astronomy

Upsilon1 Hydrae

Upsilon1 Hydrae 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 Upsilon1 Hydrae rather than just read about it. In short: Upsilon1 Hydrae, Latinised from υ1 Hydrae (Ups1 Hya, υ1 Hya) formally named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12.

Key takeaways

Upsilon1 Hydrae belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Upsilon1 Hydrae to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Upsilon1 Hydrae from memory before moving on to harder problems.

Reference excerpt

Upsilon1 Hydrae, Latinised from υ1 Hydrae (Ups1 Hya, υ1 Hya) formally named Zhang, is a yellow-hued star in the constellation of Hydra. It is visible to the naked eye, having an apparent visual magnitude of 4.12. Based upon an annual parallax shift of 12.36 mas as seen from Earth, it is located about 264 light-years from the Sun. The star is moving closer to the Sun with a radial velocity of −14.34 km/s. In 2005 it was announced that it had a substellar companion.

Nomenclature υ1 Hydrae (Latinised to Upsilon1 Hydrae, abbreviated Ups1 Hya, υ1 Hya) is the star's Bayer designation. In Chinese, 張宿 (Zhāng Xiù), meaning Extended Net, refers to an asterism consisting of Upsilon1 Hydrae, Lambda Hydrae, Mu Hydrae, HD 87344, Kappa Hydrae and Phi1 Hydrae. Consequently, Upsilon1 Hydrae itself is known as 張宿一 (Zhāng Xiù yī), "the First Star of Extended Net". In 2016, the International Astronomical Union (IAU) organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Zhang for Upsilon1 Hydrae on 30 June 2017 and it is now so included in the List of IAU-approved Star Names.

Properties With a stellar classification of G6/8 III, Upsilon1 Hydrae is an evolved G-type giant star. It has an estimated 3.3 times the mass of the Sun and has expanded to 14.7 times the Sun's radius. The star is about 270 million years old with a projected rotational velocity of just 2.11 km/s. It is radiating 162 times the Sun's luminosity from its photosphere at an effective temperature of 5,185 K.

Substellar companion The Okayama Planet Search team published a paper in 2005 reporting investigations on radial velocity variations observed for a set of class G giants and announcing the detection of a brown dwarf companion in orbit around Upsilon1 Hydrae. The orbital period for this companion is roughly 4.1 years, and it has a high eccentricity of 0.57. Since the inclination of the orbit to the line-of-sight is unknown, only a lower bound on the mass can be determined. It has at least 49 times the mass of Jupiter.

References

Illustrations

Worked examples

Example 1 — a first encounter with Upsilon1 Hydrae

Start with the simplest possible case. Write down what Upsilon1 Hydrae 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 Upsilon1 Hydrae 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 Upsilon1 Hydrae 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 Upsilon1 Hydrae

In research: Upsilon1 Hydrae 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 Upsilon1 Hydrae 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: Upsilon1 Hydrae is common in secondary-school and first-year university syllabi. It links to neighbouring topics Bayer objects, Bright Star Catalogue objects, Durchmusterung objects, so understanding it makes those chapters shorter.
In everyday life: Look for Upsilon1 Hydrae 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 Upsilon1 Hydrae in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Upsilon1 Hydrae 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 Upsilon1 Hydrae out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Upsilon1 Hydrae in simple terms?

Why does Upsilon1 Hydrae 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 Upsilon1 Hydrae?

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 Upsilon1 Hydrae.