question: How do scientists know if they`ve already discovered a certain star or planet?
comment: They don't search by a name, they search by the coordinates of the star they are looking at.
passages: Section::::Specialized catalogues.:Proper motion catalogues.
  
  A common way of detecting nearby stars is to look for relatively high proper motions. Several catalogues exist, of which we'll mention a few. The Ross and Wolf catalogues pioneered the domain:
  
  Willem Jacob Luyten later produced a series of catalogues:
  
  L - Luyten, Proper motion stars and White dwarfs
  
  LFT – Luyten Five-Tenths catalogue
  
  LHS – Luyten Half-Second catalogue
  
  LTT – Luyten Two-Tenths catalogue
  
  NLTT – New Luyten Two-Tenths catalogue
  
  LPM – Luyten Proper-Motion catalogue
  
  Around the same time period, Henry Lee Giclas worked on a similar series of catalogues:
  
  Section::::Specialized catalogues.:uvby98.
   Preliminary identification of possible star candidates starts at the Haleakala telescope in Hawaii by a team of professional astronomers. Once they identify a star that dims slightly from time to time, the information is forwarded to a team of amateur astronomers who then investigate for additional evidence suggesting this dimming is caused by a transiting planet. Once enough data is collected, it is forwarded to the University of Texas McDonald Observatory to confirm the presence of a transiting planet by a second team of professional astronomers.
  
  Section::::Equipment.
   While a number of interesting celestial objects are readily identified by the naked eye, sometimes with the aid of a star chart, many others are so faint or inconspicuous that technical means are necessary to locate them. Although many methods are used in amateur astronomy, most are variations of a few specific techniques.
  
  Section::::Common techniques.:Star hopping.
   BULLET::::- Determine the positions of stars at a magnitude of V = 10 down to a precision of 7 μas—this is equivalent to measuring the position to within the diameter of a hair from 1000 km away—between 12 and 25 μas down to V = 15, and between 100 and 300 μas to V = 20, depending on the colour of the star.
   BULLET::::- To determine how many Earth-size and larger planets there are in or near the habitable zone (often called "Goldilocks planets") of a wide variety of spectral types of stars.
  
  BULLET::::- To determine the range of size and shape of the orbits of these planets.
  
  BULLET::::- To estimate how many planets there are in multiple-star systems.
  
  BULLET::::- To determine the range of orbit size, brightness, size, mass and density of short-period giant planets.
  
  BULLET::::- To identify additional members of each discovered planetary system using other techniques.
  
  BULLET::::- Determine the properties of those stars that harbor planetary systems.
   Because very young stars (such as T Tauri stars) are usually variable, Pan-STARRS should discover a large number of these and improve our understanding of them. It is also expected that Pan-STARRS may discover a large number of extrasolar planets by observing their transits across their parent stars, as well as gravitational microlensing events.
   Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness of stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomena can also be responsible which is why the term "planetary candidate" is used.
   If a planet cannot be detected through at least one of the other detection methods, it can be confirmed by determining if the possibility of a Kepler candidate being a real planet is significantly larger than any false-positive scenarios combined. One of the first methods was to see if other telescopes can see the transit as well. The first planet confirmed through this method was Kepler-22b which was also observed with a Spitzer space telescope in addition to analyzing any other false-positive possibilities. Such confirmation is costly, as small planets can generally be detected only with space telescopes.
   Not all the planet candidates go through this process. Circumbinary planets do not show strictly periodic transits, and have to be inspected through other methods. In addition, third-party researchers use different data-processing methods, or even search planet candidates from the unprocessed light curve data. As a consequence, those planets may be missing KOI designation.
  
  Section::::Planet finding process.:Confirming planet candidates.
  
  Once suitable candidates have been found from Kepler data, it is necessary to rule out false positives with follow-up tests.
   The observing campaign uses the Keck, Magellan and Subaru telescopes, plus automated telescopes at Fairborn Observatory. Each star is observed three times over a period of several days, then checked for short period variations in radial velocity. This variation is a characteristic of gravitational perturbation caused by a hot Jupiter. Those stars showing radial velocity variations are then checked with the automated photometric telescopes from Fairborn Observatory.
   Section::::History of detection.:Candidate discoveries.
  
  As of June 2017, NASA's "Kepler" mission had identified more than 5,000 planetary candidates, several of them being nearly Earth-sized and located in the habitable zone, some around Sun-like stars.
  
  Section::::Methodology.
  
  section begin=detection /
  
  About 97% of all the confirmed exoplanets have been discovered by indirect techniques of detection, mainly by radial velocity measurements and transit monitoring techniques.section end="detection" /
  
  Section::::Formation and evolution.
  
  Planets may form within a few to tens (or more) of millions of years of their star forming. 
   Suitable bodies for celestial sights are selected, often using a Rude Star Finder. Using a sextant, an altitude is obtained of the sun, the moon, a star or a planet. The name of the body and the precise time of the sight in UTC is recorded. Then the sextant is read and the altitude ("Hs") of the body is recorded. Once all sights are taken and recorded, the navigator is ready to start the process of sight reduction and plotting.
   BULLET::::- "Kepler" – A NASA planet-finder spacecraft launched in 2009, repurposed as "K2" since the failure of a second reaction wheel prevented the telescope from continuing to monitor the same field.
  
  BULLET::::- BRITE – A constellation of nanosatellites used to study the brightest oscillating stars. FIrst two satellites launched Feb 25, 2013.
  
  BULLET::::- TESS – An NASA planet-finder that will survey bright stars across most of the sky launched in 2018.
  
  BULLET::::- PLATO – A planned ESA mission that will specifically exploit asteroseismology to obtain accurate masses and radii of transiting planets.
   There are a few different exoplanet detection methods which help to rule out false positives by giving further proof that a candidate is a real planet. One of the methods, called doppler spectroscopy, requires follow-up observations from ground-based telescopes. This method works well if the planet is massive or is located around a relatively bright star. While current spectrographs are insufficient for confirming planetary candidates with small masses around relatively dim stars, this method can be used to discover additional massive non-transiting planet candidates around targeted stars.
   BULLET::::- Discover and characterize a large number of close by exoplanetary systems, with a precision in the determination of the planet radius up to 3%, of stellar age up to 10%, and of the planet mass up to 10% (the latter in combination with on-ground radial velocity measurements)
  
  BULLET::::- Detect and characterize Earth-sized planets and super-Earths in the habitable zone around solar-type stars
  
  BULLET::::- Discover and characterize a large number of exoplanetary systems to study their typical architectures, and dependencies on the properties of their host stars and the environment
   Kepler's photometric precision is often high enough to observe a star's brightness changes caused by doppler beaming or a star's shape deformation by a companion. These can sometimes be used to rule out hot Jupiter candidates as false positives caused by a star or a brown dwarf when these effects are too noticeable. However, there are some cases where such effects are detected even by planetary-mass companions such as TrES-2b.
  
  Section::::Planet finding process.:Confirming planet candidates.:Through validation.
   The first success with this method came in 2007, when V391 Pegasi b was discovered around a pulsating subdwarf star.
  
  Section::::Established detection methods.:Transit timing.
   Lemonick describes the diverse methods with which astronomers work to try to find Earth-like planets. Some evaluate images of clumps of stars, tens of thousands of them together, in order to pick up slight reductions in brightness caused by planets passing in front of their host stars, some examine individual stars for planetary gravitation influences, and others focus on stars considerably smaller than the Earth's sun to pick up more easily detectable planetary information.
  
  Section::::Reviews.
   Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomenon can also be responsible which is why the term planetary candidate is used.
   BULLET::::- K2 - K2 (Kepler extended mission) catalog
  
  BULLET::::- KELT - Kilodegree Extremely Little Telescope (search for extrasolar planets)
  
  BULLET::::- Kemble - Father Lucian Kemble (asterisms which could be observed through binoculars)
  
  BULLET::::- Kepler — Kepler catalog
  
  BULLET::::- Kes - Kesteven (supernova remnants). For example: Kesteven 79
  
  BULLET::::- Kharchenko (for example: open star cluster Kharchenko 1 at 6:08:48 / +24:19:54)
  
  BULLET::::- K / Kg - Ivan R. King (open star clusters)
  
  BULLET::::- KIC — Kepler Input Catalog
  
  BULLET::::- KGZ — Catalogue de Zimmerman
  
  BULLET::::- KjPn - Kazaryan-Parsamyan (planetary nebulae)
   Planetary candidates were detected around the star by NASA's Kepler Mission, a mission tasked with discovering planets in transit around their stars. The transit method that Kepler uses involves detecting dips in brightness in stars. These dips in brightness can be interpreted as planets whose orbits pass in front of their stars from the perspective of Earth, although other phenomenon can also be responsible which is why the term planetary candidate is used.
   An exoplanet (extrasolar planet) is a planet located outside the Solar System. The first evidence of an exoplanet was noted as early as 1917, but was not recognized as such until 2016. No planet discovery has yet come from that evidence. However, the first scientific detection of an exoplanet began in 1988. Afterwards, the first confirmed detection came in 1992, with the discovery of several terrestrial-mass planets orbiting the pulsar PSR B1257+12. The first confirmation of an exoplanet orbiting a main-sequence star was made in 1995, when a giant planet was found in a four-day orbit around the nearby star 51 Pegasi. Some exoplanets have been imaged directly by telescopes, but the vast majority have been detected through indirect methods, such as the transit method and the radial-velocity method. This is a list of the most notable discoveries.
   Usually, Kepler candidates are imaged individually with more-advanced ground-based telescopes in order to resolve any background objects which could contaminate the brightness signature of the transit signal. Another method to rule out planet candidates is astrometry for which Kepler can collect good data even though doing so was not a design goal. While Kepler cannot detect planetary-mass objects with this method, it can be used to determine if the transit was caused by a stellar-mass object.
  
  Section::::Planet finding process.:Confirming planet candidates.:Through other detection methods.
   Orbit determination involves measuring its position on multiple occasions. The more widely separated these are in time, the more accurately the orbit can be calculated. However, for a newly discovered object, only a few days' or weeks' worth of measured positions may be available, which is only sufficient for a preliminary (imprecise) orbit calculation.
   In November 1995, the scientists published their findings in the journal "Nature"; the paper has since been cited over 1,000 times. Since that date, over 700 exoplanet candidates have been identified, and most have been detected by Doppler search programs based at the Keck, Lick, and Anglo-Australian Observatories (respectively, the California, Carnegie and Anglo-Australian planet searches), and teams based at the Geneva Extrasolar Planet Search.
  