astronomy

HD 154672

HD 154672 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 154672 rather than just read about it. In short: HD 154672 is a yellow subgiant (spectral type G3 IV). It is about 65 parsecs away from the Sun that is larger than, but of a similar mass to, the Sun.

Key takeaways

HD 154672 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 154672 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of HD 154672 from memory before moving on to harder problems.

Reference excerpt

HD 154672 is a yellow subgiant (spectral type G3 IV). It is about 65 parsecs away from the Sun that is larger than, but of a similar mass to, the Sun. However, HD 154672 is much older. The star is very metal-rich, which is one of the reasons why it was targeted for a planet search by the N2K Consortium, which discovered the gas giant planet HD 154672 b using Doppler Spectroscopy; the discovery was reported in October 2008. The N2K collaboration chose HD 154672 primarily because it aimed to discover the correlation between a star's metallicity and the mass of orbiting planets. HD 154672 was targeted by the Magellan Telescopes. It is the host of the first planet discovered from the telescopes by N2K.

Observational history HD 154672 was first targeted for a planet search in 2004 by the N2K Consortium, a collaboration of astronomers hoping to take radial velocity measurements of previously untargeted stars using Doppler spectroscopy; however, HD 154672 had been previously targeted by a series of surveys, and was previously included in the Henry Draper Catalogue and the catalog of the European Space Agency's Hipparcos satellite.

N2K deliberately biased its search towards closely orbiting Jupiter-size planets (Hot Jupiters) in the orbit of metal-rich stars, as the consortium hoped to discover how the mass of a planet relates to its host star's metal content. Initially, HD 154672 was noted as a host to a short-orbit Hot Jupiter, although additional observations revealed that the prospective planetary body had a longer orbit than previously expected, as revealed by the Magellan Telescopes at Chile's Las Campanas Observatory. Use of the Magellan Clay telescope's Magellan Inamori Kyocera Echelle spectrograph (MIKE) helped collect sixteen radial velocity measurements for HD 154672; a team of American astronomers and one from the Vatican City used these measurements to confirm the existence of planet HD 154672 b and to determine its mass. The discovery of HD 154672's planet was reported in The Astronomical Journal on October 7, 2008 along with a planet in the orbit of HD 205739.

Host star HD 154672 is a sunlike G-type star that has a mass of 1.1 times that of the Sun and a radius that is 1.3 times that of the Sun. Thus, it is slightly larger than the Sun, although it has a similar mass. The star has an effective temperature of 5,734 K, slightly cooler than the Sun; however, it is far richer in iron, with a measured metallicity of [Fe/H] = 0.26. This means that the star has 1.82 times more iron than the Sun does. HD 154672 is older than the Sun, as its estimated age is estimated at over six billion years. HD 154672's spectrum suggests that the star's chromosphere (its outer layer) is not active. HD 154672 is located 65.8 parsecs (215 light-years) away from Earth. It has an apparent magnitude (V) of 8.22, making the star too dim to see from Earth with the naked eye. The star is slightly dimmer than planet Neptune as perceived with the naked eye, which has an apparent magnitude of 7.78 at its brightest. The star's actual brightness is measured with an absolute magnitude of 4.12, similar to that of the Sun.

Planetary system

HD 154672 b is a Hot Jupiter, as it is a closely orbiting planet with a high mass. Specifically, HD 154672 has a mass that is 5.02 times greater than Jupiter's mass. It also orbits at a distance of 0.6 AU, or about 60% of the mean distance between the Earth and Sun. This orbit is completed every 163.91 days. HD 154672 b has an orbital eccentricity of 0.61, denoting a very elliptical orbit. The planet's discoverers noted that if water existed in the planet's atmosphere, it might change from a liquid state to a gaseous state as the planet swings closer to its host star, increasing its temperature.

See also HD 205739 HD 74156 54 Piscium HD 80606 HD 37605 HD 17156 HD 89744

References

Worked examples

Example 1 — a first encounter with HD 154672

Start with the simplest possible case. Write down what HD 154672 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 154672 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 154672 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 154672

In research: HD 154672 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 154672 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 154672 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Ara (constellation), Durchmusterung objects, G-type subgiants, so understanding it makes those chapters shorter.
In everyday life: Look for HD 154672 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 154672 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what HD 154672 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 154672 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is HD 154672 in simple terms?

HD 154672 is a yellow subgiant (spectral type G3 IV). It is about 65 parsecs away from the Sun that is larger than, but of a similar mass to, the Sun.

Why does HD 154672 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 154672?

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 154672.