astronomy

Pr0211

Pr0211 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 Pr0211 rather than just read about it. In short: Pr0211 (sometimes written Pr 0211, also 2MASS J08421149+1916373) is a Sun-like late G or early K-type main-sequence star in the Beehive Cluster, or Praesepe, located 600 light-years away in the constellation Cancer. It is rotationally variable and has a rotation period of 7.97 days, with its spin axis at an inclination of 76°±11° to the plane of the sky.

Key takeaways

Pr0211 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Pr0211 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Pr0211 from memory before moving on to harder problems.

Reference excerpt

Pr0211 (sometimes written Pr 0211, also 2MASS J08421149+1916373) is a Sun-like late G or early K-type main-sequence star in the Beehive Cluster, or Praesepe, located 600 light-years away in the constellation Cancer. It is rotationally variable and has a rotation period of 7.97 days, with its spin axis at an inclination of 76°±11° to the plane of the sky. Pr0211 hosts two known exoplanets, and was the first multi-planet system to be discovered in an open cluster. Pr0211 forms a double star system with a K-type main-sequence star known as NGC 2632 JC 280 or 2MASS J08421285+1916040. Although the stars share a similar distance and common proper motion, their relative space velocity appears to be high enough that the pair are not gravitationally bound.

Planetary system Pr0211 b is a gas giant exoplanet, specifically a hot Jupiter, orbiting around Pr0211. Pr0211 b along with Pr0201 b are notable for being the first exoplanets discovered in the Beehive Cluster. Pr0211 b and Pr0201 b were discovered in 2012 by Sam Quinn and his colleagues while observing 53 stars in the Beehive Cluster using the 1.5 metres (4.9 ft; 1.6 yd) telescope at the University of Georgia in the United States. Pr0211 c is a gas giant exoplanet orbiting around Pr0211. Pr0211 c was discovered in 2016 by Luca Malavolta and his colleagues while observing its host star with the HARPS-N spectrograph on the 3.6 metres (12 ft; 3.9 yd) Italian Telescopio Nazionale Galileo (TNG) in La Palma, and the Tillinghast Reflector Echelle Spectrograph (TRES) mounted at the 1.5 metres (4.9 ft; 1.6 yd) telescope at the University of Georgia in the United States.

References

Worked examples

Example 1 — a first encounter with Pr0211

Start with the simplest possible case. Write down what Pr0211 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 Pr0211 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 Pr0211 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 Pr0211

In research: Pr0211 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 Pr0211 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: Pr0211 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Cancer (constellation), K-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for Pr0211 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 Pr0211 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Pr0211 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 Pr0211 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Pr0211 in simple terms?

Why does Pr0211 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 Pr0211?

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 Pr0211.