astronomy

HD 81040

HD 81040 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 HD 81040 rather than just read about it. In short: HD 81040 is a star in the equatorial constellation of Leo. With an apparent visual magnitude of +7.73 it is too dim to be visible to the naked eye but can be viewed with a small telescope.

Key takeaways

HD 81040 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 81040 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 81040 from memory before moving on to harder problems.

Reference excerpt

HD 81040 is a star in the equatorial constellation of Leo. With an apparent visual magnitude of +7.73 it is too dim to be visible to the naked eye but can be viewed with a small telescope. The star is located at a distance of 112 light years from the Sun based on parallax. It is drifting further away with a radial velocity of +49 km/s, having come to within 48 light-years some 527,000 years ago.

Properties This is an ordinary G-type main-sequence star with a stellar classification of G0V. The Sun somewhat dwarfs HD 81040 in terms of physical characteristics: it has 87% of the Sun's mass and 91% of the radius of the Sun. It is spinning with a projected rotational velocity of 5.3 km/s, and has near solar metallicity. The age of the star is not precisely known; the ELODIE spectrograph suggested 0.8 Gyr and found it to have a young dust disk. Later measurements by modelling chromosperic activity suggested an age of 4.18 Gyr.

Planetary system On November 24, 2005, a superjovian planet was announced by Sozzetti et al. It was discovered using the radial velocity method. Astrometric measurements using Gaia, published in several papers, show that the inclination of its orbit is about 111 degrees, so its true mass is somewhat higher than that predicted from its minimum mass.

See also List of extrasolar planets List of stars in Leo

References

External links The Extrasolar Planets Encyclopaedia: HD 81040

Worked examples

Example 1 — a first encounter with HD 81040

Start with the simplest possible case. Write down what HD 81040 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 HD 81040 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 HD 81040 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 HD 81040

In research: HD 81040 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 HD 81040 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: HD 81040 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Circumstellar disks, Durchmusterung objects, G-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 81040 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 HD 81040 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 81040 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 HD 81040 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 81040 in simple terms?

HD 81040 is a star in the equatorial constellation of Leo. With an apparent visual magnitude of +7.73 it is too dim to be visible to the naked eye but can be viewed with a small telescope.

Why does HD 81040 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 HD 81040?

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 HD 81040.