Τμήμα Φυσικής
ΣΧΟΛΗ ΘΕΤΙΚΩΝ ΕΠΙΣΤΗΜΩΝ ΕΚΠΑ
ΤΜΗΜΑ ΦΥΣΙΚΗΣ
ΤΟΜΕΑΣ ΑΣΤΡΟΦΥΣΙΚΗΣ ΑΣΤΡΟΝΟΜΙΑΣ ΚΑΙ ΜΗΧΑΝΙΚΗΣ
Σ Ε Μ Ι Ν Α Ρ Ι Ο
Τετάρτη 20 Φεβρουαρίου 2019, 13:00-14:00
Αίθουσα Διαλέξεων Τομέα Αστροφυσικής, Αστρονομίας και Μηχανικής
The importance of Radio astronomy. The Hellenic radio telescope
Dr Nectaria Gizani
School of Science and Technology, Hellenic Open University
We see the world around us because our eyes detect visible light, which is only a small portion of the electromagnetic spectrum (from 400nm to 700nm). Objects on Earth and in the Universe however also emit other types of electromagnetic radiation that cannot be seen by the human eye, such as radio waves, X-rays and γ-rays. In fact there is a whole world hidden from optical light. The multiwavelength study of celestial objects is necessary to complete our knowledge of the Universe.
The study of the Universe in the radio, refers to the portion of the electromagnetic spectrum, which is between 30 MHz and 300 GHz. Radio emission comes from our solar system (sun, moon, planets) from chemicals in comets and in supernovae, from fast spinning neutron stars (pulsars) in our galaxy (the Milky Way) and other galaxies, from the center of the Galaxy itself, from other galaxies, and galaxies with active super massive black holes at their centers (called active galactic nuclei, eg. Radiogalaxies, starbursts, distant quasars) as well as from large-scale grouping of galaxies, called clusters. Radio observations of the Cosmic Microwave Background Radiation (CMB), the remnant signal of the birth of the Universe (the Big Bang), can probe the “Dark Ages” before the onset of the first stars or galaxies, and study the earliest generation of galaxies. Unlike optical emission, radio waves penetrate dust, so radio observational techniques are essential in the study of regions that cannot be seen in visible light, such as the dust-shrouded environments where stars and planets are born. Radio waves also trace the location, density, and motion of the hydrogen gas that constitutes three-fourths of the ordinary matter in the Universe. Stand-alone radio information from galactic and extragalactic objects can reveal the phenomena creating them and the mechanisms behind these phenomena that could not have been comprehended otherwise.
As the radio emission from the objects under study is faint, radio astronomers use sensitive instrumentation (electronics + large collecting area), called radio telescopes. Radio observations can be performed both with a single dish antenna as well as with many dishes linked in interferometric mode.
We are going to talk about the Hellenic radio telescope and its importance in the Hellenic society besides its undeniable scientific value.