PDS 70

PDS 70

Subject: Science

Context:   Scientists for the first time have spotted a moon-forming region around a planet beyond our solar system

Concept:

The researchers used the ALMA observatory in Chile’s Atacama Desert to detect the disc of swirling material accumulating around one of two new-born planets seen orbiting a young star called PDS 70, located 370 light years from Earth. (A light year is the distance light travels in a year, about 9.5 trillion km)

PDS 70

• It’s a Jupiter-like world surrounded by a disc of gas and dust massive enough that it could spawn three moons the size of the one orbiting Earth.
• More than 4,400 planets have been discovered outside our solar system, called exoplanets.
• No circumplanetary discs had been found until now because all the known exoplanets resided in “mature” – fully developed – solar systems, except the two infant gas planets orbiting PDS 70.
• In our solar system, the impressive rings of Saturn, a planet around which more than 80 moons orbit, represent a relic of a primordial moon-forming disc,
• The orange-coloured star PDS 70, roughly the same mass as our Sun, is about 5 million years old.
• The two planets are even younger. Both planets are similar (although larger) to Jupiter, a gas giant.
• It is PDS 70c a moon-forming disc was observed
• Birth of a moon Stars burst to life within clouds of interstellar gas and dust scattered throughout galaxies. Leftover material spinning around a new star then coalesces into planets, and circumplanetary discs surrounding some planets similarly yield moons.
• The dominant mechanism thought to underpin planet formation is called “core accretion,”

Core accretion

• Core accretion occurs from the collision and coagulation of solid particles into gradually larger bodies until a massive enough planetary embryo is formed (10-20 Earth masses) to accrete a gaseous envelope.
• A scenario where, small dust grains, coated in ice, gradually grow to larger and larger sizes through successive collisions with other grains.
• This continues until the grains have grown to a size of a planetary core, at which point the young planet has a strong enough gravitational potential to accrete gas which will form its atmosphere.