Picture of the Day – Saturn’s Rings

New unprocessed image of Saturn's rings. Credit: NASA/JPL/Space Science Institute

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From Cassini, 1,460,000,000 km away, comes this great image of the majestic rings of Saturn lit up brightly by the Sun. This is a raw image, it hasn’t been processed, that spot in the middle of the image is probably a cosmic ray hit.

Saturn’s rings are not a simple disk, but it is actually made up of thousands of separate rings. The big dark gap in the rings is called the Cassini Division, discovered by the astronomer Giovanni Domenico Cassini in the 17th century. Saturn’s moon Mimas is responsible for that gap; any particle in the Cassini Division orbits Saturn in half the time Mimas does, and so it feels a periodic tug from the moon (called a resonance). That pulls the particles clear from that region, carving a gap. Other broad gaps in the rings are from other moon resonances, while some of the narrow ones are from small moons in the gaps gravitationally clearing out nearby ring particles.The rings are made up of icy particles,they range in size from, about a grain of sand to the size of a small house, but on average they are the size of your clenched fist. The rings extend from about 74,000 kilometres to about 180,000 kilometres from Saturn’s centre, but they are very thin, less than a hundred metres thick! A scale model of the rings as thick as a single piece of tissue paper would cover an entire football field! It’s still unclear how Saturn, or the other three gas giants, got their rings, but there is more than one mechanism to get them, a moon could get hit by an asteroid or comet shattering it.

There’s a lot we don’t know about Saturn and its rings, but Cassini has been orbiting Saturn for a while, it’s taken some amazing images of Saturn and everything around it. Cassini is helping us solve the mysteries of the Saturn and its surroundings in far better detail than ever before. It has produced some of the highest resolution images of the ringed planet and its moons.

You can scour the Cassini image gallery yourself, click here.

R Coronae Australis: A Cosmic Watercolour

The R Coronae Australis region imaged with the Wide Field Imager at La Silla

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The star R Coronae Australis lies in one of the nearest and most spectacular star-forming regions. This portrait was taken by the Wide Field Imager (WFI) on the MPG/ESO 2.2-metre telescope at the La Silla Observatory in Chile. The image is a combination of twelve separate pictures taken through red, green and blue filters.

This image shows a section of sky that spans roughly the width of the full Moon. This is equivalent to about four light-years at the distance of the nebula, which is located some 420 light-years away in the small constellation of Corona Australis (the Southern Crown). The complex is named after the star R Coronae Australis, which lies at the centre of the image.

It is one of several stars in this region that belong to the class of very young stars that vary in brightness and are still surrounded by the clouds of gas and dust from which they formed.

The intense radiation given off by these hot young stars interacts with the gas surrounding them and is either reflected or re-emitted at a different wavelength.

These complex processes, determined by the physics of the interstellar medium and the properties of the stars, are responsible for the magnificent colours of nebulae. The light blue nebulosity seen in this picture is mostly due to the reflection of starlight off small dust particles.

The young stars in the R Coronae Australis complex are similar in mass to the Sun and do not emit enough ultraviolet light to ionise a substantial fraction of the surrounding hydrogen. This means that the cloud does not glow with the characteristic red colour seen in many star-forming regions.

The huge dust cloud in which the reflection nebula is embedded is here shown in impressively fine detail. The subtle colours and varied textures of the dust clouds make this image resemble an impressionist painting. A prominent dark lane crosses the image from the centre to the bottom left. Here the visible light emitted by the stars that are forming inside the cloud is completely absorbed by the dust.

These objects could only be detected by observing at longer wavelengths, by using a camera that can detect infrared radiation.

R Coronae Australis itself is not visible to the unaided eye, but the tiny, tiara-shaped constellation in which it lies is easily spotted from dark sites due to its proximity on the sky to the larger constellation of Sagittarius and the rich star clouds towards the centre of our own galaxy, the Milky Way.

Picture of the Day – M66 Poses for Hubble

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Awesome! This is amazing picture of M66 comes from the Hubble Space Telescope. Spiral galaxies are so beautiful and M66 is no exception. It’s as big as the Milky Way and it’s 35 million light years away.

Head down to Bad Astronomy where the Bad Astronomer takes an artistic look at this image and covers all the details.

Picture of the Day – Aurora Captured From The Space Station

An aurora seen over the South Pole, from the ISS. Credit: Doug Wheelock, NASA.

From Doug Wheelock’s Twitpic page, an astronaut on the International Space Station (ISS), comes this brilliant image of the Southern Lights (Aurora Australis) as seen from the ISS.

The northern (Aurora Borealis) and The southern (Aurora Australis) are caused when the charged particles (ions) from the Sun hit the Earth. The ions from the Sun excite the electrons of the atoms in the atmosphere which in turn emit a photon (light). Different atoms release light in different colours, the greenish colour seen here is emitted by oxygen atoms.

Doug Wheelock has some out of this world pictures on Twitpic page, check it out!

VISTA Peeps at The Sculptor Galaxy

The Sculptor Galaxy (NGC 253) Credit: ESO

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WOW! Just take a minute to gaze at this spectacular image.

ESO has just released this beautiful image of The Sculptor Galaxy (NGC 253) there are a few foreground stars which belong to our galaxy.  This image  is taken by VISTA (Visible and Infrared Survey Telescope for Astronomy), a 4-metre telescope at the Paranal Observatory in Chile.

NGC 253 is intermediate spiral galaxy, it’s quite close about 13 million light-years away, it can easily be seen with a good pair of binoculars as it’s one of the brightest galaxies in the sky and it is the brightest member of a small collection of galaxies called the Sculptor Group, one of the closest such groupings to our own Local Group of galaxies. Seen from Earth, the galaxy is almost edge on, with the spiral arms clearly visible in the outer parts, along with a bright core at its centre. There is intense star formation going on in this galaxy. NGC 253 is very dusty, this dust absorbs most of the visible-light coming from inside of the galaxy. But VISTA has no problems looking past this dust, instead of looking at the stuff in visible-light, VISTA looks at stuff in infrared-light. Infrared-light easily passes through the think dust clouds. The picture above is amazing, you can pick out individual stars thanks to the high resolution power of VISTA! It’s even more awesome if you download the gigantic 44MB file…It’s worth it!

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In the image above, you see the dust and gas which litters the galaxy in visible-light, just fades away to reveal a huge number of cooler stars. The majestic spiral arms look more defined in infrared. The thick dust clouds in the central part of the disc and allows a clear view of a prominent bar of stars across the nuclear region — a feature that is not seen in visible light pictures.

This video allows you to zoom in for a closer look. The sequence starts with a wide view of the southern sky far from the Milky Way. Only a few stars are visible, but then VISTA brings us in closer where the view shifts to the very detailed new infrared image of NGC 253 provided by the new telescope at Paranal. By observing in infrared light VISTA’s view is less affected by dust and reveals a myriad of cooler stars as well as a prominent bar of stars across the central region.

VISTA has allowed scientists to study the myriad of cool red giant stars in the halo that surrounds the galaxy, measuring the composition of some of NGC 253’s small dwarf satellite galaxies, and searching for as yet undiscovered new objects such as globular clusters and ultra-compact dwarf galaxies that would otherwise be invisible without the deep VISTA infrared images. Using the unique VISTA data they plan to map how the galaxy formed and has evolved.

So, these are not just pretty pictures, there is a lot of science behind them. VISTA is going to allow us to unlock hidden mysteries of the universe and provide us a lot of astonishing pictures in the process. Everybody wins!