Monday 25th April to Sunday 1st May 2022

Mercury is the closest planet to the Sun and is always a bit tricky to spot because it appears near dawn or dusk.  It's also dangerous to use binoculars or a telescope to help as the planet will be near the rising or setting Sun.


On Friday 29th April, Mercury will be located just below the familiar open cluster of stars known as the Pleiades around 10pm local time.  You will find the Pleiades towards the north west horizon.  On 29th, Mercury will be at its greatest eastern elongation which, for an observer on the Earth, means that it is at its greatest separation from the Sun and will be quite easy to spot with a magnitude of +0.4 that evening.


Mercury is the smallest planet in our Solar System - only slightly larger than our Moon.  Because it is so close to the Sun and it orbits so fast, a year on the planet only lasts 88 days.  We are further away so our year lasts 365 days.


If you are observing the planet, you are looking at a place where the surface temperature varies from -173 degrees Celsius at night to +427 degrees during the day because it has no atmosphere to protect the planet and act as a blanket!  To make matters worse, Mercury spins very slowly on its axis and a day on Mercury lasts 59 earth days, so if you were visiting, you'd be alternately frozen and cooked for long periods of time!


Confusingly, Mercury is not the hottest planet in the Solar System - that title goes to Venus because its thick atmosphere traps heat!



Monday 18th to Sunday 24th April 2022

The evening of Friday 22nd sees the peak of the Lyrid meteor shower.  The radiant point where the meteors appear to originate from is slightly above and to the right of the constellation of Lyra.  After dark, the constellation will be towards the north east and as we proceed through the night, it climbs higher in the sky.


The Moon does not rise above the horizon until 4am on the Saturday morning, so it won't be producing any light pollution to spoil your view of the shooting stars that are the debris from comet Thatcher.


Nobody in current times has seen the actual comet.  Your children will never see it either as comet Thatcher takes 417 years to orbit around the Sun and it's currently 107 Astronomical Units away which is 107 times further away from the Sun than we are.  In 45 years the comet will be at its furthest point from the Sun, to use the correct term, at Apogee and will then begin a slow return towards the centre of our Solar System!


An interesting event occurs around 5am on the morning of Sunday 24th.  If you look to the east, you will see four of our neighbouring planets forming a straight diagonal line - from left to right - Jupiter, Venus, Mars and Saturn with a Last Quarter Moon thrown in for good measure to the right of that!


Please don't be tempted to use a telescope or binoculars to obtain a better view as the Sun will be rising and you must never catch even a glimpse of the Sun through a telescope as it will cause instant and permanent blindness!



Monday 11th to Sunday 17th April 2022

There's nothing particularly special happening on the astronomy front next week, but Saturday 16th brings a Full Moon, easy to spot after dark towards the south east.  If you are looking for faint deep sky objects with your telescope, this is the worst possible time as the Moon will be very bright and the sunlight reflecting from it creates the ultimate light pollution.


On the other hand, it is a great opportunity to observe some of the lunar features, especially the large dark flat areas that early astronomers used to think were seas or oceans.  Of course we now know that these "mare", derived from the Latin word for "sea", are really large basaltic plains, created by ancient asteroid impacts.

They cover approximately 16% of the lunar surface facing us and appear dark because of their iron-rich composition.  Curiously, there are only a few small mare on the dark side of the Moon that is always facing away from us.

The mare are easy to identify with the naked eye, but if you fancy a bit more of a challenge you could have a go at locating some of the lunar craters that were formed by smaller impacts.  The Moon has 9,137 of them in total!  The most obvious crater towards the south of the Moon is called Tycho.  It is a relatively young crater, estimated to be only 108 million years old!  Stretching away from Tycho is a prominent ray system and you can almost imagine the object that created the crater going "splat" as it hit!

Image courtesy of Wikipedia



Monday 4th to Sunday 10th April 2022

Back in February, I mentioned an open star cluster called Melotte 111 that is located in the constellation of Coma Berenices, between the constellations of Bootes and Leo.  It is visible in the late evening towards the south east and the month of April is an ideal time as Coma Berenices reaches its highest point in the night sky.

To the left of Melotte 111 is an area of sky originally given the wonderful-sounding name "The Realm of Galaxies".  It is now more-commonly known as the Coma Galaxy Cluster.

The centre of the cluster is some 320 million light years away from us and the galaxies in it are moving away from us at a speed of 15 million miles per hour.


A dark sky location and medium-size telescope will enable you to see some of the 10,000 galaxies located in that area.  There is a mixture of spiral galaxies like our own Milky Way and elliptical galaxies that are formed when two galaxies merge together.  The galaxies are listed in catalogues such as the NGC "New General Catalogue" and IC "Index catalogue" rather than the more familiar Messier Catalogue as Charles Messier didn't discover them!


The American astronomer Edwin Hubble studied galaxies in depth and came up with a classification system for all the different types.  I have included a copy of what is known as his "Tuning Fork" diagram.  Our Milky Way is actually a barred spiral galaxy which is given a Hubble classification of SB.


If Hubble's name sounds familiar - that's because the Hubble Space Telescope was named in his honour.