There is only one wide angle lense from Sony, FE 16-35mm F2.8 GM
You may actually learn how to read catalogs. Because there are MORE wide angle lenses. Note that for Full Format Wide Angle is anything BELOW 50mm.
I have a good 28mm, plus adapters to make it wider.
There also is a 28-135, which covers quite a lot of wide angle too (all under 50mm). Then there is a 24-70 (again, good part wide angle)
Then we have the Sonnar 35mm. Then a 24-105.
Seriously, saying there ONLY is a 16-35 is not really showing that you know the definition of wide angle.
is it the choice to go for landscape astro photography?
Depends what you shoot. I have shot Landscape with 85mm at times - not everything is about "wide angle" and sometimes you have something that is a little further than you want ;)
Astro is generally tricky - StarEater (google is your friend) is still there, so other cameras are better. Especially with removed Sensor filters. Not sure something like this: http://noctilove.co.uk/astro-modification-guide/ even exists for Sony. And that is hobby - you want to make good astro, this looks more like it... https://www.digitalrev.com/article/the-d5500a-cooled-is-the-most-insane-astrophotography-mod-camera-ever
But generally, what is Astro? Shooting the sky? Or actually mounting the camera on a telescope? Not a lot of wide angle then. No actualy a lens ;)