Editing Stellar parallax (section)

== Space astrometry ==
[[File:Hubble stretches the stellar tape measure ten times further.jpg|thumb|Hubble precision stellar distance measurement has been extended 10 times further into the [[Milky Way]].<ref>{{cite news |title=Hubble stretches the stellar tape measure ten times further |url=http://www.spacetelescope.org/images/opo1423a/ |access-date=12 April 2014 |newspaper=ESA/Hubble Images}}</ref>]]
In 1989, the satellite [[Hipparcos]] was launched primarily for obtaining parallaxes and [[proper motion]]s of nearby stars, increasing the number of stellar parallaxes measured to milliarcsecond accuracy a thousandfold.  Even so, Hipparcos is only able to measure parallax angles for stars up to about 1,600 [[light-year]]s away, a little more than one percent of the diameter of the [[Milky Way Galaxy]].

The Hubble telescope [[WFC3]] now has a precision of 20 to 40 microarcseconds, enabling reliable distance measurements up to {{convert|3066|parsec|light-year|sigfig=1}} for a small number of stars.<ref>{{cite web |last1=Harrington |first1=J.D. |last2=Villard |first2=Ray |title=NASA's Hubble Extends Stellar Tape Measure 10 Times Farther into Space |url=http://www.nasa.gov/press/2014/april/nasas-hubble-extends-stellar-tape-measure-10-times-farther-into-space |date=10 April 2014 |work=[[NASA]] |access-date=17 October 2014 }}
{{cite journal
|title=Parallax Beyond a Kiloparsec from Spatially Scanning the Wide Field Camera 3 on the Hubble Space Telescope
|author-link1= Adam Riess
|first1=Adam G.|last1=Riess
|first2=Stefano|last2= Casertano
|first3=Jay|last3= Anderson
|first4=John|last4=Mackenty
|first5=Alexei V.|last5=Filippenko
|arxiv=1401.0484
|year= 2014|doi=10.1088/0004-637X/785/2/161|volume=785|issue= 2
|journal=The Astrophysical Journal|page=161|bibcode=2014ApJ...785..161R
|s2cid= 55928992
}}</ref> This gives more accuracy to the [[cosmic distance ladder]] and improves the knowledge of distances in the Universe, based on the dimensions of the Earth's orbit.

As distances between the two points of observation are increased, the visual effect of the parallax is likewise rendered more visible. [[NASA]]'s [[New Horizons|New Horizons spacecraft]] performed the first interstellar parallax measurement on 22 April 2020, taking images of [[Proxima Centauri]] and [[Wolf 359]] in conjunction with earth-based observatories. The relative proximity of the two stars combined with the 6.5 billion kilometer (about 43 AU) distance of the spacecraft from Earth yielded a discernible parallax of arcminutes, allowing the parallax to be seen visually without instrumentation.<ref>{{Cite web |last=Talbert |first=Tricia |date=2020-06-10 |title=New Horizons Conducts the First Interstellar Parallax Experiment |url=http://www.nasa.gov/feature/nasa-s-new-horizons-conducts-the-first-interstellar-parallax-experiment |url-status=live |archive-url=https://web.archive.org/web/20231104161749/https://www.nasa.gov/solar-system/nasas-new-horizons-conducts-the-first-interstellar-parallax-experiment/ |archive-date=2023-11-04 |access-date=2021-05-20 |website=NASA}}</ref>

[[File:New Horizons Proxima Centauri Parallax Animation.gif|thumb|Parallax of Proxima Centauri as observed from New Horizons and Earth.<ref>{{cite web |last=Talbert |first=Tricia |date=2020-07-10 |title=New Horizons Conducts the First Interstellar Parallax Experiment |url=http://www.nasa.gov/feature/nasa-s-new-horizons-conducts-the-first-interstellar-parallax-experiment |url-status=live |archive-url=https://web.archive.org/web/20231104161749/https://www.nasa.gov/solar-system/nasas-new-horizons-conducts-the-first-interstellar-parallax-experiment/ |archive-date=2023-11-04 |access-date=2020-07-14 |website=NASA |language=en}}</ref>]]

The [[European Space Agency]]'s [[Gaia mission]], launched 19 December 2013, is expected to measure parallax angles to an accuracy of 10 micro[[arcsecond]]s for all moderately bright stars, thus mapping nearby stars (and potentially planets) up to a distance of tens of thousands of light-years from Earth.<ref>{{cite web | last = Henney | first = Paul J. | title = ESA's Gaia Mission to study stars | publisher = Astronomy Today | url = http://www.astronomytoday.com/exploration/gaia.html | access-date = 8 March 2008}}</ref> Data Release 2 in 2018 claims mean errors for the parallaxes of 15th magnitude and brighter stars of 20–40 microarcseconds.<ref name=dr2>{{cite DR2}}</ref>

=== Radio astrometry ===
[[Very long baseline interferometry]] in the radio band can produce images with angular resolutions of about 1 milliarcsecond, and hence, for bright radio sources, the precision of parallax measurements made in the radio can easily exceed{{dubious|date=November 2021}} those of optical telescopes like Gaia.  These measurements tend to be sensitivity limited, and need to be made one at a time, so the work is generally done only for sources like pulsars and X-ray binaries, where the radio emission is strong relative to the optical emission.{{citation needed|date=September 2020}}