What is Exoplanets: Definition and 50 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 Predicting frequency of Earthlike planets and systems

    Each new report of a confirmed exoplanet adds to the database of knowledge. For obvious reasons, our confirmations seem to stack up in the areas we are currently best able to detect. eg.: Large bodies: Jupiter-sized down to Sub-Neptune-sized, with a smattering of super-Earths. Nape-of-star...
  2. sbrothy

    Science Fiction Media Representations of Exoplanets...

    Stumbled over this one. Thought it might be pertinent. Science Fiction Media Representations of Exoplanets: Portrayals of Changing Astronomical Discoveries. "Interest in science fiction's (SF's) potential science communication use is hindered by concerns about SF misrepresenting science. This...
  3. Astroxzip

    B How to use the Binary Mass Function for exoplanets?

    Hi. I am working on a research paper for my high school and I am trying to calculate the mass of KELT-8b using the radial velocity values of its star. However, I am confused as to the binary mass function and what units you would use. I was under the impression you would use solar masses however...
  4. Astronuc

    I Early Catalog of Planet-Hosting Multiple Star (≥ 3) Systems

    Interesting paper of triple and higher order star systems with planets. An Early Catalog of Planet Hosting Multiple Star Systems of Order Three and Higher https://arxiv.org/abs/2209.11346 https://phys.org/news/2023-05-astrophysicists-planet-hosting-three-star.html Interesting comment: "
  5. thegroundhog

    I Finding Exoplanets: How Astronomers Do It

    As the stars in the milky way are only ever going to be seen as pinpricks even with the most powerful telescopes, how do astronomers find exoplanets, and further how can they tell their size and atmosphere etc?
  6. cindersky

    B Looking for Simulations of Exoplanets

    Is there any good simulation to test out radial velocity and/or maybe mess around with exoplanets? If there is please let me know! I want to try out this simulation where I change the luminosity of a star and see how the accuracy of the radial velocity changes, but a basic simulation would...
  7. A

    B The search for habitable exoplanets in Alpha Centauri

    In October 2012, astronomers announced the discovery of an exoplanet orbiting the star Alpha Centauri B. However, three years later, they concluded that it probably doesn’t exist. In 2013, astronomers also detected another possible exoplanet, but it hasn’t been confirmed yet. As of today, no...
  8. A

    How Close is the Nearest Potentially Habitable Exoplanet?

    Hi! If you are interested in exoplanets, you might want to know these little known facts about exoplanets. Source: In our stellar neighborhood there might be around 130 potentially (p.) habitable exoplanets, 10 of them being Earth-like. The closest p. Earth-like planet is called Tau Ceti e...
  9. A

    The 5 closest potentially habitable exoplanets

    As of September 2019, these are the 5 potentially habitable exoplanets closer to Earth: Source: www.youtube.com/watch?v=GK6owRTFz0Q1.GLIESE 273 b Gliese 283 b orbits the red dwarf star Luyten, located 12 light years away. - The exoplanet is 84% similar to Earth. - It has an orbital period of...
  10. PaulCam

    B Exoplanets - Suspicious evidence and fantastical conclusions

    Hi, I thought I would come and ask here as something has been bugging me for quite a while. Exoplanets. I'm not being bugged by the fact we are looking for them or that they exist. I am a bit suspicious of some of the evidence and how it's interpreted. While the adage is "Extraordinary...
  11. 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...
  12. A

    I Detect exoplanets by yourself with the cheapest equipment

    Hi guys, I detected my first exoplanet (hd 189733 b) and made a video about it showing step by step how I did it. I thought it could be useful for the people interested in the topic or already starting with transit photometry. The star has an apparent magnitude of 7.7 and the exoplanet...
  13. Jenab2

    I The Trouble with TESS: Examining its Limitations in Exoplanet Observations

    The time required for the observation of three successive transits of an exoplanet in front of its primary star is the minimum time necessary for the confirmation of the exoplanet. Three transits, not two, are needed to establish the periodicity of the transits. Given only two dips in...
  14. 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.
  15. jim mcnamara

    I Extragalactic Planets Observed Using Microlensing

    http://iopscience.iop.org/article/10.3847/2041-8213/aaa5fb/meta (abstract). Using microlensing the authors observed (my bolding): Does someone know the reason why unbound planets are the only reasonable way to explain their data? This is not my field, but looks like a big stretch to me, a...
  16. sophiecentaur

    I Were all these exoplanets a surprise?

    For years I have read and heard that the Solar System is there because of angular momentum issues. That is to say, the Sun itself can only rotate at some maximum rate in order to stay intact and the planets are there to equalise the angular momentum of the original nebula and produce a stable...
  17. wolram

    B Life is less likely on exoplanets

    https://www.sciencedaily.com/releases/2017/11/171130180031.htm However, the question of habitability is highly complex. Researchers led by space physicist Chuanfei Dong of the U.S. Department of Energy's (DOE) Princeton Plasma Physics Laboratory (PPPL) and Princeton University have recently...
  18. S

    Stargazing Impact of Kepler Telescope Findings on the Drake Equation

    How much more refined are the various variables of the Drake Equation in view of the recent findings by the Kepler Telescope? I imagine fp and ne would surely be better estimates. Is there a study on this anywhere?
  19. S

    B Should we search for non-biological "life"?

    I am very interested in Astrobiology and just came across this 7-year old abstract by Seth Shostak (of SETI): http://www.sciencedirect.com/science/article/pii/S0094576510002195 There is a lot of emphasis on searching for biological life outside of our solar system, especially with the...
  20. 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...
  21. C

    B Super-Earth Found in Habitable Zone of Nearby Red Dwarf

    The interview: John Batchelor Show The scientific paper: https://www.nature.com/nature/journal/v544/n7650/full/nature22055.html[/PLAIN] ]Nature and ArXiv The basic facts: Star Name: LHS 1140 Constellation: Cetus the Whale Distance from Sun: 41 light-years Star type: Red dwarf (much...
  22. J

    A Series of Exoplanets in Our Solar System

    In this alternate universe, Earth is the same as back home--8,000 miles wide, 25,000 around, six sextillion tons, orbiting a G-type main-sequence star from a distance of 93 million miles. But here, the similarities end. MOON DIAMETER--3,273 miles MASS--0.025x that of Earth DISTANCE FROM...
  23. mfb

    I 7 exoplanets around TRAPPIST-1

    NASA announcement Wednesday, 1 pm EST. You can use the forum for time zone conversion: This post was posted 3:55 pm EST. While the announcement doesn't have any details, digging a bit deeper: The livestream website calls the event "Spitzer Exoplanet Science Briefing", and of course we can see...
  24. |Glitch|

    I Are Red Dwarfs Home to Earth-Sized Water Worlds?

    It has always been my impression than spectral type M stars were notorious for being flare stars. As a result of their small radius and relatively low effective surface temperature, the Habitable Zone has to be relatively close to the surface of the star and small in size. As a result, it...
  25. Paul Colby

    I Light fluctuations and finding exoplanets

    All light sources fluctuate and I've wondered if auto correlation of the natural fluctuation of a star's output might be used to range it's planets? The concept is to stare at a star (like Kepler does) and record high frequency intensity fluctuations say at a sample rate of 10 times per second...
  26. mfb

    I First atmospheric spectroscopy of Earth-sized exoplanets

    The Hubble telescope lead to the first spectroscopy of the atmospheres of two Earth-sized exoplanets, TRAPPIST-1b and TRAPPIST-1c. A large hydrogen/helium atmosphere could be ruled out - not that surprising, but still nice to have this confirmed. The main star, TRAPPIST-1, is just 40 light...
  27. mfb

    NASA NASA: 1284 more planets from Kepler

    Source: NASA to Announce Latest Kepler Discoveries During Media Teleconference Livestream Time conversion reference: this post was posted at 7:45 pm EDT. My guess: various roughly Earth-sized exoplanets around dwarf stars, probably at least one in the habitable zone. Edit: More than 1000...
  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. F

    How to check a statement about orbital angles of exoplanets?

    Hi, everybody. Mi name is Fabio Onier Osorio Pelaez and I'm from Colombia. I hope to be finishing my Bachelor´s degree in Physics at University of Antioquia by next August. I'm doing my final project on the detection of planets by the Radial Velocity technique and I have a question about an...
  30. C

    Getting to Habitable Exoplanets

    According to Wikipedia, there could be as many as 11 billion planets in the habitable zone of sun-like stars, with the closest potentially 12 light years away. That number goes up to 40 billion if you include red dwarfs. How would we even go about getting to the nearest Exoearth?
  31. lpetrich

    Classifying Exoplanets: Size & Surface Temperature

    http://phl.upr.edu/projects/habitable-exoplanets-catalog/media/pte has an interesting classification, though it's a general grid rather than a wrap-around table. Here are the planet sizes: Mercurian / Miniterran ... 10^(-5) - 0.1 Me ... 0.03 - 0.4 Re Subterran ... 0.1 - 0.5 Me ... 0.4 - 0.8 Re...
  32. G

    Methods to find exoplanets more easily

    When I watched the story about the difficulties to find an object around other stars I started to think in alterinatives that could exist to make the object larger. The presented alternatives will reduce the amount of objects that can be found but can help to find more easy some planets...
  33. moriheru

    Books on Exoplanets and habitable zones

    I am looking for a good book on Exoplanets and habbitable zones. So that I would be familiar with a large range of exoplanets and the criteria of exoplanets and so on... Please don't hold back on the mathematics (if there is any) or on any scoentific issue, as I am asking for a good scientific...
  34. M

    Programs Exploring Exoplanets: A Roadmap to Astrophysics Career

    I have a love and passion for astrophysics, most specifically exoplanets. I do wish to be in the profession. I am 2.5 years away from college, so I have ample time to think about my future. From what I gather from some sources is that the best progression to become one is : BS Physics, MS...
  35. wolram

    Why Do We Search for Exoplanets?

    What is the reason for searching for exoplanets? i can think of many reasons why not, including we will never build a spacecraft to visit them, when we get there conditions for human life may not be suitable for human life, this would mean building a spacecraft that could return to earth, which...
  36. S

    Habitability of tidally locked exoplanets

    There's been a recent upsurge of interest in evidence for rocky planets orbiting red dwarf stars. Red dwarfs are very common in the the Milky Way and can live much longer than larger stars such as our Sun. The possible existence of several rocky planets in the habitable zone of Gliese 581 has...
  37. H

    Exploring Exoplanets: Could We Zoom In on Their Surfaces?

    I keep seeing reports about how all the planets similar to Earth in other nearby planetary systems are now being discovered. Since we won't have the technology to send probes or go there ourselves for some time, all we can do is look at them. My question is: Could we ever get better resolution...
  38. C

    Average value of sin(i) in radial velocities (exoplanets)

    When a stars radial velocity is measured in search for a planet, the planet imparts a radial velocity shift proportional to m\sin i\text{ where }i is the orbital inclination of the planet with respect to our line of sight and m is the planet mass. I've heard that even though the inclinations are...
  39. FtlIsAwesome

    Habitable exoplanets of white dwarfs

    A while back a new arxiv paper was published. "Transit surveys for Earths in the habitable zones of white dwarfs" http://arxiv.org/PS_cache/arxiv/pdf/1103/1103.2791v2.pdf I finally got around to fully reading it, but I'll probably have to reread it to make it stick in my memory. What would...
  40. O

    Programs What kind of degree to study exoplanets?

    Would a Physics/Astronomy degree be ideal, or would it be more appropriate to study Earth Sciences like Geology, etc.?
  41. A

    What is the relationship between stars, lithium, and exoplanets?

    “There are several ways in which a planet can disturb the internal motions of matter in its host star, thereby rearrange the distribution of the various chemical elements and possibly cause the destruction of lithium. It is now up to the theoreticians to figure out which one is the most likely...
  42. C

    Exoplanets seem all to have elliptical orbits

    exoplanets seem all to have elliptical orbits, and when you look at our solar system the orbits are all nice and defined, how come. And the gaz giants all seem to be star huggers where as in out solar system they are not, any explanations on this difference?
  43. 8

    Can We Detect Moons Around Earth-Sized Exoplanets?

    how far are we from detecting a moon around an Earth sized planet in another star system? i read an article recently (http://www.newscientist.com/article/mg20126932.100-why-are-the-sun-and-moon-the-same-size-in-the-sky.html") about how the moon being so close to Earth wasn't, or doesn't...
  44. L

    Exploring Exoplanets: Refining My Interests and Goals

    Hi, I have posted here a few times but lately I think I have been refining my interests somewhat so I want to compare my goals up against the reality. I think I would like to work in a field of study exasolar planets in particular terrestrial ones that may harbor Earth like life. Now some...
  45. marcus

    Center for Exoplanets and Habitable Worlds (news of improved instrumentation)

    Steinn Sigurdsson reports on sensitivity of new planet-search instruments, how slow a wobble can they pick up? If they can see the central body wobble at a speed of only 1 meter/second then they can pick up lower-mass planets, more earthlike planets going in more earthlike orbits, than if they...
  46. A

    A Look at the Naming of Exoplanets

    Why most extrasolar planet names start with the letters HD
  47. F

    Exploring Exoplanets - Data, Information & References

    Was wondering if anyone has any good references on exo planets, how their data is listed, a compilation of any relevant information. Much appreciated. :bugeye:
  48. Z

    How many exoplanets with an atmospheric oxygen signature would be necessary?

    Currently 241 exoplanets. [URL="[PLAIN]http://en.wikipedia.org/wiki/Gliese_581_c"][http://en.wikipedia.org/wiki/Gliese_581_c/URL][/PLAIN] A few are terrestrial such as Gliese c, d at 5x and 8x Earth mass; sufficient mass to be geologically active, and hence a magnetosphere, diverting a stellar...
  49. F

    Top 10 Exoplanets: Unbelievable Discoveries

    These are pretty weird. I doubt that a sci-fi author could have come up with them: http://www.space.com/scienceastronomy/extrasolar_planets.html
  50. marcus

    What is the Latest Exoplanet Catalog from Geoff Marcy and Paul Butler?

    this was posted today on arxiv by Geoff Marcy, Paul Butler, and team (usual exoplanet people) http://arxiv.org/abs/astro-ph/0607493 The abstract has links to ONLINE exoplanet catalogs some or all of which may be already familiar. Online exoplanet catalogs are not new. However this...