astronomy

Kappa Ursae Majoris

Kappa Ursae Majoris is a astronomy 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 Kappa Ursae Majoris rather than just read about it. In short: Kappa Ursae Majoris (κ Ursae Majoris, abbreviated Kappa UMa, κ UMa) is a binary star in the constellation of Ursa Major. With a combined apparent magnitude of +3.60, the system is approximately 358 light-years from Earth.

Key takeaways

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

Reference excerpt

Kappa Ursae Majoris (κ Ursae Majoris, abbreviated Kappa UMa, κ UMa) is a binary star in the constellation of Ursa Major. With a combined apparent magnitude of +3.60, the system is approximately 358 light-years from Earth. The two components are designated Kappa Ursae Majoris A (officially named Alkaphrah , a traditional name of the system) and B.

Nomenclature κ Ursae Majoris (Latinised to Kappa Ursae Majoris) is the system's Bayer designation. The designations of the two components as Kappa Ursae Majoris A and B derives from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU). A traditional name of the system is Alkafzah (corrupted to Alkaphrah or El Koprah), from the Arabic القفزة al-qafzah "the leap [of the gazelle]", which refers to an asterism consisting of ι, κ, λ, μ, ν, and ξ Ursae Majoris. The name Alkafzah (and variants) was also (mis)attributed to χ Ursae Majoris. κ and ι Ursae Majoris formed the third leap of the gazelle, and sometimes shared the name Talitha, from Arabic al-thālitha "third", with κ rarely called Talitha Australis, "southern Talitha" in Latin. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems. It approved the name Alkaphrah for the component Kappa Ursae Majoris A on 5 September 2017 and it is now so included in the List of IAU-approved Star Names. The name Talitha was approved for ι Ursae Majoris Aa. In Chinese astronomy, 三台 (Sān Tái), meaning Three Steps, refers to an asterism consisting of Kappa Ursae Majoris, Iota Ursae Majoris, Lambda Ursae Majoris, Mu Ursae Majoris, Nu Ursae Majoris and Xi Ursae Majoris. Consequently, the Chinese name for Kappa Ursae Majoris itself is 上台二 (Shàng Tái èr, English: Star of Second Upper Step).

Properties Both components of the binary star are white A-type main sequence dwarfs. They have apparent magnitudes of +4.2 and +4.5. The orbital period of the binary is 35.6 years (13,007.2 days), and the two stars are separated by 0.18 arcseconds. An infrared excess indicates a debris disk with a mean temperature of 165 K is orbiting the primary at a separation of 55.2 AU.

References

Worked examples

Example 1 — a first encounter with Kappa Ursae Majoris

Start with the simplest possible case. Write down what Kappa Ursae Majoris claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, 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 Kappa Ursae Majoris 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 Kappa Ursae Majoris 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 Kappa Ursae Majoris

In research: Kappa Ursae Majoris appears in astronomy 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 Kappa Ursae Majoris 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: Kappa Ursae Majoris is common in secondary-school and first-year university syllabi. It links to neighbouring topics A-type main-sequence stars, Bayer objects, Binary stars, so understanding it makes those chapters shorter.
In everyday life: Look for Kappa Ursae Majoris 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 Kappa Ursae Majoris in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kappa Ursae Majoris 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 Kappa Ursae Majoris out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kappa Ursae Majoris in simple terms?

Why does Kappa Ursae Majoris matter?

Because it connects several astronomy 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 Kappa Ursae Majoris?

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 Kappa Ursae Majoris.