astronomy

Gliese 758

Gliese 758 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 758 rather than just read about it. In short: Gliese 758 is a star in the northern constellation of Lyra. At about magnitude 6 it is a challenge to view with the naked eye even in good seeing conditions, but can be easily seen through a small telescope or binoculars.

Key takeaways

Gliese 758 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 758 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 758 from memory before moving on to harder problems.

Reference excerpt

Gliese 758 is a star in the northern constellation of Lyra. At about magnitude 6 it is a challenge to view with the naked eye even in good seeing conditions, but can be easily seen through a small telescope or binoculars. Parallax measurements from the Hipparcos mission give it an estimated distance of around 50.9 light-years (15.6 parsecs) from Earth.

Properties This is a Sun-like star with 97% of the Sun's mass and 88% of the radius of the Sun. The spectrum matches a stellar classification of G8V, identifying it as a G-type main-sequence star that is generating energy through the nuclear fusion of hydrogen at its core. It is radiating this energy into space from its outer envelope at an effective temperature of 5,425 K. Estimates of its age put it at about 7.7–8.7 billion years old, although some measurements give it an age as low as 720 million years. The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, are 51% higher than in the Sun.

Companion In November 2009, a team using the HiCIAO instrument of the Subaru Telescope imaged a substellar companion orbiting the star. This brown dwarf, designated Gliese 758 B, was estimated to be of approximately 10 to 40 Jupiter masses. A second candidate object was also detected, which was given the designation Gliese 758 C. Follow-up studies of the system refined the mass range of Gliese 758 B, indicating it to be a companion with approximately 30 to 40 Jupiter masses, and revealed that Gliese 758 C is a background star which is not physically associated with the Gliese 758 system. On the other hand, a younger age was suggested from the kinematic stellar grouping. The most recent parameters for Gliese 758 B as of 2022 come from a combination of data from radial velocity, astrometry, and imaging, showing that it is about 36 times the mass of Jupiter, and on an eccentric orbit with a semi-major axis of about 25.4 astronomical units and an orbital period of about 131 years. First near-infrared spectroscopy was published in 2017. This team used the Hale Telescope at Palomar Observatory to obtain a low-resolution spectrum. Comparison with archived IRTF/SpeX spectra of brown dwarfs resulted in a best fit to a spectral type of T7.0 ±1.0. The modelling of the spectrum indicates a temperature of 741 ± 25 K, which is slightly hotter than previously thought. A later spectral type and lower temperature is not excluded.

See also Direct imaging of extrasolar planets Lists of exoplanets

References

External links Animation of GJ 758 system compared to Solar System

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 758

Start with the simplest possible case. Write down what Gliese 758 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 758 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 758 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 758

In research: Gliese 758 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 758 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 758 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Bright Star Catalogue objects, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 758 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 758 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 758 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 758 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 758 in simple terms?

Why does Gliese 758 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 758?

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 758.