astronomy

Gliese 649

Gliese 649 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 Gliese 649 rather than just read about it. In short: Gliese 649 is a small star with an orbiting exoplanet in the constellation Hercules. It has an apparent visual magnitude of 9.7, which is too faint to be seen with the naked eye.

Key takeaways

Gliese 649 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gliese 649 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 649 from memory before moving on to harder problems.

Reference excerpt

Gliese 649 is a small star with an orbiting exoplanet in the constellation Hercules. It has an apparent visual magnitude of 9.7, which is too faint to be seen with the naked eye. The system is located at a distance of 33.9 light years based on parallax, and is drifting further away with a radial velocity of 3.8 km/s. This is an M-type main-sequence star, a red dwarf, with a stellar classification of M1.0V. It has 52% of the mass of the Sun and 53% of the Sun's girth. In the visible light band, the star is radiating 4.4% of the luminosity of the Sun from its photosphere at an effective temperature of 3,621 K. It is spinning slowly with a rotation period of 24.9 days.

Planetary system A Saturn-mass planet was detected around the red dwarf star by J. A. Johnson and associates in 2010. It has a minimum mass 32.8% of Jupiter's mass and is located 1.15 astronomical units from its star in eccentric orbit (e=0.3). Assuming a luminosity of 4.5% that of the Sun, the habitable zone is located at 0.21 AU, thus the planet should be as cold as if it were located at 5.5 AU from a Solar-like star. Also accounting for different periastron and apastron positions of 0.8 and 1.49 AU respectively, the planet could likely show seasonal temperature changes.

Debris disk Using results from the Herschel Space Observatory survey of 21 late-type stars carried out in 2010, a debris disk was discovered between approximately 6 and 30 AU. The disk was not detected at 22μm by NASA's Wide-field Infrared Survey Explorer so therefore it is likely to be below 100 Kelvin and similar to the Kuiper belt. The disk was marginally resolved, appearing very asymmetric, and so is probably consistent with being closer to edge-on, rather than face-on, in its inclination.

References

See also Gliese 317 Gliese 849 List of extrasolar planets

Worked examples

Example 1 — a first encounter with Gliese 649

Start with the simplest possible case. Write down what Gliese 649 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 Gliese 649 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 Gliese 649 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 Gliese 649

In research: Gliese 649 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 Gliese 649 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: Gliese 649 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Circumstellar disks, Durchmusterung objects, Gliese and GJ objects, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 649 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 Gliese 649 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 649 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 Gliese 649 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 649 in simple terms?

Gliese 649 is a small star with an orbiting exoplanet in the constellation Hercules. It has an apparent visual magnitude of 9.7, which is too faint to be seen with the naked eye.

Why does Gliese 649 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 Gliese 649?

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 Gliese 649.