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If we're talking about spacefaring aliens, they'd have to have some kind of sensitivity to light (i.e. sight) artificial or otherwise, or they wouldn't even know what a star is.
I don't know how you'd make tools without prehensile limbs. Many animals can utilize found objects, but the ability to reliably fasten or shape parts requires pinching and holding with multiple dextrous limbs. Telekinesis seems physically unlikely.
Mouths are likely necessary for acquiring large amounts of macronutrients. Absorbtion through the skin or plant-like synthesis doesn't produce enough energy for organisms to manipulate tools.
It's difficult to amass resources or explore much of anything without locomotion. A lower limb in the form of a leg, fin, or flagella accomplishes that. Other fluid-based propulsion systems are possible, as are organic wheels and axles, although the intermediate evolutionary stages seem unworkable.
Combustion is very difficult to achieve safely in a non-terrestrial environment. Without it, originating metal production is almost impossible. One could make use of volcanism to melt metals in e.g. a olivine bowl with a very long handle, but proper smelting is impractical.
Without an Earth-like gravitational pull, open-top vessels don't contain or pour liquid well, preventing even the most basic chemistry.
Off the top of my head, I'd expect space-faring aliens to have eyes, hands, a mouth, legs, and be adapted to a terrestrial environment with reasonably Earth-like gravity. A creature without those features would suggest it was created artificially.
