I would actually strongly suggest that since astrophotography is such a big issue for you, that you should get a Pentax K-70.
Any DSLR will be a tremendous improvement over what you're using now. A Canon T series will be just fine. What you will need with a Canon or Nikon is a lens that has a maximum aperture of at least f/2.8 or better. Why? Because at f/2.8 you can now use an ISO of about 3200 and a shutter speed of 30 seconds to get a proper exposure of the night sky. You do not want to use a shutter speed longer than 30 seconds because then your stars won't be pinpoints but instead, they'll show up as smudges. If you want star trails, then fine, but if you want pinpoints such as when photographing the Milky Way, then you need an f/2.8 lens so that you can keep your ISO down to a tolerable 3200.
This is where Pentax not only excels but actually does things simply not possible with any other brand of camera. Pentax uses in-body image stabilization while Canon and Nikon use an in-lens solution. Because Pentax can move the sensor, it uses this to cancel out the rotation of the Earth which causes the stars to "move" during the exposure. What this means for you is that not only do you not need to spend a lot of money on an f/2.8 lens, but if you do you can now use much, much lower ISO and get vastly sharper, clearer images with much better color and contrast. This feature which is unique to Pentax is called AstroTracer. It allows you to use shutter speeds longer than 30 seconds and still have the stars show up as pinpoints.
You can achieve similar results with any other DSLR or mirrorless camera, but you will need to invest in a sturdy tripod and a motorized head that slowly moves the camera during the exposure. Personally, I'd skip this option if you aren't already invested in a specific brand. However, the cost is relatively high and the added bulk and weight can be a huge problem for some people.
As for lenses, when taking night shots you're actually taking a landscape of the night sky. And as with any landscape photo, you will want a wide-angle lens. The wider, the better. A 14mm Samyang at about $500 is a great lens. It's a manual focus only lens, but that's fine since you normally turn the AF off when taking sky shots anyway. You don't want the lens to shift its focusing for obvious reasons. So look for a super-wide lens with an aperture of at least f/2.8 or better. Or, if you go with a Pentax like their KR or K-70 (the K-70 is among the best APS-C DSLRs on the market today), you can get a used ultra-wide and not have to worry if its aperture is big enough.