What is Planetary: Definition and 306 Discussions

A planetary nebula (PN, plural PNe), is a type of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from red giant stars late in their lives.The term "planetary nebula" is a misnomer because they are unrelated to planets. The term originates from the planet-like round shape of these nebulae observed by astronomers through early telescopes. The first usage may have occurred during the 1780s with the English astronomer William Herschel who described these nebulae as resembling planets; however, as early as January 1779, the French astronomer Antoine Darquier de Pellepoix described in his observations of the Ring Nebula, "very dim but perfectly outlined; it is as large as Jupiter and resembles a fading planet".
Though the modern interpretation is different, the old term is still used.
All planetary nebulae form at the end of the life of a star of intermediate mass, about 1-8 solar masses. It is expected that the Sun will form a planetary nebula at the end of its life cycle. They are relatively short-lived phenomena, lasting perhaps a few tens of millennia, compared to considerably longer phases of stellar evolution. Once all of the red giant's atmosphere has been dissipated, energetic ultraviolet radiation from the exposed hot luminous core, called a planetary nebula nucleus (P.N.N.), ionizes the ejected material. Absorbed ultraviolet light then energizes the shell of nebulous gas around the central star, causing it to appear as a brightly coloured planetary nebula.
Planetary nebulae probably play a crucial role in the chemical evolution of the Milky Way by expelling elements into the interstellar medium from stars where those elements were created. Planetary nebulae are observed in more distant galaxies, yielding useful information about their chemical abundances.
Starting from the 1990s, Hubble Space Telescope images revealed that many planetary nebulae have extremely complex and varied morphologies. About one-fifth are roughly spherical, but the majority are not spherically symmetric. The mechanisms that produce such a wide variety of shapes and features are not yet well understood, but binary central stars, stellar winds and magnetic fields may play a role.

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  1. Gunter1977

    How to Calculate Forces on Sun Wheels in a Planetary Gear System?

    Hello everyone, I hope somebody can assist me with this. I am working on a calculation for a planet gear with 4 sun wheels and 1 planet wheel. The aim is to determine the forces on the sun wheel. Initially, I have 3 equations and 4 unknowns. By making an assumption based on symmetry, I now have...
  2. F

    Tusi discovering laws of planetary motion before Kepler?

    I was reading about the Tusi couple and read it "as a solution for the latitudinal motion of the inferior planets, and later used extensively as a substitute for the equant". Since the Tusi couple is related to plotting out an ellipse, did Nasir al-Din al-Tusi already discover the laws for...
  3. Parziter

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    TL;DR Summary: Solar sytem forces on Unity Hello ! For my last year in my school, I've got a project to do, and I wanted to recreate the Solar system with forces on Unity. My forces are Velocity and Acceleration (I'm using the Frenet's formulas). I'm sorry I'm not a physicist and that's why...
  4. D

    B Planetary Orbits - Elliptical or Wavelike?

    I was running a simulation in Universe Sandbox where I placed a 10 million solar mass black hole about 10 light years from the Solar System, initially stationary relative to the Sun. I noticed once the Sun had reached about 70km/s relative to the black hole, all the orbits became wavelike rather...
  5. Astronuc

    B Evolution of planetary system around a white dwarf

    An article came up on Phys.org about a white dwarf drawing in material from the planetary system surrounding it. Is this the ultimate fate of our solar system? https://phys.org/news/2022-06-dead-star-cannibalism-planetary-far-reaching.html...
  6. F

    A What is a Bern model in planetary population synthesis?

    Hello. I'm writing my Master Thesis about planetary population synthesis and one of the chapters is about the different models. I found that most of them are Bern models with some modifications. What is a Bern model in planetary population synthesis and what references can I read about it...
  7. rudransh verma

    B What is the relationship between force and distance in planetary motion?

    https://www.feynmanlectures.caltech.edu/I_09.html 9-7 "From this figure we see that the horizontal component of the force is related to the complete force in the same manner as the horizontal distance x is to the complete hypotenuse r, because the two triangles are similar. Also, if x is...
  8. neilparker62

    Stargazing Planetary Lineup and Eclipse Viewing Tips for Cruise Ship Passengers

    Looking East this morning about 5:15 am. No telescope needed. But the pic is not actual - it is from Stellarium.
  9. S

    Writing: Input Wanted Help needed comparing planetary "calendars"

    Summary:: Writing a YA Space Opera series, but I'm lost on trying to create a formula for calculating "Earthbirth Days" Short run down: Earth was no long hospitable to humans so we left to colonize a new planet, Nemesyne. People on Nemesyne still celebrate their "Earthbirth Days" and count...
  10. Frabjous

    Looking for review article on planetary interiors

    I am looking for a modern review article on high pressure equations of state and planetary interiors. Preferably post 2010. Does anyone know of one? Thanks.
  11. G

    I Planetary Formation: Could Collisions Explain Our Solar System?

    I'm very much an amateur with a keen interest in space/the universe and it occurred to me the other day that our solar system could have been formed in exactly the same way that it is hypothesised that the Moon/Earth system formed through the (proposed) collision of Theia and the proto-Earth...
  12. P

    Compound planetary gear problem

    Hi, I need a little help with this problem with compound planetary gears. I don't know how to apply the formulas for this specific type of placement. I need to know the final speed of the engine knowing the number of teeth z1 = -104 ring gear which is internal, z2,3,4 = 22 for small planets...
  13. D

    I Planetary orbits - the 2-body problem

    Hi I am confused about certain aspects of deriving the planetary orbit equation by considering it as 2-body problem. I will ask my first question now before i get to my other questions. In the David Tong notes on "Dynamics & Relativity" he states that a particle in central force potential...
  14. lomidrevo

    B Planetary debris found in white dwarf atmospheres

    I read this interesting article today, the original paper here. Abstract:
  15. V

    Programs Astrophysics or planetary science?

    Hi I am a computer science undergraduate working as a data scientist. I generally love studying physics and planetary science. I am aspiring to research in biomarkers and bio signatures in planets. If I have to choose this research path should I study masters in, astrophysics or...
  16. Leo Liu

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    The answer to (c) is ##-2\pi AGMm##. Answer to (d) For sub-question d, I used a different approach and I don't know why the solution to (d) is an appropriate approximation. What I did was that I use Newton's laws to obtain two differential equation in polar coordinate, as shown: $$\text{Assume...
  17. Orange_Squash

    Planetary scientist/atmospheric physicist - hi

    Hi there, I'm a research scientist having worked in various fields and institutions, I'm now out on my own as an independent contractor. I don't have my computer guy down the hall to ask computer questions to, or the building of experts to quiz when I'm stuck on a problem. I also miss helping...
  18. J

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    Why is it that all of the planets in our solar system (to our knowledge) orbit the sun in such a way that they all go around the sun in roughly similar orbital planes? Why don’t we have planets with orbital planes at significantly different angles?
  19. Bill McKeeman

    B Molten Core of Mars: Could Tidal Action from a Moon Create a Magnetic Field?

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  20. T

    Planet Gear System: Sun Gear Input, Same Torque in Ring & Carrier?

    Hello all, In a planetary gear system, there is: sun gear planet gear Ring gear Carrier Suppose the SUN gear delivers the input torque to the system. (I do not care about the planet gears in this system.= There are two torques that can result. The ring can deliver a torque and the carrier...
  21. S

    Gravitation (planetary motion)

    Homework Statement: The particle is moving in circular orbit such a way that the net force (F) is always towards the point p (point p is on the circumference of circle). Find the variation of force F with respect to r. i.e find the value of n in the expression F=kr^n Homework Equations: F=kr^n...
  22. hiddenname

    I Electricity & Planetary Magnetic Field Reversal: Implications & Studies

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  23. I

    Rockstrøm et al - Planetary boundaries

    Does anyone have any research material for up to date research about these planetary boundaries? https://www.stockholmresilience.org/research/planetary-boundaries.html
  24. V

    Studying Advice on How to Pursue a Career in Planetary Research

    Hi. Currently I’m 17 and I’m coming to the end of my first year of A levels. I have to start writing my ucas and applying for unis later this year. I’m really interested in space and have always wanted to go down that route, however I’ve not had much guidance as what to do with my future in...
  25. R

    I What physical mechanisms are involved in heating planetary bodies?

    Many asteroids and planets have undergone enough heating so that they were at some point completely or partially melted. What physical mechanisms are in play here? I'm assuming a solar system such as our own. Thanks!
  26. gleem

    I Some comments on the 2019 Planetary Defense Conference

    The 6th Annual International Academy of Astronautics Conference on Planetary Defense ended this past Friday. I watched about half of the presentations. I have little astronomy background but was interested in what was being done about NEO detection, characterization effects and mitigation...
  27. S

    I Isn't planetary rock dating really supernova dating?

    The age of the oldest rocks on Earth & Moon are about 4.5 Gy old. But doesn't the material that made the Earth come from the supernova that had occurred prior to the formation of the Solar System, and doesn't the radioactivity dating measure the age of the creation of that material in that...
  28. M

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  29. T

    Planetary collision that formed the Moon made life possible on Earth

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  30. Drakkith

    I What factors determine the composition of a planet's atmosphere?

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  31. L

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    The thought of increasing a satellite's (for example) speed to allow it to transfer from a "higher energy" elliptical orbit to a "lower energy" circular orbit (in reference to the effective potential energy plot that arises after introducing the concept of an effective mass to simplify the...
  32. K

    I Can I Simulate Planetary Accretion with Disksim?

    Hi - having come up blank when searching, I figured I'd ask here: do you know of any (free, preferably open source) planetary accretion models/simulators available for download? I'm primarily looking for solar system formation / evolution rather than planetary geochemistry (although I'd have an...
  33. X

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  34. R

    I Exploring Planetary Orbits and the Sun's Rotation

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  35. RpWinter

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    Hey, this is how i tried solving the differential equation The solution however does not match the general solution of the equation. Also differentiating it twice does not give me the previous equation. Please tell me if i did some mistake while solving. I already know how to solve by finding...
  36. W

    B Who drew the first model of the atom?

    Does anybody know who first drew (not just described but actually drew, even roughly) a model of the atom like the one below, and when: I'd appreciate it if anybody can point me to an evidence.
  37. itsarah55

    Other Industry Jobs for a Planetary Scientist

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  38. F

    I Is Jupiter Responsible for the Majority of the Solar System's Angular Momentum?

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  39. I

    I Data Model of Kepler's Second Law of Planetary Motion

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  40. J

    Tension of Rope: Cosmonaut & Spaceship Orbit in Planetary Gravity

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  41. M

    I Orbit simulations, tidal forces and planetary oblateness

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  42. A

    I What Are the Best Academic Journals for Aspiring Planetary Scientists?

    Hi all, I'm an undergraduate Physics major looking to jump into Planetary. Through either a reasonably priced subscription, or free, and in paper or online, what would you suggest as a journal or professional level news aggregate for me to get the latest updates and literature in planetary...
  43. hhhp8cec1

    Semi major axis - planetary Science

    Homework Statement A comet with a perihelion distance of d = 1.242 is currently 211(degrees) from pericenter, and 4.499 AU from the Sun. Compute the semi-major axis a of this comet’s orbit. Homework Equations P(^2) = a^3The Attempt at a Solution I tried to use Kepler's third law but I don't...
  44. M

    Question about calculation of planetary gear ratios

    So I've found the following formula for calculating the gear ratio of a planetary gear. Tr Turns of the ring gear Ts Turns of the sun gear Ty Turns of the planetary gear carrier R Ring gear teeth S Sun gear teeth P Planet gear teeth ( R + S ) ×Ty = R × Tr + Ts × S The example I saw on the same...
  45. P

    Stable Circular Orbits in Planetary Motion: A Homework Solution

    Homework Statement Consider a particle moving in the potential U (r)= -A/r^n, where A>0. What are the values of n which admit stable circular orbits? Homework EquationsThe Attempt at a Solution I tried to solve by putting dr/dt=0 in the total energy equation E= T + Ueff. But it didn't work...
  46. Hawksteinman

    I Questions about planetary magnetic fields

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  47. BillTre

    How Will the New Planetary Protection Officer Impact Mars Exploration Protocols?

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  48. 10Exahertz

    I Taking Projectile Motion to make Planetary Trajectories

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