fasterthanjoao said:
Generally, there will be reviewers that will make a first decision on the submission within a few weeks - again it depends on the journal (and of course your work) but the journals I'm familiar with have ~70% rejection rates in this time.
Different journals and different fields have different philosophies. Astrophysical Journal has a publication rate of 70% of submissions, and in astrophysics the philosophy seems to be publish everything that isn't totally crazy and let readers sort it out. Nature and Science have <5% publication rates.
The process then normally takes somewhere in the region of months but I have seen papers take upwards of a year to reach a final decision.
This poses a problem with astrophysics since anything that is a year old is hopelessly outdated. This is why no one reads journals for current research, everyone just reads preprints. Technologically pretty much anyone can publish on the Los Alamos preprint server, but people are careful about what they upload, because they don't want to look like an idiot if they upload something really, really silly.
The other thing is that if you discover something really, really big (i.e. you contact space aliens), then you generally keep very quiet about it, and undergo a huge amount of informal and formal peer review before saying anything, because you don't want to look like a fool if you get it wrong. If you have fifty people look at something before going public, you might still get it wrong, but it won't be wrong because of something very, very silly.
However, most papers in astronomy and astrophysics are "I ran this computer program or I looked in the telescope, and this is what I found."