Astrophysicist/#scicomm'er at @DAWNCopenhagen, admirer of galaxies, amateur boxer, and appreciator of comic books, indiepop, and white chocolate.
Jul 21, 2022 β’ 7 tweets β’ 4 min read
1/7 Why does the Carina Nebula that #JamesWebb recently showed us have such a sharp edge?
A thread:
π΅The top part of the picture is full of very hot stars emitting intense UV radiation.
π€The bottom part is a dense gas cloud of dust, molecules, and atoms, mostly hydrogen. 2/7 In neutral gas, UV photons can't travel very far before hitting an atom.
This πͺπ°π―πͺπ»π¦π΄ the atom into a proton β and an electron β
So the top part is ionized, while the bottom part is neutral.
Ionized gas is largely transparent, while neutral gas is largely opaque.
