Come out of your house and look around, what do you see? Trees, cars, some animals and other species….Now, look up in the sky. You see the sun and realize you are the part of the solar system along with 8 planets, 5 dwarf planets, 181 moons, more than 1 billion asteroids, more than 100,000 known Kuiper belt objects and uncountable numbers unknown of small bits. We all know that our Sun is the heart of our solar system which was formed 4.6 billion years ago. Talking about our sun, the sun produces a constant stream of particles which blow out into space. In fact, 1 million tons of particles come from the Sun every second! This stream of particles is called the solar wind.

The solar wind plasma is very thin. As it streams away from the Sun it races out toward space. And as space is not ‘empty’ and contains traces of gas and dust, the solar wind blows against this material and clears out a bubble-like region in this gas. This bubble that surrounds the Sun and the solar system is called the Heliosphere. It accounts for the boundary of the solar system.

Outside the Heliosphere the solar wind slows down and begins to interact with the interstellar medium is called the Heliosheath. The Heliosheath has the parts namely: the termination shock (the innermost part of the boundary), the Heliopause (the outermost part of the boundary) and the part in between the inner and outer boundary-the Heliosheath. The speed of the solar wind, when blown into space, is of 200-800km/sec (Supersonic speed) but when it reaches the termination shock it interacts with the Interstellar medium(ISM) and its speed reduces slower than the speed of sound (subsonic speed). This accounts the termination of the influence of Sun in space.

The objects are thrown out of the solar system while the formation of the Gas Giants formed an icy shell surrounding the solar system called the Oort cloud. It is so distant that it is even disrupted by the nearby stars (like Alpha Centauri), nebula and by the actions of the disc of Milky Way.

The Sun and the nearby stars reside in a great cavity in the interstellar medium (ISM) called the Local Bubble.

This cavity lies in the Orion Arm of the Milky Way, a which is at a distance of 35,000 light years from the center of the Milky Way

Our spiral galaxy along with the dozens of other galaxies forms a cluster called the Local Group. The galaxies are separated from each other by a few hundred thousand light years and the nearest galaxy, the Andromeda is about two million light-years away. The Local Group as one of the smaller members, along with thousands of other such clusters, forms the Virgo Supercluster.

There is yet another bigger structure, the Laniakea Supercluster, the galaxy supercluster in which our Milky Way and approximately 100,000 more nearby galaxies reside. It contains about 300 to 500 other galaxy clusters and is centered on the Great Attractor in the HydraCentaurus Supercluster. The Observable Universe contains large number of such superclusters of the clusters of galaxies along with the empty space extended more than ten billion light years in all the direction leaving us as mere tiny dots in the vastness of the cosmos.

So next time when you come out of your house you know what you are a part of. And here is your current Cosmic Address:

Indian Institute of Science Education and Research Berhampur (Area~100 km2 )

Odisha (Area~105 km2 )

India (Area~106 km2 )

Planet Earth (Diameter~105 km)

Solar System (Radius~4.5 billion km)

Heliosphere (Dist~18 billion km from sun)

Heliosheath (~18 billion km from sun)

Oort Cloud (Dist~104 billion km from sun)

Local Bubble (Dist~107 billion km from sun)

Orion Arm of Milky Way (Dist~108 billion km from sun)

Milky Way Galaxy (~1010 billion km across containing the solar system)

Local Group (~10 million light years, 1 light year~10000 billion km)

Virgo Supercluster (Dist~65 million light years)

Laniakea (~250 million light years)

Observable Universe (~46 billion light years)

Reference: Cosmos by Carl Sagan, ISBN: 0-345-53943-5