SRON astronomer Floris van der Tak is the first to have observed acidic particulate clouds outside of our own Milky Way galaxy. He did this by focusing the James Clerk Maxwell Telescope, located on Hawaii, on two nearby Milky Way galaxies. Astronomers think that acidification inhibits the formation of stars and planets in the dust clouds. Now it is a case of waiting for precise measurements from the SRON-built HIFI space instrument that will be launched on the Herschel space telescope next year. Van der Tak: ‘I have already submitted my observation proposal’.

M82 is een melkwegstelsel dat relatief dichtbij staat, op 12 miljoen lichtjaar. Aan de sterrenhemel staat M82 in het sterrenbeeld Grote Beer. (beeld: Hubble Space Telescope, NASA/ESA)

‘The quantity of charged molecules in the dust cloud appears to have an inhibitory effect’, says Floris van der Tak. ‘These ensure that the magnetic fields can exert a greater influence on the cloud, as a result of which the entire cloud becomes agitated and the star-forming process is disrupted’. Observing these charged molecules directly is difficult. The ratio of acidic water molecules to ordinary water molecules is a measure of the quantity of charged molecules.

De James Clerk Maxwell Telescope op Hawaii. (beeld: JCMT)

‘Amazingly, what causes these acid water molecules to be present in both Milky Way galaxies is completely different’, says Van der Tak. ‘In Arp 220 they develop under the influence of X-rays in the vicinity of the central supermassive black hole. In M82, the cause is the ultraviolet radiation emitted by hot young stars in the star-forming area. Therefore, in these particular galaxies the process of star formation inhibits itself, due to more and more charged molecules being created.’

HIFI wordt op dit moment gemonteerd op de ruimtetelescoop Herschel van de Europese ruimtevaartorganisatie ESA.(beeld: Astrium/ESA)

The results of Floris van der Tak's research are published this week in the scientific journal Astronomy & Astrophysics.