|
|
|
|
|
|
by T-A
3332 days ago
|
|
|
A bit of both. They say that with the model depicted in Fig 1, based on Spitzer/GLIMPSE surveys [1], nine of eleven extinction events which they identify (the six "canonical" ones plus five other significant drops in marine biodiversity, Section 2.2) occurred while the solar system was passing through a spiral arm (Section 3). They then point out that it's easy enough to modify the model to fit all eleven events: we can't see what's on the other side of the galaxy, so we can hypothesize a "spur" there, similar to the Orion spur on our side, with some support for that idea coming from the symmetry of other galaxies. But even without such modifications, nine out of eleven is not bad. Spiral arms need not necessarily explain every single one of them. [1] http://inspirehep.net/record/817646?ln=en |
|
|