Posts Tagged ‘dark matter’

Yesterday (Thursday the 21st of March 2013), the European Space Agency (ESA) released its first results from the Planck satellite. The picture is shown below.


This picture is a picture of the temperature differences in the earliest image we can obtain of the baby Universe. These temperature differences, technically called “anisotropies” are what have led to the structure we see in today’s Universe. They provide a powerful way for us to determine all kinds of things about our Universe, including its age, geometry, and what makes up our Universe.


The first satellite to provide us with a view of these anisotropies was COBE, the Cosmic Background Explorer, a NASA satellite launched in the late 1980s. In 1992 it released this image, which caused a sensation.


The reason the image looks so “fuzzy” is because the detail with which COBE could see was limited, it only had a resolution of 7 degrees (a 7 degree patch, about 14 full Moons across, was the smallest patch it could see). The day it was released happened to be the day that Sir Arnold Wolfendale, who was then the “astronomer Royal” England, was visiting Cardiff, where I was finishing up my PhD. The press were constantly ringing the department to speak to him, and of course this was a time before mobile phones so the press kept the university’s switchboard pretty busy that day fielding calls for him.

Onwards to WMAP

Some 10 years later, a more detailed map was provided by NASA’s WMAP satellite. WMAP (Wilkinson Microwave Anisotropy Probe) had a much better resolution that COBE, as the image below shows.


Between COBE and Planck were a number of important experiments such as BOOMERANG (a ballo-borne experiment) and DASI (based at the South Pole and led by John Carlstrom of the University of Chicago where I was based at the time) which gave some very important information, but I think it is fair to say that it was WMAP that heralded in the era of what we now call “precision observational cosmology”. Using technical analyses of the WMAP image shown above, cosmologists have been able to determine the age of the Universe (13.7 billion years), its geometry (flat), and even that only some 5% is made up of ordinary matter, with about 28% being made up of the mysterious “dark matter” and some 67% made up of the even more mysterious “dark energy”.

Why launch Planck?

Planck was launched in March 2009 by the European Space Agency. It was actually launched on the same rocket which launched the Herschel Space Observatory which I blogged about here. Planck has a number of improvements over WMAP, and over the next few years results will be released of measurements WMAP did not have the capability to make. But, its first result is its map of the anisotropies. As this fantastic article from the New York Times explains, there are a number of confirmations of our already accepted theories in this first image, but also a number of things which will require us to re-think some things we thought we knew.

For example, initial analysis of the Planck image suggests the Universe is 13.8 billion years old, not 13.7 as calculated by the WMAP data. Also, it has determined the composition of the Universe to be 4.9% normal matter, 27 dark matter and 68% dark energy, slightly different from values determined by WMAP. The value for how quickly the Universe is expanding is also found to be different, WMAP determined a value of 67 km/s/Megaparsec and Planck determines a value of 69 km/s/Megaparsec. Some of the features in the WMAP image which some argued were an artifact of the way the image was produced are still present in the Planck image, which has been produced with an entirely different satellite and processed with an entirely different method. This suggests some of these features are, in fact, real.

A lot more analysis of even this first image will be done over the next several months, and Planck will continue to make measurements over the next several years to refine the image shown above, as well as to make measurements of things like the polarisation of the radiation coming from this earliest view of the Universe.

I will leave you with this wonderful graphic from the above mentioned New York Times article.


There has never been a more exciting time to be a cosmologist!

Read Full Post »