astronomy

PHL 5038

PHL 5038 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 PHL 5038 rather than just read about it. In short: PHL 5038AB (or just PHL 5038) is a binary system consisting out of a white dwarf and a brown dwarf on a wide orbit. The system is 240 light years (74 parsec) distant from earth.

Key takeaways

PHL 5038 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PHL 5038 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PHL 5038 from memory before moving on to harder problems.

Reference excerpt

PHL 5038AB (or just PHL 5038) is a binary system consisting out of a white dwarf and a brown dwarf on a wide orbit. The system is 240 light years (74 parsec) distant from earth. The white dwarf PHL 5038A was discovered in 2006 in data from the Sloan Digital Sky Survey and the brown dwarf companion was discovered in 2009 from UKIDSS infrared excess and confirmed with Gemini North to be a spacially resolved binary. It was only the fourth known brown dwarf to orbit a white dwarf at the time. The others were GD 165B, WD 0137-349B and GD 1400B.

Physical parameters The white dwarf was first classified as a DA white dwarf, which indicates a hydrogen-dominated atmosphere without any metal pollution. A later work found weak pollution due to calcium in the atmosphere of the white dwarf thanks to XSHOOTER spectra from the Very Large Telescope. The calcium is detected as the K-line in two spectra. No infrared excess due to a disk was detected. PHL 5038A has either accreted all debris or is surrounded by a thin disk. The mass and temperature was also overestimated in the past and later works found a mass of around 0.53 to 0.57 M☉, an effective temperature of around 7500 to 7800 Kelvin and a surface gravity of around 7.9 dex. The progenitor main-sequence star had a mass of around 1.07 M☉ and it existed for around 9 billion years until it became an AGB star and around 1 billion years ago it became a white dwarf. The brown dwarf has a spectral type of around L8-L9. Its mass was initially estimated to be 60 MJ, but this mass was likely an underestimate and more recent estimates find a mass of around 0.070 M☉ (or 73 MJ) and an effective temperature of 1425 K. The same team that discovered the metal pollution of the white dwarf also re-observed the system with Gemini North to determine the orbital parameters. The semi-major axis is 66+12−24 astronomical units and the inclination is 132 ±11°. The eccentricity is unconstrained, but likely lower than 0.615. In the past the white dwarf was more massive, making the semi-major axis half as large at 33 AU.

Evolution

Casewell et al. suggest the following evolution of the system: The PHL 5038 system during the main-sequence had a star with a mass similar or more massive than the sun and it had a brown dwarf at an orbit of 33 AU, similar to the orbital distance of Neptune. It also likely had rocky debris in the form of planetesimals in orbit around the star, maybe similar to the asteroid belt. At the end of its lifetime the star became an AGB star with a size smaller than 2.5 AU, leaving the rocky debris mostly intact. As the star lost around half of its mass, the orbit of the brown dwarf and the planetesimals increased. The debris would be stable within 17-32 AU (circular orbit of the brown dwarf) or 5-8 AU (e=0.6 for the brown dwarf orbit). A debris belt with an increased size might be close to the edge of this stable zone and gravitational interactions with the brown dwarf would scatter planetesimals into all kinds of directions, eroding the edge of the debris belt. Some of these planetesimals will be scattered inwards and are being disrupted by the tidal forces of the white dwarf, leading to the pollution of the white dwarf atmosphere. Alternatively the disk could have been larger than the stable zone, resulting in chaotic scattering at the beginning of the white dwarf stage, until the scattering decreased.

See also List of exoplanets and planetary debris around white dwarfs GD 165B is the first brown dwarf discovered around a white dwarf

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with PHL 5038

Start with the simplest possible case. Write down what PHL 5038 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 PHL 5038 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 PHL 5038 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 PHL 5038

In research: PHL 5038 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 PHL 5038 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: PHL 5038 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aquarius (constellation), Binary stars, L-type brown dwarfs, so understanding it makes those chapters shorter.
In everyday life: Look for PHL 5038 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 PHL 5038 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PHL 5038 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 PHL 5038 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PHL 5038 in simple terms?

PHL 5038AB (or just PHL 5038) is a binary system consisting out of a white dwarf and a brown dwarf on a wide orbit. The system is 240 light years (74 parsec) distant from earth.

Why does PHL 5038 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 PHL 5038?

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 PHL 5038.