Seeing beyond the visible
Because radio waves are so large — about 100 000 times longer than visible light waves — astronomers need colossal telescopes to collect them. Building a single telescope large enough to collect them is impossible, so arrays have been built. The Very Large Array (VLA) in New Mexico, United States is one such series of radio telescopes working together as one. With VLA observations, astronomers working on the EU-funded 'New science enabled with the Expanded Very Large Array' (NEWEVLA) project hoped to learn more about the debris from supernova explosions. Supernova explosions, which mark the violent death of a star, release tremendous amounts of energy and spew heavy elements into interstellar space. Some supernova explosions can be seen with optical telescopes across half of the Universe, but when they are in this murk the details of their evolution can be missed. Exploiting the high resolution of VLA, NEWEVLA astronomers were able to follow the radio emission of the supernova 2011dh over the first 100 days. Its explosion in the famous Whirlpool galaxy M51 was discovered in May 2011. In the rapidly expanding blast wave of the supernova, energetic electrons produced synchrotron emission. Taking into consideration the reabsorption of synchrotron radiation by the electrons themselves, NEWEVLA astronomers modelled the radio emission to estimate the average expansion velocity. The model predictions revealed a central compact star left behind, in addition to the expanding remnant. VLA observations also allowed NEWEVLA astronomers to have a close-up view of galaxies in the neighbourhood of our Milky Way. In particular, the proper motion of Andromeda has been sought for almost a century, but VLA was capable of such precise measurements that small transverse motions were captured. The findings will be used to probe theories of how galaxies are attracted by their mutual gravity. A series of papers with the new scientific discoveries of the largest ever camp of telescopes looking at the neighbourhood of our galaxy was published in peer-reviewed journals. Beyond offering major advances to our understanding of how the Local Group of galaxies evolves, NEWEVLA has handed astronomers unique tools for unveiling the secrets of the cosmos.
Keywords
Cosmos, radio waves, radio telescope, visible light, Very Large Array
