What if you could fly through the universe and see dark matter? While the technology for taking such a flight remains under development, the technology for visualizing such a flight has taken a grand leap forward with the completion of the Bolshoi Cosmological Simulation.
After 6 million CPU hours, the world’s seventh fastest supercomputer output many scientific novelties including the above flight simulation. Starting from the relatively smooth dark matter distribution of the early universe discerned from the microwave background and other large sky data sets, the Bolshoi tracked the universe’s evolution to the present epoch shown above, given the standard concordance cosmology. The bright spots in the simulation above are all knots of normally invisible dark matter, many of which contain normal galaxies. Long filaments and clusters of galaxies, all gravitationally dominated by dark matter, become evident.
Statistical comparison between the Bolshoi and current real sky maps of actual galaxies show good agreement. Although the Bolshoi simulation bolsters the existence of dark matter, many questions about our universe remain, including the composition of dark matter, the nature of dark energy, and how the first generation of stars and galaxies formed.
- For more information about the Bolshoi Cosmological Simulation, click here.
Credit: A. Klypin (NMSU), J. Primack (UCSC) et al., Chris Henze (NASA Ames), NASA’s Pleiades Supercomputer
Problem fixed? Finally fitting two observables at once in galaxy models.
Astronomers don’t just want to find interesting objects in space, they also want to understand them. To this end, many astronomers spend time trying to explain what they see with physical models and creating simulations to compare with their observations.
But, as you can guess, nothing ever goes completely to plan.
Semi-analytic models (SAMs) are a type of cheap, cut-and-paste simulation. Instead of simulating the entire Universe in a massive super computer (which is a bit expensive and tricky), only dark matter (and Newton’s Law of gravity) is simulated, which is a lot less complicated. Then, using a combination of rules derived from physics and best-guesses, a catalog of millions of galaxies is made and then placed where the dark matter is densest. This gives you a fake Universe to work with.
One problem: SAMs just don’t fit the observations. The Tully-Fisher relation is an observed trend between the luminosity (intrinsic brightness) of a galaxy and the speed at which the galaxy is spinning. But SAMs that fit the Tully-Fisher relation don’t have the right number of galaxies at particular luminosities (the luminosity function)! SAMs only fit one of these two observations. You can see the problem in figure 1, the x-axis is the rotation speed and the y-axis is the absolute magnitude (related to luminosity) with the black line of the old model not fitting the Tully-Fisher relation shown with the black data-points.
The authors of the paper (Cattaneo, Salucci and Papastergis) believe they’ve found a way to sort this problem out. They show that (like previous papers) the rotation speed of a galaxy’s disk is not the same as the speed at which the dark matter clump the galaxy is in would be spinning. It instead varies with the mass of the galaxy. Figure 4 is like figure 1 but shows the improved model fitting really well when you take this difference into account. Tada!
Paper: Cattaneo, Salucci, Papastergis 2014
Known to be behind the characteristic odor of rotting eggs, sulfur is essential for all living cells. Cells make proteins that form strong chemical bonds called disulfide bridges between two adjacent sulfur atoms. These bridges give strength to our hair, outer skin, and nails. Eggs are loaded with sulfur because disulfide bridges are needed to form feathers, which explains why eggs smell on rotting. Because sulfur is easy to smell, natural gas lines—which are normally odorless—have sulfur additives to help people identify and smell a gas leak when it occurs.
Image by Dr. Edward Gafford.
(image: optical in greyscale overlaid with radio in blue, showing the strength of radio light from these galaxies. The top-left galaxy was an unknown radio emitter before this study. Allison et al, 2014)
All atoms and molecules have a fingerprint. When light passes through a gas, very particular wavelengths of light are absorbed by the atoms and molecules. This makes it possible to identify elements within gases by looking at absorption in light passing through it. The element helium was first discovered in the Sun when we couldn’t match a mystery fingerprint to anything we knew then on Earth.
As hydrogen is the most common element in the Universe, looking for the fingerprint, or “spectrum”, of hydrogen imprinted in light coming from distant galaxies can tell you a lot about the gas absorbing it, from the speed the gas is travelling, the distance from Earth and how much is there. The brightest line in the hydrogen atom spectrum is at a wavelength of 21cm (in the radio), aka the “21cm line”, which in coming years will be a hot topic of research in astronomy.
A recent study of over 200 nearby galaxies has shown that it’s possible to detect the 21cm absorption line where the background radio light has come from the galaxy itself. Usually the background light comes from a bright but distant radio source, or observers pick galaxies with known bright radio light rather than taking a wider sample. This study shows that it’ll be possible in the future, with telescopes like the SKA (the Square Kilometre Array), to use the 21cm line to find out more about a wider, less biased selection of galaxies. Read more in the paper [here].
An extratropical cyclone over the United Kingdom, imaged by NASA’s Terra Satellite on February 12th, 2014. This storm caused heavy rains, flooding, winds in excess of 160 kilometers per hour, and power outages for more than 700,000 people. January was recently declared the wettest month on record by the UK Met Office.
A cluster of galaxies 10 billion years old has been found!
A group of astronomers in the HerMES consortium led by Dave Clements (Hi Dave! And co-authors Filiberto and Ashley! :waves:) have found four new galaxy clusters, one of which contains galaxies whose light has been travelling towards Earth for about 10 billion years.
The blobs in the image (from the Herschel Space Observatory, a far-infrared space telescope) are very distant galaxies. On the whole, the redder the galaxies the further away they are (blue would be closer). Finding groups of red galaxies would be tricky from this image alone, but the team used whole-sky data from another space telescope (the Planck satellite) which has a lower resolution, with blobs the size of the green circle. It’s a bit like a blurry version of the Herschel images. So by finding the really red areas in the Planck data, then double-checking what they look like in the Herschel, you can check whether you’ve found distant galaxy clusters!
These clusters show us where the densest parts of the Universe are. The number and sizes of clusters we find can also tell us about the different amounts of matter/dark energy/etc the Universe has (i.e. the Cosmology).
Read more: here
Image credit: Clements et al 2013
Saturn’s rotation in three different infrared wavelengths.
Credit: Cassini-Huygens mission/JPL/Space Science Institute
I feel that as a photographer, creativity and experimentation are two extremely important things. I decided to play around with the idea of a composite image, and this is the result. Needless to say, composites are definitely a work in progress for me. Nevertheless, it’s always fun and exciting learning and trying new things/methods for photography
Curiosity rover on Mars has captured its first view of Earth from the surface of the red planet — a striking image that shows our home planet as a bright light in the Martian sky.
“Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. ” — Carl Sagan on Pale Blue Dot
Read more here. Credit: NASA/JPL-Caltech/MSSS/TAMU
"GAIA comes into focus"
ESA’s GAIA is getting ready to take data! Images like this one of the star cluster NGC1818 in the Large Magellanic Cloud are allowing the GAIA team to calibrate the telescope in preparation for the main show; observations of the brightest ~1% of stars in our galaxy (plus loads of other exciting astronomy going on in the background of images!).
Read More: at ESA.int
Image Credit: NGC1818, ESA/DPAC/Airbus DS