Scientists have created a detailed map of the Milky Way using two of the world’s largest fully steerable radio telescopes in Germany and Australia. The research looked at neutral atomic hydrogen—the most abundant element in space and the main component of stars and galaxies—across the whole sky in a survey known as HI4PI.
The project required more than a million individual observations and about ten billion individual data points.
University of Bonn astronomer Dr Juergen Kerp said although neutral hydrogen is fairly easy to detect with modern radio telescopes, mapping the whole sky is a significant achievement.
“Radio ‘noise’ caused by mobile phones and broadcast stations pollute the faint emissions coming from stars and galaxies in the Universe,” he said.
“So sophisticated computer algorithms have to be developed to clean each individual data point of this unwanted human interference.
“Next to the thousands of observing hours an even larger amount of time has been spent creating the final scientific data product released today.”
The HI4PI survey used CSIRO’s Parkes Observatory and the Effelsberg 100m Radio Telescope operated by the Max-Planck Institute for Radio Astronomy.
It improves the previous neutral hydrogen study, the Leiden-Argentine-Bonn (LAB) survey, by a factor of two in sensitivity and a factor of four in angular resolution.
Professor Lister Staveley-Smith, from the International Centre for Radio Astronomy Research, said the study reveals fine details of structures between stars in the Milky Way for the first time.
“These structures had been smeared out by the coarse sampling of the sky in the LAB survey,” he said.
“Pilot studies of the HI4PI data show a wealth of filamentary structures never seen before.
“Tiny clouds become visible that appear to have fueled star formation in the Milky Way for billions of years.
“These objects are too dim and too small to be detected even in the other galaxies closest to us.”
Dr Benjamin Winkel, from the Max Planck Institute for Radio Astronomy, said having a clearer picture of the hydrogen in the Milky Way would also help astronomers to explore galaxies even at cosmological distances.
“Like the clouds at the sky, all observations we receive from the distant Universe have to pass through hydrogen in our own Milky Way,” he said.
“The HI4PI data allows us to correct accurately for all these hydrogen clouds and clean the window we are watching through.”
The research has been published in the journal Astronomy and Astrophysics.
HI4PI data will be freely available to scientists around the world through the Strasbourg astronomical data centre.