M94, Multi-ring galaxy
M94 is a complex galaxy in Canes Venatici. It has both inner and outer rings surrounding an unusually bright and active core. The blue areas in the innermost ring are areas of intense star formation. In this image, the outer ring shows hints of the very faint spiral structure seen in recent professional images.
Credit: Bruce Waddington
Saturn has a great many more moons than our planet – a whopping 62. A single moon, Titan, accounts for an overwhelming 96% of all the material orbiting the planet, with a group of six other smaller moons dominating the rest. The other 55 small satellites whizzing around Saturn make up the tiny remainder along with the gas giant’s famous rings.
One of the subjects of this Cassini image, Rhea, belongs to that group of dominating six. Set against a backdrop showing Saturn and its intricate system of icy rings, Rhea dominates the scene and dwarfs its tiny companion, one of the 55 small satellites known as Epimetheus.
Although they appear to be close to one another, this is a trick of perspective – this view was obtained when Cassini was some 1.2 million km from Rhea, and 1.6 million km from Epimetheus, meaning the moons themselves had a hefty separation of 400 000 km.
However, even if they were nearer to each other, Rhea would still loom large over Epimetheus: at 1528 km across and just under half the size of our own Moon, Rhea is well over 10 times the size of Epimetheus, which is a modest 113 km across.
As is traditional for the earliest discovered moons of Saturn, both are named after figures from Greek mythology: the Titan Rhea (“mother of the gods”) and Prometheus’ brother Epimetheus (“after thinker” or “hindsight”).
Image credit: NASA/JPL-Caltech/Space Science Institute, G. Ugarković
Read more about Cassini and it’s mission here. Logikblok.
Helix Nebula Hubble
The Helix Nebula, also known as The Helix, NGC 7293, is a large planetary nebula located in the constellation Aquarius.