From UPSC perspective, the following things are important :
Prelims level : Lagrange Points, Lucy Mission
Mains level : Not Much
The NASA has launched Lucy, the spacecraft on a 12-year cruise to look back into the origins of the solar system through Trojans.
- Lucy will fly by eight Jupiter asteroids—seven Trojans and one main-belt asteroid — over the next 12 years.
- It is NASA’s first single spacecraft mission in history to explore so many different asteroids.
- Lucy will run on solar power out to 850 million kilometers away from the Sun.
- This makes it the farthest-flung solar powered spacecraft ever, according to NASA.
What is Jupiter Trojan Asteroids?
- Simply known as Trojans, they are a large group of asteroids that share Jupiter’s orbit around the Sun.
- Thousands of such asteroids exist in a gravitationally stable space.
- The swarms lead and follow the planet Jupiter along its orbit around the Sun.
What exactly are Trojans?
- Lucy’s Trojan destinations are trapped near Jupiter’s Lagrange (L) points, which are gravitationally stable locations — it is where the gravity from the Sun and from Jupiter cancel each other out.
- This means their orbits are stable and the Trojans are trapped in the space between.
- This also means that asteroids are as far away from Jupiter as they are from the Sun.
- Jupiter’s leading and trailing Lagrangian points (L4 and L5) have been stable over the age of the solar system.
- This means that their orbits have accumulated many, many asteroids.
- It makes sense to call a Trojan a co-orbital object, which moves around one of the two stable Lagrangian points.
When and how were they discovered?
- It took many a scientist to understand Trojans, and subsequently, name them so.
- A German astro-photographer in 1906 made an important discovery: An asteroid with a particularly unusual orbit. As Jupiter moved, this asteroid remained ahead of Jupiter.
- It was observed that the asteroid was nearly 60 degrees in front of Jupiter.
Students with engineering background would better understand who Lagrange was. Rest need not care.
- This specific position of a peculiar behaviour was predicted by the Italian-French mathematician Joseph-Louis Lagrange over 100 years earlier.
- Lagrange had argued that if a small celestial body is placed at one of two stable points in a planet’s orbit around the Sun (the L4 and L5), the asteroid would remain stationary from the planet’s perspective.
- This is due to the combined gravitational forces of the planet and the Sun.
- Thus, Lagrange’s prediction acquired credibility. More such asteroids were discovered over subsequent months in Jupiter’s Lagrange point L5.
Behind the name: Lucy
- It is the fossil of a hominin that lived 3.2 million years ago.
- She is known to be one of the most famous pre-human fossil in history.
- Nearly 40 per cent of the fossilised skeleton of this hominin was discovered in 1974 by a team of paleoanthropologists led by Donald Johanson.
- The name was inspired from the famous Beatles song “Lucy in the Sky With Diamonds,” which Johanson’s team listened to at camp the night of their discovery.
Back2Basics: Lagrange Points
- Lagrange points are positions in space where objects sent there tend to stay put.
- They are named after Italian-French mathematician Josephy-Louis Lagrange.
- At Lagrange points, the gravitational pull of two large masses precisely equals the centripetal force required for a small object to move with them.
- These points in space can be used by spacecraft to reduce the fuel consumption needed to remain in position.
- There are five special points where a small mass can orbit in a constant pattern with two larger masses.