn is a little further East and can be seen against the background stars of Capricorn.

Uranus and Neptune: These planets are not visible this month.

Astronomers refer to the stars as 'background' because, although the planets are millions of miles distant from us, the stars are billions and even trillions of miles away and so not related or influenced by the planets in any way. We see the planets against this background since we are looking out through the Solar System towards the distant stars. It is purely a line-of-sight circumstance.

Meteor shower: The Cotswold Meteorite filmed and recovered last month was a rare event, 1 in 30 years for this country.

However, the Earth experiences a continual fine shower of dust-like material from space and sometimes we can predict when it is possible to see this material burning up as it enters the atmosphere.

We call these shooting stars, or more formally meteors and the predictable occurrences, meteor showers.

One such shower falls in April. It appears to come from a point in the sky lying in the direction of the background constellation of Lyra and so is known as the April Lyrids. Look out for these meteors between April 16-25. The peak time falls on the night of April 22 -23.

Meteors are the remnants left in the path of comets as they orbit the Sun. We see them when the Earth passes through a cloud of these remnants. The April Lyrids are the remnants of Comet Thatcher.

Comet: There is a comet in our skies during April, but it is quite faint and will need large binoculars or a telescope to be seen. The comet has been named according to an astronomical cataloguing system and is known as Comet C/2020R4 (ATLAS). This tells us the year and part of year that it was discovered, what number discovery it was for that period and who, or what (in the case of satellites or automated observatories) discovered it. The closest point in the comets orbit to the Earth (perigee) is on April 23.

The Last Quarter Moon occurred on April 3 with New Moon on April 12. First Quarter follows on April 19 with Full Moon at the end of the month on April 27.

Data supplied by Simon Harding, observations secretary of Torbay Astronomical Society.

Diary Dates

The next meeting of the Torbay Astronomical Society, complying with the current Covid regulations, will be online via Zoom. For details contact the Secretary TAS on astrosecretary@gmail.com . Visitors and prospective members especially welcome.