July 12, 2010
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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.
July 9, 2010
The sample canister of Hayabusa, the troubled probe which had a dramatic re-entry back in June, has now been opened and it has some material in it! This is great news! Due to malfunctions it wasn’t clear if the probe managed to collect material from the rubble pile asteroid Itokawa, but JAXA has found a very small amount of dust particles in the container. It isn’t clear if the dust grains which are very small, about 0.01-millimeter in size, are from the asteroid itself, or if it could be from Earth — left in the container from before launch, or it possibly could have made its way in there during the landing/post landing handling. “Material on the planet or asteroid or particulate matter is at this stage is unknown, we will consider in detail,” is the Google translate version of the JAXA press release. The image above was taken on June 28, 2010, and below is a magnified view of one of the particles.
This magnified view was taken on June 29, and shows a magnified view of one very small particle being picked up by a quartz manipulator, which appears as a stripe on the image. It will take several weeks to confirm whether the particles are from the asteroid, but if so, would be the first-ever asteroid sample return.
What do you think about this? Do you think Hayabusa brought some asteroid dust back? Or maybe we can just ask Paul the Octopus! Leave a comment!
Astronomers have now confirmed that an object imaged back in 2008 is a direct image of an exoplanet orbiting a star.
This image, taken in 2008 by the Gemini North telescope in Hawaii, shows the star 1RXS J160929.1-210524 (I’ll call it 1RXS 1609) in the center, and the planet (1RXS 1609b) indicated by the red circle. The star is a bit smaller and slightly cooler than our sun.
The problem was, that the object might have been a background object like a star or a background galaxy. It has happened before. However, follow-up observations have shown that it is neither a star nor a galaxy, it is indeed a planet orbiting the star.
On this graph, the separation of the object and the star are shown in the y-axis, and time is shown on the x. The star is moving slowly as it orbits the centre of our galaxy. If the object was moving separately it would be near the or on the purple line, changing as they moved separately. If the object were a planet the separation wouldn’t change much as they moved together across the sky. The observation of the planet is shown as black dots in this picture, they fall right on the line making it an object orbiting a star, which pretty much makes this a planet.
The star is about 500 light years away and the planet has a mass 8 times that of Jupiter, it orbits the star 47 billion kilometres away, that’s about 300 times the distance of Earth form the sun and has a temperature of about 1500 C. The star is a bit less massive than the sun and not nearly hot enough to heat the planet up to that temperature. The reason the planet is so hot is that it’s very young. The contraction of the planet under its own gravity during its formation quickly raised its temperature to thousands of degrees. Once this contraction phase is over, the planet will slowly cool down by radiating infrared light. In billions of years, the planet will eventually reach a temperature similar to that of Jupiter.
This discovery is a great technological achievement because the planet and the star are very close together, it’s very difficult to separate them. From the ground the Earth’s atmosphere blurs out the image and scatters the light of the star, making it very difficult to see objects like this. Even more remarkable thing is that they even got the spectra of the planet and used that to determine the temperature of the planet.
However, it’s not he the first the first planet which has been directly imaged. That title belongs to planet 2M1207b, which orbits a brown dwarf about 230 light years away. While brown dwarfs are cooler and smaller than the Sun, and they don’t fuse hydrogen into helium in their core, some people don’t consider them real stars. So it’s not really a sun-like star. But a planet orbiting a sun-like star has already been observed by telescopes in space. Since this observation was made from a ground based telescope, it is the first planet directly observed orbiting another star from a ground based telescope, which is very cool. It’s easier to make observations from space than it is from the ground, on the ground there is a lot of atmospheric scattering which makes the task a lot more difficult and that makes it much more remarkable.
We’re directly seeing worlds orbiting other stars from our world…THAT’S AWESOME!
July 1, 2010
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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.