astronomy

TOI-700 d

TOI-700 d 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 TOI-700 d rather than just read about it. In short: TOI-700 d is a dense, rocky, near-Earth-sized exoplanet orbiting within the habitable zone of the red dwarf TOI-700. It is located roughly 101.4 light-years (31.1 pc) away from Earth in the constellation of Dorado and is the outermost of four confirmed exoplanets around its star.

Key takeaways

TOI-700 d belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect TOI-700 d to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of TOI-700 d from memory before moving on to harder problems.

Reference excerpt

TOI-700 d is a dense, rocky, near-Earth-sized exoplanet orbiting within the habitable zone of the red dwarf TOI-700. It is located roughly 101.4 light-years (31.1 pc) away from Earth in the constellation of Dorado and is the outermost of four confirmed exoplanets around its star. The exoplanet is the first Earth-sized exoplanet in the habitable zone discovered by the Transiting Exoplanet Survey Satellite (TESS). TOI-700 d orbits its star at a distance of 0.161 AU (24,100,000 km; 15,000,000 mi) from its host star with an orbital period of roughly 37.4 days and has a radius of around 1.19 times that of Earth. It has been estimated that the planet receives about 88% the energy that the Earth receives from the Sun. It was discovered on 3 January 2020 by the Transiting Exoplanet Survey Satellite (TESS).

Physical characteristics

Mass, radius and temperature TOI-700 d is slightly larger than Earth with a radius of about 1.16 R🜨. However, it is significantly more massive at about 2.40 M🜨 with a density around 8.5 g/cm3. The planet's high density indicates a rocky composition with a higher fraction of iron than Earth and may be explained by high-energy giant impact events during its formation. The planet's equilibrium temperature would be about 268.8 K (−4.3 °C; 24.2 °F), and it receives 88% as much sunlight as Earth does from the Sun. The surface temperature of TOI-700d is likely higher if it has an atmosphere. A small chance of a runaway greenhouse effect exists.

Host star

TOI-700 is a red dwarf of spectral class M that is about 40% the mass and radius, and very roughly 50% of the temperature of the Sun. The star is bright with low levels of stellar activity. Over the 11 sectors observed with TESS, the star does not show a single white-light flare. The low rotation rate is also an indicator of low stellar activity.

Orbit TOI-700 d orbits its host star with an orbital period of 37.42 days. It has an orbital radius of about 0.161 AU (24.1 million km; 15.0 million mi), less than half of that of Mercury to the Sun in the Solar System. It receives about 88% of Earth's sunlight from its host star.

Habitability

TOI-700 d orbits in the habitable zone of its host star. The solar wind ram pressure and intensity of the interplanetary magnetic field are expected to be similar to the Earth's, therefore retention of the planetary atmosphere is likely. The presence of an extended hydrogen/helium envelope on TOI-700c indicates the star's high energy emission was insufficient to strip its atmosphere. Therefore, TOI-700d, which receives less than half the insolation as c, may have been able to maintain a secondary high mean molecular weight atmosphere even less susceptible to photoevaporation.

History and discovery TOI-700 d was discovered by a team of astronomers led by Emily Gilbert using the Transiting Exoplanet Survey Satellite (TESS) in early January 2020. This was the first Earth-sized exoplanet in the habitable zone discovered by TESS.

Illustrations

Worked examples

Example 1 — a first encounter with TOI-700 d

Start with the simplest possible case. Write down what TOI-700 d 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 TOI-700 d 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 TOI-700 d 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 TOI-700 d

In research: TOI-700 d 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 TOI-700 d 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: TOI-700 d is common in secondary-school and first-year university syllabi. It links to neighbouring topics Dorado, Exoplanets discovered by Planet Hunters, Exoplanets discovered by TESS, so understanding it makes those chapters shorter.
In everyday life: Look for TOI-700 d 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 TOI-700 d in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what TOI-700 d 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 TOI-700 d out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is TOI-700 d in simple terms?

Why does TOI-700 d 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 TOI-700 d?

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 TOI-700 d.