Wednesday 20 May 2009
Friday 15 May 2009
Planck and the Cosmic Microwave Background
The European Planck surveyor satellite will map the entire sky at microwave wavelengths - why is this important? Scientist will be able to scrutinize models which explain the formation of galaxies by measuring fluctuations in the distribution of dark matter, only a mere 300 000 years after the big bang. These fluctuations manifest themselves as small variations of the mean sky temperature of 3 degrees Kelvin and have been generated when the first atoms were formed in cosmic history. From these seed fluctuations larger and larger objects were assembled by gravity which finally resulted in the formation of galaxies and clusters of galaxies. Important cosmological parameters are the amplitude of these seed fluctuations and the mean density of matter, which Planck will be able to measure.
A large part of the scientific programme is devoted to so-called secondary anisotropies: these are fluctuations of the sky temperature which are generated by the interaction of photons of the microwave background with the large-scale distribution of galaxies. There are basically two categories of interactions: gravitational lensing, which can be used for precision measurements of cosmological parameters, and Compton-interactions with electrons of the hot gas inside clusters of galaxies - a potential new powerful way of detecting clusters of galaxies.
Planck's advantage over previous experiments is its high sensitivity and angular resolution: it can measure fluctuations of a few microKelvin, and its angular resolution is better than a tenth of a degree. The survey will be carried out from the Lagrange-point L2, at roughly 1.5 million kilometers from Earth - 5 times the mean Earth-Moon distance. The science team of Planck comprises about 500 scientists who are anxious to see the satellite launched on 14 May 2009, after 15 years of preparation.
Written by Bjoern Malte Schaefer
Appeared in the Italian translation on Il Denaro, 14.05.2009
Image: map of the microwave sky as observed by NASA's satellite WMAP, launched in 2001. Different colours represent the tiny fluctuations in temperature: the difference between red and blue spots is only 0.0002 degrees. Planck's maps will be even more precise than that. Credits: NASA/WMAP team.
A large part of the scientific programme is devoted to so-called secondary anisotropies: these are fluctuations of the sky temperature which are generated by the interaction of photons of the microwave background with the large-scale distribution of galaxies. There are basically two categories of interactions: gravitational lensing, which can be used for precision measurements of cosmological parameters, and Compton-interactions with electrons of the hot gas inside clusters of galaxies - a potential new powerful way of detecting clusters of galaxies.
Planck's advantage over previous experiments is its high sensitivity and angular resolution: it can measure fluctuations of a few microKelvin, and its angular resolution is better than a tenth of a degree. The survey will be carried out from the Lagrange-point L2, at roughly 1.5 million kilometers from Earth - 5 times the mean Earth-Moon distance. The science team of Planck comprises about 500 scientists who are anxious to see the satellite launched on 14 May 2009, after 15 years of preparation.
Written by Bjoern Malte Schaefer
Appeared in the Italian translation on Il Denaro, 14.05.2009
Image: map of the microwave sky as observed by NASA's satellite WMAP, launched in 2001. Different colours represent the tiny fluctuations in temperature: the difference between red and blue spots is only 0.0002 degrees. Planck's maps will be even more precise than that. Credits: NASA/WMAP team.
A high for geeks
Ok, these days all the astronomers and astrophysicists I know - and, with me being a geek, this is a substantial fraction of the people I know and hang out with - have been overly excited with the launch of Planck and Herschel, the two satellites I mentioned in the previous post.
Will they launch them?
When?
Why is the launch being constantly delayed later and later?
Will they be launched eventually?
Today?
Tomorrow?
In two weeks?
Please, shoot the freaking rocket!
And indeed, they did. :-)
And, although I would have never expected neither me nor some of my friends exhibit a similar reaction, we were in fact all somehow high, and strangely happy for the two big thermometers finally flying in the sky.
They say Planck is super-cool.
The coolest thing in the universe.
Literally.
Well, almost.
Well, only for a year.
Well, whatever. Once a geek, always a geek.
In the previous post, I promised to write more about Planck and what it's going to probe, the CMB. Which is great, and cool, yay! However, I'm also *pretty* busy with something else, just this little thing, you know... my phd defense... so sorry, Planck high or not, I'm clearly busy. Busy freaking out.
But don't despair! I delegated the explanation of the mysteries of the universe that will be unravelled by Planck to my friend and colleague Bjoern, who happens to be a much more respected authority than myself, mainly about everything, and in the specific case, about the CMB, of course --> see next post.
Image: abridged from Andy Riley, The Book of Bunny Suicides.
Credits: well, my friends :-)
Disclaimer: the US flag is not supposed to be there!!! Planck is not a US mission, but mostly European (ESA)!!!
We decline responsabilities.
It's a poetic licence.
Please, forgive us.
Turns out, we're not that geek, after all.
Will they launch them?
When?
Why is the launch being constantly delayed later and later?
Will they be launched eventually?
Today?
Tomorrow?
In two weeks?
Please, shoot the freaking rocket!
And indeed, they did. :-)
And, although I would have never expected neither me nor some of my friends exhibit a similar reaction, we were in fact all somehow high, and strangely happy for the two big thermometers finally flying in the sky.
They say Planck is super-cool.
The coolest thing in the universe.
Literally.
Well, almost.
Well, only for a year.
Well, whatever. Once a geek, always a geek.
In the previous post, I promised to write more about Planck and what it's going to probe, the CMB. Which is great, and cool, yay! However, I'm also *pretty* busy with something else, just this little thing, you know... my phd defense... so sorry, Planck high or not, I'm clearly busy. Busy freaking out.
But don't despair! I delegated the explanation of the mysteries of the universe that will be unravelled by Planck to my friend and colleague Bjoern, who happens to be a much more respected authority than myself, mainly about everything, and in the specific case, about the CMB, of course --> see next post.
Image: abridged from Andy Riley, The Book of Bunny Suicides.
Credits: well, my friends :-)
Disclaimer: the US flag is not supposed to be there!!! Planck is not a US mission, but mostly European (ESA)!!!
We decline responsabilities.
It's a poetic licence.
Please, forgive us.
Turns out, we're not that geek, after all.
Monday 4 May 2009
surprise surprise!
as this picture shows, the (visible) light that we see with our own eyes is just a teeny tiny portion of what is called the electromagnetic spectrum:
the picture actually comes from a t-shirt (but if you happen to land on that page, please do not read any of the comments, they're all wrong!!!) but the designer borrowed the idea from a science book, so it's pretty useful. look at the names above: don't they evoke any memories?? gamma rays, x-rays, ultra-violet, infra-red, microwave, radio... although we might relate different real-life concepts to each of them, they are basically the same thing: radiation, light, just like the one we see with our very own eyes. just, with different, very different energy, the gamma rays being the most energetic, and down all the way to the radio.
astronomical objects, such as stars, galaxies and other stuff, emit all these sorts of radiation, from gamma to radio. fortunately for us, the earth's atmosphere absorbs most of them (because they would be dangerous or even lethal to living creatures), that means that from earth we can only observe in the visible and in the radio band. yes, they are also referred as spectral bands.
but if we shoot a nice (and super expensive) satellite up into the skies, so that it orbits the earth, then we can observe in the whole spectrum, and gain a lot more information about all sorts of astronomical sources and the physical processes happening there. that's why Planck and Herschel will be launched soon (check prev post) and many other satellites are already up there doing this job.
beware: recently i'm reading over and over people writing that waves in other bands besides the visible are sound waves. like that we could listen to the sound of the stars. SO NOT TRUE. sound waves are one thing, electromagnetic waves (ie. light) are a totally different thing. maybe it's the "radio" word that creates confusion. maybe the word "frequency". whatever. the only difference between radio and visible and gamma rays is THEIR ENERGY!!!
don't know if i managed to be clear enough. maybe not. i'd need to get started with an intro to waves. and if you happened to be on this blog, you probably already know.
anyway: don't listen to stars - or to whatever other weird ideas crazy people have!!!
Image credits: Threadless - www.threadless.com
the picture actually comes from a t-shirt (but if you happen to land on that page, please do not read any of the comments, they're all wrong!!!) but the designer borrowed the idea from a science book, so it's pretty useful. look at the names above: don't they evoke any memories?? gamma rays, x-rays, ultra-violet, infra-red, microwave, radio... although we might relate different real-life concepts to each of them, they are basically the same thing: radiation, light, just like the one we see with our very own eyes. just, with different, very different energy, the gamma rays being the most energetic, and down all the way to the radio.astronomical objects, such as stars, galaxies and other stuff, emit all these sorts of radiation, from gamma to radio. fortunately for us, the earth's atmosphere absorbs most of them (because they would be dangerous or even lethal to living creatures), that means that from earth we can only observe in the visible and in the radio band. yes, they are also referred as spectral bands.
but if we shoot a nice (and super expensive) satellite up into the skies, so that it orbits the earth, then we can observe in the whole spectrum, and gain a lot more information about all sorts of astronomical sources and the physical processes happening there. that's why Planck and Herschel will be launched soon (check prev post) and many other satellites are already up there doing this job.
********
beware: recently i'm reading over and over people writing that waves in other bands besides the visible are sound waves. like that we could listen to the sound of the stars. SO NOT TRUE. sound waves are one thing, electromagnetic waves (ie. light) are a totally different thing. maybe it's the "radio" word that creates confusion. maybe the word "frequency". whatever. the only difference between radio and visible and gamma rays is THEIR ENERGY!!!
don't know if i managed to be clear enough. maybe not. i'd need to get started with an intro to waves. and if you happened to be on this blog, you probably already know.
anyway: don't listen to stars - or to whatever other weird ideas crazy people have!!!
Image credits: Threadless - www.threadless.com
so cute!
ok, i'm not usually this cheesy, but i really find this photo so cute!
it shows the satellite Herschel reflected in the mirror of the satellite Planck, which will (hopefully!) be launched next week, sharing the same rocket. that's why i actually found the picture totally sweet!
Herschel will observe the sky in the infrared, whereas Planck will scan it in the microwave, focussing on the CMB (cosmic microwave background), ie. the relic signature coming from the big bang.
ok, maybe it's a bit confusing... if infrared and microwave don't tell you much, check the next post for clarification. and check this blog soon for more about the CMB and Planck...
Image credits: ESA
it shows the satellite Herschel reflected in the mirror of the satellite Planck, which will (hopefully!) be launched next week, sharing the same rocket. that's why i actually found the picture totally sweet!Herschel will observe the sky in the infrared, whereas Planck will scan it in the microwave, focussing on the CMB (cosmic microwave background), ie. the relic signature coming from the big bang.
ok, maybe it's a bit confusing... if infrared and microwave don't tell you much, check the next post for clarification. and check this blog soon for more about the CMB and Planck...
Image credits: ESA
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