Astropy — Astronomy & Astrophysics Toolkit

Overview

Astropy is the core Python package for astronomy, providing essential functionality for astronomical research: unit-aware calculations, celestial coordinate transformations, FITS file I/O, cosmological calculations, precise time handling, tabular data operations, and WCS image coordinate mapping.

When to Use

• Converting between celestial coordinate systems (ICRS, Galactic, FK5, AltAz)
• Working with physical quantities and units (Jy→mJy, parsec→km, spectral equivalencies)
• Reading, writing, or manipulating FITS files (images and tables)
• Cosmological calculations (luminosity distance, lookback time, comoving volume)
• Precise time handling with multiple scales (UTC, TAI, TT, TDB) and formats (JD, MJD, ISO)
• Cross-matching astronomical catalogs by sky position
• WCS transformations between pixel and world coordinates
• For general tabular data: use pandas or polars instead
• For radio interferometry: use CASA instead

Prerequisites