astronomy

V901 Orionis

V901 Orionis 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 V901 Orionis rather than just read about it. In short: V901 Orionis is a variable star in the equatorial constellation of Orion. It is sometimes known as Landstreet's Star and has the designation HD 37776 from the Henry Draper Catalogue; V901 Ori is the variable star designation.

Key takeaways

V901 Orionis belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect V901 Orionis to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of V901 Orionis from memory before moving on to harder problems.

Reference excerpt

V901 Orionis is a variable star in the equatorial constellation of Orion. It is sometimes known as Landstreet's Star and has the designation HD 37776 from the Henry Draper Catalogue; V901 Ori is the variable star designation. With an apparent visual magnitude that varies around seven, it is a challenge to view with the naked eye. Based on parallax measurements from Earth, it is located at a distance of 1,280 ± 30 light-years (393 ± 8 pc). The star is drifting further away from the Sun with a radial velocity of 15 km/s.

Properties

This object was found to be a helium-rich variable star in 1976. It was shown to have a high rotation rate and display an infrared excess. Magnetic field measurements showed a multipole distribution and a period of 1.5 days. This was the first star discovered in which a quadrupole-like geometry of the magnetic field dominated over the dipole field found in most stars. In 2007, HD 37776 was discovered to undergo change in rotation, probably due to loss of angular momentum from a magnetically-confined stellar wind. The rotational braking in this star is 0.54±0.02 s per year, a record level for magnetic chemically-peculiar stars. Surprisingly, a long-term study of the rotation period showed a steady increase until 2003, after which the period began to decrease. This may be the result of an interaction between a thin, magnetically-confined outer envelope and a faster rotating inner body. This is a massive, helium-strong, magnetic chemically peculiar star with a stellar classification of B2V. It is classified as an SX Arietis variable that ranges in visual magnitude from 6.97 to 7.02 with a period of 1.5385 days. The light variation is believed due to uneven surface distribution of helium and silicon. The topology of the magnetic field is the most complex ever found for an early-type star (i.e. a higher mass main sequence star). Stellar models paint this as a young star with an estimated age of four million years, that is spinning with a projected rotational velocity of 101 km/s. It has an estimated 8.3 times the mass of the Sun and 3.2 times the Sun's radius. The star is radiating nearly 2,000 times the luminosity of the Sun from its photosphere at an effective temperature of around 22,000 HD 37776 is a member of the Orion OB1 association of co-moving stars and is embedded in the emission nebula IC 432. It is a candidate member of the Orion B Complex star forming region.

References

Illustrations

Worked examples

Example 1 — a first encounter with V901 Orionis

Start with the simplest possible case. Write down what V901 Orionis 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 V901 Orionis 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 V901 Orionis 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 V901 Orionis

In research: V901 Orionis 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 V901 Orionis 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: V901 Orionis is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ap stars, B-type main-sequence stars, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for V901 Orionis 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 V901 Orionis in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what V901 Orionis 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 V901 Orionis out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is V901 Orionis in simple terms?

Why does V901 Orionis 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 V901 Orionis?

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 V901 Orionis.