Ask an Astronomer

I believe that you can use the principle of similar triangles to solve this problem.   Let D_sun be the diameter of the Sun (1.392×10^9 m), D_poles be the spacing between the poles (30 m) , d_perihelion be the Earth-Sun distance at perihelion (1.471×10^(11) m), and x be the unknown distance to the Sun from the poles.  Solve for x: x = 30m * (1.471×10^(11) m)/(1.392×10^9 m) =~ 3170.26 m  

A Tatooine-like planet, or a planet that orbits a binary star system, would very likely orbit at a relatively large distance from the binary star system in order for the planet’s orbit to be stable.  Since seasons on a planet result from the tilt of the planet’s rotational axis relative to its orbit around its host star(s), the planet’s rotational axis inclination would drive seasonal variations on this hypothetical Tatooine-like system.  I believe that the light from the binary star system would be quite diminished, though, due to the larger orbital distance that the planet would be required to orbit…

To varying degrees radio astronomical measurements are affected by the Earth’s atmosphere, including changes in water vapor content.  These effects tend to be more extreme at shorter (less than about 1 cm) wavelengths.  A similar question to this blog has been addressed in our response to “Do Radio Sources “Twinkle”?“.

I believe that this question has been answered several times in the past on this blog.  I think that if you use the blog search function and enter “How Does a Radio Interferometer Work?” in the search box that the results will provide a number of responses to previous questions on this subject.

I believe that this question has been answered before in two posts which addressed questions about single radio telescopes (How Does a Single Dish Telescope Make Images?) and collections of radio telescopes which work together to make an astronomical image (How Does a Radio Interferometer Work?).

No, the International Space Station (ISS) does not have red or blue lights that are visible from Earth. The ISS is primarily visible from Earth due to sunlight reflecting off its large solar panels and other light-colored surfaces. The ISS appears as a bright, steady light, like a fast-moving star or a plane without flashing lights.

I believe what you are seeing is the apparent “retrograde”, or backwards, motion of Mars as the Earth overtakes Mars on an inside track (orbit) around the Sun.  Mars was most recently in an apparent retrograde motion in the sky from December 6, 2024 until February 23, 2025.

“OII” is singly-ionized oxygen, in what is called spectroscopic notation.

I have not been able to find any evidence of observed auroral phenomena associated with Jupiter’s “Great Blue Spot”.  Note, though, that the study of this unusual feature in Jupiter’s atmosphere is still a very active area of research that will likely provide more clarity regarding the Great Blue Spot’s properties in the future.

Planets that are in orbits that are closer to the Sun than Earth (Venus and Mercury) generally follow the Sun in the sky, so in general will rise (and set) at about the same azimuth as the Sun.  All other planets, except when they are in conjunction with the Sun, will rise (and set) at a different azimuth than the Sun.  Using your example, on January 18 2025 from Homer Alaska, Mars rose at an azimuth of about 38 degrees at about 01 UT (which would have been 16::00 on January 17 local Homer Alaska time).  The differences in azimuth…

I believe that the folks at the SETI Institute provide the best resources for information on the search for life and intelligence beyond Earth.

At any given time it is the Earth’s equator that receives the most sunlight throughout the year.  Hopefully I have understood your question correctly.