Massive gas discs raise questions about the theory of planet formation, Astronomers using the Atacama Large Millimeter / Submillimeter Array (ALMA) have discovered young stars surrounded by extraordinary masses of gas. The star, called 49 sets, is 40 million years old, and conventional planetary theories predict that gas should disappear at that age.
A large amount of confusing gas requires a revision of our current understanding of planet formation.
The planets formed into gas dust discs called protoplanetary discs around young stars. Dust particles gather on planets that resemble Earth or to the core of larger planets and collect large amounts of gas from discs to form giant gas planets like Jupiter.
According to modern theories, the gas in the disc is embedded in the planets from time to time or fascinated by the radiation pressure from the central star. However, the star is surrounded by dusty planets and discs. This dusty disk, called a debris disk, shows that the process of planet formation is almost complete.
The latest advances in radio telescopes in this area are surprising. Astronomers have found that some of the remaining disk still contains some gas. If gas stays in debris discs for a long time, the planet’s seeds may have enough time and material to develop into a giant planet like Jupiter. Therefore, the gas in the disc waste affects the composition of the resulting planetary system.
The team first discovered the spatial distribution of carbon atoms in the disc waste. Carbon atoms are more common than carbon monoxide, with the second most common molecule among young stars being the most common hydrogen molecule.
The number of carbon atoms is so large that the team found even weak radio waves from the more rare form of carbon, 13C. This is the first evidence of 13C emission at 492 GHz in astronomical objects which are usually hidden behind normal 12C emission.
“The amount of 13C is only 1% of 12C, so finding 13C in a waste disc is completely unexpected,” Higuchi said. “The clear evidence is that 49 Networks has a very large amount of gas.”
What is the origin of gas? The researchers offer two options. First, the remaining gas survived the scattering process in the final phase of planet formation. The amount of gas around 49 Ceti is comparable to around stars that are much younger in the active formation phase of the planet. There is no theoretical model that explains how much gas can last for so long.
Or, gas can be released through collisions with small objects such as comets. However, the number of collisions needed to explain the large amount of gas by 49 sets is too large to be accepted in current theory. The results of the ALMA are currently pushing for a revision of the pattern of planet formation.