astronomy

Omicron Ursae Majoris

Omicron 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 Omicron Ursae Majoris rather than just read about it. In short: Omicron Ursae Majoris (ο Ursae Majoris, abbreviated Omicron UMa, ο UMa), formally named Muscida , is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of +3.35 and is located at a distance of around 179 light-years (55 parsecs) from the Sun.

Key takeaways

Omicron 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 Omicron Ursae Majoris to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Omicron Ursae Majoris from memory before moving on to harder problems.

Reference excerpt

Omicron Ursae Majoris (ο Ursae Majoris, abbreviated Omicron UMa, ο UMa), formally named Muscida , is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of +3.35 and is located at a distance of around 179 light-years (55 parsecs) from the Sun. In 2012, an exoplanet designated Omicron Ursae Majoris Ab was found to be orbiting the primary.

Nomenclature ο Ursae Majoris (Latinised to Omicron Ursae Majoris) is the star's Bayer designation. The traditional name Muscida derives from the post classical Latin musus, meaning "snout, or muzzle [of the bear]". This name was shared with the optical double star Pi Ursae Majoris. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Muscida for this star. In Chinese, 內階 (Nèi Jiē), meaning Inner Steps, refers to an asterism consisting of ο Ursae Majoris, 16 Ursae Majoris, 6 Ursae Majoris, 23 Ursae Majoris, 5 Ursae Majoris and 17 Ursae Majoris. Consequently, the Chinese name for ο Ursae Majoris itself is 內階一 (Nèi Jiē yī, English: the First Star of Inner Steps.).

Properties and observations The stellar classification of this star, G5 III, indicates that it is in the giant stage of its evolution. The interferometry-measured angular diameter of this star is about 2.42 mas, which, at its estimated distance, equates to a physical radius of about 14 times the radius of the Sun. It has about three times the mass of the Sun and radiates 116 times the Sun's luminosity from its outer atmosphere at an effective temperature of 5,282 K, giving it the yellowish hue of a G-type star. In 1963, East German astronomer Gerhard Jakisch reported this star as a variable with a period of 358 days and an amplitude of 0.08 magnitude. The 1982 edition of the New Catalogue of Suspected Variable Stars listed it with a variability from 3.30 to 3.36 in the visual band. However, in 1992 American astronomer Dorrit Hoffleit noted that the two comparison stars used to determine the variability may themselves be variable. Hence the actual variability of this star may be suspect. Muscida has a magnitude 15.2 common proper motion companion at an angular separation of 7.1 arcseconds. With a probability of 99.4%, this companion is the source for the X-ray emission from the system. Omicron Ursae Majoris is sometimes listed with two more companions, but, based on proper motion data, these appear to be optical companions. No other companions were detected by 2016. This system is a member of the thin disk population and is following an orbit through the Milky Way galaxy with an eccentricity of 0.12. It comes as close to the Galactic Center as 23.5 kly (7.2 kpc) and as distant as 30.2 kly (9.3 kpc). This orbit carries it no more than about 330 ly (100 pc) above the galactic plane. It is considered a runaway star because it has a high peculiar velocity of 35.5 km s−1 relative to the typical motion of stars in its vicinity. The star has no detectable magnetic fields.

Planetary system In 2012, an exoplanet designated Omicron Ursae Majoris Ab and orbiting the primary at 3.9 astronomical units, was found. This gas giant (4.1 times as massive as Jupiter) completes an orbit in 1630 days.

References

Worked examples

Example 1 — a first encounter with Omicron Ursae Majoris

Start with the simplest possible case. Write down what Omicron 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 Omicron 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 Omicron 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 Omicron Ursae Majoris

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

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

Frequently asked questions

What is Omicron Ursae Majoris in simple terms?

Why does Omicron 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 Omicron 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 Omicron Ursae Majoris.