How radiation affects the formation of planets
Hubble image of the Orion Nebula and zoom with the James Webb Space Telescope (JWST) on the system d203-506
Source: Hubble Image: NASA/STScI/Rice Univ./C.O’Dell et al. JWST image: O. Berné / I. Schroetter / PDRs4All
It was suspected for a long time, but has now been observed for the first time with the “James Webb” space telescope: Large stars can prevent the formation of large gas planets in smaller stars in their surroundings – through a certain mechanism.
DThe high-energy radiation from massive stars can prevent the formation of large gas planets when smaller stars surround them. An international research team observed this long-suspected influence for the first time using the “James Webb” space telescope and an antenna system in Chile. Like the scientists in the journal “Science” report that ultraviolet radiation from large stars destroys the outer disk of gas around a young star in the Orion Nebula faster than planets can form there.
After their formation, young stars are enveloped in a rotating disk of gas and dust in which planets can form through slow compression. In the inner region of such a protoplanetary disk, rocky planets like our Earth usually form because the radiation from the young star blows away the lighter gases. Further out in the disk, however, there is enough cool gas that can condense into large gas planets such as Jupiter. But even this area is not immune to destructive radiation.
“Most small stars form in larger clusters that also contain massive stars,” explain Olivier Berné from the University of Toulouse and his colleagues. Models predict that the high-energy UV radiation from these large stars can dissolve the outer disk, influencing the formation of planets there. This has not yet been directly observed – and it therefore remains unclear how strong this influence is.
Berné and his colleagues used the James Webb Space Telescope and ALMA (Atacama Large Millimeter Array) to target the protoplanetary disk around the star d203-506, 1,350 light-years away, in the Orion Nebula, a star-forming region. In the vicinity of the red dwarf star, which contains about a third as much mass as our sun, there are several stars with ten times the mass of the sun that emit 100,000 times more radiation than our central star.
Observations show that the UV radiation from these massive stars heats the gas in the outer region of the disk so much that it evaporates. The disk around d203-506 loses so much gas through this photoevaporation, i.e. evaporation through radiation, that it should completely dissolve within 130,000 years. “And that is much faster than planets can form,” said Berné and his colleagues.
Astronomers know of over 4,000 planetary systems in other stars. The discovery of all these exoplanets showed that the more massive a star is, the more likely it is to also have large gas planets. As the team’s observations show, this connection is explained by the high-energy radiation from large stars in the area.
With their gravitational pull, dwarf stars like d203-506 can offer less resistance to photoevaporation than stars with a lot of mass and correspondingly greater gravity. Our sun is apparently already massive enough, as evidenced by the large gas planets in the outer solar system.