Wednesday, October 5, 2011

Nobel Prize in physics and ESA Cosmic Vision

Two things happened on October 4, 2011 –
  1. the Nobel committee announced that its physics award goes to Saul Perlmutter and Adam Riess of the US and Brian Schmidt from Australia for  the research that identified the "accelerating expansion of the Universe", see
  2. ESA Cosmic Vision panel approved two middle size missions as a part of its Cosmic Vision 2015-2025 plan. These are Euclid and Solar Orbiter.
Saul Perlmutter, Adam Riess and Brian Schmidt studied Type Ia supernovae and found that the most distant of them are moving back quicker that those that are close. This observation, in turn led, to the theory that the Universe is expanding and that some mysterious energy – the “dark energy” must be behind the expansion. However, currently, we have no idea what it might be.
ESA's Euclid is a mission that will investigate this "dark energy", which is believed to be responsible for driving the Universe apart. As is states on the ESA web site “the mission will map out the large-scale structure of the Universe with unprecedented accuracy. The observations will stretch across 10 billion light years into the Universe, revealing the history of its expansion and the growth of structure during the last three-quarters of its history”, see Euclid supposes to launch in 2017.
However, the methods the Euclid will use to investigate dark energy (I am dropping “” for dark energy here) are different than those that Noble trio and their colleagues used.
Euclid is designed to study the influence of dark energy by probing Weak gravitational Lensing (WL) and Baryonic Acoustic Oscillations (BAO).

- WL allows registering very faint distortions in the way galaxies appear as on the sky, which, in tur,n allows detecting mass inhomogeneities along the line-of-sight.
- BAO are wiggle patterns in the three dimensional distribution of clusters of galaxies. By measuring them, we can determine the redshifts of galaxies with accuracy better than 0.1%. This method can be used as a standard ruler to measure dark energy and the expansion in the Universe.
For more information, refer to

In terms of instruments WL requires extremely high image quality and BAO requires fine spectroscopy. Both techniques employ fine infrared detectors which ESA currently buys from US.

The mission that  has the concept of using Type Ia supernovae to probe dark energy is the future NASAs  Wide-Field Infrared Survey Telescope or WFIRST.

The Astro2010 Decadal panel identified WFIRST ( as the top priority mission for the upcoming decade. However, NASA's James Webb Space Telescope is scheduled to launch in 2018 and this large mission is keeping WFIRST from being implemented until perhaps the 2020s.

As proposed, WFIRST will measure the properties of more than a thousand supernovae which can be used to directly calculate the luminosity distance (DL). On the other hand, certain spectral features in the supernova light can be used to identify z (redshift) and provide the distance-redshift relation D(z), which is a primary observable of the effect of dark energy. For more information, see

But WFIRST is delayed to 2020s the soonest.

I wonder if S. Perlmutter's and colleagues' Nobel price can help NASA find the money to build WFIRST sooner?

As alternative, NASA can ask about participation in Euclid. I know that in the past ESA offered NASA a 20% partnership in the mission.  NASA, for example, could provide the infrared detectors which are not available in Europe (yet). I don’t think NASA can get more participation, especially after issues with IXO ( But it would be great to have at least 20%, although I wonder if it would be possible.

S. Perlmutter, G. Aldering, G. Goldhaber, R.A. Knop, P. Nugent, P.G. Castro, S. Deustua, S. Fabbro, A. Goobar, D.E. Groom, I. M. Hook, A.G. Kim, M.Y. Kim, J.C. Lee, N.J. Nunes, R. Pain, C.R. Pennypacker, R. Quimby, C. Lidman, R.S. Ellis, M. Irwin, R.G. Mc (1998). Measurements of Omega and Lambda from 42 High-Redshift Supernovae Astrophysical Journal
BBC news -