astronomy

Gliese 317

Gliese 317 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 317 rather than just read about it. In short: Gliese 317 is a small red dwarf star with two exoplanetary companions in the southern constellation of Pyxis. It is located at a distance of 49.6 light-years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +87.8 km/s.

Key takeaways

Gliese 317 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 317 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 317 from memory before moving on to harder problems.

Reference excerpt

Gliese 317 is a small red dwarf star with two exoplanetary companions in the southern constellation of Pyxis. It is located at a distance of 49.6 light-years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of +87.8 km/s. This star is too faint to be viewed with the naked eye, having an apparent visual magnitude of 11.98 and an absolute magnitude of 11.06. This is an M-type main-sequence star with a stellar classification of M2.5V. Photometric calibrations and infrared spectroscopic measurements indicate that the star is enriched in heavy elements compared to the Sun. The star is estimated to be roughly five billion years old and has a low activity level for a star of its class. It has 42% of the mass and radius of the Sun and is spinning with a rotation period of 69 days. The star is radiating 2.2% of the Sun's luminosity from its photosphere at an effective temperature of 3,510 K.

Planetary system In 2007, a jovian planet (designated Gliese 317 b) was announced to orbit the star. The planet orbits about 95% the distance between Earth to the Sun. Despite this, it takes about 1.9 years, due to the lower mass of the central M dwarf. Astrometric measurements on Gliese 317 provided a significant update to the distance, putting the star at 15.3 pc, which is 65% further out than previously assumed. Using mass-luminosity calibrations, the new distance implies the star is significantly more massive and so are the planet candidates. The same astrometric measurements allowed to constrain the orbital inclination and put an upper limit to the mass of Gliese 317 b (98% confidence level) of 2.5 MJ. The second planet in the system was also confirmed with the additional new RV measurements, but the period and orbital parameters of Gliese 317 c were very uncertain (P>2000 days). A stability analysis on this putative system suggest that the pair of gas giant planets are in a 4:1 mean motion resonance. The second planet, remote from its host star, is a good candidate for direct imaging. Revised elements of this companion were presented in 2020, demonstrating this is a Jupiter analog.

See also Gliese 649 Gliese 849 HD 108874 List of exoplanets discovered between 2000–2009 - Gliese 317 b List of exoplanets discovered in 2020 - Gliese 317 c

References

External links "Notes for star GJ 317". Extrasolar Planets Encyclopaedia. Archived from the original on 6 November 2007. Retrieved 9 August 2008. Extrasolar Planet Interactions Archived 5 May 2016 at the Wayback Machine by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona

Worked examples

Example 1 — a first encounter with Gliese 317

Start with the simplest possible case. Write down what Gliese 317 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 317 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 317 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 317

In research: Gliese 317 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 317 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 317 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gliese and GJ objects, M-type main-sequence stars, Planetary systems with two confirmed planets, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 317 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 317 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 317 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 317 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 317 in simple terms?

Why does Gliese 317 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 317?

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 317.