What is the Solar and Heliospheric Observatory (SOHO)?

About Solar and Heliospheric Observatory (SOHO)

• It is a project of international collaboration between the European Space Agency (ESA) and the U.S. National Aeronautics and Space Administration (NASA).
• Launched in December 1995, SOHO was designed to study the Sun.
• In order to provide continuous observations, it was maneuvered to orbit the first Lagrangian point (L1), a point some 1.5 million km (900,000 miles) from Earth toward the Sun where the gravitational attraction of Earth and the Sun, combine in such a way that a small body remains approximately at rest relative to both. 
• It carries 12 scientific instruments to study the solar atmosphere, helioseismology, and the solar wind. 
• Information from the mission has allowed scientists to learn more about the Sun’s internal structure and dynamics, the chromosphere, the corona, and solar particles.
• Though its mission was scheduled to run until only 1998, it has continued collecting data, adding to scientists' understanding of our closest star, and making many new discoveries, including thousands of comets.
• SOHO is the longest-lived Sun-watching satellite to date. 

Q1) What is a Comet?

Comets are defined as icy bodies of frozen gases, rocks and dust left over from the formation of the solar system about 4.6 billion years ago. They orbit the sun in highly elliptical orbits that can take hundreds of thousands of years to complete.

Source: ESA, NASA Solar Observatory Discovers Its 5,000th Comet