astronomy

WR 46

WR 46 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 WR 46 rather than just read about it. In short: WR 46 (DI Crucis) is a Wolf–Rayet star in the constellation of the Southern Cross of apparent magnitude +10.8. It is located at 55 arcmin north of Theta2 Crucis.

Key takeaways

WR 46 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect WR 46 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WR 46 from memory before moving on to harder problems.

Reference excerpt

WR 46 (DI Crucis) is a Wolf–Rayet star in the constellation of the Southern Cross of apparent magnitude +10.8. It is located at 55 arcmin north of Theta2 Crucis. The star is a member of the distant stellar association Cru OB4, and is around 2,900 parsecs or 9,300 light years from the Solar System.

Features WR 46 has spectral type WN3, with peculiarities in the spectrum including unusually broad emission lines. Its spectrum is characterized by the presence of strong lines of NV and HeII and the absence of hydrogen lines. It is known as a weak-lined WNE star because of the high temperature but relatively weak emission strength. The physical parameters of WR 46 are all estimates from assumptions about the distance and models for stars of its type, complicated by the suspicion that there is a companion star. The effective temperature is over 110,000K, the luminosity greater than 200,000 times the solar luminosity (L☉), the mass around 14 times that of the Sun (M☉) and a radius of 1.36 times the solar radius (R☉). The terminal velocity of the stellar wind reaches 2450 km/s with a total mass loss rate of 4 × 10−6 M☉ per year. WR 46 is a known source of X-rays, an aspect that was discovered by the Einstein Observatory. The X-ray luminosity between 0.2 and 10.0 keV is 7.7 × 1032 erg/s. Its X-ray spectrum is dominated by a soft component but there is also a hard component above 3 keV (a hard tail).

Variability

WR 46 exhibits complex variability on relatively short time scales of a few hours. In the past there have been regular but intermittent changes in the radial velocity, multiple periods and photometric variation at some wavelengths, particularly ultraviolet. It has been proposed that this short-term behavior is due to non-radial pulsations, fast rotational modulation, or the presence of a lower-mass companion. Theories that are now discounted include WR 46 being a Super soft X-ray source or a V Sagittae star, The radial velocity changes of the spectral lines originating most deeply within the stellar wind show clear radial velocity variations with a period of 7.9 hours. However the lines do not change their shape or intensity, which would be expected from a pulsating star Non-radial pulsations have been proposed, with multiple pulsation periods of varying amplitude accounting for the apparently irregular brightness changes.

Binary star WR 46 has been suspected to be a binary system with an OB companion. The orbital period of the system has been reported at 0.311 days and 0.329 days. Most recent research refutes the idea of a companion, instead favoring the single WN star theory.

References

Illustrations

Worked examples

Example 1 — a first encounter with WR 46

Start with the simplest possible case. Write down what WR 46 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 WR 46 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 WR 46 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 WR 46

In research: WR 46 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 WR 46 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: WR 46 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Crux, Durchmusterung objects, Henry Draper Catalogue objects, so understanding it makes those chapters shorter.
In everyday life: Look for WR 46 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study WR 46 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WR 46 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 WR 46 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WR 46 in simple terms?

WR 46 (DI Crucis) is a Wolf–Rayet star in the constellation of the Southern Cross of apparent magnitude +10.8. It is located at 55 arcmin north of Theta2 Crucis.

Why does WR 46 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 WR 46?

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 WR 46.