astronomy

Heartbeat star

Heartbeat star 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 Heartbeat star rather than just read about it. In short: Heartbeat stars are pulsating variable binary star systems in eccentric orbits with vibrations caused by tidal forces. The name "heartbeat" comes from the similarity of the light curve of the star with what a heartbeat looks like through an electrocardiogram if their brightness was mapped over time.

Key takeaways

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

Reference excerpt

Heartbeat stars are pulsating variable binary star systems in eccentric orbits with vibrations caused by tidal forces. The name "heartbeat" comes from the similarity of the light curve of the star with what a heartbeat looks like through an electrocardiogram if their brightness was mapped over time. Many heartbeat stars have been discovered with the Kepler Space Telescope.

Orbital information Heartbeat stars are binary star systems where each star travels in a highly elliptical orbit around the common mass center, so that the separation of two stars varies from a few stellar radii to as much as 10 times that distance during one orbit. As the star with the more elliptical orbit swings closer to its companion, gravity will stretch the star into a non-spherical shape, changing its apparent light output. At their closest point in orbit, the tidal forces cause the shape of the heartbeat stars to fluctuate rapidly. When the stars reach the point of their closest encounter, the mutual gravitational pull between the two stars will cause them to become slightly ellipsoidal in shape, which is one of the reasons for their observed brightness being so variable.

Discoveries Heartbeat stars were studied for the first time on the basis of OGLE project observations. The Kepler Space Telescope with its long monitoring of the brightness of hundreds of thousands of stars enabled the discovery of many heartbeat stars. One of the first binary systems discovered to show the elliptical orbits, KOI-54, has been shown to increase in brightness every 41.8 days. A subsequent study in 2012 characterized 17 additional objects from the Kepler data and united them as a class of binary stars. A study which measured the rotation rate of star spots on the surface of heartbeat stars showed that most heartbeat stars rotate slower than expected. A study which measured the orbits of 19 heartbeat star systems, found that surveyed heartbeat stars tend to be both bigger and hotter than the Sun. The star HD 74423, discovered using NASA's Transiting Exoplanet Survey Satellite, was found to be unusually teardrop-shaped, which causes the star to pulsate only on one side, the first known heartbeat star to do so.

References

Further reading Hambleton, K.; Fuller, J.; Thompson, S.; Prša, A.; Kurtz, D. W.; Shporer, A.; Isaacson, H.; Howard, A. W.; Endl, M.; Cochran, W.; Murphy, S. J. (13 October 2017). "KIC 8164262: a heartbeat star showing tidally induced pulsations with resonant locking". Monthly Notices of the Royal Astronomical Society. 473 (4): 5165–5176. arXiv:1706.05051. doi:10.1093/mnras/stx2673. ISSN 0035-8711. Retrieved 29 February 2020. Manuel, Joseph; Hambleton, Kelly (January 2018). "Binary Model for the Heartbeat Star System KIC 4142768". AAS. 231: 146.01. Bibcode:2018AAS...23114601M.

Illustrations

Worked examples

Example 1 — a first encounter with Heartbeat star

Start with the simplest possible case. Write down what Heartbeat star 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 Heartbeat star 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 Heartbeat star 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 Heartbeat star

In research: Heartbeat star 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 Heartbeat star 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: Heartbeat star is common in secondary-school and first-year university syllabi. It links to neighbouring topics Binary stars, Kepler space telescope, Variable stars, so understanding it makes those chapters shorter.
In everyday life: Look for Heartbeat star 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Heartbeat star in 20 minutes

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

Frequently asked questions

What is Heartbeat star in simple terms?

Why does Heartbeat star 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 Heartbeat star?

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 Heartbeat star.