astronomy

XY Ursae Majoris

XY 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 XY Ursae Majoris rather than just read about it. In short: XY Ursae Majoris is a short period binary star system in the northern circumpolar constellation of Ursa Major. It is an eclipsing binary with a baseline apparent visual magnitude of 9.50.

Key takeaways

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

Reference excerpt

XY Ursae Majoris is a short period binary star system in the northern circumpolar constellation of Ursa Major. It is an eclipsing binary with a baseline apparent visual magnitude of 9.50. The system is located at a distance of 221.5 light years from the Sun based on parallax measurements, but is drifting closer with a radial velocity of −10 km/s. It has a relatively high proper motion, traversing the celestial sphere at the angular rate of 0.191″·yr−1. The variability of this system was discovered by W. Strohmeier and its period was determined by R. Kippenhahn, with the findings announced in 1955. It was found to be a detached eclipsing binary system, and by 1963 a variable primary component had been noted. E. H. Geyer made intermittent light curve studies of the system starting with its discovery up until 1975, ascribing variability in the light curve to star spot activity on the primary component. The orbital period of the pair was determined to be 0.479 d, with the orbital plane inclined at an angle of 79.84° to the line of sight from the Earth. By 1990, enough data had been collected to identify a long term variation of the period, and it was hypothesized this was caused by a third body in the system orbiting the close binary. The orbital period of this component was estimated to be ~30 years in 2001, then refined to 26.7 years by 2010. If the orbital plane of this component is the same as the inner pair, its mass would be 18% of the mass of the Sun. An alternative solution to the period change suggests magnetic activity causes shifts in the angular momentum of the system, but this is considered less likely. This is a double-lined spectroscopic binary star system with an orbital period of 11.5 h. The primary component is a G-type main-sequence star with a stellar classification of G2V. It is an RS Canum Venaticorum-type variable that is magnetically active and a bright X-ray source. Despite this, relatively few optical flares have been observed. The cooler secondary is a K-type main-sequence star of class K5V that is smaller and less massive than the primary.

References

Illustrations

Worked examples

Example 1 — a first encounter with XY Ursae Majoris

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

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

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

Frequently asked questions

What is XY Ursae Majoris in simple terms?

XY Ursae Majoris is a short period binary star system in the northern circumpolar constellation of Ursa Major. It is an eclipsing binary with a baseline apparent visual magnitude of 9.50.

Why does XY 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 XY 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 XY Ursae Majoris.