science

WD 0137−349

WD 0137−349 is a science 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 WD 0137−349 rather than just read about it. In short: WD 0137−349 is a binary star in the constellation of Sculptor. It is located about 330 light-years (100 parsecs) away, and appears exceedingly faint with an apparent magnitude of 15.33.

Key takeaways

WD 0137−349 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect WD 0137−349 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WD 0137−349 from memory before moving on to harder problems.

Reference excerpt

WD 0137−349 is a binary star in the constellation of Sculptor. It is located about 330 light-years (100 parsecs) away, and appears exceedingly faint with an apparent magnitude of 15.33. It is composed of a white dwarf with a brown dwarf in orbit around it, and is one of the few systems composed of a white dwarf and an associated brown dwarf. The brown dwarf orbits with a period of 116 minutes, or nearly 2 hours.

Properties The primary is a typical hydrogen white dwarf, as indicated by its spectral type of DA. It has about 39% of the Sun's mass and is only 1.86% as wide (12,900 km). With a high effective temperature of 16,500 K, it emits radiation mostly in the ultraviolet range. The brown dwarf, designated WD 0137−349B, can be detected from an infrared excess. Although it glows with an effective temperature of 1300 to 1400 K, the side facing the white dwarf's intercepts 1% of its light, and heats it up to around 2000 K. The "night" side spectrum of WD 0137−349B therefore matches that of a mid-T-type brown dwarf, while the "day" side spectrum matches that of an early L-type brown dwarf. The brown dwarf is suspected to be a white dwarf or even a strange star, as a hydrogen-dominated substellar object may be unstable in such a small orbit.

Evolution The brown dwarf is known to have survived being engulfed when the primary star was a red giant, because it was relatively massive. At that time, the red giant had a radius of 100 R☉. It is thought that the red giant phase of the current white dwarf was shortened from around 100 million years on average, to a few decades—while the brown dwarf was within the red giant, it hastened the expulsion of matter during this phase by rapidly heating gas and accreting a portion of it. During this phase, drag from the red giant also decreased the orbital speed of the brown dwarf, causing it to fall inwards. The orbit of the brown dwarf is slowly decaying. In about 1.4 billion years, it is thought that the orbit of the brown dwarf will have decayed sufficiently to allow the white dwarf to draw matter away and accrete it on its surface, leading to a cataclysmic variable. As of 2006, this is the coldest known companion to a white dwarf. This brown dwarf was also the object with the lowest mass known to have survived being engulfed by a red giant. Previously, only red dwarfs had been known to survive being enveloped during a red giant phase. It is thought that objects smaller than 20 Jupiter masses would have evaporated.

Post common envelope white dwarf-brown dwarf binaries WD 0137−349 represents the first confirmed post common envelope binary (PCEB) containing a white dwarf and a brown dwarf. As of 2018 only 8 of these wd+bd PCEBs are known. The first with a confirmed spectral type was GD 1400, but this second confirmed wd+bd binary after GD 165B was confirmed as a PCEB in 2011, five years later than WD 0137−349.

References

External links "WD 0137-349". SIMBAD. Centre de données astronomiques de Strasbourg. "Special Stars: WD0137-349". Jumk.de Webprojekte. 3 August 2006.

Illustrations

Worked examples

Example 1 — a first encounter with WD 0137−349

Start with the simplest possible case. Write down what WD 0137−349 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 WD 0137−349 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 WD 0137−349 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 WD 0137−349

In research: WD 0137−349 appears in science 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 WD 0137−349 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: WD 0137−349 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Brown dwarfs, L-type brown dwarfs, Sculptor (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for WD 0137−349 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 WD 0137−349 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WD 0137−349 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 WD 0137−349 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WD 0137−349 in simple terms?

WD 0137−349 is a binary star in the constellation of Sculptor. It is located about 330 light-years (100 parsecs) away, and appears exceedingly faint with an apparent magnitude of 15.33.

Why does WD 0137−349 matter?

Because it connects several science 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 WD 0137−349?

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 WD 0137−349.