astronomy

Gliese 900

Gliese 900 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 Gliese 900 rather than just read about it. In short: Gliese 900 (GJ 900, BD+00 5017) is a triple star system, located 68 light-years from Earth in the constellation Pisces. It is made up of three main sequence stars: one is a K-type star, the two others are M-dwarf stars.

Key takeaways

Gliese 900 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Gliese 900 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Gliese 900 from memory before moving on to harder problems.

Reference excerpt

Gliese 900 (GJ 900, BD+00 5017) is a triple star system, located 68 light-years from Earth in the constellation Pisces. It is made up of three main sequence stars: one is a K-type star, the two others are M-dwarf stars. The two M-dwarfs form a binary system with a period of 36 years, and this system has a period of 80 years around the primary component. With an apparent magnitude of 9.546, Gliese 900 is not visible to the naked eye. A widely separated planet has been detected around the system.

Stellar system

Gliese 900 is a hierarchical star system, made up of three main sequence stars: The primary component (Gliese 900 A) is a K5-K7 type star, that has 0.64–0.67 times the mass of the Sun, 0.72 times its radius, and 12% its luminosity. A light curve from the Transiting Exoplanet Survey Satellite (TESS) shows that its rotational period is 12 days. Gliese 900 A has a high level of chromospheric and coronal activity, although its apparent brightness presents little variation. The other components are red dwarf stars. Gliese 900 B has a spectral type of M3–M4 and a mass between 0.24 and 0.34 solar masses. Gliese 900 C has a spectral type of M5–M6 and a mass between 0.16 and 0.24 solar masses. The system is young, about 200 million years old, and is a likely member (99.7% probability) of the nearby moving group Carina-Near. It is a source of X-ray emission, with an observed flux of 9.13×102 mW M-2, and is also a source of ultraviolet emission. The emission of X-rays is typical of young stars, and classifies it as one. The TESS light curve identifies stellar flares on this star.

Orbit Gliese 900 B and C form an inner pair (named Gliese 900 BC) with an orbital period of around 36 years. Gliese 900 BC and Gliese 900 A orbit the system's center of mass with a period of 80 years. As of November 2004, B was separated from A by 751 milliarcseconds and C was separated from A by 708 mas. This separation changes over time. It was identified as a multiple star system in 2002 by Eduardo L. Martín, using adaptive optics-corrected images at the 8.2 m Subaru Telescope. When first observed, the A–B and A–C separations were of 0.51 and 0.76 arcsecs respectively. A further study by Malogolovets et al. (2007) identified this system as a hierarchical triple.

Other stars in the system Malogolovets et al. (2007) reported two other objects in 2MASS images (potentially late red dwarfs) that would be the components D and E and make the system quintuple, being "very likely" to be bound to the system. However, these faint stars have not been confirmed as members of the GJ 900 system, and are likely not associated.

Motion Gliese 900 is located 68 light-years from Earth, based on parallax measurements by the Gaia spacecraft. The BP-RP spectra suggest a distance of 67.7 ly. The space velocity components of this system are U = −28.7, V = −15 and W = 0.2. Gliese 900 is part of the thin disk population of the Milky Way. It was once classified as part of the IC 2602 supercluster. A newer analysis using kinematics from the Gaia spacecraft suggest that Gliese 900 has a 99.7% chance of being a member of the Carina-Near moving group and a 0.3% chance of being a field star, i.e. not associated to any star cluster or stellar association.

Planetary system A 2024 study led by Austin Rothermich identified CWISE J233531.55+014219.6 (abbreviated to CW2335+0142) as a proper motion companion to Gliese 900, with 99.5% probability. This object, also called Gliese 900 b or Gliese 900 (ABC)b, is a planetary-mass object that has 10.5 times the mass of Jupiter (0.01 times the mass of the Sun), a spectral type T9 and a temperature of 500 K. It was found to be at an angular separation of 587" from Gliese 900. At the estimated distance to this system, it translates to a projected separation of 12,000 AU. As of 2024, Gliese 900 b has the largest observed separation of any known planet, and assuming a circular orbit, the longest orbital period. The orbital period is estimated at 1.27 million years based on the projected separation. Due to the similar spectral type, orbital separation and age, Gliese 900 b has been compared to COCONUTS-2b by the discovery team. Also in 2024, a study using data from Wide-field Infrared Survey Explorer found a red W2-W3 color for Gliese 900 b, which the researchers interpret as a sign of low gravity for T-dwarfs. Low gravity is often seen as an indicator of a young age and a low mass.

See also Circumtriple planet, a category of planets to which Gliese 900 b belongs List of exoplanets discovered in 2024 - including Gliese 900 b

Notes

References

Illustrations

Worked examples

Example 1 — a first encounter with Gliese 900

Start with the simplest possible case. Write down what Gliese 900 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 Gliese 900 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 Gliese 900 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 Gliese 900

In research: Gliese 900 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 Gliese 900 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: Gliese 900 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Gliese and GJ objects, Hipparcos objects, K-type main-sequence stars, so understanding it makes those chapters shorter.
In everyday life: Look for Gliese 900 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 Gliese 900 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Gliese 900 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 Gliese 900 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Gliese 900 in simple terms?

Why does Gliese 900 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 Gliese 900?

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 Gliese 900.