FAQ
Q: I’ve found a galaxy with several clear tidal features. Where should I share it?
A: Tag it as #multiple-features on Talk, or post it in this discussion thread. Great examples help the whole community improve at spotting tidal structures.
Q: When should I classify a tidal feature as “other”?
A: Use “other” if you’re confident the structure is real and caused by a merger, but it doesn’t resemble any of the listed categories.
If it mostly looks like a tail, stream, fan, or shell, choose that instead. “Other” should be reserved for genuinely odd or ambiguous shapes.
Q: How do I tell the difference between a tidal feature and a spiral arm?
A: Spiral arms connect smoothly to the galaxy’s disk and follow a coherent pattern.
Tidal features often look misaligned and asymmetric from the galaxy. They may appear lopsided, faint, or disconnected. If the structure fits cleanly into the spiral pattern, it’s probably not tidal.
Q: How do I avoid mistaking two overlapping galaxies for a real merger?
A: Overlapping galaxies often look like two clean, intact shapes with no distortion, no bridges, and no stretched light between them.
True mergers usually show asymmetry, warping, or material connecting the galaxies.
If you don’t see signs of interaction, it’s likely just a chance alignment.
Q: The feature is very faint, should I mark it?
A: Yes, if you can see a coherent shape, even faintly. Euclid’s images are deep, and faint structures are often scientifically important.
Q: What counts as a “shell”? I hardly ever see them.
A: Shells are subtle, curved arcs of light that sit outside the main body of a galaxy. They’re usually faint, smooth, and stacked in layers.
They appear most often around ellipticals. If you see bright clumps or irregular shapes, it’s probably another feature type.
Q: Sometimes the galaxy looks distorted, but I don’t see a companion. Is it still a merger?
A: Yes, very often! The companion may have already coalesced or been disrupted beyond recognition.
A single distorted galaxy with tails or shells still counts as a merger remnant.
Q: What if I see more than one feature?
A: Mark every tidal feature you can confidently identify. Mergers often produce multiple structures (e.g., two tails + a fan). More detail helps the science.
Q: Should I flag stars or artifacts if they confuse the image?
A: No—just do your best to ignore them. Bright foreground stars, cosmic rays, and image artifacts are common. Unless they truly hide a feature, continue with the classification.
Q: I want to learn more!
A: Visit the Education section on the About page for curated resources on tidal features, mergers, and galaxy evolution.
Q: What opportunities besides people-powered research exist that let people with an interest in science and space exploration get involved?
A: Check out the NASA website (nasa.gov/get-involved) to learn about hackathons, challenges, competitions, and events open to the public.