science

Strömgren photometric system

Strömgren photometric system is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Strömgren photometric system rather than just read about it. In short: The Strömgren photometric system, abbreviated also as uvbyβ or simply uvby, and sometimes referred as Strömgren - Crawford photometric system, is a four-colour medium-passband photometric system plus Hβ (H-beta) filters for determining magnitudes and obtaining spectral classification of stars. Its use was pioneered by the Danish astronomer Bengt Strömgren in 1956 and was extended by his colleague the American astron…

Key takeaways

Strömgren photometric system belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Strömgren photometric system to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Strömgren photometric system from memory before moving on to harder problems.

Reference excerpt

The Strömgren photometric system, abbreviated also as uvbyβ or simply uvby, and sometimes referred as Strömgren - Crawford photometric system, is a four-colour medium-passband photometric system plus Hβ (H-beta) filters for determining magnitudes and obtaining spectral classification of stars. Its use was pioneered by the Danish astronomer Bengt Strömgren in 1956 and was extended by his colleague the American astronomer David L. Crawford in 1958. It is often considered to be a powerful tool and successful investigating the brightness and effective temperature of stars. This photometric system also has a general advantage as it can be used to measure the effects of reddening and interstellar extinction. This system also allows calculation of parameters from the b {\displaystyle b} and y {\displaystyle y} filters ( b − y ) {\displaystyle (b-y)} without the effects of reddening, termed m 1 {\displaystyle m_{1}} and c 1 {\displaystyle c_{1}} .

Wavelength and half-width response functions The following table shows the characteristics of each of the filters used (represented colors are only approximate):

Note: colors are only approximate and based on wavelength to sRGB representation (when possible).

Indices There are four main highly applied and technical indices: ( b − y ) {\displaystyle (b-y)} ; m 1 {\displaystyle m_{1}} ; c 1 {\displaystyle c_{1}} ; and β {\displaystyle \beta } .

m 1 = ( v − b ) − ( b − y ) {\displaystyle m_{1}=(v-b)-(b-y)}

c 1 = ( u − v ) − ( v − b ) {\displaystyle c_{1}=(u-v)-(v-b)}

β = β n a r r o w − β w i d e {\displaystyle \beta =\beta _{narrow}-\beta _{wide}}

Where;

y {\displaystyle y} magnitudes are well-correlated with Johnson-Morgan V magnitudes (its V band).

( b − y ) {\displaystyle (b-y)} is sensitive to stellar temperature (measure of Paschen continuum).

c 1 {\displaystyle c_{1}} is sensitive to the surface gravity (measures Balmer discontinuity strength).

m 1 {\displaystyle m_{1}} is sensitive to the metallicity (measure of line blanketing).

See also Photometric systems Stellar classification

References

External links The Asiago Database on Photometric Systems The uvby photometric system Stromgren photometric system tutorial SAGA: Strömgren survey for Asteroseismology and Galactic Archaeology

Worked examples

Example 1 — a first encounter with Strömgren photometric system

Start with the simplest possible case. Write down what Strömgren photometric system claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Strömgren photometric system before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Strömgren photometric system ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Strömgren photometric system

In research: Strömgren photometric system appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Strömgren photometric system in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Strömgren photometric system is common in secondary-school and first-year university syllabi. It links to neighbouring topics Photometric systems, so understanding it makes those chapters shorter.
In everyday life: Look for Strömgren photometric system outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Strömgren photometric system in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Strömgren photometric system means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Strömgren photometric system out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Strömgren photometric system in simple terms?

Why does Strömgren photometric system matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Strömgren photometric system?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Strömgren photometric system.