Object Atlas / M31
M31 is the nearest large spiral galaxy and the Milky Way's major Local Group neighbor. Its resolved stellar populations preserve a record of billions of years of evolution.
Image: NASA, ESA, and the PHAT collaboration. Credit and survey context checked against the linked NASA record on 9 October 2026.
Direct observation
A high-surface-brightness central region, structured dust lanes, and many resolved point sources appear across the surveyed disk. Display color combines measurements from different filters; it is not a single naked-eye exposure.
Interpretation
Color-magnitude diagrams and multi-band photometry help researchers infer stellar populations, extinction, and star-formation history. “Blue” does not by itself prove an age without calibration and a population model.
Scale limit
The PHAT footprint covers part of M31's disk, not every component of the galaxy or its environment. Conclusions about the whole galaxy must account for the survey footprint and selection effects.
Atlas task
Use the distance calculator to convert 2.5 million light-years to parsecs. Then explain why converting units does not reduce uncertainty in the original distance estimate.
Check: the result is about 766,500 parsecs. It carries the precision of the approximate 2.5-million-light-year input, not all displayed calculator digits.
Signal interpretation console · atlas
Identify wavelength, exposure, field of view and observing date before reading the image.
Separate object signal from point-spread function, noise, saturation and selection.
Track background removal, alignment, scaling and color mapping as part of the measurement.
Connect “Our Galactic Neighbor” to “The Coming Collision” through an explicit model.
Our nearest major galactic neighbor, 2.5 million light-years away, containing over 1 trillion stars and visible to the naked eye on clear nights.
Separate projected morphology from three-dimensional structure, and connect rotation, stellar populations, gas and distance measurements through independent observations. Projection, distance, extinction or adopted parameters may offer another explanation.
Query NASA: Hubble Traces Andromeda's History and MAST: Panchromatic Hubble Andromeda Treasury and seek an independent wavelength, spectrum, motion or catalogue measurement.