Adrian Dening's Stars Over Somerset

Monday 6th to Sunday 12th June 2022

On the evening of Thursday 9th, the Moon will be a couple of days past its First Quarter phase and this is a great opportunity to spot one of the more unusual Lunar features known as the Hortensius Dome Field. At around 11pm, the Moon will be situated towards the south west.

Firstly find the large crater Copernicus. Looking at the nearside face of the Moon, it is slightly to the left of centre and is quite easy to see without resorting to a telescope or binoculars.

To the left of Copernicus is the much smaller crater Hortensius. It is an impact crater with a diameter of only 15Km, so best to dig your telescope out at this point!

Just above the crater are six lumps in the Lunar surface - these are called the Hortensius Domes. The four larger ones have been named with Greek letters, the smaller two have never been named. Some of them have a dimple at the top which is given the cute term "craterlet". I have provided diagrams to help locate them, courtesy of the Znith Observatory in Malta.

The domes are evidence of volcanic activity in the Moon's distant past and they were formed by a highly viscous type of lava. Calling them domes isn't very technical and the correct term is "shield volcanoes", so named because they have a low profile and are meant to look like an ancient Greek warrior's shield lying on the ground - how technical is that!! Shield volcanoes are found on other planets in the Solar System, including our own. The best example is Mauna Loa on Hawaii and I have included a photograph of it, courtesy of Wikipedia, in case you've never been there!

Screenshots courtesy of Stellarium
Copyright Adrian Dening and Radio Ninesprings 2022