Introduction
In our observable universe, our solar system is the only star system where we have directly discovered and observed the planets and its motion around the star. All the exoplanets we discover are observed using either by radial velocity spectrometry method or by using infrared telescopes. Direct imaging of a planet and its formation is yet to be done. Currently, we are developing large telescopes like James Webb space telescope and extremely large telescope with which we can directly observe and image a planet formation. In 2017, researchers found a twist and turn in the cosmic gas and dust orbiting the star AB Aurigae by using ALMA (Atacama Large Millimeter/submillimeter Array) telescope of European Space Observatory. Now, few scientists from Paris observatory observed this distinctive twist and speculated that a new planet is about to born in that star system.
How a Planet is born?
Planets are the bodies that orbit a star or a star system. Stars are formed from the gravitational collapse of cosmic ionized gas and dust under extreme temperatures and pressures under the influence of strong gravity. After a star is born, the remnant gases and dust orbit around the star and forms an accretion disk around it. The disk is of two types. The one which is nearer to the star is called inner protoplanetary disk or inner disk. The next one is called the outer disk. These disks are composed of cosmic gases and dust revolving around the star at extreme temperature and pressure. Due to the heavy gravitational influence of the star on the gases, they collapse under their gravity and form spiral-shaped swirls of hot gases and dust with two arms. One arm falls into the sun and the other arm extends outward of the disk and forms as planets. The composition of planets depends on the type of disk from which it is developed. If a planet is born in the inner disk, it is a terrestrial planet with a rocky surface and small size and gravity and high temperature. If a planet is formed in the outer disk region, it would be a gas giant with greater mass, high pressure, high gravity, and extremely low temperatures. Planets from Mercury to Mars fall in the inner disk region and have a rocky surface whereas the planets from Jupiter to Neptune fall in the outer disk region and have extremely high pressures and mass.
Direct Observation of a Planet Formation
In 2017, scientists have observed a gravitational collapse of cosmic dust around the inner disk of the star AB Aurigae using the ALMA telescope of ESO. They theorized that a new planet is forming in the star system. Now, scientists of Paris Observatory have observed the same star system for the second time using the SPHERE instrument on a Very Large Telescope (VLT). At the first observation, they saw the formation of cosmic spirals in the inner region which is an indication of gravitational collapse and a parent of planet formation. Now, we have observed that the one arm of the spiral is extending outward connecting the giant spiral of the outer disk. Within the twist of spiral dust data obtained from the first observation, they have spotted another spiral that contradicts the previous data and they saw the density wave simulations and found that the new spiral is produced from the older one with the similar superposition and perfection. With the two observations, SPHERE spotted a fainter light near the AB Aurigae star system’s inner disk that indicates a giant planet is forming over there. The calculations state that the newly forming planet has a mass of 4 to 13 times that of Jupiter and has the same orbital distance of Neptune with our Sun.
Conclusion
The recent observations of the ALMA and SPHERE instruments on the AB Aurigae gave the first experience of viewing a formation of planets around a star. A planet formation around a star takes place around a star system in the first million years of star formation as that budding star has extremely high temperature and pressure to gravitationally collapse the cosmic gases and dust in its proto-planetary disk and tend to planet formation.
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