astronomy

HD 104985

HD 104985 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 HD 104985 rather than just read about it. In short: HD 104985, formally named Tonatiuh (), is a solitary star with an exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli ().

Key takeaways

HD 104985 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect HD 104985 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 104985 from memory before moving on to harder problems.

Reference excerpt

HD 104985, formally named Tonatiuh (), is a solitary star with an exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli (). This star has an apparent visual magnitude of 5.78 and thus is dimly visible to the naked eye under favorable seeing conditions. It is located at a distance of approximately 329 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −20 km/s. The stellar classification of this star is G8.5IIIb, indicating this is an evolved giant star that has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. It is located in the red clump region of the HR diagram, suggesting it is on the horizontal branch and generating energy through core helium fusion. The star is approximately 4.4 billion years old with 1.2 times the mass of the Sun and has expanded to 10.6 times the Sun's radius. It is radiating 51 times the luminosity of the Sun from its enlarged photosphere at an effective temperature of 4,730 K.

Naming HD 104985 is the star's entry in the Henry Draper Catalogue. Following its discovery in 2003 the planet was designated HD 104985 b. In July 2014 the International Astronomical Union launched NameExoWorlds, a process for giving proper names to certain exoplanets and their host stars. The process involved public nomination and voting for the new names. In December 2015, the IAU announced the winning names were Tonatiuh for this star and Meztli for its planet. The winning names were those submitted by the Sociedad Astronomica Urania of Morelos, Mexico. 'Tonatiuh' was the Aztec god of the Sun; 'Meztli' was the Aztec goddess of the Moon. In 2016, the IAU organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. In its first bulletin of July 2016, the WGSN explicitly recognized the names of exoplanets and their host stars approved by the Executive Committee Working Group Public Naming of Planets and Planetary Satellites, including the names of stars adopted during the 2015 NameExoWorlds campaign. This star is now so entered in the IAU Catalog of Star Names.

Planetary system In 2003, radial velocity measurements made by the Okayama Planet Search Program led to the announcement of an exoplanetary companion. It is orbiting at a distance of 0.95 AU (142 Gm) with a period of 199.5 days with an eccentricity (ovalness) of 0.09. Since the inclination of the exoplanet's orbital plane is unknown, only a lower bound on its mass can be determined. It has at least 8.3 times the mass of Jupiter.

Illustrations

Worked examples

Example 1 — a first encounter with HD 104985

Start with the simplest possible case. Write down what HD 104985 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 HD 104985 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 HD 104985 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 HD 104985

In research: HD 104985 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 HD 104985 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: HD 104985 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bright Star Catalogue objects, Camelopardalis, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for HD 104985 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 HD 104985 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 104985 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 HD 104985 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 104985 in simple terms?

HD 104985, formally named Tonatiuh (), is a solitary star with an exoplanetary companion in the northern constellation of Camelopardalis. The companion is designated HD 104985 b and named Meztli ().

Why does HD 104985 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 HD 104985?

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 HD 104985.