astronomy

Gliese 65

Gliese 65 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 65 rather than just read about it. In short: Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at 8.8 light-years (2.7 parsecs) from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.

Key takeaways

Gliese 65 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 65 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 65 from memory before moving on to harder problems.

Reference excerpt

Gliese 65, also known as Luyten 726-8, is a binary star system that is one of Earth's nearest neighbors, at 8.8 light-years (2.7 parsecs) from Earth in the constellation Cetus. The two component stars are both flare stars with the variable star designations BL Ceti and UV Ceti.

Star system The star system was discovered in 1948 by Willem Jacob Luyten in the course of compiling a catalog of stars of high proper motion; he noted its exceptionally high proper motion of 3.37 arc seconds annually and cataloged it as Luyten 726-8. The two stars are of nearly equal brightness, with visual magnitudes of 12.7 and 13.2 as seen from Earth. They orbit one another every 26.5 years. The distance between the two stars varies from 2.1 to 8.8 astronomical units (310 to 1,320 Gm). The Gliese 65 system is approximately 2.63 parsecs (8.58 ly) from Earth's Solar System, in the constellation Cetus, and is thus the seventh-closest star system to Earth. Its own nearest neighbor is Tau Ceti, 0.98 pc (3.20 ly) away from it. If R v = + 29 {\displaystyle R_{v}=+29} km/s then approximately 28,700 years ago Gliese 65 was at its minimal distance of 2.21 pc (7.2 ly) from the Sun. Gliese 65 A was later found to be a variable star and given the variable star designation BL Ceti. It is a red dwarf of spectral type M5.5V. It is also a flare star, and classified as a UV Ceti variable type, but it is not nearly as remarkable or extreme in its behavior as its companion star UV Ceti.

Soon after the discovery of Gliese 65 A, the companion star Gliese 65 B was discovered. Like Gliese 65 A, this star was also found to be variable and given the variable star designation UV Ceti. Although UV Ceti was not the first flare star discovered, it is the most prominent example of such a star, so similar flare stars are now classified as UV Ceti type variable stars. This star goes through fairly extreme changes of brightness: for instance, in 1952, its brightness increased by 75 times in only 20 seconds. UV Ceti is a red dwarf of spectral type M6V. Both stars are listed as spectral standard stars for their respective classes, being considered typical examples of the classes. In approximately 31,500 years, Gliese 65 will have a close encounter with Epsilon Eridani at the minimal distance of about 0.93 ly. Gliese 65 can penetrate a conjectured Oort cloud about Epsilon Eridani, which may gravitationally perturb some long-period comets. The duration of mutual transit of two star systems within 1 ly from each other is about 4,600 years. Gliese 65 is a possible member of the Hyades Stream.

Candidate planet In 2024, a candidate super-Neptune-mass planet was detected in the Gliese 65 system via astrometry with Very Large Telescope's GRAVITY instrument. If it exists, it would orbit one of the two stars (it is unclear which) with a period of 156 days. The planet's properties change slightly depending on which star it orbits, but in general its mass is estimated to be about 40 M🜨 and the semi-major axis is about 30% of an astronomical unit. It is estimated to be about seven times the size of Earth based on mass-radius relationships.

Notes

References

Further reading Durand, E.; Oberly, J. J.; Tousey, R. (1949). "Analysis of the First Rocket Ultraviolet Solar Spectra". The Astrophysical Journal. 109: 1. Bibcode:1949ApJ...109....1D. doi:10.1086/145099. Luyten, W. J. (1949). "New stars with proper motions exceeding 0.5" annually". The Astronomical Journal. 55: 15. Bibcode:1949AJ.....55...15L. doi:10.1086/106322. Geyer, David W.; Harrington, Robert S.; Worley, Charles E. (June 1988). "Parallax, orbit, and mass of the visual binary L726-8". Astronomical Journal. 95: 1841–1842. Bibcode:1988AJ.....95.1841G. doi:10.1086/114781. Delfosse, Xavier; et al. (December 2000). "Accurate masses of very low mass stars. IV. Improved mass-luminosity relations". Astronomy and Astrophysics. 364: 217–224. arXiv:astro-ph/0010586. Bibcode:2000A&A...364..217D.

External links http://www.aavso.org/vstar/vsots/fall03.shtml Archived 2004-03-05 at the Wayback Machine http://www.solstation.com/stars/luy726-8.htm Archived 2009-03-27 at the Wayback Machine

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 65

Start with the simplest possible case. Write down what Gliese 65 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 65 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 65 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 65

In research: Gliese 65 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 65 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 65 is common in secondary-school and first-year university syllabi. It links to neighbouring topics BY Draconis variables, Binary stars, Cetus (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 65 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 65 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 65 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 65 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 65 in simple terms?

Why does Gliese 65 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 65?

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 65.