Object Atlas / M51 / NGC 5194

Whirlpool Galaxy

The frame records a grand-design spiral and its projected companion. Explaining how the encounter shaped the arms requires kinematics and simulations in addition to morphology.

Reviewed 9 October 2026 · Source record accessed 9 October 2026

Object type
Interacting spiral galaxy system
Distance
about 31 million light-years
Constellation
Canes Venatici
Coordinates
RA 13h 29m 53s / Dec +47 deg 11 min 43 sec
Shown image
Hubble ACS mosaic
Image data
Broad optical filters plus hydrogen-emission-sensitive data

Image credit: NASA, ESA, S. Beckwith (STScI), and the Hubble Heritage Team (STScI/AURA). Details follow the linked ESA/Hubble image record.

Pixel evidence

What the image supports

Dark lanes trace across luminous spiral arms, compact blue-looking sources cluster along them, and pink-looking regions are concentrated in parts of the disk. These are filter-composite colors.

Rendering

What color separates

Broad optical and emission-sensitive exposures help separate dust absorption, stellar continuum and ionized-gas emission. Pixel color is not by itself an age, temperature or chemical-abundance measurement.

Evidence boundary

Interaction claims

The companion and distorted outer structure motivate an interaction model, but a still image does not show motion or prove that a specific cluster was triggered by the encounter.

Atlas task

Test your reading

Trace one arm from the center and list three pixel patterns. Turn only one into an interaction hypothesis, then name the velocity or modeling evidence needed to test it.

Signal interpretation console · atlas

Whirlpool Galaxy / observation pipeline

INPUT

Photons

Identify wavelength, exposure, field of view and observing date before reading the image.

STAGE A

Detector

Separate object signal from point-spread function, noise, saturation and selection.

STAGE B

Calibration

Track background removal, alignment, scaling and color mapping as part of the measurement.

OUTPUT

Physical claim

Connect “Grand-Design Spiral” to “Galactic Interaction” through an explicit model.

PRIMARY READOUT

A classic example of a grand-design spiral galaxy interacting with a smaller companion. The gravitational interaction triggers intense star formation throughout both galaxies.

MODEL WARNING

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.

CROSS-CHECK

Query ESA/Hubble: Whirlpool Galaxy M51 and seek an independent wavelength, spectrum, motion or catalogue measurement.

CONFIDENCE_PROTOCOL

For Whirlpool Galaxy, label each statement as pixel-level observation, calibrated measurement, model-dependent inference or open hypothesis. Advance a claim only when the preceding stage is documented.