SpaceX's Starlink constellation could place up to 42000 satellites around the Earth. Would aliens with their own telescopes notice them? They would be about 150 km apart and could reflect light of this wavelength produced by the Sun's corona. Waves bouncing off the ionosphere could perhaps form a detectable diffraction pattern.
Not in any way that is special to the Starlink satellites. Many satellites can interfere with earth-based astronomy because they are very close to the earth. A reflection off a satellite that is a few hundred miles away can be brighter than a star that is a few tens of trillions of miles away. But, from a different star, both our sun and the satellites are a few tens of trillions of miles away, and the satellites' reflected light is negligible.
Of course, it is possible to imagine faraway supertelescopes that could detect human artifacts. But such a telescope could also detect the ISS and Iridium flares, among many other things. The Starlink satellites' nuisance effect for earthly astronomers doesn't really make them easier to detect from Alpha Centauri.