Scientific research

The Dwingeloo Radio Telescope was used for astronomical research for over forty years. The most important scientific contributions are:

  • Investigation of the structure of the Milky Way using the 21 cm hydrogen line of the neutral hydrogen. This revealed a structure of the Milky Way more complicated than originally thought. For example, astronomers found a spiral arm in the inner part of the Milky Way that made an expanding movement and they discovered clouds of hydrogen gas above the Milky Way moving towards us with great velocity.
  • In the same way, the structure of a number of extragalactic systems has been investigated, such as the Andromeda Nebula (M31), the Triangle Nebula (M33) and the Pinwheel Galaxy (M101).
  • Observations with the 21 cm line showed that the radio source Sagittarius A (Sgr A) coincides with the center of the Milky Way.
  • Research of radio waves from the Milky Way, and their polarization, on various frequencies around 400, 500, 600, 800 and 1400 MHz produced a first catalog of discrete radio sources, insight into the structure of the magnetic field of the Milky Way and fragmented shells of very old supernova remnants.
  • Observations on a different radio spectral line, the 18 cm OH line of the OH molecule, which were combined with observations in infrared in areas of active star formation.
  • Determination of the absolute radio spectra of the four strongest radio sources:
    – Cassiopeia A (Cas A), a supernova remnant in the Milky Way;
    – Cygnus A (Cyg A), an extragalactic system;
    – Taurus A (Tau A), the Crab Nebula (M1), a supernova remnant in the Milky Way;
    – Virgo A (Vir A), an elliptical galaxy (M87) in the Virgo cluster.
  • Surveys for radio sources with special spectral properties for follow-up research with larger radio telescopes such as the Westerbork Synthesis Radio Telescope (Hooghalen, the Netherlands) and the 100 meter radio telescope of the Max-Planck Institute for Radio Astronomy (Effelsberg, Germany).
  • Prolonged observations of the sun and solar bursts in the frequency range 160-320 MHz produced radio spectra of solar flares in the inner part of the corona and insight into the radiation mechanism, the strength of the magnetic field and the number of electrically charged particles in situ.
  • Various other projects, including the antenna pattern or directional sensitivity diagram of the radio telescope at 800 and 1400 MHz.

Discovery of Dwingeloo I and II

By thoroughly analyzing the radio waves, astronomers can determine which radio waves are approaching from nearby and which are from further away. Once the radio waves from the Milky Way were mapped, the researchers were able to penetrate the dense curtain of gas and dust in the Milky Way and to look deeper into the universe. Behind this initially opaque layer, they found a new galaxy in 1994. It was spotted before but never recognized as a galaxy. Within a few days this discovery was confirmed by infrared observations. Because of the role the Dwingeloo Radio Telescope played, the discoverer astronomer Renée Kraan-Korteweg named the galaxy Dwingeloo I. The galaxy has two satellite systems: one of these satellites is named Dwingeloo II.

Continuous development

In this way the Dwingeloo Radio Telescope functioned as a particularly useful and prominent instrument for Dutch radio astronomy. However, scientists want more because new questions continuously arise. To answer these, a larger dish was needed. Hence, ASTRON developed the Westerbork Synthesis Radio Telescope in the 1960s, which was inaugurated by Queen Juliana in 1970. Again the world’s largest radio telescope.