astronomy

WD 1145+017

WD 1145+017 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 WD 1145+017 rather than just read about it. In short: WD 1145+017 (also known as EPIC 201563164) is a white dwarf approximately 476 light-years (146 parsecs) from Earth in the constellation of Virgo. It is the first white dwarf to be observed with a transiting minor planet orbiting it.

Key takeaways

WD 1145+017 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect WD 1145+017 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of WD 1145+017 from memory before moving on to harder problems.

Reference excerpt

WD 1145+017 (also known as EPIC 201563164) is a white dwarf approximately 476 light-years (146 parsecs) from Earth in the constellation of Virgo. It is the first white dwarf to be observed with a transiting minor planet orbiting it.

Stellar characteristics The white dwarf has a mass of 0.6 M☉, radius of 0.012 R☉ (1.34 R🜨) and a temperature of 15,020 K, typical for white dwarf stars. It has been a white dwarf for 224 million years. The star's spectrum includes strong absorption lines due to magnesium, aluminium, silicon, calcium, iron and nickel. These elements commonly found in rocky planets are polluting the surface of the star, and would normally be expected to mix through the star and disappear from view after a million years. A circumstellar dust cloud and disk (likely due to disintegrating asteroids, located at 97 to 103 R_wd, and emitting thermal IR radiation) surrounds the star. In addition, a circumstellar gas disk (located ~ 25 to 40 R_wd, and undergoing relativistic precession with a period of ~ 5 years) surrounds the star as well. Based on 2018 studies and calculations, it is believed that the star initially was an early A-type main sequence star with a mass of about 2.48±0.14 M☉, remaining so for an estimated 550±100 million years. Afterwards, following the exhaustion of hydrogen within its core, it evolved and expanded into a red giant before eventually ejecting its layers and contracting into a white dwarf, and has gradually cooled over the last 224±30 million years. This gives the star an estimated total age of around 774 million years. The apparent magnitude of the star, or how bright it appears from Earth's perspective, is about 17. Therefore, it is too dim to be seen with the naked eye.

Planetary system

The supposed planetesimal, WD 1145+017 b, with a 4.5 hour orbit, is being ripped apart by the star and is a remnant of the former planetary system that the star hosted before becoming a white dwarf. It is the first observation of a planetary object being shredded by a white dwarf. Several other large pieces have been seen in orbit as well. All the various larger pieces have orbits of 4.5 to 4.9 hours. Rocky material is raining down onto the star, and showing up in the star's spectrum. The system was detected by the Kepler space telescope in its extended K2 mission. Though the system was not a target of interest, it was within the field of view of observing sessions, and analysis of the observed data revealed the system. An excess of infrared radiation indicates that there is a dusty disk with a temperature of 1,150 K (880 °C). Supporting observational data, along with data from the Chandra X-ray Observatory, were also found related to dust debris orbiting WD 1145+017.

Similar systems In September 2020, astronomers reported the discovery, for the first time, of a very massive Jupiter-sized planet, named WD 1856+534 b, closely orbiting, every 36 hours, a tiny white dwarf star, named WD 1856+534, a left-over remnant of an earlier much larger Sun-like star. This is the first true planet observed to transit a white dwarf, as opposed to the planetesimals transiting WD 1145+017.

See also Disrupted planet List of stars that have unusual dimming periods List of exoplanets and planetary debris around white dwarfs Other planetesimals around white dwarfs:

ZTF J0139+5245 WD 0145+234 SDSS J1228+1040 b ZTF J0328-1219

References

External links EPIC Catalog at MAST Harvard Center for Astrophysics, EPIC 201563164 AstronomyNow, WD 1145+017 AmericaSpace, WD 1145+017

Illustrations

Worked examples

Example 1 — a first encounter with WD 1145+017

Start with the simplest possible case. Write down what WD 1145+017 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 WD 1145+017 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 WD 1145+017 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 WD 1145+017

In research: WD 1145+017 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 WD 1145+017 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: WD 1145+017 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Planetary systems with one confirmed planet, Virgo (constellation), White dwarfs, so understanding it makes those chapters shorter.
In everyday life: Look for WD 1145+017 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 WD 1145+017 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what WD 1145+017 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 WD 1145+017 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is WD 1145+017 in simple terms?

Why does WD 1145+017 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 WD 1145+017?

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 WD 1145+017.