astronomy

Groombridge 1618

Groombridge 1618 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 Groombridge 1618 rather than just read about it. In short: Groombridge 1618 is a star in the northern constellation Ursa Major. With an apparent visual magnitude of +6.6, it lies at or below the threshold of stars visible to the naked eye for an average observer.

Key takeaways

Groombridge 1618 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Groombridge 1618 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Groombridge 1618 from memory before moving on to harder problems.

Reference excerpt

Groombridge 1618 is a star in the northern constellation Ursa Major. With an apparent visual magnitude of +6.6, it lies at or below the threshold of stars visible to the naked eye for an average observer. It is relatively close to Earth, at 15.89 light-years (4.87 pc). This is a main sequence star of spectral type K7.5 Ve, having just 67% of the Sun's mass.

Properties This star was first identified as entry 1618 in the work A Catalog of Circumpolar Stars by Stephen Groombridge published posthumously in 1838. Its large proper motion across the sky suggested that it was relatively nearby and made it an early candidate for parallax measurements. In 1884 the parallax angle was measured as 0″.322 ± 0″.023, which is larger than the modern value of 0″.205. Groombridge 1618 has a stellar classification of K8 V, which means it is a K-type main sequence star that is generating energy by fusing hydrogen at its core. It has 67% of the mass of the Sun, 61% of the Sun's radius, but radiates only 15% of the Sun's energy and only 4.6% of the Sun's energy in the visible light spectrum. The effective surface temperature of the star's photosphere is about 4,000 K, giving it an orange hue. It is a BY Draconis variable with a surface magnetic field strength of 750 G. The chromosphere is relatively inactive and produces star spots comparable to Sun spots. However, like UV Ceti, it has been observed to undergo increases in luminosity as a flare star.

Search for planets A search for excess infrared emission from this star by the Infrared Space Observatory came up negative, implying that Groombridge 1618 does not possess a nearby debris disk (such as Vega does). However, observations using the Herschel Space Observatory showed a small excess suggesting a low-temperature debris disk. The data can be modeled by a ring of coarse, highly-reflective dust at a temperature below 22 K orbiting at least 51 AU from the host star. If this star does have a companion, astrometric measurements appear to place an upper bound of 3–12 times the mass of Jupiter on such a hypothetical object (for orbital periods in the range of 5–50 years). Observations collated by Marcy & Benitz (1989), tend towards a single notable object with periodicity of 122 days as a planetary object with minimum mass 4 times that of Jupiter. This candidate planet was never confirmed and the signal the authors had found could have been due to intrinsic stellar activity. If confirmed, the planet would be within the star's habitable zone. An examination of this system in 2010 using the MMT telescope fitted with adaptive optics failed to detect a planetary companion. The habitable zone for this star, defined where liquid water could be present on an Earth-like planet, is at a radius of 0.26–0.56 AU, where 1 AU is the average distance from the Earth to the Sun. The star is among five nearby K-type stars of a type in a 'sweet spot’ between Sun-analog stars and M stars for the likelihood of evolved life, per analysis of Giada Arney from NASA’s Goddard Space Flight Center.

See also Stephen Groombridge List of nearest stars List of nearest K-type stars

Notes

References

Notes

External links "Groombridge 1618". Sol Company. Archived from the original on April 17, 2002. Retrieved 2007-06-24. "ARICNS 4C00785". Astronomisches Rechen-Institut. Archived from the original on 2007-06-10. Retrieved 2007-06-24.

Worked examples

Example 1 — a first encounter with Groombridge 1618

Start with the simplest possible case. Write down what Groombridge 1618 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 Groombridge 1618 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 Groombridge 1618 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 Groombridge 1618

In research: Groombridge 1618 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 Groombridge 1618 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: Groombridge 1618 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Flare stars, Gliese and GJ objects, so understanding it makes those chapters shorter.
In everyday life: Look for Groombridge 1618 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 Groombridge 1618 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Groombridge 1618 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 Groombridge 1618 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Groombridge 1618 in simple terms?

Why does Groombridge 1618 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 Groombridge 1618?

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 Groombridge 1618.