Since the beginning of the Space Age, man has sent many manned and unmanned missions into space. Very powerful telescopes, built around the world, broaden our vision and understanding of the universe. Spacecraft, whether visiting other worlds or orbiting the Earth send us images and data collected from our outer atmosphere to the outer planets and beyond.
However, all this was only possible thanks to the incredibly rapid development of technology in recent years. Only then, could the essential resources for the construction of the current generation of spaceships be developed.
So, let us talk a little about some of the most important of space exploration’s tools and its greatest discoveries in this series, called Astronomy Tech.
In this first post, let’s get to know Cassini-Huygens a bit better. It is a joint mission between NASA, the European Space Agency (ESA) and the Italian Space Agency (ISA), which has uncovering the secrets of Saturn, including its rings and moons, as its primary objective.
On October 15th, 1997, the Cassini-Huygens spacecraft – composed of NASA’s Cassini orbiter and the ESA’s Huygens probe – was launched, beginning a long and complex seven-year journey, including gravitational slingshot manoeuvres around Venus, Earth and Jupiter. After arriving at its destination, the mother ship; Cassini, began its main objective exploring Saturn, whilst the Huygens probe was lunched and landed on Titan –Saturn’s largest moon and the second largest in the Solar System, after Jupiter’s moon Ganymede.
The spacecraft’s name was a tribute to the Italian Jean-Dominique Cassini (1625-1712) – discover of the Saturnine satellites Iapetus, Rhea, Tethys and Dione. In 1675 he discovered what is known today as the ‘Cassini Division’, the narrow gap separating Saturn’s A and B rings. Christiaan Huygens (1629-1695) was a Dutch scientist who first described Saturn’s rings and, in 1655 he discovered the moon Titan.
The Cassini spacecraft has a set of 12 instruments on-board. Some of them work in similar ways to our own. However, the instruments on the Cassini spacecraft are much more advanced than our own.
Cassini can “see” in wavelengths of light that the human eye cannot. The instruments on the spacecraft can “feel” things about magnetic fields and tiny dust particles that no human hand could detect. This means that Cassini can, for example ‘see the temperature’ of the objects it observes.
The magnetic field and particle detectors take direct sensing measurements of the environment around the spacecraft. These instruments measure magnetic fields, mass, electrical charges and densities of atomic particles. They also measure the quantity and composition of dust particles, the saturation of plasma (electrically charged gases), and radio waves.
Exploring the Ringed Planet
The expected return to Saturn – which hadn’t been visited by any spacecraft since Voyager 2 left Saturn’s orbit in 1981, – happened in July 2004. Since then, Cassini has made great discoveries about the Saturnine System and taken some terrific pictures, like the one below.
A few days after reaching Saturn, Cassini released the Huygens probe to land on Titan. On January 14, 2005, during its fall, six instruments analysed Titan’s atmosphere. According to the returned data, Titan has a nitrogen rich atmosphere. It also confirmed that Titan’s orange colour is due to the presence of hydrocarbons, formed when sunlight breaks down the abundant methane molecules within the atmosphere.
These results have given scientists a glimpse of what Earth might have been like before life evolved. They now believe Titan possesses many similarities to the Earth, including lakes, rivers, channels, dunes, rain, snow, clouds, mountains and possibly volcanoes.
Isn’t over yet; every day, it sends us vast amounts of data back to astronomers allowing them to resolve and answer questions about Saturn and our own planet.
As we prepare to announce the results of this year’s competition tomorrow it seems fitting that last year’s results are published now.
So lets take a fond look back at some of the many wondrous astronomical images 2010 brought us -
The best image of a body within our Solar System 2010 was-
Enceladus captured by NASA’s Cassini Orbiter.
It captures the beauty of Saturn’s moon Enceladus. Despite being only 500 kilometres in diameter Enceladus is a dynamic world with cryovolcanic processes in action that create huge geysers spouting high above the moon wherever they can find a weak point in the frozen surface.
Several of these geysers have been captured in this image, and it is these features that exposed Enceladus to be more than a ball of ice.
You can view more Cassini images here.
2010′s best image of an object outside our own galaxy was-
NGC 3982 as seen by Hubble.
This stunning galaxy is a face on spiral, located around 68 million light years from us here on Earth. It lies within the Northern constellation Ursa Major (The Great Bear).
The galaxy displays beautiful clouds of active hydrogen gas (pink spots), new formed star clusters (blue spots) and lashings of dust lanes which will one day collapse to form the next generation of stars.These features, combined with the galaxy’s beautiful spiral arms, make the galaxy a stunning sight.
Despite its beauty the galaxy is somewhat petit being a ‘mere’ 30,000 light years across which makes it 1/3 the size of our our galaxy the Milky Way.
The image was created using exposures obtained between 2000 and 2009 by Hubble’s Wide Field Planetary Camera 2 (WFPC2), the Advanced Camera for Surveys (ACS), and the Wide Field Camera 3 (WFC3).
Finally the one you have all been waiting for the best image outside our Solar System though within the Milky Way, which is also the best image overall 2010 is -
The Lagoon Nebula as seen by Hubble.
The nebula is located somewhere between 4,000 and 5,000 light years from the Earth and lies in the constellation Sagittarius (meaning it is in the direction of the centre of our galaxy).
The image is a close up of the gas and dust near the centre of the nebula. It is being illuminated by the fierce ultraviolet light of young, high mass stars nearby making the gas and dust glow and emit their own light allowing the nebula to be classed as an emission nebula rather than a reflection nebula like DC 129. The nebula is a huge star producing factory(over 100 light years across) with its clouds slowly collapsing into the next generation of stars.
Some of these new stars are trying to absorb more material than they can stomach and the result is a stream of material being blown out at their poles (by bi-polar outflow for those interested), called Herbig-Haro objects. Several new such objects have been discovered in the nebula in recent years allowing astronomers to gain a deeper insight into how young stars form and interact with their environment.
This image carries spectacular detail showing ‘tiny’ ripples in the nebula making its maritime name seem fitting. Unlike the patterns on the surface of the sea, these are not caused by tides or the wind, but by the immense power of ultraviolet radiation blowing away the gas and dust that forms the nebula. The patterns result from tiny differences in the density of the gas making some sections harder to blow away than others.
If you are lucky enough to live away from light pollution and have clear skies it is possible to see the Lagoon nebula with your own eyes as a fuzzy grey patch in the Milky Way, though it takes a reasonable sized telescope to make out any details.
The image was captured by Hubble’s Advanced Camera for Surveys (ACS) and shows hydrogen in red. Light from ionised nitrogen in green and light through a yellow filter in blue.
You can read more about this image here.
Be sure to return tomorrow when we announce the results of this year’s competition!
NASA’s Cassini Orbiter never ceases to produce stunning images;
The image shows Saturn clearly on the right hand side, with spectacular storm patterns visible in its atmosphere. The planet’s rings are also clearly visible, complete with their shadow falling on the upper clouds of their parent planet.
The large moon is the monstrous Titan – at nearly 5200 kilometres across Titan is Saturn’s largest moon and the second largest in the Solar System after Jupiter’s Ganymede. Titan is also the only moon in the Solar System to have a substantial atmosphere. A permanent orange smog rich in methane and hydrocarbons surrounds the moon making it impossible to study its surface without the use of radar and I-R imaging techniques.
The tiny dot sitting just below the rings on the far right is the smaller icy moon Enceladus. Famous for its cryovolcanic jets that fire huge amounts of water high above its surface. Enceladus is much smaller than Titan at just 504 kilometres across but even this is massive compared to the third moon in the image.
To the far left is a tiny speck that marks the tiny moon Pandora. At just 81 kilometres across Pandora is a tiny ball of rock. In fact it is so small it was increased in brightness by a factor of two in this image to make it visible at all. Unfortunately we cannot use the full resolution image here on our website so as far a I can see Pandora is not visible in the image displayed above however it is visible in the full resolution image available here.
Saturn is the sixth planet out from the sun and is the second of the gas giants, it is also the second largest planet after Jupiter. It has been a popular target for observation for many centuries, and it formed the outer limit of the early solar system as it is the last planet clearly visible to the naked eye.
Saturn has many interesting features: – Despite it being the second largest planet in solar system it is also the least dense. It is so diffuse that if Saturn was placed in a trough of water (it would have to be impossibly large of course! ) it would float, this means that Saturn’s average density is less than 1gcm3.
Saturn also possesses the most spectacular ring system in the solar system. Ten complete ring have been discovered with another two discovered incomplete rings or ring arcs. The most recent ring to be discovered is the Phoebe Ring, this is a massive ring on the exterior of the ring system. It is a tenuous collection of dust particles and is believed to extend from around 59 Saturn radii out to around 300 Saturn radii. It is nearly invisible and is undetectable by the human eye and amateur telescopes. Despite being difficult to detect the ring has been shown to be around 20 times the thickness of the planet itself.Its creation is believed to be a result of micrometeorid and larger impacts on the moon Phoebe (from which the ring gets its name). The moon Phoebe has an average orbital distance Saturn radii which puts well within the ring itself. Material from the ring slowly moves inwards towards the planet due to a process called infalling – this in itself is caused by incoming solar radiation destabilising the ring’s components orbits. This added to Saturn’s gravity is slowly causing the breakup of all the rings as they slowly migrate towards the planet’s upper atmosphere where they are absorbed. Don’t worry though the rings will remain a prominent feature for millions of years yet! If the Phoebe was visible to the naked eye it would make Saturn appear larger in the sky than the full moon!
The other main rings in the Saturnine system are (travelling from the outer atmosphere) D, C, B, A, F – All of these are found in the main ring system – G, E – these are found outside the main ring ‘belt’. There are numerous divisions or gaps in the rings, small separations are called gaps with larger ones called divisions. Some of the main divisions are: – The Cassini division between rings A & B and the Roche division between rings A & F. Some of the gaps include the Encke and Keeler gaps both are found within A ring.
This image is only here to demonstrate the diversity of the rings. For a detailed look at them I advise you to open the image in another tab of your browser, unfortunately site limitations prevent me from doing it full justice directly in the post.
The rings are held in place and maintained by some of Saturn’s 63 moons – these are fittingly called shepherd moons. Each of the shepherd moon’s gravity helps keep the rings orbit stable and helps to maintain its structure. In some cases particular orbital resonances - orbital distance ratios – have created the many gaps in the ring and it is also this phenomenon that prevents these gaps from ‘closing’. Sometimes shepherd moon work in pairs, an example Pandora and Prometheus - This pair is responsible for maintaining the G ring.
NASA’s Cassini Orbiter continues to send us fantastic images of Saturn, its rings and its moons. This latest image is no exception, it shows Saturn’s rings almost edge on along with five of the majestic planet’s expansive collection of moons.
Going from the right hand side of the image and moving to the left, we have – Rhea, Mimas (a.k.a. the Death Star moon after its uncanny resemblance to the infamous space station), Enceladus, Pandora and Janus.
Although the image is black and white it was created using the green section of the electromagnetic spectrum.
Cassini will continue to produce stunning images like this for quite some time to come.
You can read more here
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