herve fontaine
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herve's posts
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We've come too far
To give up who we are

#music   #daftpunk   #welovemusicwednesday  ﻿
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How do we determine the shape of an asteroid ?

Even though some asteroids may be big (several tens of kilometers, even hundreds), they're also very far from us. Even with big telescopes, we can't determine the shape of the asteroid we're looking at.
But there's a technique that even amateur astronomers can use, and which is very helpful to compute the approximative shape of an asteroid : drawing its lightcurve !

As you can see with the animation of the asteroid (433)Eros attached, taken by the NEAR probe, it rotates.
The visible part of the asteroid receives light from the Sun, and if the asteroid is not round, as it rotates, the shape of the illuminated part changes. Some illuminated craters become dark, some hidden craters become illuminated ... All this contributes to the variation of brightness of the asteroid.

From Earth, you just can see a star-like point. But you can easily measure its brightness.
This is an example of lightcurve I got for the asteroid (22) Kalliope : http://www.flickr.com/photos/econseil/9784872335/
You can see 4 periods of rotation stuck together in what we call a phase diagram. The shape of the lightcurve repeats itself with a 4 hours period. The brightening and the fading of the asteroid are caused by its rotation. It's very easy to determine its period of rotation with such a curve.

All these lightcurves, mostly made by amateur astronomers, are gathered on this website : http://obswww.unige.ch/~behrend/page1cou.html
There are plenty of lightcurves shapes, corresponding to plenty of asteroid typical shapes (from pebbles to peanuts).
If you repeat such observations for months, you'll see the shape of the lightcurve move, as the angle from which we see the asteroid changes.

Then a 3D modelisation software is used by astronomers to build a 3D image of what the asteroid looks like. These modelisation have been successfully tested with asteroids that have been visited after by space probes, such as Eros. Here's an example with the asteroid Lutetia : http://benoit.carry.free.fr/news/big/2010-07-ESA-Lutetia.jpg

Image Credit : NASA & NEAR probe

#astronomy  #asteroid #shape﻿
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Taste of the Ocean on Europa's Surface (Artist's Concept)
Based on new evidence from Jupiter's moon Europa, astronomers hypothesize that chloride salts bubble up from the icy moon's global liquid ocean and reach the frozen surface where they are bombarded with sulfur from volcanoes on Jupiter's innermost large moon, Io. The new findings propose answers to questions that have been debated since the days of NASA's Voyager and Galileo missions. This illustration of Europa (foreground), Jupiter (right) and Io (middle) is an artist's concept. NASA/JPL-Caltech http://photojournal.jpl.nasa.gov/jpeg/PIA16826.jpg
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Last nights moon over the Blue River﻿
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Ya Know What Rock N Roll Is?
It isn't being extra loud.. or rude...or disrespectful or crass..
I'ts showing up KNOWING that whatever you do is going to absolutely win over every single soul in your presence and TOGETHER you're going to elevate to a level where everything feels just awesome!!!
THATS ROCK N ROLL.
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Everything Flows.

#surreal   #digitalart  ﻿
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Grandeur I

I've worked on a few images in the past for multiple hours, but this one is far and away the longest I've worked on a single image. I've put over 20 hours into this image over the last couple of weeks after capturing the initial data early one morning at the beginning of the month.
Although I love the result I'm not sure I can do many of these types of edits too often! ;-)

Image on my blog - http://www.andrewsgray.com/2013/09/new-image-grandeur-bamburgh-castle/
Image in my print shop - http://photos.andrewsgray.com/gallery2013/e7ad22181

#bwfineartle #longexposurephotography
#landscapephotography   ﻿
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СЕЙЧАС ДОБАВИМ ОСТРЫХ ОЩУЩЕНИЙ! )﻿