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62-566: In 1965, anomalous velocity gas clouds were found in the region of the Magellanic Clouds. The gas stretches for at least 180 degrees across the sky. This corresponds to 180 kpc (600,000 ly ) at an approximate distance of 55 kpc (180,000 ly ). The gas is very collimated and polar with respect to the Milky Way . The velocity range is huge (from −400 to 400 km s in reference to Local Standard of Rest ) and velocity patterns do not follow

124-639: A Lissajous orbit around the Sun – Earth L 2 Lagrangian point . The Gaia space telescope has its roots in ESA's Hipparcos mission (1989–1993). Its mission was proposed in October 1993 by Lennart Lindegren ( Lund Observatory , Lund University , Sweden) and Michael Perryman (ESA) in response to a call for proposals for ESA's Horizon Plus long-term scientific programme. It was adopted by ESA's Science Programme Committee as cornerstone mission number 6 on 13 October 2000, and

186-554: A combination of Gaia and Tycho-2 data for those objects in both catalogues; "light curves and characteristics for about 3,000 variable stars; and positions and magnitudes for more than 2000 ... extragalactic sources used to define the celestial reference frame ". The second data release (DR2), which occurred on 25 April 2018, is based on 22 months of observations made between 25 July 2014 and 23 May 2016. It includes positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 300 million stars in

248-424: A feature leading the Magellanic Clouds. These early models were 'tidal' models. Just like tides on Earth are induced by the gravity of the 'leading' Moon , the models predicted two directions opposite each other, in which particles are preferentially pulled. However, the predicted features were not observed. This led to a few models that did not require a leading element but which had problems of their own. In 1998

310-498: A fully relativistic model, the influence of the gravitational field of the solar-system must be taken into account, including such factors as the gravitational light-bending due to the Sun, the major planets and the Moon. The expected accuracies of the final catalogue data have been calculated following in-orbit testing, taking into account the issues of stray light, degradation of the optics, and

372-473: A piece of mylar insulation broke loose and floated into the line-of-sight of the telescope causing corrupted data. The testing of stray-light and baffles is a noted part of space imaging instruments. In April 2024, a micrometeoroid hit and damaged Gaia's protective cover, creating "a little gap that allowed stray sunlight – around one billionth of the intensity of direct sunlight felt on Earth – to occasionally disrupt Gaia ’s very sensitive sensors". In May,

434-413: A precision one hundred times greater, Gaia consists of two telescopes providing two observing directions with a fixed, wide angle of 106.5° between them. The spacecraft rotates continuously around an axis perpendicular to the two telescopes' lines of sight, with a spin period of 6 hours. Thus, every 6 hours the spacecraft scans a great circle stripe approximately 0.7 degrees wide. The spin axis in turn has

496-443: A slower precession across the sky: it maintains a fixed 45 degree angle to the Sun, but follows a cone around the Sun every 63 days, giving a cycloid-like path relative to the stars. Over the course of the mission, each star is scanned many times at various scan directions, providing interlocking measurements over the full sky. The two key telescope properties are: Each celestial object was observed on average about 70 times during

558-752: A special data set, the Gaia Andromeda Photometric Survey (GAPS). The full data release for the five-year nominal mission, DR4, will include full astrometric, photometric and radial-velocity catalogues, variable-star and non-single-star solutions, source classifications plus multiple astrophysical parameters for stars, unresolved binaries, galaxies and quasars, an exo-planet list and epoch and transit data for all sources. Additional release(s) will take place depending on mission extensions. Most measurements in DR4 are expected to be 1.7 times more precise than DR2; proper motions will be 4.5 times more precise. DR4

620-463: A study analysing the full sky survey made by the HIPASS team at Parkes Observatory generated important new observational data. Putman et al. discovered that a mass of high-velocity clouds leading the Magellanic Clouds was actually fully connected to the Magellanic Clouds. So, the leading arm feature had its existence finally established. Furthermore, Lu et al. (1998) and Gibson et al. (2000) established

682-570: Is HD 74438 , which was, in a paper published in 2022, identified as a possible progenitor of a sub-Chandrasekhar Type Ia supernovae . In November 2017, scientists led by Davide Massari of the Kapteyn Astronomical Institute , University of Groningen , Netherlands released a paper describing the characterization of proper motion (3D) within the Sculptor dwarf galaxy , and of that galaxy's trajectory through space and with respect to

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744-480: Is a space observatory of the European Space Agency (ESA), launched in 2013 and expected to operate until 2025. The spacecraft is designed for astrometry : measuring the positions, distances and motions of stars with unprecedented precision, and the positions of exoplanets by measuring attributes about the stars they orbit such as their apparent magnitude and color . The mission aims to construct by far

806-543: Is expected that there will be "complete sky coverage at the bright end" with standard errors of "a few dozen μas". On 30 August 2014, Gaia discovered its first supernova in another galaxy. On 3 July 2015, a map of the Milky Way by star density was released, based on data from the spacecraft. As of August 2016, "more than 50 billion focal plane transits, 110 billion photometric observations and 9.4 billion spectroscopic observations have been successfully processed." In 2018

868-479: Is expected to be released no earlier than mid-2026. The final Gaia catalogue, DR5, will consist of all data collected during the lifespan of the mission. It will be 1.4 times more precise than DR4, while proper motions will be 2.8 times more precise than DR4. It will be published no earlier than the end of 2030. All data of all catalogues will be available in an online data base that is free to use. An outreach application, Gaia Sky , has been developed to explore

930-413: Is more likely. Independent measurements have demonstrated that the greatest Gaia radial velocity among the hypervelocity stars is contaminated by light from nearby bright stars in a crowded field and cast doubt on the high Gaia radial velocities of other hypervelocity stars. In late October 2018, the galactic population Gaia-Enceladus , the remains of a major merger with the defunct Enceladus dwarf,

992-587: Is more severe for the RVS spectrograph than for the astrometry measurements, because it spreads the light of the star onto a much larger number of detector pixels which each collect scattered light. This kind of problem has some historical background. In 1985 on STS-51-F , the Space Shuttle Spacelab -2 mission, another astronomical mission hampered by stray debris was the Infrared Telescope (IRT), in which

1054-428: Is no longer applicable, the name Gaia remained to provide continuity with the project. The total cost of the mission is around €740 million (~ $ 1 billion), including the manufacture, launch and ground operations. Gaia was completed two years behind schedule and 16% above its initial budget, mostly due to the difficulties encountered in polishing Gaia 's ten silicon carbide mirrors and assembling and testing

1116-592: Is providing the basic observational data to analyze a wide range of important questions related to the origin, structure and evolutionary history of the Milky Way galaxy. The successor to the Hipparcos mission (operational 1989–1993), Gaia is part of ESA's Horizon 2000+ long-term scientific program. Gaia was launched on 19 December 2013 by Arianespace using a Soyuz ST-B / Fregat-MT rocket flying from Kourou in French Guiana. The spacecraft currently operates in

1178-513: Is relatively young, which is a sign of recent star formation in the leading arm. High-velocity cloud Too Many Requests If you report this error to the Wikimedia System Administrators, please include the details below. Request from 172.68.168.132 via cp1112 cp1112, Varnish XID 392044548 Upstream caches: cp1112 int Error: 429, Too Many Requests at Fri, 29 Nov 2024 05:39:59 GMT Gaia (spacecraft) Gaia

1240-607: Is thought that the tidal forces mostly affect the Small Magellanic Cloud, since it has lower mass, and is less gravitationally bound. In contrast, ram pressure stripping mostly affects the Large Magellanic Cloud, because it has a larger reservoir of gas. In 2018, research confirmed that the chemical composition of the gas in the Magellanic Stream Leading Arm more closely resembles the composition of

1302-619: The ESTRACK network in Cebreros , Spain, Malargüe , Argentina and New Norcia , Australia, receive the data. In October 2013 ESA had to postpone Gaia 's original launch date, due to a precautionary replacement of two of Gaia 's transponders. These are used to generate timing signals for the downlink of science data. A problem with an identical transponder on a satellite already in orbit motivated their replacement and reverification once incorporated into Gaia . The rescheduled launch window

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1364-491: The Gaia mission was extended to 2020, and in 2020 it was further extended through 2022, with an additional "indicative extension" extending through 2025. The limiting factor to further mission extensions is the supply of nitrogen for the cold gas thrusters of the micro-propulsion system. The amount of dinitrogen tetroxide (NTO) and monomethylhydrazine (MMH) for the chemical propulsion subsystem on board might be enough to stabilize

1426-586: The International Celestial Reference Frame (ICRF3) . Included is the Gaia Catalogue of Nearby Stars (GCNS), containing 331,312 stars within (nominally) 100 parsecs (330 light-years). The full DR3, published on 13 June 2022, includes the EDR3 data plus Solar System data; variability information; results for non-single stars, for quasars, and for extended objects; astrophysical parameters; and

1488-506: The Milky Way , using data from Gaia and the Hubble Space Telescope . Massari said, "With the precision achieved we can measure the yearly motion of a star on the sky which corresponds to less than the size of a pinhead on the Moon as seen from Earth." The data showed that Sculptor orbits the Milky Way in a highly elliptical orbit; it is currently near its closest approach at a distance of about 83.4 kiloparsecs (272,000 ly), but

1550-454: The B2 phase of the project was authorised on 9 February 2006, with EADS Astrium taking responsibility for the hardware. The name "Gaia" was originally derived as an acronym for Global Astrometric Interferometer for Astrophysics . This reflected the optical technique of interferometry that was originally planned for use on the spacecraft. While the working method evolved during studies and the acronym

1612-565: The Earth, which the Minor Planet Center catalogued as object 2015 HP 116 . It was soon found to be an accidental rediscovery of the Gaia spacecraft and the designation was promptly retracted. Shortly after launch, ESA revealed that Gaia was suffering from a stray light problem. The problem was initially thought to be due to ice deposits causing some of the light diffracted around the edges of

1674-485: The Magellanic Stream. In 2019 astronomers discovered the young star cluster Price-Whelan 1 using Gaia data. The star cluster has a low metallicity and belongs to the leading arm of the Magellanic Clouds. The discovery of this star cluster suggests that the leading arm of the Magellanic Clouds is 90,000 light-years away from the Milky Way, only half as far from the Milky Way as previously thought. The star cluster

1736-472: The Small Magellanic Cloud, rather than the Large Magellanic Cloud, by looking at light from background quasars shining through the Stream and analysing the spectrum of light that is either absorbed by, or let through it. This analysis confirmed that the gas most likely originated from the Small Magellanic Cloud, thereby indicating that the Large Magellanic Cloud is 'winning' in the gravity tug of both Clouds working on

1798-666: The Solar System by using the astrometry method, 500,000 quasars outside this galaxy and tens of thousands of known and new asteroids and comets within the Solar System. The Gaia mission continues to create a precise three-dimensional map of astronomical objects throughout the Milky Way and map their motions, which encode the origin and subsequent evolution of the Milky Way. The spectrophotometric measurements provide detailed physical properties of all stars observed, characterizing their luminosity , effective temperature , gravity and elemental composition. This massive stellar census

1860-479: The Sun–Earth Lagrange point L2 located approximately 1.5 million kilometres from Earth, arriving there 8 January 2014. The L2 point provides the spacecraft with a very stable gravitational and thermal environment. There, it uses a Lissajous orbit that avoids blockage of the Sun by the Earth, which would limit the amount of solar energy the satellite could produce through its solar panels , as well as disturb

1922-633: The acceleration of the solar system towards the galactic center as 0.23 nanometers/s . In March 2021, the European Space Agency announced that Gaia had identified a transiting exoplanet for the first time. The planet was discovered orbiting solar-type star Gaia EDR3 3026325426682637824. Following its initial discovery, the PEPSI spectrograph from the Large Binocular Telescope (LBT) in Arizona

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1984-451: The basic angle instability. The best accuracies for parallax, position and proper motion are obtained for the brighter observed stars, apparent magnitudes 3–12. The standard deviation for these stars is expected to be 6.7 micro-arcseconds or better. For fainter stars, error levels increase, reaching 26.6 micro-arcseconds error in the parallax for 15th-magnitude stars, and several hundred micro-arcseconds for 20th-magnitude stars. For comparison,

2046-463: The best parallax error levels from the new Hipparcos reduction are no better than 100 micro-arcseconds, with typical levels several times larger. The overall data volume that was retrieved from the spacecraft during the nominal five-year mission at a compressed data rate of 1 Mbit/s is approximately 60  TB , amounting to about 200 TB of usable uncompressed data on the ground, stored in an InterSystems Caché database. The responsibility of

2108-584: The brighter stars is measured by an integrated spectrometer observing the Doppler effect . Because of the physical constraints imposed by the Soyuz spacecraft, Gaia 's focal arrays could not be equipped with optimal radiation shielding, and ESA expected their performance to suffer somewhat toward the end of the initial five-year mission. Ground tests of the CCDs while they were subjected to radiation provided reassurance that

2170-512: The chemical similarity between the streams and Magellanic Clouds. Newer, increasingly sophisticated models all tested the Leading Arm Feature hypothesis. These models make heavy use of gravity effects through tidal fields . Some models also rely on ram pressure stripping as a shaping mechanism. Most recent models increasingly include drag from the halo of the Milky Way as well as gas dynamics , star formation and chemical evolution. It

2232-525: The closeness of the Magellanic Clouds and the ability to resolve individual stars and their parallaxes , and proper motion , subsequent observations gave the full 6-dimensional phase space information of both clouds (with very large relative errors for the transverse velocities). This enabled the calculation of the likely past orbit of the Large and the Small Magellanic Cloud in relation to the Milky Way. The calculation necessitated large assumptions, for example, on

2294-509: The commissioning phase indicated that Gaia could autonomously identify stars as bright as magnitude 3. When Gaia entered regular scientific operations in July 2014, it was configured to routinely process stars in the magnitude range 3 – 20. On the bright side of that limit, special operational procedures download raw scanning data for the remaining 230 stars brighter than magnitude 3; methods to reduce and analyse these data are being developed; and it

2356-538: The creation and maintenance of a high-precision celestial reference frame, the Barycentric Celestial Reference System (BCRS) , which is essential for both astronomy and navigation. This reference frame serves as a fundamental grid for positioning celestial objects in the sky, aiding astronomers in various research endeavors. All observations, regardless of the actual positioning of the spacecraft, must be expressed in terms of this reference system. As

2418-669: The data processing, partly funded by ESA, is entrusted to a European consortium, the Data Processing and Analysis Consortium (DPAC), which was selected after its proposal to the ESA Announcement of Opportunity released in November 2006. DPAC's funding is provided by the participating countries and has been secured until the production of Gaia 's final catalogue. Gaia sends back data for about eight hours every day at about 5 Mbit/s. ESA's three 35-metre-diameter radio dishes of

2480-430: The electronics of one of the CCDs failed, which caused a high rate of false detections. After that, the engineers refocused Gaia' s optics "for the final time". The testing and calibration phase, which started while Gaia was en route to SEL2 point, continued until the end of July 2014, three months behind schedule due to unforeseen issues with stray light entering the detector. After the six-month commissioning period,

2542-497: The fine pointing to focus on stars many light years away, the only moving parts are actuators to align the mirrors and the valves to fire the thrusters. It has no reaction wheels or gyroscopes. The spacecraft subsystems are mounted on a rigid silicon carbide frame, which provides a stable structure that will not expand or contract due to temperature. Attitude control is provided by small cold gas thrusters that can output 1.5 micrograms of nitrogen per second. The telemetric link with

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2604-447: The five years of the nominal mission, which has been extended to approximately ten years and will thus obtain twice as many observations. These measurements will help determine the astrometric parameters of stars: two corresponding to the angular position of a given star on the sky, two for the derivatives of the star's position over time (motion) and lastly, the star's parallax from which distance can be calculated. The radial velocity of

2666-541: The focal plane camera system. The Gaia space mission has the following objectives: Gaia was launched by Arianespace , using a Soyuz ST-B rocket with a Fregat-MT upper stage, from the Ensemble de Lancement Soyouz at Kourou in French Guiana on 19 December 2013 at 09:12 UTC (06:12 local time). The satellite separated from the rocket's upper stage 43 minutes after launch at 09:54 UTC. The craft headed towards

2728-498: The galaxy in three dimensions using Gaia data. In July 2017, the Gaia-ESO Survey reported using Gaia data to find double-, triple-, and quadruple- stars. Using advanced techniques they identified 342 binary candidates, 11 triple candidates, and 1 quadruple candidate. Nine of these had been identified by other means, thus confirming that the technique can correctly identify multiple star systems. The possible quadruple star system

2790-484: The largest and most precise 3D space catalog ever made, totalling approximately 1 billion astronomical objects , mainly stars, but also planets, comets, asteroids and quasars , among others. To study the precise position and motion of its target objects, the spacecraft monitored each of them about 70 times over the five years of the nominal mission (2014–2019), and about as many during its extension. Due to its detectors not degrading as fast as initially expected,

2852-461: The magnitude range g = 3–20, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million stars between magnitude 4 and 13. It also contains data for over 14,000 selected Solar System objects. Due to uncertainties in the data pipeline, the third data release, based on 34 months of observations, has been split into two parts so that data that

2914-483: The mission was given an extension. As of March 2023, the spacecraft has enough micro-propulsion fuel to operate until the second quarter of 2025. Gaia targets objects brighter than magnitude 20 in a broad photometric band that covers the extended visual range between near-UV and near infrared; such objects represent approximately 1% of the Milky Way population. Additionally, Gaia is expected to detect thousands to tens of thousands of Jupiter-sized exoplanets beyond

2976-636: The orbit can take it out to around 222 kiloparsecs (720,000 ly) distant. In October 2018, Leiden University astronomers were able to determine the orbits of 20 hypervelocity stars from the DR2 dataset. Expecting to find a single star exiting the Milky Way , they instead found seven. More surprisingly, the team found that 13 hypervelocity stars were instead approaching the Milky Way, possibly originating from as-of-yet unknown extragalactic sources. Alternatively, they could be halo stars to this galaxy, and further spectroscopic studies will help determine which scenario

3038-422: The primary mission's objectives can be met. An atomic clock on board Gaia plays a crucial role in achieving the mission's primary objectives. Gaia rotates with angular velocity of 60"/sec or 0.6 microarcseconds in 10 nanoseconds. Therefore, in order to meet its positioning goals, Gaia must be able to record the exact time of observation to within nanoseconds. Furthermore, no systematic positioning errors over

3100-483: The rest of the Milky Way. Hence, it was determined to be a classic high-velocity cloud . However, the gas was not mapped, and the connection to the two Magellanic Clouds was not made. The Magellanic Stream as such was discovered as a Neutral Hydrogen (HI) gas feature near the Magellanic Clouds by Wannier & Wrixon in 1972. Its connection to the Magellanic Clouds was made by Mathewson et al. in 1974. Owing to

3162-402: The rotational period of 6 hours should be introduced by the clock performance. For the timing error to be below 10 nanoseconds over each rotational period, the frequency stability of the on-board clock needs to be better than 10 . The rubidium atomic clock aboard the Gaia spacecraft has a stability reaching ~ 10 over each rotational period of 21600 seconds. Gaia' s measurements contribute to

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3224-411: The satellite is about 3 Mbit/s on average, while the total content of the focal plane represents several Gbit/s . Therefore, only a few dozen pixels around each object can be downlinked. The design of the Gaia focal plane and instruments. Due to the spacecraft's rotation, images cross the focal plane array right-to-left at 60 arcseconds per second. Similar to its predecessor Hipparcos , but with

3286-421: The satellite started its nominal five-year period of scientific operations on 25 July 2014 using a special scanning mode that intensively scanned the region near the ecliptic poles ; on 21 August 2014 Gaia began using its normal scanning mode which provides more uniform coverage. Although it was originally planned to limit Gaia ' s observations to stars fainter than magnitude 5.7, tests carried out during

3348-410: The shapes and masses of the 3 galaxies, and the nature of dynamical friction between the moving objects. Observations of individual stars revealed details of star formation history. Models describing the formation of the Magellanic Stream had been produced since 1980. Following computing power, the initial models were very simple, non-self-gravitating, and with few particles . Most models predicted

3410-444: The spacecraft at L2 for several decades. Without the cold gas, though, the space craft can no longer be pointed on a microarcsecond scale. In March 2023, the Gaia mission was extended through the second quarter of 2025, when it is expected that the spacecraft will run out of cold gas propellant. It will then enter a post-operations phase that is expected to be completed by the end of 2030. Several Gaia catalogues are released over

3472-494: The spacecraft's thermal equilibrium. After launch, a 10-metre-diameter sunshade was deployed. The sunshade always maintains a fixed 45 degree angle to the Sun, while precessing to scan the sky, thus keeping all telescope components cool and powering Gaia using solar panels on its surface. These factors and the materials used in its creation allow Gaia to function in conditions between -170 ° C and 70 ° C. The Gaia payload consists of three main instruments: In order to maintain

3534-501: The star cluster Price-Whelan 1 was discovered. The cluster belongs to the Magellanic Clouds and is located in the leading arm of these Dwarf Galaxies . The discovery suggests that the stream of gas extending from the Magellanic Clouds to the Milky Way is about half as far from the Milky Way as previously thought. The Radcliffe wave was discovered in data measured by Gaia , published in January 2020. In November 2020, Gaia measured

3596-472: The sunshield and entering the telescope apertures to be reflected towards the focal plane. The actual source of the stray light was later identified as the fibers of the sunshield, protruding beyond the edges of the shield. This results in a "degradation in science performance [which] will be relatively modest and mostly restricted to the faintest of Gaia 's one billion stars." Mitigation schemes are being implemented to improve performance. The degradation

3658-492: The years each time with increasing amounts of information and better astrometry; the early releases also miss some stars, especially fainter stars located in dense star fields and members of close binary pairs. The first data release, Gaia DR1, based on 14 months of observation was on 14 September 2016. The data release includes "positions and ... magnitudes for 1.1 billion stars using only Gaia data; positions, parallaxes and proper motions for more than 2 million stars" based on

3720-633: Was discovered. This system is associated with at least 13 globular clusters, and the creation of the Thick Disk of the Milky Way. It represents a significant merger about 10 billion years ago in the Milky Way Galaxy. In November 2018, the galaxy Antlia 2 was discovered. It is similar in size to the Large Magellanic Cloud , despite being 10,000 times fainter. Antlia 2 has the lowest surface brightness of any galaxy discovered. In December 2019

3782-524: Was from 17 December 2013 to 5 January 2014, with Gaia slated for launch on 19 December. Gaia was successfully launched on 19 December 2013 at 09:12 UTC . About three weeks after launch, on 8 January 2014, it reached its designated orbit around the Sun-Earth L2 Lagrange point (SEL2), about 1.5 million kilometers from Earth. In 2015, the Pan-STARRS observatory discovered an object orbiting

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3844-407: Was ready first, was released first. The first part, EDR3 ("Early Data Release 3"), consisting of improved positions, parallaxes and proper motions, was released on 3 December 2020. The coordinates in EDR3 use a new version of the Gaia celestial reference frame ( Gaia –CRF3), based on observations of 1,614,173 extragalactic sources, 2,269 of which were common to radio sources in the third revision of

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