Relevance: GS III (Science & Tech – Space) | Source: The Hindu; European Space Agency (ESA)

1. The Discovery: A Strange Family

Astronomers using the Cheops Telescope (from Europe) have found a very strange planetary system called LHS 1903.

• Location: It is about 117 light-years away from Earth.
• The Star: It orbits a Red Dwarf, which is a star much smaller and cooler than our own Sun.

2. The Puzzle: Why is it Weird?

To understand why this system is strange, we first need to look at our own Solar System:

• Normal Rule: Rocky planets (like Earth/Mars) form close to the star where it’s hot. Gas Giants (like Jupiter/Saturn) form far away where it’s cold.
• The LHS 1903 Exception: This system is like a mixed-up sandwich. It has a rocky planet, then gaseous planets, and then—surprisingly—another rocky planet on the outside!
• The Mystery: Finding a rocky planet so far out (where gas giants usually live) has confused scientists. It suggests our theories about how planets grow might be incomplete.

3. Scientific Guesses

Scientists have two main guesses for how this happened:

• The Greedy Siblings: Maybe the inner gaseous planets formed first and “ate” all the available gas, leaving none for the outer planet, forcing it to remain a bare rock.
• The Lost Coat: Maybe the outer planet was born as a gas giant, but a violent event (like a collision) stripped away its thick atmosphere, leaving only the rocky core behind.

UPSC Value Box

In the context of space exploration, what makes the planetary system “LHS 1903” unique?

1. It is the first system found with liquid water on all its planets.
2. It has a rocky planet orbiting outside the gaseous planets, which challenges standard formation theories.
3. It orbits a Black Hole instead of a star.