1610 — the Orion nebula was discovered. The Orion Nebula is an emission and reflection nebula, as well as a star formation region in the constellation Orion. It has an apparent brightness of about 4m, which makes it not only visible to the naked eye, but also the brightest diffuse nebula and one of the brightest objects in deep space. The nebula was discovered by Nicolas-Claude Fabry de Peyresc in 1610.
Due to its brightness, the Orion Nebula is popular in amateur astronomy. Its angular diameter is more than 1°, the area is more than 4 times the area of the Moon. The nebula is illuminated by the bright stars of the Orion Trapezoid, a young scattered star cluster located inside the nebula.
1612 — the discovery of the Andromeda Nebula.
1647 — Jan Hevelius made a detailed map of the moon. In 1647, Polish astronomer Jan Hevelius published a book "Selenography, or description of the Moon", in which he placed his own sketches of the Moon during observations in a telescope. However, the lunar maps of Hevelius were not detailed. This was due to the fact that Hevelius used telescopes with a very large focal length (length 5 m, lens diameter 15-20 cm), which greatly distorted the image.
1655 — On March 25, Christian Huygens discovers Saturn's moon Titan. And next year, the rings of Saturn. The diameter of Titan is 5152 km (this is 1.48 times larger than that of the Moon), while Titan is 80% larger than the Earth's satellite in mass. Titan is also larger than the planet Mercury, although it is inferior to it in mass. The gravity on it is approximately one-seventh of that on Earth. The mass of Titan is 95% of the mass of all the moons of Saturn.
The surface of Titan is mainly composed of water ice and sedimentary organic matter. It is geologically young and mostly flat, with the exception of a small number of rock formations and craters, as well as several cryovolcanoes. The dense atmosphere surrounding Titan made it impossible to see the surface of the satellite for a long time — until the arrival of the Cassini-Huygens spacecraft in 2004.
The atmosphere is predominantly nitrogen; there is also a small amount of methane and ethane, which form the local ocean and clouds, which are a source of liquid and possibly solid precipitation. There are methane-ethane lakes and rivers on the surface. The pressure at the surface is about 1.5 times the pressure of the earth's atmosphere. The surface temperature is minus 170-180 °C.
Despite the low temperature, Titan is compared with the Earth in the early stages of development, and it cannot be excluded that the simplest forms of life may exist on the satellite; in particular, in underground reservoirs, where conditions can be much more comfortable than on the surface.
1657 — the first exposition of the Copernican system in Russian — Epiphanius Slavinetsky, "The Mirror of the Whole Universe"; this book was a translation of the "Introduction to Cosmography" by I. Bleu.
1665 — discovery of a Red Spot on Jupiter (Cassini, Hooke). The period of rotation of Jupiter (and in 1666, Mars) around its axis (Cassini) was measured.
1666 — the Paris Observatory was founded together with the Paris Academy of Sciences. Cassini becomes the first director of this observatory. Of his achievements in his new post (together with Zh. Richet) — the first fairly accurate definition (1671-1673) of the parallax of the Sun (9.5") and the astronomical unit (140 million km), the discovery of the "Cassini gap" in Saturn's ring (1675).
1675 — an estimate of the speed of light (Remer), which clarified the idea of the distances to the planets. The Greenwich Observatory was founded, headed by John Flamsteed.
1676 — Edmund Halley discovers the "great inequality" of Saturn and Jupiter, and in 1693 — the secular acceleration of the Moon. The explanation of these phenomena after 100 years was given by Laplace.
In the history of science, Halley is most famous for his studies of comets. After processing years of data, he calculated the orbits of more than 20 comets and noted that several of their appearances, including 1682, refer to the same comet (named after him). He scheduled a new visit of his comet for 1758, although Halley himself was not destined to be convinced of the accuracy of his prediction.
1687 — Isaac Newton formulates the law of gravitation and deduces all 3 of Kepler's laws from it. Another important consequence of Newton's theory was the explanation of why the orbits of celestial bodies deviate slightly from the Keplerian ellipse. These deviations are especially noticeable for the moon. The reason is the influence of other planets, and for the Moon — also the Sun. Taking this into account allowed Newton to discover new deviations (inequalities) in the motion of the Moon — annual, parallactic, backward movement of nodes, etc. Newton very accurately calculated the precession value (50" per year), highlighting the solar and lunar components in it.
Newton discovered the cause of chromatic aberration, which he mistakenly believed to be irreversible; in fact, as it turned out later, the use of multiple lenses in the lens can significantly weaken this effect. Newton went the other way and invented a mirror telescope-reflector; having a small size, it gave a significant magnification and an excellent clear image.