Why in the News?

Astronomers from the Indian Institute of Astrophysics (IIA) have utilized 100 years of daily solar records from the Kodaikanal Solar Observatory to map the Sun's differential rotation for the first time. The study reveals varying rotation speeds across latitudes, with the equator rotating every 25 days and the poles every 35 days, crucial for understanding solar dynamics and cycles.

Sun

• Type: It is a G-type main-sequence star (G dwarf) located at the center of our solar system.
• Distance from Earth: Approximately 93 million miles (150 million kilometers), known as an astronomical unit (AU).
• Age: Estimated to be about 4.6 billion years old.
• Structure: It consists of multiple layers, each with distinct characteristics and temperatures -
  • Photosphere: The visible surface marking the boundary between the interior and the atmosphere.
  • Chromosphere: An irregular layer above the photosphere where the temperature rises from 6000°C to about 20,000°C.
  • Transition Region: A thin and very irregular layer of the atmosphere that separates the hot corona from the much cooler chromosphere.
  • Corona: It is the outer atmosphere. It is much hotter than the underlying chromosphere or photosphere.
  • Beyond the corona lies the solar wind, which is an outward flow of charged particles (plasma) originating from the corona.
• The solar wind extends far into space affecting planetary atmospheres and causing phenomena like the auroras on Earth.
• Richard Carrington, an English astronomer in the 19^th century, first discovered differential rotation by observing sunspots.
• Its equator rotates at 13.98 degrees per day, while at 80 degrees latitude, the rotation rate slows to 10.5 degrees per day.

Sun’s Structure

Kodaikanal Solar Observatory

• Location: Kodaikanal, Tamil Nadu
• The observatory was established in 1899 by the Indian Institute of Astrophysics (IIA) to study solar phenomena and better understand monsoon patterns.
• Solar observations at this observatory over more than 100 years provide one of the longest continuous series of solar data.
• One of the major milestones was the discovery of the Evershed Effect in 1909, which is related to the movement of gases in the solar atmosphere.
• The Kodaikanal 15-cm Solar Telescope, which is one of the oldest solar telescopes still in use.

Indian Institute of Astrophysics (IIA)

• Headquarters: Bangalore
• Established: 1971
• Director: Annapurni Subramaniam
• Aim: To conduct advanced research in various fields of astrophysics and space sciences, including stellar astronomy, planetary science, solar physics, and cosmology.