What does this signify?
- What do the horizontal and vertical bar signify?
- The bars almost seem mirror images of each other -- is this normal?
My pet name for them is 'compass points' 😃
They are 'diffraction spikes', and are common in SDSS images of bright stars. More about them in this recent OotD (Object of the Day) in the GZ forum: Diffraction Spikes, of the SDSS Kind