astronomy

PSO J318.5−22

PSO J318.5−22 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 PSO J318.5−22 rather than just read about it. In short: PSO J318.5−22 is an extrasolar planetary-mass object that does not orbit any star, an analog to directly imaged young gas giants. There is no consensus yet among astronomers whether the object should be referred to as a rogue planet, as a young brown dwarf, or as a sub-brown dwarf.

Key takeaways

PSO J318.5−22 belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect PSO J318.5−22 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of PSO J318.5−22 from memory before moving on to harder problems.

Reference excerpt

PSO J318.5−22 is an extrasolar planetary-mass object that does not orbit any star, an analog to directly imaged young gas giants. There is no consensus yet among astronomers whether the object should be referred to as a rogue planet, as a young brown dwarf, or as a sub-brown dwarf. It is approximately 80 light-years away and belongs to the Beta Pictoris moving group. The object was discovered in 2013 in images taken by the Pan-STARRS PS1 wide-field telescope. PSO J318.5-22's age is inferred to be 23 million years, the same age as the Beta Pictoris moving group. Based on its calculated temperature and age, it is classified under the brown dwarf spectral type L7.

Discovery PSO J318.5−22 was discovered in data of Pan-STARRS and 2MASS in 2013. Follow-up observations were carried out with URKIRT (photometry), NASA IRTF and Gemini North (both spectroscopy). The team leader, Michael Liu of the Institute for Astronomy at the University of Hawaii, stated, "We have never before seen an object free-floating in space that looks like this. It has all the characteristics of young planets found around other stars, but it is drifting out there all alone."

Characteristics The spectrum of PSO J318.5−22 is in its redness in between low-gravity brown dwarfs and the planetary-mass companion 2M1207b, which is redder than PSO J318.5−22. The Gemini spectrum also shows several absorption features, such as weak iron hydride, sodium and potassium. Their weakness and a triangular H-band spectrum indicate a low gravity. Molecular absorption from water vapor and carbon monoxide are also detected. Low abundance of methane was detected in the L-band Keck/NIRSPEC spectrum of PSO J318.5−22. The team found that strong vertical mixing and photospheric clouds can explain the spectrum of PSO J318.5−22. PSO J318.5−22 was initially suspected to be a member of the Beta Pictoris Moving group, but radial velocity was not available at this time. Later radial velocity measurement with the help of high-resolution spectroscopy from Gemini North confirmed it as a Beta Pictoris member. This group also revised the physical properties due to Beta Pictoris being older than previously thought. It has a mass of 8.3 ± 0.5 MJ.

Variability and Clouds Variability was first detected with the New Technology Telescope, showing a rotation period larger than 5 hours and an amplitude of 7% to 10% in the Js band. The team found that the variability is likely driven by an inhomogeneous cloud cover. Later the rotational velocity helped to constrain the inclination to >29° and the rotation period to 5–10.2 hours. Later PSO J318.5−22 was observed simultaneously with Hubble WFC3 and Spitzer IRAC. This helped to narrow down the rotation period to 8.6 ± 0.1 hours and the inclination to 56.2 ± 8.1°. The amplitude is 3.4 ± 0.1% for Spitzer channel 2 (4.5 μm) and 4.4–5.8% for WFC3 (1.07–1.67 μm). The near-infrared and mid-infrared light curves have a phase offset between 200° and 210°, likely due to a depth-dependent longitudinal atmospheric structure. Another group did observe PSO J318.5−22 with the NTT Js and Ks-band and found a rotation period of 8.45 ± 0.05 hours and an amplitude of 2.4 ± 0.2 % in Js and 0.48 ± 0.08 % in Ks.

Cloud composition Estimated temperatures inside its clouds exceed 1,100 K (800 °C). The clouds, made of hot dust and molten iron, show how widespread clouds are in planets and planet-like objects. However, by 2020, modeling showed that the brightness variability could not be unambiguously attributed to clouds. The clouds are suspected to be a patchy haze layer over thick iron clouds. This patchy haze layer could be made of sodium sulfide, chromium or manganese sulfide. Observations with the James Webb Space Telescope found a pronounced absorption features at 10 Micron. This was reproduced with high-altitude cloud layer with small amorphous SiO grains. The researchers hypothesize that their observations probe homogeneous cloud nucleation of SiO cloud seeds from the gas phase. At lower latitudes these cloud seeds could then form into clouds. This is consistent with a "top-down" cloud formation approach. The clouds are likely made of a thick iron cloud deck and a silicate cloud layers at top. The observations do however challenge the models used to describe the atmosphere.

Formation Current theories about such objects include the possibility that gravitational perturbations may have kicked them out of their planetary systems soon after they formed through planetary accretion, or they may have been formed by some other means.

See also CFBDSIR 2149−0403 2MASS J1119–1137 OTS 44 Cha 110913−773444 CWISE J0506+0738 Jupiter

References

Illustrations

Worked examples

Example 1 — a first encounter with PSO J318.5−22

Start with the simplest possible case. Write down what PSO J318.5−22 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 PSO J318.5−22 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 PSO J318.5−22 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 PSO J318.5−22

In research: PSO J318.5−22 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 PSO J318.5−22 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: PSO J318.5−22 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Astronomical objects discovered in 2013, Beta Pictoris moving group, Capricornus, so understanding it makes those chapters shorter.
In everyday life: Look for PSO J318.5−22 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 PSO J318.5−22 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what PSO J318.5−22 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 PSO J318.5−22 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is PSO J318.5−22 in simple terms?

Why does PSO J318.5−22 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 PSO J318.5−22?

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 PSO J318.5−22.