All posts by Garrelt Mellema

A cold dawn for the first stars

This morning, as I was walking from Tekniska Högskolan metro station to AlbaNova through the Siberian cold which has hit Stockholm, I was thinking about even colder temperatures than the -15 C that I felt on my skin. Did you know that the temperature of Universe was only 3 Kelvin (-270 C) when the first stars were born?! At least that’s what the authors of an article published in ’Nature’ this week claim to have measured and until proven differently they might well be right… Having worked on the … Continue Reading ››

LOFAR starts Cycle 0 observing

Last Saturday, December 1st, at 0:00 UT, LOFAR started its first official observing season, known as Cycle 0. The season will last 6 months and the observations that will be done are based on proposals that were sent in earlier this year. So as of last Saturday LOFAR can be said to be an operational telescope. I do not have detailed information on how the observing time in Cycle 0 will be distributed, but based on the decisions the Swedish LOFAR consortium made regarding the Swedish time, all different science … Continue Reading ››

The end for supermassive population III stars?

Are the first stars really very massive? Some 10 years ago, the idea that the first, metal-free stars would be very massive, became popular. Simple theoretical arguments about radiative cooling and complex numerical simulations both seemed to point to the formation of metal-free stars of masses of several 100s solar masses. Because of their zero metallicity they were dubbed Pop III stars. Early simulations of their formation are commonly associated with Tom Abel and Volker Bromm.

Spring time for LOFAR Sweden

As the Sun is finally warming up both the nature and people this far north, also the efforts to construct the Swedish LOFAR station awake from their winter sleep. From November until now snow and frozen soil stopped the work in its tracks, but today at Onsala near Göteborg on the west coast of Sweden, the building activities will recommence.

LOFAR is a European wide radio telescope consisting of stations spread out over the Netherlands, Germany, the UK, France and Sweden, with possibly more countries joining in the future.