astronomy

HD 136118

HD 136118 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 136118 rather than just read about it. In short: HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93.

Key takeaways

HD 136118 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 136118 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 136118 from memory before moving on to harder problems.

Reference excerpt

HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93. It is located at a distance of 165 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −3 km/s. This object is an F-type main-sequence star with a stellar classification of F7V. The absolute visual magnitude of this star suggests that it has begun to evolve away from the main sequence. The abundances of the stellar atmosphere are similar to the Sun, and it has only a modest level of chromospheric activity. HD 136118 has 84% more mass compared to the Sun, and is 70% larger in radius. The star is an estimated 3.5 billion years old and is spinning with a projected rotational velocity of 8.5 km/s.

Brown dwarf companion The astronomer Debra Fischer discovered a substellar companion, originally thought to be a very massive exoplanet, which was announced on February 7, 2002. Designated HD 136118 b, it is orbiting the host star with a period of 3.25 years. This object has a minimum mass of 11.9 MJ. On November 25, 2009, its inclination was calculated to be 163.1° and its true mass 42 MJ, classifying it as a brown dwarf. Later studies in 2022 and 2023 found true masses of about 13-16 MJ, closer to the minimum mass, but still classifying the companion as a brown dwarf by most definitions. Due to its high mass the object is likely to be very hot and possibly glowing faintly. The orbit of the object has a semimajor axis of 1.45 astronomical units from the parent star, taking 1,188 days (3.25 years) to complete one eccentric orbit.

Illustrations

Worked examples

Example 1 — a first encounter with HD 136118

Start with the simplest possible case. Write down what HD 136118 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 136118 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 136118 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 136118

In research: HD 136118 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 136118 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 136118 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Brown dwarfs, Durchmusterung objects, F-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for HD 136118 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study HD 136118 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 136118 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 136118 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 136118 in simple terms?

HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93.

Why does HD 136118 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 136118?

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 136118.