Skip to ContentSkip to Navigation
About us Latest news News News articles

Cosmological 21cm experiments: Searching for a needle in a haystack

07 May 2010

Promotie: dhr. V. Jelić, 16.15 uur, Academiegebouw, Broerstraat 5, Groningen

Proefschrift: Cosmological 21cm experiments: Searching for a needle in a haystack

Promotor(s): prof.dr. S. Zaroubi, prof.dr. L.V.E. Koopmans, prof.dr. A.G. de Bruyn

Faculteit: Wiskunde en Natuurwetenschappen

Contact: Vibor Jelić, tel. +31 611445449, +31 503634050, e-mail:

Cosmological 21cm experiments: Searching for a needle in a haystack

About four hundred million years after the birth of our Universe the first objects were formed, which then started to ionize the surrounding gas with their strong radiation. Six hundred million years later, the all-pervasive gas was transformed from a neutral to an ionized state. This pivotal period in the history of the Universe is called the Epoch of Reionization (EoR). It holds the key to structure formation and evolution, but also represents a missing piece of the puzzle in our current knowledge of the Universe. Currently, this is changing with the completion of a new generation of radio telescopes, which are capable of directly probing the EoR. LOFAR is the first telescope of this kind, and will use an array of simple radio antennas to hunt for the radiation emitted by the neutral hydrogen during the EoR. The wavelength of this radiation is 21 cm, but on its way to us it is stretched by the Universe's expansion to the radio wavelengths of 1-2 m. However, its detection will be quite a challenge due to a number of complicating factors. For example, the desired signal is so weak that it is like a needle in a haystack, overwhelmed by the prominent foreground emission of our own Galaxy and other extragalactic radio sources. This thesis examines both the properties of the "haystack" and the way it influences the LOFAR-EoR experiment, and discusses the Cosmic Microwave Background radiation (the oldest radiation in the Universe) as an additional probe of the EoR.

Last modified:13 March 2020 01.16 a.m.
View this page in: Nederlands

More news

  • 13 October 2023

    Moniek Tromp appointed Captain of Science of the Top Sector Chemistry

    Prof. Moniek Tromp has been appointed Captain of Science of the Chemistry Top Sector by the Minister of Economic Affairs and Climate Policy. As from 1 July 2023, she succeeded Prof. Bert Weckhuysen from Utrecht University.

  • 12 September 2023

    Art in times of AI

    Leonardo Arriagada Beltran conducted his PhD research on the interface of computer-generated art and the constantly evolving field of Artificial Intelligence (AI). He will defend his Phd thesis on 21 September. His research offers valuable insights...

  • 28 August 2023

    Harish Vedantham and Casper van der Kooi nominated for 'Wetenschapstalent 2023'

    Harish Vedantham and Casper van der Kooi have been nominated by New Scientist for Wetenschapstalent 2023 (Science Talent 2023). This election is meant to give young scientists and their research a stage.