Spectral Classification of Stars Concept Map
See how stars are sorted by spectrum, temperature and luminosity in one visual map. Then build your own from lecture notes or a PDF.
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CogniGuide at a glance
- What you get
- Interactive mind maps of the main ideas and how they connect. Free: overview maps (detailed maps on your first 3 creations). Plus: detailed maps with supporting concepts.
- Exports
- Your first PDF or PNG export is free; Plus exports anytime.
- Price
- Free plan: 5 creations a week, up to 3 a day. Plus: $9.99/month or $99.90/year (USD; local prices at checkout).
- Sign-up
- A free account is required before you create anything (Google or email). No credit card.
- What you can upload
- PDF, Word (.docx), PowerPoint (.pptx), plain text or Markdown, and images (PNG, JPG, WebP, GIF), or type a topic. One file per creation on the free plan; several at once on Plus.
How it compares: vs Knowt · vs Quizlet · vs NotebookLM · vs Mapify
Build a Star Classification Map Your Way
Turn your textbook chapter or lecture slides into a map of spectral types and their properties.
Map from your own notes
Upload a PDF, Word file, PowerPoint or text file, and the AI builds the branches for you.
Clear spectral structure
See how the O, B, A, F, G, K and M classes link to temperature, color and spectral lines.
Study with a quiz
Turn the finished map into a quiz, or make flashcards from the same notes to test recall.
How to Make a Spectral Classification Map
Three steps from your astronomy notes to a study-ready map.
- 1
Add your material
Upload your notes or slides on stellar spectra, or simply type the topic.
- 2
AI builds the map
The AI organizes spectral classes, temperatures, lines and luminosity classes into branches.
- 3
Study, expand and quiz
Expand any node, edit it, export as PNG or PDF, or turn the map into a quiz.
Spectral Classification of Stars Explained
Spectral classification of stars sorts stars by the features in their light spectrum. The main scheme is the Harvard sequence, O, B, A, F, G, K and M, ordered from the hottest blue stars to the coolest red ones. Each class is then split into subclasses from 0 to 9, and stars are also grouped by luminosity class.
- Spectral types: O, B, A, F, G, K and M, from hottest to coolest.
- Temperature: surface temperature drops from tens of thousands of kelvin to about 3,000 K.
- Spectral lines: absorption lines of hydrogen, helium, calcium and metals identify each class.
- Luminosity classes: Roman numerals I to V separate supergiants from main-sequence dwarfs.
- Subclasses: decimal subdivisions such as G2 refine position within a class.
Use a map like this to revise the sequence and link each class to its temperature and lines. You can generate a personalized version from your own notes with CogniGuide.
Explore related topics
Spectral Classification Questions
Common questions about star classes and how to map them.
What does the OBAFGKM sequence mean?
OBAFGKM is the order of stellar spectral types, from the hottest, most massive blue O stars to the coolest red M stars. A common mnemonic is Oh Be A Fine Girl Kiss Me. The sequence reflects surface temperature rather than age.
Why are stars classified by their spectra?
A star's spectrum shows absorption lines that depend on its surface temperature and chemical composition. Measuring these lines lets astronomers assign a spectral type, temperature and luminosity class without measuring distance first.
Which file types can I use to build this map?
You can upload PDF, Word (DOCX), PowerPoint (PPTX), text or Markdown files, or images of your notes. You can also type a topic such as stellar spectral classes.
Can I turn a star classification map into a quiz?
Yes. Once the map is created, you can turn it into a quiz to test yourself on spectral types and their properties. The same notes can also become flashcards.