astronomy

LP 40-365

LP 40-365 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 LP 40-365 rather than just read about it. In short: LP 40-365 is a low-mass white dwarf star in the constellation Ursa Minor. It travels at high speed through the Milky Way and has a very unusual elemental composition, lacking hydrogen, helium or carbon.

Key takeaways

LP 40-365 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect LP 40-365 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of LP 40-365 from memory before moving on to harder problems.

Reference excerpt

LP 40-365 is a low-mass white dwarf star in the constellation Ursa Minor. It travels at high speed through the Milky Way and has a very unusual elemental composition, lacking hydrogen, helium or carbon. It may have been produced in a subluminous Type Iax supernova that failed to destroy its host star totally. The "LP" name is derived from the Luyten-Palomar proper motion catalogue in which it appeared in the 1960s. Another catalog name for this star is "GD 492". The star was cataloged as a Giclas object with the designation "GD 492" being assigned by Henry Giclas in 1970. The abundance analysis of LP 40-365 did show that the atmosphere is dominated by oxygen and neon, with substantial traces of intermediate-mass elements such as aluminium and silicon. The white dwarf core on the other hand is likely composed of a mix of carbon, oxygen and neon. Additional observations did suggest the atmosphere is dominated by helium. This is in contrast to the previous analysis. Later helium was excluded with high quality spectra for other similar stars and therefore a oxygen-neon dominated atmosphere is favoured for LP 40-365. Neon has the highest mass fraction of below 60%, oxygen has a mass fraction of around 30%, followed by around 8% of magnesium. 11 other elements are detected in the atmosphere, but they make up 1–2% of the mass. The atmospheric composition is a strong indicator of partial carbon-, oxygen- and silicon-burning, likely connected to a thermonuclear explosion that did not entirely disrupt the progenitor. The origin could be either a peculiar Type Iax or electron-capture supernova. In the future LP 40-365 and similar objects are predicted to evolve into oxygen-rich white dwarfs. The new parallax with Gaia helped to refine the radius to 18% of the radius of the Sun. This is 15 times larger than other white dwarfs. The new kinematic analysis showed that LP 40-365 is leaving the Milky Way with 1.5 times the escape velocity of the solar neighbourhood. The object crossed the galactic disk 5.3±0.5 Ma ago in the direction of Carina, likely coming from beneath the plane. The team estimated that it was ejected with a speed of 600 km/s from its progenitor binary. This speed suggests a close binary consisting of a white dwarf and a helium-star donor. This donor-star had a mass of 0.8 to 1.32 M☉ and the binary had an orbital period of 30 to 60 minutes. Today LP 40-365 has a rest-frame velocity of 852±10 km/s. Variability was detected with the help of TESS, Hubble and WISE. TESS in the optical showed an amplitude of 1.0%, Hubble in the ultraviolet showed an amplitude of 5.8% and WISE in the infrared shows an amplitude of around 2.2%. The rotation period was measured at 8.914 hours. The researchers suggest the variations are caused by an inhomogeneity on the surface, rotating in and out of view. Additional stars with similar characteristics are called LP 40-365 stars, making LP 40-365 the prototype of chemically peculiar runaway stars that are the survivors of thermonuclear explosions.

Notes

References

External links ESO Online Digitized Sky Survey

Illustrations

Worked examples

Example 1 — a first encounter with LP 40-365

Start with the simplest possible case. Write down what LP 40-365 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 LP 40-365 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 LP 40-365 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 LP 40-365

In research: LP 40-365 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 LP 40-365 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: LP 40-365 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Runaway stars, Ursa Minor, White dwarfs, so understanding it makes those chapters shorter.
In everyday life: Look for LP 40-365 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 LP 40-365 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what LP 40-365 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 LP 40-365 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is LP 40-365 in simple terms?

Why does LP 40-365 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 LP 40-365?

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 LP 40-365.