Free Astronomy Magazine January-February 2024

T he image reveals temper- ature fluctuations dating back 13.77 billion years (shown as color differences) that correspond to the seeds that eventually grew into galaxies. The signal from the Milky Way was sub- tracted using multi-frequency data. This image shows a temperature range of ±200 microKelvin. [NASA/ WMAP Science Team] 8 JANUARY-FEBRUARY 2024 ASTRO PUBLISHING e x - plained in the sta- tionary universe scenario. Furthermore, in this type of universe, if the mecha- nisms of tired light were valid, the surface brightness of stars, and therefore of galaxies, should be constant, in the sense that the fur- ther away an object is, the less light we receive, and since its apparent area decreases, there should be a constant ratio between received light and apparent area. But this is not the case: what is observed is that the surface brightness of ob- jects (essentially galaxies) decreases with distance, a phenomenon com- patible with an expanding universe; as they recede, they appear to emit photons at a reduced rate, since each photon must cover a greater distance to reach the observer than the previous photon. the Hubble Space Telescope, many observations have been made which have unequivocally demonstrated how the tired light hypothesis was not the most suitable to explain the redshift of distant galaxies. In par- ticular, the cosmic background radi- ation, a cornerstone of cosmology based on the Big Bang and precisely mapped between 2010 and 2013 by the Planck space telescope (in mi- crowaves and infrared), cannot be ing Zwicky’s afloat. Nevertheless, starting from the 1990s and also thanks to the entry into the scene of T his video summarizes some of the many discoveries made by ESA’s Planck space telescope during its 4.5-year observation mis- sion, from new discoveries in the Milky Way to the first moments after the Big Bang, 13.8 billion years ago. [ESA]