For countless generations, citizenry have looked out at the night sky and wondered if they were alone within the Universe. With the invention of other planets in our system, truth extent of the Milky Way galaxy, and other galaxies beyond our own, this question has only deepened and become more profound.
Astronomers and scientists have an idea for long that other star systems in our galaxy and therefore the Universe had orbiting planets of their own, it’s only been within the previous couple of decades that any are observed. The methods for finding these “extrasolar planets” is getting better over time, and the list of these existed planets has been confirmed has grown accordingly (over 4000 and counting!)
An extrasolar planet (aka. exoplanet) may be a planet that orbits a star (i.e. is a component of a solar system) aside from our own. Our system is merely one of billions and lots of them presumably have their own system of planets. As early because the sixteenth century, there are astronomers who hypothesized the existence of extrasolar planets.
The first recorded mention was made by Italian philosopher Bruno, an early supporter of the Copernican theory. Additionally, to supporting the thought that the world and other planets orbit the Sun (heliocentrism), he suggests the view that the fixed stars are almost like the Sun and are likewise amid planets.
Newton made an identical proposal in the eighteenth century within the “General Scholium” section which concludes his Principia. Comparing to the Sun’s planets he said that “And if the fixed stars are the centers of comparable systems, they’re going to all be constructed consistent with an identical design and subject to the dominion of 1.”
Since Newton’s time, various discovery claims are made, but all were rejected by the scientific community as false positives. within the 1980s, a gaggle of astronomers claimed that that they had identified some extrasolar planets in nearby star systems, but were unable to verify their existence until years later.
The main reason why extrasolar planets are so difficult to detect is because they’re even fainter than the celebs they orbit. Furthermore, these stars emit light that “washes” the planets out i.e. obscure them from direct observation. As a result, the primary discovery wasn’t made until 1992 by astronomers Aleksander Wolszczan and Dale Frail.
The pair observed several terrestrial-mass planets with the help of Arecibo Observatory in Puerto Rico orbiting the pulsar PSR B1257+12. it had been not until 1995 that the primary exoplanet confirmation around a main-sequence star was made. during this case, the earth observed was 51 Pegasi b, an enormous planet found during a four-day orbit round the Sun-like star 51 Pegasi (approx. 51 light-years from our Sun).
Most of the planets that were detected in the beginning were gas giants almost like, or larger than, Jupiter – which led to the term “Super-Jupiter” being coined. faraway from suggesting that gas giants were more common than rocky i.e. Earth-like planets, and because of the very fact it made the findings were simply that Jupiter-sized planets are simply easier to detect due to their size.
Named after the Renaissance astronomer Kepler, the Kepler space observatory was launched by NASA on March 7th, 2009 for the aim of discovering Earth-like planets orbiting other stars. As a part of NASA’s Discovery Program, a series of relatively low-cost projects focused on research project, Kepler ‘s mission was to seek out evidence of extrasolar planets and estimate what percentage stars in our galaxy have planetary systems.
Relying on the Transit Method of detection (see below), Kepler ‘s sole used a photometer to repeatedly monitor the brightness of over 145,000 main sequence stars during a fixed field of view. This data was then transmitted back to Earth where it had been analysed by scientists to seem for any signs of periodic dimming caused by extrasolar planets transiting (passing) ahead of their host star.
The lifetime of the Kepler mission is extended after its initial timeline of 3.5 years, because of the greater-than-expected results. In 2012, the mission was expected to last until 2016, but this changed because of the failure of two of the spacecraft’s reaction wheels – which are used for pointing the spacecraft. This disabled the gathering of science data and threatened the continuation of the mission.
On August 15th, 2013, NASA announced that that they had given up trying to repair the 2 failed reaction wheels and modified the mission accordingly. instead of scrap Kepler, NASA proposed changing the mission to utilizing Kepler to detect habitable planets around smaller, dimmer red dwarf star stars. This proposal, which became referred to as K2 “Second Light “, was approved on May 16th, 2014.
The K2 mission till it lasted concentrated more on brighter stars like G and K-class stars. As of February 6th, 2021, astronomers have confirmed the presence of 4,341 exoplanets in 3,216 planetary systems, the bulk of which were found using data from Kepler. All told, the guided missile observed over 530,506 stars within the course of its primary and K2 missions.
In November of 2013, astronomers reported (based on Kepler space mission data) that 1 in 5 stars within the Milky Way could have Earth-sized planets orbiting within their habitable zones – between 40 and 80 billion. They further estimated that 7 to fifteen of those planets (average of 5.6 billion) orbit Sun-like stars – aka. main sequence G-type yellow dwarfs.
The first exoplanet confirmed by Kepler to possess a mean orbital distance that placed it within its star’s habitable zone was Kepler-22b. This planet is found about 600 light-years from Earth within the constellation of Cygnus and was first observed on May 12th, 2009, then confirmed on Dec 5th, 2011. supported all the info obtained, scientists believe that this world is roughly 2.4 times the radius of Earth and either has oceans or a watery outer shell.
The discovery of exoplanets has also intensified interest within the look for extraterrestrial life, particularly for people who orbit within the host star’s habitable zone. Also referred to as the “goldilocks zone “, this is often the region of the system where conditions are warm enough (but not too warm) in order that it’s possible for liquid water to present on the planet’s surface. Prior to the deployment of Kepler, the overwhelming majority of confirmed exoplanets fell into the category of Jupiter-sized or larger. Meanwhile ahead of its missions Kepler takes care of about 6000 potential candidates, many of them falling into the categories of Earth-size or “Super-Earth” size. Many of those are located within the habitable zone of their parent stars, and a few even around Sun-like stars.
As a result, confirmation from another method is typically needed. Nevertheless, it remains the foremost widely used method and is liable for more exoplanet discoveries than all other methods combined. Both the Kepler Space Telescope and TESS were specifically designed to conduct this type of photometry.
NASA launched the Transiting Exoplanet Survey Satellite (TESS) to space on April 18th, 2018. This mission has effectively picked up the trail blazed by Kepler, using an equivalent method but superior instruments to watch thousands of stars simultaneously. Equipped with four wide-angle telescopes and associated charge-coupled device (CCD) detectors, TESS is currently carrying the primary spaceborne all-sky transiting exoplanet survey.
Currently, Gaia is in an extended a part of its mission which will last until December 31st, 2022, though it’s expected to receive another extension to December 31st, 2025. To date, the mission has been in continuous operation for 7 years, 1 month, and 18 days, and can still map the cosmos for the sake of making the most important and most precise 3D space catalog ever made.
This will be followed by the Cosmic Vision’s fourth-medium mission, referred to as the Atmospheric Remote-sensing Infrared Exoplanet Large-survey (ARIEL). This mission, which can launch sometime in 2029, will observe a minimum of 1,000 known exoplanets as they transit ahead of their stars to review and characterize the composition and thermal structures of their atmospheres. There’s a whole Universe of worlds out there to get, and we’ve barely scratched the surface!