astronomy

LTT 1445

LTT 1445 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 LTT 1445 rather than just read about it. In short: LTT 1445 is a triple M-dwarf system 22.4 light-years (6.9 parsecs) distant in the constellation Eridanus. The primary LTT 1445 A hosts two exoplanets—one discovered in 2019 that transits the star every 5.36 days, and another found in 2021 that transits the star every 3.12 days, close to a 12:7 resonance.

Key takeaways

LTT 1445 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect LTT 1445 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of LTT 1445 from memory before moving on to harder problems.

Reference excerpt

LTT 1445 is a triple M-dwarf system 22.4 light-years (6.9 parsecs) distant in the constellation Eridanus. The primary LTT 1445 A hosts two exoplanets—one discovered in 2019 that transits the star every 5.36 days, and another found in 2021 that transits the star every 3.12 days, close to a 12:7 resonance. As of October 2022 it is the second closest transiting exoplanet system discovered, with the closest being HD 219134 bc.

Stellar system All three stars in the system are M-dwarfs, with masses between 0.16 M☉ and 0.26 M☉. LTT 1445 A and LTT 1445 BC are separated by about 34 astronomical units and orbit each other with a period of about 250 years. The BC pair orbit each other about every 36 years in an eccentric orbit (e= ~0.5). The alignment of the three stars and the edge-on orbit of the BC pair suggests co-planarity of the system. The existence of transiting planets suggests that the entire system is co-planar, with orbits in one plane. The TESS light curve showed stellar flares and rotational modulation due to starspots, likely on either the B or C component. Observations with Chandra showed that component C is the dominat X-ray source, with some contributions by component B. Flares are detected for component A in ultraviolet with Hubble and in x-rays with Chandra. Hubble observations also revealed an ultraviolet flare for component C, which was invisible at optical wavelengths.

Planetary system

LTT 1445 Ab LTT 1445 Ab is an exoplanet located approximately 22 light years away from Earth. Astrophysicists of the Harvard Center for Astrophysics discovered it in June 2019 with data from the Transiting Exoplanet Survey Satellite. The team obtained follow-up observations, including HARPS radial velocity measurements to constrain the mass of the planet. LTT 1445 Ab takes 5 days to orbit its star. In July 2021, the mass of the planet was measured as 2.87±0.25 Earth masses, confirming an Earth-like composition. LTT 1445 Ab likely has a rocky composition, and because it orbits close to the M-dwarf, it has an equilibrium temperature of 431±23 K (158 °C; 316 °F). In 2022, a planetary transmission spectrum showed no evidence for an atmosphere, although an atmosphere with high altitude hazes cannot be ruled out yet. In 2025 a transmission spectrum with Hubble was published. The spectrum is consistent with a flat line. Only the infrared shows potential features consistent with hydrogen cyanide. Some retrievals weakly favour an atmosphere, but these could be stellar contamination. A thermal emission spectrum of LTT 1445 Ab was detected with JWST MIRI low resultion spectroscopy (LRS). The observation observed the planet during the secondary eclipse at the 5-12 μm range. During a secondary eclipse the planet disappears behind the star. This allowed the scientists to determine the dayside brightness temperature of 525 ± 15 K (252 °C; 485 °F). This measurement is consistent with a dark rocky surface. The observations disfavour a very thick CO2 atmosphere, but it is uncertain if a moderately thin atmosphere is possible (atmospheres like those on Mars, Titan or Earth).

LTT 1445 Ac A second planet, LTT 1445 Ac, was also found in 2021 on a 3.12 day orbital period, with a mass of 1.54+0.20−0.19 Earth masses. Although it transits the star too, its smaller size made it difficult to detect before the radial velocity measurements, and still makes it difficult to estimate its exact size. The planets orbit near a 12:7 orbital resonance with one another - Ac orbiting 11.988 times for every 7 orbits Ab makes - oscillating one full orbit away from a 'perfect' resonance every 104 years. The planet's existence was independently confirmed in 2022. In 2023, observations with the Hubble Space Telescope allowed a more precise determination of the planet's size, supporting a rocky composition for both planets. Its equilibrium temperature is 516±28 K (243 °C; 469 °F).

LTT 1445 Ad A third planetary candidate on a 24.3-day orbit, LTT 1445 Ad, was found in 2022. This is a possibly rocky super-Earth orbiting within the habitable zone.

See also List of star systems within 20–25 light-years List of nearest exoplanets EZ Aquarii nearby M-dwarf triple GJ 1245 nearby M-dwarf triple Gliese 667 Cc

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with LTT 1445

Start with the simplest possible case. Write down what LTT 1445 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 LTT 1445 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 LTT 1445 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 LTT 1445

In research: LTT 1445 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 LTT 1445 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: LTT 1445 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Durchmusterung objects, Eridanus (constellation), Hipparcos objects, so understanding it makes those chapters shorter.
In everyday life: Look for LTT 1445 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 LTT 1445 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what LTT 1445 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 LTT 1445 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is LTT 1445 in simple terms?

Why does LTT 1445 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 LTT 1445?

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 LTT 1445.