Context
- Our solar system consists of our star, the Sun, and everything bound to it by gravity — the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, dozens of moons and millions of asteroids, comets and meteoroids. The planetary system we call home is located in an outer spiral arm of the Milky Way galaxy.
- Beyond our own solar system, there are more planets than stars in night sky. So far, we have discovered thousands of planetary systems orbiting other stars in the Milky Way, with more planets being found all the time. Most of the hundreds of billions of stars in our galaxy are thought to have planets of their own, and the Milky Way is but one of perhaps 100 billion galaxies in the universe.
Size and Distance
- Solar system extends much farther than the eight planets that orbit the Sun. The solar system also includes the Kuiper Belt that lies past Neptune’s orbit. This is a sparsely occupied ring of icy bodies, almost all smaller than the most popular Kuiper Belt Object, dwarf planet Pluto.
| FACTS • The stars forming a group that has a recognisable shape is called a constellation. One of the most famous constellations which you can see during summer time in the early part of the night is Ursa Major. • Orion is another well-known constellation that can be seen during winter in the late evenings. It is one of the most magnificent constellations in the sky. • Cassiopeia is another prominent constellation in the northern sky. It is visible during winter in the early part of the night |
Formation
- Solar system formed about 4.5 billion years ago from a dense cloud of interstellar gas and dust. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova. When this dust cloud collapsed, it formed a solar nebula—a spinning, swirling disk of material.
- At the center, gravity pulled more and more material in. Eventually the pressure in the core was so great that hydrogen atoms began to combine and form helium, releasing a tremendous amount of energy. With that, our Sun was born, and it eventually amassed more than 99 percent of the available matter.
- Matter farther out in the disk was also clumping together. These clumps smashed into one another, forming larger and larger objects. Some of them grew big enough for their gravity to shape them into spheres, becoming planets, dwarf planets and large moons.
- In other cases, planets did not form: the asteroid belt is made of bits and pieces of the early solar system that could never quite come together into a planet. Other smaller leftover pieces became asteroids, comets, meteoroids, and small, irregular moons.
| List Of Some Great Missions To The Sun • Genesis (2001-04) • Solar and Heliospheric Observatory (SOHO) (1995-present) • Transition Region and Coronal Explorer (TRACE) (1998-2010) • Ulysses (1990-2009) • Solar Maximum Mission (1980-1989) • Solar Terrestrial Relations Observatory (STEREO) (2006-present) • Aditya – L1 First Indian mission to study the Sun. |