Context:

• Earth doesn’t have just one moon, it has three. The existence of the two extra ‘moons’ was hotly debated for over 50 years but as per a recent National Geographic report, Hungarian astronomers and physicists have finally provided enough data to confirm that our moon has at least two other companions — made entirely of dust.

Facts about the newly discovered dust moons

• The presence of the dust ‘moons’ or Kordylewski clouds had been been inferred by researchers since long before

• But the first glimpse of the clouds was seen only in 1961 by Polish astronomer Kazimierz Kordylewski, after whom the dust clouds were named

• The new findings note that each Kordylewski cloud is about 15 by 10 degrees wide, or equal to 30 by 20 lunar disks in the night sky

• They are spread over a space area that is almost nine times the width of Earth — about 65,000 by 45,000 miles in actual size

• The dust ‘moons’ are huge but they are made of tiny dust particles that barely measure one micrometre across

• When sunlight hits the dust particles, they glow very faintly, much like the zodiacal light we receive from the dust scattered in between planetary orbits

• Since these satellite dust clouds emit an extremely faint light, they are very difficult to find amidst the star light, sky glow, galactic light and zodiacal light in the sky though they are as close to us as the moon

• The recent study revealing the existence of the two dust ‘moons’ used special polarizing filters on cameras to reveal the scattered light coming from the reflection of the individual dust particles in the clouds

Kordylewski clouds are always changing

• The Kordylewski clouds are always changing. They might be stable in orbit and may have existed for millions of years, but the ingredients that make the clouds — the dust particles — are always getting swapped for others.
• Some escape to gravitational pulls from Earth or the moon, while others come from interplanetary spaces and meteor showers

How Lagrange points in space helped find the extra ‘moons’

• Speculations about Earth having multiple moons have taken turns in astronomer circles for years. It was realised that if extra moons did exist, they could only do so in stable points in Earth’s orbit.
• Lagrange points are sweet spots in a planetary orbit where the pull of gravity working from two opposing celestial bodies is balanced due to the centripetal force of their orbits.
• Thus, an object at a Lagrange point will remain fixed at a constant distance from both the moon and Earth.
• In the 1950s, Kordylewski searched two Lagrange points — L4 and L5 — where he found the first glimpse of the two dust clouds orbiting Earth.

Can these dust ‘moons’ be dangerous or will they help us?

• These huge clouds of dust could add much to space exploration efforts when it comes to fuel consumption and safety issues.
• Sometimes, satellites need to be parked at the Lagrange points so that the spacecraft consumes minimal fuel and can still stay in orbit.
• The James Webb Space Telescope will be set up at the L2 Lagrange point in 2020 for this purpose.
• Moreover, space agencies are also planning to use Lagrange points as transfer stations for Mars missions.

Source: India Today