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!
June 18, 2010
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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!