A Century of Cosmic Discoveries

This extended volume (in total 700+ pages, 124 b/w illustrations, 338 in colour) starts with an interesting Foreword entitled The Nature of beings and the Reasons of beings by the Rev. Dr. Nikolaos Chatzinikolaou Metropolitan of Mesogaia and Lavreotiki, a physics trained theologian and philosopher whom the author met while he was doing his postgraduate studies in the Department of Astronomy at Harvard University.

The Prologue briefly mentions the discoveries of some pioneering classical astronomers, who left their indelible marks on the evolution of early astronomy: Aristarchos of Samos (310230 BC), the systematic proposer of the heliocentric system, the so-called Copernicus of antiquity, Eratosthenes of Cyrene (276194 BC), who measured with admirable accuracy the circumference of the Earth and Hipparchos of Rhodes (190120 BC), the prince of observational astronomers of antiquity, a classical astronomer. It also briefly mentions some other early mathematicians, astronomers and cosmic thinkers depicted in the well known fresco by Raphael, the School of Athens, painted between 1509 and 1511, at the Stanze di Raffaello in the Apostolic Palace in the Vatican City.

An extended Table provides a brief chronology of a selection of key astronomical discoveries, from the early 20th century, e.g., from Hale's discovery of magnetic fields in sunspots (1908) to the recent Proba-3 formation flying observations of the solar corona, (2026), including 20 Astrophysics-related Nobel prizes in physics.

Chapter 1 , entitled The amazingly variable and active Sun , is extensive (144 pages) unfolding more than a century of great discoveries which led to the present understanding of our life-giving star, the Rosetta Stone of Astrophysics. Actually, this chapter's preface starts with what Gene Parker once said: "If it were not for its variable magnetic field, the Sun would have been a rather uninteresting star.." and, "out of the trillions of stars in our own Milky Way galaxy and those in the other trillions of galaxies in total about 10² stars - it is only our Sun that is resolved in great detail and also affects our technology in space via space weather and our lives here on Earth.". The periodical appearance of sunspots and solar cycle 1 (1755-1766) and the strongest solar flare ever recorded (1869) have been among the oldest indicators of solar activity, while recently we have observed unlucky exoplanets around wild flare stars. Actually, the closest known exoplanet to Earth orbits Proxima Centauri, a notorious red dwarf flare star, which was blasted by a massive superflare that increased the star's brightness by 1,000 times in just 10 seconds, threatening the planet's atmosphere. The same year (1869) marks the emergence of Space Weather with solar effects on power grids and expensive blackouts, solar effects on satellites and navigation, communications & GPS, as well as effects of the SolarTerrestrial interaction and solar variability on Earth's climate. The first discovery of strong magnetic fields in the Sun and of their dominant role in sunspots and the solar atmosphere was made by Hale (1908). The rise of magnetic flux tubes from the solar interior in the solar photosphere has been shown to be similar to the rise of air bubbles in an aquarium, or a swimming pool (1980). In 1961 the first theory of the solar dynamo was proposed and in 1962 Helioseismology allowed us to listen to the music and thus decipher the secrets of the solar interior, which led in 1980 to the discovery of the (invisible) internal rotation of the Sun, while since 2002 we similarly observe pulsations in other stars via asteroseismology. In 1968 the famous solar neutrino problem was realized and was eventually solved in 1999 (Physics Nobel prizes 2002, 2015). In 1970-1971 coronal mass ejections (elevating from the Sun the mass of a mountain range) and coronal holes were discovered. In 1974-1975 detailed observations became available of solar prominences (huge floating unstable curtains of cooler/denser plasma which when erupt are launched into the interplanetary medium IPM), chromospheric networks (luminous spider webs spread over the photosphere and chromosphere), chromospheric jets (a burning meadow, with hundreds of thousands flames) and solar coronal loops (the ubiquitous magnetic arches of the solar atmosphere, building blocks of the solar corona). It also contains a detailed reference to the legacies and anekdotal discussions with Gene Parker, the founder of modern solar physics and author's PhD advisor and S. Chandrasekhar, physics Nobel prize in 1985, both emblematic scientists with whom the author enjoyed a fruitful interaction on topics of plasma astrophysics and magnetohydrodynamics at the Un. of Chicago. In particular, Parker's theoretical discoveries, such as the solar wind, the dynamo mechanism, magnetic buoyancy and the physics of magnetic flux tubes, magnetic reconnection, the shape of the solar wind bubble within the IPM, the Parker limit on the flux of magnetic monopoles based upon the survival of the galactic magnetic field, the theorem on the non-equilibrium of non-invariant magnetic fields and the spontaneous formation of tangential discontinuities creating coronal heating in thin electrical current sheets, are outstanding. From a more general perspective, one may think in the following way for Parker's theory of the solar wind, a milestone in solar physics and Astrophysics, wherein one may draw the following comparison. Kepler was the first to discover observationally the physical laws governing the motion of the planets around the Sun (1609). In 1687, 78 years later, Newton was able to theoretically explain Kepler's laws of planetary motions, by using his theory of classical mechanics and the law of the gravitational attraction of the Sun on each planet, in the well known two-body problem. As it happens in most of physics and astrophysics, observation/experiment was ahead of theory. Nevertheless, both, Kepler and Newton assumed an empty interplanetary medium for the planets to move around the Sun, without a solar wind. In 1957, i.e., 348 years after Kepler and 270 years after Newton, it was left to Parker to discover, theoretically this time, that the interplanetary medium is not empty at all, but is flood with the supersonic solar wind that travels at millions of kilometers per hour across the planets. And, this is one of the few cases of physical phenomena where theory was ahead of observations. Nevertheless, Kepler, Newton and Parker were lucky, because such fundamental physical laws and phenomena can be discovered only once! The experience of the author as a PI of space missions, such as the Solar Orbiter and the novel formation flying ESA Proba 3 mission and respective interaction with Ester Antonucci (PI of Metis, the Solar Orbiter coronagraph), and Andrei Zhukov (PI of the Proba 3 Coronagraph), Angelos Vourlidas project scientist for the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) instrument suite onboard NASA's STEREO (Solar-Terrestrial Relations Observatory), together with theoretical solar physicists, such as Eric Priest, Vasilis Archontis, Costis Gontikakis, Spiros Patsourakos, all have been very useful in reviewing the material in this Chapter 1.

Chapter 2 entitled Our privileged solar planetary system discusses the impressive in situ exploration of our home planetary system, from the dawn of the Space Age (1957) and the first landing on the Moon (1969), to the robotic exploration of Mars and the other planets and satellites, to the longest journey of the two Voyager spacecrafts launched in 1977, to the exit of Voyager 1 from the Heliosphere at 121 AU from the Sun (2012). The author has benefited from discussions with Tom Krimigis, who has led or has participated in space physics experiments that have explored all nine planets of our solar system and designed, developed, sent into s…