From Astronomy Picture of the Day for 18/5/21.

This beautiful celestial apparition is known as the Necklace Nebula. It is a so-called planetary nebula. These are formed by gases thrown off by stars nearing the end of their lives. The Nebula Necklace’s “Diamonds” are knots of glowing gas.

Only 24 people have ever had the chance to see a view like this – or photograph it. The 24 astronauts of the Apollo Programme who made it to the Moon and back.

From Astronomy Picture of the Day for 29/4/21, a digitally restored photograph of the whole of planet Earth from its nightside, the last picture of its kind so far to be taken by human hands.

Two kites have been flown in the past twenty four hours.

One of them was on another planet.

The other might as well have been.

These are the days of miracle and wonder.

But also of greed and thoughtlessness.

O tempora, o mores.

With bonus rings.

Another great picture from the Cassini Probe, taken from Astronomy Picture of the Day for 4/4/2021.

The most obvious moon is the bright Dione, hovering on the centre of the frame, with shadowy but much larger Titan in the background. Titan is the tenth largest object in the Solar System bigger than the planet Mercury.

To the extreme right of the rings is Pandora, a moon which shepherds Saturn’s F ring.

Just in the gap in the rings (the Encke gap) is Pan, only 35 kilometres across but which keeps the gap free of ring particles.

I found this (copyrighted) image on Astronomy Picture of the Day for 18/1/21.

The text on APOD’s post refers to it as looking like a brain – hence its name, the Medulla Nebula.

To me, though, it looks more like an eyeball – with the optic nerve going off to the right as in the diagram below.

Remember those days when Pluto was just a blip on a photographic plate, then merely a fuzzy set of dots on a Hubble telescope image?

No more.

Astronomy Picture of the Day for 15/1/21 featured this photo taken by the New Horizons probe 15 minutes after its closest approach to the (dwarf) planet when it was 18,000 kilometres away from the surface.

Some of the mountains on show are comparable in height to the highest on Earth but of course they are not composed of rock but most likely of ice. The plains below them may contain solid nitrogen or carbon dioxide.

Also visible above Pluto’s horizon is its tenuous atmosphere.

From Astronomy Picture of the Day for 9/1/21 here is a view of Saturn’s moon Titan that you would never see if you were somehow be able to be on Saturn itself.

Titan is tide-locked to its primary and so always presents the same face to it. Its reverse side however was however visible to the Cassini probe.

Since Titan has an atmosphere its surface is not seen directly but the fuzziness around its edges – seen against the thick line of Saturn’s rings and the planet itself beyond – shows the atmosphere’s thickness relative to the satellite.

This is an oddity. From You Tube via Astronomy Picture of the Day for 16/12/20.

It’s a sonified image of the Bullet Cluster with low tones assigned to Dark Matter, mid-range to visible light and higher tones to X-rays.

It may be though that Dark Matter does not exist, as this post from the Daily Galaxy argues.

The Arecibo Telescope was the largest single-dish radio telescope in the world for over 50 years. Among its achievements in Astronomy it has been used to measure the spin of Mercury, map the surface of Venus, discover the first planets outside our Solar System, verify the existence of gravitational radiation and search for extraterrestrial intelligence, but it seems it was first built for military purposes.

While being decommissioned the structure had a total collapse early this month.

The collapse was captured on video:-

What a gem this is. Another from the Hubble telescope via Astronomy Picture of the Day for 18/10/20.

This is galaxy UGC 810. Its odd shape is because it is in collision with UGC 1813 (out of picture below the frame.) Altogether the configuration is known as Arp 273. See previous photo here.