astronomy

Gliese 625

Gliese 625 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 625 rather than just read about it. In short: GJ 625 (AC 54 1646-56) is a small red dwarf star with an exoplanetary companion in the northern constellation of Draco. The system is located at a distance of 21.1 light-years (6.4 parsecs) from the Sun based on parallax, but is drifting closer with a radial velocity of −13 km/s.

Key takeaways

Gliese 625 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 625 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 625 from memory before moving on to harder problems.

Reference excerpt

GJ 625 (AC 54 1646-56) is a small red dwarf star with an exoplanetary companion in the northern constellation of Draco. The system is located at a distance of 21.1 light-years (6.4 parsecs) from the Sun based on parallax, but is drifting closer with a radial velocity of −13 km/s. It is too faint to be visible to the naked eye, having an apparent visual magnitude of 10.13 and an absolute magnitude of 11.06. This is an M-type main-sequence star with a stellar classification of M1.5V. It is spinning slowly with a rotation period of roughly 78 days, and has a low magnetic activity level. The star has about a quarter of the mass and size of the Sun, and the metal content is 40% the abundances in the Sun's atmosphere. It is radiating just 1.5% of the luminosity of the Sun from its photosphere at an effective temperature of 3,557 K.

Planetary system On May 18, 2017, a planet was detected orbiting GJ 625 by the HARPS-N telescope. The planet, GJ 625 b, orbits near the inner edge of the optimistic circumstellar habitable zone of its star, and the discoverers speculate it may support liquid water, depending on atmospheric conditions. Based on the habitable zone model of Kopparapu et al. 2013, the planet is not considered to be in the habitable zone as it would likely experience a runaway greenhouse effect, similar to Venus. Since the star is considered quiescent (having a low X-ray emission and flare rate), the radio emission from the system may be auroral in nature and coming from a short-period planet. Further observations will be needed to confirm this.

References

Worked examples

Example 1 — a first encounter with Gliese 625

Start with the simplest possible case. Write down what Gliese 625 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 625 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 625 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 625

In research: Gliese 625 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 625 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 625 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Draco (constellation), Gliese and GJ objects, Hipparcos objects, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 625 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 625 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 625 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 625 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 625 in simple terms?

Why does Gliese 625 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 625?

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 625.