For centuries, man believed that the Sun was only the round and yellow sphere he had always seen when gazing into the sky. This is not the case. Today, we know that the Sun we can see is only a small part of our star. We know that the "real" Sun is three or four times bigger and has a very different shape. Even the ancient astronomers knew about the surprising phenomenon that occurred during total eclipses, when the Moon comes between the Earth and the Sun and covers the entire disk that normally shines in the sky. During an eclipse, the Earth enters a strange type of darkness, as if night has suddenly fallen. But that darkness is not as absolute and total as we might think, because a feeble but extensive bluish halo, called the "corona" shines around the Sun's disk, which is completely covered by the Moon. What is this luminous ghost that appears only during an eclipse and disappears immediately afterwards? It was anything but easy to study, because total eclipses are rare and don't last very long. A special instrument was needed that could reproduce the conditions of an eclipse at any time. The problem was solved in 1930 by the French astronomer Bernard Lyot, who invented the coronograph, a telescope in which a special disk completely covers the Sun's disk, creating a sort of artificial eclipse. By eliminating the luminosity of the Sun's disk, which made it impossible to observe the surrounding fainter details, the coronograph provided the final confirmation: the Sun is much larger and has a very different shape than what we can normally observe with the naked eye. This corona, a feeble, irregularly-shaped halo of incandescent matter, consisting mainly of electrons, extends for more than eight million kilometers around the central and more compact body.
For centuries, man believed that the Sun was only the round and yellow sphere he had always seen when gazing into the sky. This is not the case. Today, we know that the Sun we can see is only a small part of our star. We know that the "real" Sun is three or four times bigger and has a very different shape. Even the ancient astronomers knew about the surprising phenomenon that occurred during total eclipses, when the Moon comes between the Earth and the Sun and covers the entire disk that normally shines in the sky. During an eclipse, the Earth enters a strange type of darkness, as if night has suddenly fallen. But that darkness is not as absolute and total as we might think, because a feeble but extensive bluish halo, called the "corona" shines around the Sun's disk, which is completely covered by the Moon. What is this luminous ghost that appears only during an eclipse and disappears immediately afterwards? It was anything but easy to study, because total eclipses are rare and don't last very long. A special instrument was needed that could reproduce the conditions of an eclipse at any time. The problem was solved in 1930 by the French astronomer Bernard Lyot, who invented the coronograph, a telescope in which a special disk completely covers the Sun's disk, creating a sort of artificial eclipse. By eliminating the luminosity of the Sun's disk, which made it impossible to observe the surrounding fainter details, the coronograph provided the final confirmation: the Sun is much larger and has a very different shape than what we can normally observe with the naked eye. This corona, a feeble, irregularly-shaped halo of incandescent matter, consisting mainly of electrons, extends for more than eight million kilometers around the central and more compact body.
