Hi all,
We have had a run of very clear, but very cold, nights here
in Sydney. A fantastic cold front swept
in over the weekend dumping snow down to 800m in the mountains to Sydney’s
west. This has also meant that
transparency has been excellent along with very good seeing conditions.
Last night while scanning the terminator (the area of the
Moon where the light and dark meet, NOT a homicidal robot…) and came across a
huge feature that I had never seen before – an enormous round blister of a dome
smack on a seemingly featureless Mare!
Lunar domes are volcanic features. Some of these are magma displacements that
had pushed up from below the lunar surface but did not breach the surface. Others are actual volcanos. The “Valentine Dome” is a volcano.
It gets its nickname from being a little heart shaped. I did not give it this nickname! I found it while researching this feature
after I sketched it. Who says
astronomers are not romantic?!
The Valentine dome is some 35km in diameter, but only 300
meters tall. For this reason it requires
the Sun to be at a very shallow angle for the low mound to be visible. It is a very short volcano because lunar
volcanoes are shield type volcanoes, just like the ones on Hawaii.
Its official lunar designation is Linne A 1. The “1” refers to it being a volcanic
feature, with volcanic features having numerals in the same way that lesser
craters have letters.
Valentine Dome would also have been one of the last volcanic
features to form on Mare Serenitatis, forming over the long cooled lava plains
of Serenitatis. But all volcanic
features are very old.
Conversely, crater Linne is a relatively young feature. Though small (3km), its collar of ejecta
material is still very bright. As time
wears on, the solar wind will weather this bright material until it loses its
brilliance and the bright collar fades to blend into the surrounding grey
material. There are other craters in
this sketch that are larger than Linne. Linne
A, B & F are all larger than the principal (4km, 5km & 5km
respectively). But all of these have
lost their bright ejecta collars, hence giving clues to the relative ages of these features,
volcanic and crater.
It was a thrill to chance upon this lunar feature. It was also the first lunar volcano that I
was able to show my wife as it was so distinct and free from other distracting
features. I hope you are able to find it
for yourself one day.
Alex.
Object: “Valentine
dome” Linne A 1
Scope: Santel 9”
Maksutov Cassegrain
Gear: 10mm Vixen SSW
eyepiece, 310X
Date: 25th
of August, 2020
Location: Sydney,
Australia
Materials: White &
grey soft pastel, charcoal and white gel ink on A4 size black paper (no
blending stump used).
Your sketch work is always breathtakingly stunning. TYSM for sharing. I am glad you still post to your blog since I can no longer find the astronomy forum where I first found your posted work.
ReplyDelete