astronomy

HD 213637

HD 213637 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 HD 213637 rather than just read about it. In short: HD 213637 is a solitary variable star in the zodiac constellation of Aquarius. It has the variable star designation MM Aquarii.

Key takeaways

HD 213637 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 213637 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 213637 from memory before moving on to harder problems.

Reference excerpt

HD 213637 is a solitary variable star in the zodiac constellation of Aquarius. It has the variable star designation MM Aquarii. With an apparent visual magnitude of 9.6, it is too faint to be visible to the naked eye. Based on parallax measurements, this star is located at a distance of approximately 692 light-years (212 pc) from the Earth. It is drifting further away with a line of sight velocity component of 5.3 km/s.

Observations This was identified as a chemically peculiar star by N. Houk and M. Smith-Moore in 1988. The stellar spectrum indicates strong metallicity and line blocking in the visual band, which are characteristic of rapidly oscillating Ap stars. The rapid p-mode oscillation of this star was discovered in 1997 by P. Martinez and associates. The spectrum of the measured light curve peaks at a pulsation period of 11 minutes. Pulsation amplitudes vary based on the element measured. This roAP star presents a strong surface magnetic field. The strength of the field was measured at 740±141 G, with a surface field of 5.5 kG. The effective temperature is one of the lowest measured for a magnetic chemically peculiar star, including roAp stars. Iron peak elemental abundances appear to be at or below solar, while it is overabundant in the elements strontium, yttrium, and zirconium. HD 213637 is an estimated 570 million years old, with 1.5 times the mass and 1.48 times the radius of the Sun. It is radiating 5.5 times the Sun's luminosity from its photosphere at an effective temperature of 7,030 K. The star appears to be rotating slowly with a projected rotational velocity of 3.5±0.5 km/s. Evolutionary models suggest this star is near or past the end of its time on the main sequence.

See also Przybylski's Star, another cool roAP star

References

Worked examples

Example 1 — a first encounter with HD 213637

Start with the simplest possible case. Write down what HD 213637 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 HD 213637 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 HD 213637 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 HD 213637

In research: HD 213637 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 HD 213637 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: HD 213637 is common in secondary-school and first-year university syllabi. It links to neighbouring topics A-type main-sequence stars, Aquarius (constellation), Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 213637 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 HD 213637 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 213637 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 HD 213637 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 213637 in simple terms?

HD 213637 is a solitary variable star in the zodiac constellation of Aquarius. It has the variable star designation MM Aquarii.

Why does HD 213637 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 HD 213637?

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 HD 213637.