Module 05 · 6 min · Intermediate
Moving Objects
How motion is measured
Concept: positions across four visits
A moving source changes position consistently between visits; stationary stars stay put. Consistency across ≥3 visits separates real motion from noise.
01
Visits and epochs
SPHEREx revisits each point roughly every six months, with many visits clustered in each epoch. Sources that shift between visits may be asteroids or high-proper-motion stars.
02
Pixels aren't angles
Displacement must be converted with each frame's WCS and timestamp into arcsec per day; registration errors can masquerade as motion.