astronomy

MWC 560

MWC 560 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 MWC 560 rather than just read about it. In short: MWC 560 is a symbiotic binary star system in the equatorial constellation of Monoceros. The identifier comes from the Mount Wilson Calatogue of class O, B and A stars with bright hydrogen lines, published in 1933 by P.

Key takeaways

MWC 560 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MWC 560 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MWC 560 from memory before moving on to harder problems.

Reference excerpt

MWC 560 is a symbiotic binary star system in the equatorial constellation of Monoceros. The identifier comes from the Mount Wilson Calatogue of class O, B and A stars with bright hydrogen lines, published in 1933 by P. W. Merrill and associates. It has the variable star designation V694 Monoceros. This system has a typical apparent visual magnitude of 9.70, which is too dim to be visible to the naked eye. Based on parallax measurements, it is located at a distance of approximately 7,700 light years from the Sun.

Observations N. Sanduleak and C. B. Stephenson included this in a list of objects in the southern Milky Way with strong emission lines in 1973. They found bands of TiO in the spectrum and indicators of variable emission lines. A stellar classification of M4ep was found. In 1984, H. E. Bond and associates classified this as a symbiotic binary system consisting of an M-type giant star with an orbiting compact companion. The profiles of absorption lines show changes on a day to day basis. They theorized that matter is being transferred from the M–giant at a higher rate than the companion is able to accrete it, producing a flickering appearance. In 1990, absorption lines were found to be coming from high velocity components, possibly from a jet-like ejecta nearly along the line of sight. The high velocity aspect was confirmed by the IUE during an outburst, which suggested the ejection of a cool, optically-thick shell from the compact object. Velocities of up to 6,000 km/s were recorded, and during the outburst the brightness increased from magnitude 12.5 up to as high as 9.2. Meanwhile the emission lines showed a stable radial velocity. The high rate of mass transfer inferred that an accretion disk is orbiting the compact object, with a thick envelop hiding the inner disk and compact object from direct sight. This disk is probably perpendicular to the line of sight from Earth, so it is being viewed nearly face-on. Observation of the system over a ten year period demonstrated a light variation with a period of 1,930 days, which may be explained by precessing of the disk. The system shifted between active and stable states, with outflow much higher during the active stage. Meanwhile, infrared observations in the i band suggested that the M-giant may undergo pulsations with a period of around 5 months. In 2007, this was refined to a period of about 340 days, making this a semiregular variable probably consisting of a thermally pulsing asymptotic giant branch star. X-ray emission was detected from this system in 2009, with the data being consistent with an accreting white dwarf source. It is accreting mass at a rate of (1 to 20)×10−7 M☉·yr−1, with just a few percent of this rate being ejected in the jet. The optical flickering persisted from 1984 until 2016. After a short pause it resumed until 2018, when it disappeared. At that point the system underwent steady brightness increase with periodicities of 331 and 1860 days. As of 2023, it remains in a non-flickering state, with maximum brightness achieved in October 2021.

References

Illustrations

Worked examples

Example 1 — a first encounter with MWC 560

Start with the simplest possible case. Write down what MWC 560 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 MWC 560 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 MWC 560 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 MWC 560

In research: MWC 560 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 MWC 560 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: MWC 560 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cataclysmic variable stars, M-type giants, MWC objects, so understanding it makes those chapters shorter.
In everyday life: Look for MWC 560 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 MWC 560 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MWC 560 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 MWC 560 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MWC 560 in simple terms?

Why does MWC 560 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 MWC 560?

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 MWC 560.