astronomy

Pherkad

Pherkad 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 Pherkad rather than just read about it. In short: Pherkad , Bayer designation Gamma Ursae Minoris (γ Ursae Minoris, abbreviated Gamma UMi, γ UMi), is a star in the northern constellation of Ursa Minor. Together with Beta Ursae Minoris (Kochab), it forms the end of the dipper pan of the "Little Dipper", which is an asterism forming the tail of the bear.

Key takeaways

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

Reference excerpt

Pherkad , Bayer designation Gamma Ursae Minoris (γ Ursae Minoris, abbreviated Gamma UMi, γ UMi), is a star in the northern constellation of Ursa Minor. Together with Beta Ursae Minoris (Kochab), it forms the end of the dipper pan of the "Little Dipper", which is an asterism forming the tail of the bear. Based upon parallax measurements obtained during the Hipparcos mission, it is approximately 487 light-years (149 parsecs) from the Sun.

Nomenclature γ Ursae Minoris (Latinised to Gamma Ursae Minoris) is the star's Bayer designation. The fainter 11 Ursae Minoris has been called γ1 Ursae Minoris, in which case Gamma Ursae Minoris would be designated γ2. However this usage is rarely seen. Gamma Ursae Minoris bore the traditional name Pherkad, which derived from the Arabic فرقد farqad "calf", short for aḫfa al farkadayn "the dim one of the two calves", that is Pherkad and Kochab (the full name Ahfa al Farkadain is traditionally applied to Zeta Ursae Minoris). Gamma Ursae Minoris was mostly called Pherkad Major to distinguish it from Pherkad Minor (11 Ursae Minoris). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Pherkad for Gamma Ursae Minoris on 21 August 2016 and it is now so included in the List of IAU-approved Star Names. In Chinese, 北極 (Běi Jí), meaning North Pole, refers to an asterism consisting of Gamma Ursae Minoris, Beta Ursae Minoris, 5 Ursae Minoris, 4 Ursae Minoris and Σ 1694. Consequently, the Chinese name for Gamma Ursae Minoris itself is 北極一 (Běi Jí yī, English: the First Star of North Pole), representing 太子 (Tàizǐ), meaning Crown Prince.

Properties Gamma Ursae Minoris has apparent magnitude +3.05 and can be readily observed with the naked eye even in a city-lit night sky. It has an absolute magnitude of –2.84. Measurement of the star's spectrum resulted in a stellar classification of A2 III, with the luminosity class of 'III' indicating this is an expanding giant star that left the main sequence after exhausting its core supply of hydrogen. Based on stellar evolutionary theory, Pherkad might become a Cepheid variable before settling as a red giant similar to its neighbor Kochab, before becoming a white dwarf of roughly 0.85 solar masses. The effective temperature of the star's outer envelope is 8,280 K, giving it the typical white hue of an A-type star. It is rotating rapidly, with the projected rotational velocity of 180 km s−1 providing a lower limit on the azimuthal velocity along the star's equator. This is classified as a shell star that has a circumstellar disk of gas around the star's equator, which may be causing it to vary in magnitude. It is 1100 times more luminous than the Sun, and possesses a radius 15 times that of the Sun.

Pherkad in fiction Pherkad (spelled as Pherkard) features in Cthulhu Mythos.

References

Illustrations

Worked examples

Example 1 — a first encounter with Pherkad

Start with the simplest possible case. Write down what Pherkad 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 Pherkad 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 Pherkad 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 Pherkad

In research: Pherkad 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 Pherkad 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: Pherkad is common in secondary-school and first-year university syllabi. It links to neighbouring topics A-type giants, Bayer objects, Bright Star Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for Pherkad 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 Pherkad in 20 minutes

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

Frequently asked questions

What is Pherkad in simple terms?

Why does Pherkad 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 Pherkad?

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 Pherkad.