astronomy

Gliese 777

Gliese 777 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 777 rather than just read about it. In short: Gliese 777, also known as HD 190360, is a binary star system approximately 52 light-years (15.9 parsecs) away in the constellation of Cygnus. The system is made up of two stars and possibly a third.

Key takeaways

Gliese 777 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 777 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 777 from memory before moving on to harder problems.

Reference excerpt

Gliese 777, also known as HD 190360, is a binary star system approximately 52 light-years (15.9 parsecs) away in the constellation of Cygnus. The system is made up of two stars and possibly a third. Three exoplanets are known to orbit the primary star.

Stellar components The primary star of the system (catalogued as Gliese 777 A) is a yellow subgiant, a Sun-like star that is ceasing fusing hydrogen in its core. The star is older than the Sun, about 4.79 billion years old. It is 4% less massive than the Sun. It is also rather metal-rich, having about 70% more "metals" (elements heavier than helium) than the Sun, which is typical for stars with extrasolar planets. The secondary star (Gliese 777 B) is a distant, dim red dwarf star orbiting the primary at a distance of 3,000 astronomical units (0.047 light years). A faint companion has been reported, but not confirmed.

Planetary system In 2002, a discovery of a long-period, wide-orbiting, planet (Gliese 777 Ab) was announced by the Geneva extrasolar planet search team. The planet was estimated to orbit in a circular path with low orbital eccentricity, but that estimate was increased with later measurements (e=0.36). Initially therefore, the planet was believed to be a true "Jupiter-twin" but was later redefined as being more like an "eccentric Jupiter", with a mass of at least 1.5 times Jupiter and about the same size. In 2021, the true mass of Gliese 777 Ab was measured via astrometry. In 2005, further observation of the star showed another amplitude with a period of 17.1 days. The mass of this second planet (Gliese 777 Ac) was only 18 times more than Earth, or about the same as Neptune, indicating it was one of the smallest planets discovered at the time. Initially thought to be on a circular orbital path (e = 0.01), Gliese 777 c was revealed to have a more eccentric orbit with later measurements. Evidence for a third candidate planet with an orbital period around 89 days was presented in 2025. It was confirmed in 2026.

There was a METI message sent to Gliese 777. It was transmitted from Eurasia's largest radar, 70-meter Eupatoria Planetary Radar. The message was named Cosmic Call 1; it was sent on July 1, 1999, and it will arrive at Gliese 777 in April 2051.

See also 47 Ursae Majoris 51 Pegasi Gliese 229

References

External links Extrasolar Planet Interactions Archived 2016-05-05 at the Wayback Machine by Rory Barnes & Richard Greenberg, Lunar and Planetary Lab, University of Arizona

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 777

Start with the simplest possible case. Write down what Gliese 777 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 777 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 777 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 777

In research: Gliese 777 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 777 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 777 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Bright Star Catalogue objects, Cygnus (constellation), so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 777 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 777 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 777 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 777 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 777 in simple terms?

Gliese 777, also known as HD 190360, is a binary star system approximately 52 light-years (15.9 parsecs) away in the constellation of Cygnus. The system is made up of two stars and possibly a third.

Why does Gliese 777 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 777?

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 777.