Stellar parallax is the apparent shift of position of any nearby star (or other object) against the background of distant objects. Created by the different orbital positions of Earth, the extremely small observed shift is largest at time intervals of about six months, when Earth arrives at opposite sides of the Sun in its orbit, giving a baseline distance of about two astronomical units between observations. The parallax itself is considered to be half of this maximum, about equivalent to the observational shift that would occur due to the different positions of Earth and the Sun, a baseline of...
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For the purposes of this question, I wish to consider active, hydrogen-burning stars, not deuterium-burning brown dwarfs, or stellar remnants like black holes or neutron stars. (Though including those would be interesting questions in and of themselves)
What is the upper limit of distance that w...
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Wikipedia's Thorne–Żytkow object begins:
A Thorne–Żytkow object (TŻO or TZO), also known as a hybrid star, is a conjectured type of star wherein a red giant or red supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. Such objects were hypo...
