What is Exoplanet: Definition and 69 Discussions

An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917, but was not recognized as such. The first confirmation of detection occurred in 1992. This was followed by the confirmation of a different planet, originally detected in 1988. As of 22 June 2021, there are 4,768 confirmed exoplanets in 3,527 planetary systems, with 783 systems having more than one planet.There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star. About 1 in 5 Sun-like stars have an "Earth-sized" planet in the habitable zone. Assuming there are 200 billion stars in the Milky Way, it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if planets orbiting the numerous red dwarfs are included.The least massive planet known is Draugr (also known as PSR B1257+12 A or PSR B1257+12 b), which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter, although according to some definitions of a planet (based on the nuclear fusion of deuterium), it is too massive to be a planet and may be a brown dwarf instead. Known orbital times for exoplanets vary from a few hours (for those closest to their star) to thousands of years. Some exoplanets are so far away from the star that it is difficult to tell whether they are gravitationally bound to it. Almost all of the planets detected so far are within the Milky Way. There is evidence that extragalactic planets, exoplanets farther away in galaxies beyond the local Milky Way galaxy, may exist. The nearest exoplanets are located 4.2 light-years (1.3 parsecs) from Earth and orbit Proxima Centauri, the closest star to the Sun.The discovery of exoplanets has intensified interest in the search for extraterrestrial life. There is special interest in planets that orbit in a star's habitable zone, where it is possible for liquid water, a prerequisite for life on Earth, to exist on the surface. The study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life.Rogue planets are those that do not orbit any star. Such objects are considered as a separate category of planet, especially if they are gas giants, which are often counted as sub-brown dwarfs. The rogue planets in the Milky Way possibly number in the billions or more.

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  1. DaveC426913

    B SubNeptune planet K2-18b shows methane and dimethyl sulfide

    "A new investigation with NASA’s James Webb Space Telescope into K2-18 b, an exoplanet 8.6 times as massive as Earth, has revealed the presence of carbon-bearing molecules including methane and carbon dioxide. ... The abundance of methane and carbon dioxide, and shortage of ammonia, support the...
  2. Strato Incendus

    Writing: Input Wanted Postulating Life on Jupiter's moon Europa

    Even an offhanded remark by some character in a sci-fi story can have major implications. With my story based on a generation ship in the late 25th century, I considered it self-evident that humanity would already have explored most of the planets and moons within the solar system before trying...
  3. Astronuc

    B Exoplanet TOI-4603 b, ~13x Jupiter mass, ~1.04 Jupiter diameter

    https://phys.org/news/2023-03-massive-giant-exoplanet-tess.html It is one of the most massive and densest exoplanets. For comparison, Mo has a density of 10.22 g/cm3 and Ta has a density of 16.6 g/cm3. I would suspect that some of the density is derived from the high compressive pressure of...
  4. M

    B Would the Giant Arc be visible from a hypothetical exoplanet?

    I recently watched History of the Universe and they talked about the Giant Arc, a large scale structure that spans 3.3 billion light years long, exceeding the hypothetical limit of 1.2 billion. The Arc was discovered last year. https://en.wikipedia.org/wiki/The_Giant_Arc They said if the Giant...
  5. S

    B Why is the momentum of a star equal to the momentum of a planet?

    I was wathcing a video about radial velocity method for seeking exoplanet(video) and on 3:05 author writes that momentum of a star equal momentum of a planet. Why?
  6. D

    B How much in the past do we see these planets?

    The HR 8799 star is 129 light-years away from us, in this image we can see thermal emissions coming from these planets. Do these emissions move at the speed of light? If so does it mean that what we are seeing in this image is how the planets looked like in infrared 129 years in the past?
  7. bland

    B Nobel Prize for first exoplanet discovery

    Summary: Why is the Nobel committee acting as though the discovery was of the same order as the discovery that Andromeda was another galaxy. Now this has been bugging me since ever. but the Nobel committee brought it up again "This discovery (1995 exoplanet) has opened up a Universe far...
  8. phinds

    B Water found on potentially habitable exoplanet

    Summary: water found on potentially habitable exoplanet from the BBC https://www.bbc.com/news/science-environment-49648746
  9. A

    A The Habitable Exoplanet Hunting Project

    Hi all! We are looking for more observatories and amateur astronomers who might want to join the project. The Habitable Exoplanet Hunting Project is a worldwide network of amateur astronomers searching for new potentially habitable exoplanets. I am coordinating over 20 observatories located in...
  10. A

    I BREAKING: New potentially habitable exoplanet found around Teegarden

    Astronomers have discovered a potentially habitable exoplanet around Teegarden's Star. Teegarden is an old red dwarf star 12 light-years away in the Aries constellation. The exoplanet found, called Teegarden b, has a minimum mass almost identical to Earth. It orbits within the star's...
  11. wolram

    Stargazing Efficient Follow-Up of Exoplanet Transits Using Small Telescopes

    1903.11078.pdf Would it not be cool to find an exoplanet from your back lawn. This paper is to introduce an online tool1 for the prediction of exoplanet transit light curves. Small telescopes can readily capture exoplanet transits under good weather conditions when the combination of a bright...
  12. Cerenkov

    B Ratio of Earth-Sized exoplanets to other sizes of exoplanet?

    Hello. In this issue of the American Scientist magazine, https://www.americanscientist.org/magazine/issues/2018/september-october, there's an article by Dominik Kraus of the Helmholtz-Zentrum Dresden-Rossendorf Institute of Radiation Physics about the internal composition of the planets Uranus...
  13. A Alex P

    A Difference between eclipsing binaries and exoplanets

    Kepler space mission has discovered thousands of exo-planet candidates. Why are they just candidates ? Why followup ground based study is required ? Why is Kepler unable to confirm them ? Second thing, how are scientists going to differentiate between eclipsing binaries mimicking to be exoplanets.
  14. nearc

    I Tight grouping of exoplanets 295RA 45dec

    does anyone have any information on why the vast majority of exoplanets are located in one spot? any papers on the topic? the following link does not graph RA vs DEC but instead does something about planet size, if you wish to use it please select RA for the x-axis and DEC for the y-axis, both...
  15. F

    Life on other planets, are we looking at the wrong planets?

    Scientists are looking for Earth like planets/bodies to find life on other planets/bodies, somewhere that is warm enough that liquid water can exist, and somewhere with basic organic molecules. Here's where I have a concern, in the 4 billion years of Earth's life, to our knowledge life had only...
  16. Chatterton

    Guide to Inferring Colors on Alien Worlds: Star Class, Luminosity, Atmosphere

    Is there a guide, based on existing evidence, that I could use to infer realistically how color would be affected on alien worlds due to factors like star class, luminosity, atmospheric composition, etc? I'm planning to develop a not-too-too-distant future scenario where all the stars in...
  17. J

    B Transit of newly discovered exoplanet of Proxima centuri

    In descriptions of the newly discovered exoplanet, named Proxima Cen b, orbiting Proxima Centuri, it is mentioned that a determination of its size could be established by observing the planet’s transit in front of Proxima centuri, which would reveal the exoplanet’s diameter. It is my...
  18. Brage Eidsvik

    I Exoplanet Climate: Can Planets Have Multiple Liquid Layers?

    Is it possible for planets to have multiple liquid layers? Like a ocean made of water, with an ocean within, consisting of a heavier liquid. And could it have a sirculation, as water does on Earth?
  19. G

    A Finding an exoplanet via its magnetosphere's effect on starlight?

    Following the same way to detect a black hole via gravitational lens. Is it possible? Use the same methodology to detect exoplanet via its magnetic field and the distortion caused in the light of Star? Can we find a phase or polarization change in part of a light from a star caused by an...
  20. collinsmark

    NASA NASA discovers new exoplanet (The Onion, funny)

    http://www.theonion.com/article/nasa-discovers-distant-planet-located-outside-fund-53595 "WASHINGTON—Noting that the celestial body lies within the habitable zone of its parent star and could potentially harbor liquid water, NASA officials announced at a press conference Thursday they have...
  21. Ygggdrasil

    B A terrestrial, temperate planet around Proxima Centauri

    Published today in Nature: Anglada-Escudé et al. (2016) A terrestrial planet candidate in a temperate orbit around Proxima Centauri. Nature: 536: 437. doi:10.1038/nature19106 Popular press summary...
  22. M

    I Calculating semi-major axis and minimum mass of an exoplanet

    Hello guys, I'm doing my physics coursework on kepler's third law and I'm finding the minimum mass and semi-major axis of a unknown planet. I have the following data: Stellar mass Mstar = 1.31 ± 0.05 Msun Orbital period P = 2.243752 ± 0.00005 days Radial velocity semi-amplitude: V = 993.0 ±...
  23. AstroCody

    B Tidally Locked Planets: How Close to the Star?

    How close must a planet be to its parent star in order for it to be tidally locked?
  24. RooksAndBooks

    New Closest Earth-like Planet (20/12/15)

    Welcome to my thread. As you have seen from the title, scientists have just discovered a new potentially earth-like planet; it's the closest to us. It's four times the mass of the Earth and it's only 14 light years away. The planet is called Wolf 1060c. Read more about it here. What do you...
  25. DuckAmuck

    Online Sources for Kepler Exoplanet Data

    Does anyone know the best online source(s) for kepler exoplanet data? Thank you.
  26. DaveC426913

    Newest exoplanet close enough to study its potential atmosphere

    GJ 1132b, the new neighbour is a rocky, Earth-sized planet that's located only 39 light-years away - so lcose we could almost hit it with a rock. http://www.sciencealert.com/the-closest-earth-like-exoplanet-so-far-has-been-discovered-and-it-s-got-astronomers-excited?perpetual=yes&limitstart=1
  27. C

    Future time measurement units for a tidal locked exoplanet

    Lets assume that a human colony wants to reform time measurement units for more practical. Reasoning: -circadian rhythm a bit exceeds 24h, so perfect day would be around 24h and 10 minutes ( http://www.circadiansleepdisorders.org/info/cycle_length.php ) -readjusting year zero, somewhere...
  28. PWiz

    New rocky exoplanet discovered is the closest to Earth

    Say hello to HD 219134b - a rocky exoplanet recently discovered using HARPS-North instrument on the Italian 3.6-meter Galileo National Telescope in the Canary Islands, who's existence has been confirmed by NASA's Sptizer Space Telescope. At a distance of 21 light years, it is the closest...
  29. C

    A realistic mine turned in to an underground city

    As you probably know every respectable RPG needs an underground complex below a city... Usually it involves high gov spending on spacious severs full of mutated creatures... such constructions are usually hard to justify to taxpayers :D OK, more seriously, the setting: 1) the city is located on...
  30. Ikon Rahu

    Distance of GJ 436b to GJ 436 - doesn't work out.

    In an article on phys.org [http://phys.org/news/2015-06-red-dwarf-planet-hydrogen-massive.html] , it states that the exoplanet GJ 436b is 33x closer to its parent star than the Earth is to our sun. It also states that the exoplanet is less than 2 million miles away from the star. If I assume an...
  31. C

    Ground effect for blended wing body turboprop planes

    I wondered about possibility of using ground effect by blended wing body, turboprop planes. Purposes: -to save fuel (for example for flying tankers); -to return partially damaged plane; -to hide under radar and become visible for ships in the last moment; -to allow flight of overloaded plane...
  32. C

    How to quickly survey an exoplanet before colonization?

    Assumptions: -more or less contemporary technology -virgin planet which is glared by lustful humans ;) -habitable (oxygen, reasonable temperature) -no requirement for 100% certainty, reasonable guess is OK (the point is to find quite good place for colony very soon, not a perfect one in a few...
  33. M

    Transit duration of an exoplanet

    Homework Statement Hi, I'm a senior taking a course on exoplanets right now. I have a question regarding their transit across a star. I understand how it works in theory, but I had some questions regarding the equation to use. Here's the problem: A 0.05 solar radius planet orbits a...
  34. Drakkith

    Exoplanet Eccentricity vs Orbital Period

    I have a question concerning the eccentricity vs orbital period of observed exoplanets. Going to this link let's you plot different exoplanet properties on each axis of a graph. Plugging in Orbital Period for the X-axis and Eccentricity for the Y-axis shows that a trend towards decreasing...
  35. C

    Tidal lock and landmass on a Earth-like planet

    Would an Earth-like planet while getting a tidal lock, get it influenced by landscape of surface? So that the most stable state would be to have a continent on the center of the side close to its star and the other on the exactly opposite side? Or maybe because of hydrostatic equilibrium such...
  36. C

    Consequences of denser atmosphere on Earth-like planet

    I made a brain storming, but hope that someone would be able to point out what I may have missed out. Assumptions - atmospheric pressure is 3 atm, but molar concentration of oxygen is comparable to earth. The rest is mostly nitrogen. (there are a few more assumptions like tidal lock, a bit lower...
  37. C

    Dense exoplanet atmosphere, choice zeppelin vs. plane

    Would on a exoplanet with dense atmosphere zeppelin/blimp better idea than a plane? If I get it right there would be: -much higher buyancy (argument for zeppelin) -higher drag (argument against plane) -higher lift (argument for plane) (but I'm not good enough to know what would matter)...
  38. B

    Time Dilation Effects on a Probe

    I was having a discussion with a colleague earlier today regarding exoplanet exploration. Being that the biggest challenge for mankind to travel to distant planets is that time dilation would make such an extreme effect that by the time we reached our destination thousands of years may have...
  39. GiantSheeps

    Stargazing Help with telescope/observatory data and images

    I was wondering if anyone would help me get my hands on some telescope data and images of exoplanets. I know they must exist somewhere in databases on the internet, but I haven't been able to find them myself. It would be great if one of you could show me where I could get them or even if you...
  40. mfb

    Giant ring system around exoplanet discovered

    At least that is the interpretation of the scientists - 200 times larger than the system around Saturn, and thick enough to make a complicated light curve during stellar transit. The transit happened in 2007 and took nearly two months. A gap in the ring system hints at an exomoon. As they just...
  41. C

    Planet with dense neon atmosphere and streams of CO2

    Idea is a cold planet with dense atmosphere (10 atm) where human can survive, while a liquid carbon dioxide would be possible. As the main component of atmosphere I think about neon, because it should not cause nitrogen narcosis: http://en.wikipedia.org/wiki/Nitrogen_narcosis#Causes...
  42. C

    How to get really deep depresion on an exoplanet?

    I want an exoplanet/exomoon with really deep depression. It would be the only place on that planet that's really habitable for humans without breating aid. Idea: -lower gravity (somewhere around 0.8 g) so the mountains should be able to be a bit taller -one supercontinent that's slowly...
  43. Greg Bernhardt

    Optical DIY Exoplanet Detector with a DSLR

    Great project to do! DIY Exoplanet Detector with a DSLR
  44. C

    How would you organize arbitrary day cycle on an exoplanet?

    Assumption: -there is no serious astronomical phenomena determining that - either the planet is tidally locked, has too long day cycle, or is too far away from its star and inside bases anyway humans rely on artificial light; -there is a colony of a size of at least medium city; -post scarcity...
  45. avito009

    Detecting more than 1 exoplanet using Radial Velocity Method.

    How do we detect if there is more than 1 exoplanet orbiting a star using radial velocity method? I read this but I didnt understand it. Can someone explain the answer in Laymans terms? "Multiple planets will cause a stars radial velocity curve to show two periods: a long gradual change due...
  46. mfb

    Name Exoplanets: IAU Plans to Name 305 Exoplanets

    The IAU plans to name 305 exoplanets. Currently, organizations can make suggestions, in 2015 the public can vote on those suggestions. This is organized on nameexoworlds.org (IAU press release) While a proper name is certainly nicer than "HD 121504 b", it won't be an easy task to keep up...
  47. Q

    Radius of the smallest exoplanet detectable with the transit method

    Please help me with this astronomy problem. I am supposed to calculate the smallest planet that is detectable with the transit method, given a signal to noise ratio and a star's radius: Suppose the star is seen at its distance D with a signal to noise ratio of S/N = 10^4. This means that in...
  48. reenmachine

    Earth-sized exoplanet spotted in star’s habitable zone

    http://www.nasa.gov/ames/kepler/nasas-kepler-discovers-first-earth-size-planet-in-the-habitable-zone-of-another-star/index.html#.U1BUR1csSuQ Don't know if this is the right section to post this , but I'm a sucker for any news on exoplanets so here goes.
  49. B

    Exoplanet Maps: Northern and Southern Hemisphere Locations

    Exoplanet discoveries continue to be made using various sensitive techniques. Since there is no evidence to the contrary none of them are thought to harbor life forms. Here is a new set of maps showing where the exoplanets are located in both the Northern and Southern Hemispheres...