question: There is a post today on r/spaceporn showing where the sun is in relation to the galaxy, how do we know where we are if we can’t actually view the Galaxy we are in?
comment: What do you mean we can't image our Galaxy? We can see all the stars with telescopes and plot their positions. That means we can make a three dimensional map of the Galaxy. Sort of like you can make a map of the four walls of the room you're sitting in, even though you're not outside it.
passages: Section::::Orbit and location.:Orbit in Milky Way.
  
  The Sun orbits the center of the Milky Way, and it is presently moving in the direction of the constellation of Cygnus. A simple model of the motion of a star in the galaxy gives the galactic coordinates , , and as:
   The Milky Way Galaxy is moving through space and many astronomers believe the velocity of this motion to be approximately relative to the observed locations of other nearby galaxies. Another reference frame is provided by the Cosmic microwave background. This frame of reference indicates that the Milky Way is moving at around .
  
  Section::::List of "imperceptible" human motions.:Sun and solar system.
   The NASA Origins Program was created in the 1990s to ultimately search for the origin of the universe. The theory that the Origins Program is based on is: since light travels at a constant speed until it is absorbed by something; there is still light that was part of the first light ever created traveling about the universe and ultimately some of that light is coming in the general direction of Earth. So a satellite system capable of collecting light from the beginning of the universe would be able to tell us more about where we came from.
   VVV Survey
  
  The VVV Survey is an ESO public survey scanning the Milky Way bulge and adjacent section of the southern mid-plane in the near-infrared. This area, is active in star formation and very rich in dust and interstellar gas, which makes it impossible to see through in the visible as the extinction and crowding are high. There are though, some ‘clear windows’ thought the whole survey area, where optical surveys can be carried out, like MACHO, OGLE and EROS.
  
  Section::::The VVV Survey.
   This chapter asks the reader to consider our place in the vast universe and the “limitless hunting ground” that awaits all who care to take up a pair of binoculars or a telescope.
  
  Section::::The Universe in Eleven Steps.
  
  Explains the Milky Way Galaxy in 11 steps beginning with Earth, the moon and the solar system, and then farther and farther away in distance and time to the Hubble Deep Field and the end of the universe.
  
  Section::::Backyard Astronomy.
   Historically, observations of transits of Venus were crucial in determining the AU; in the first half of the 20th century, observations of asteroids were also important. Presently the orbit of Earth is determined with high precision using radar measurements of distances to Venus and other nearby planets and asteroids, and by tracking interplanetary spacecraft in their orbits around the Sun through the Solar System.
  
  Section::::Direct measurement.:Parallax.
   In 2005 Masters moved to Harvard University to work as a postdoctoral researcher with John Huchra on a project to make the most complete map of the local Universe. Masters "unveiled the most complete 3-D map of the local universe (out to a distance of 380 million light-years) ever created" in 2011 at the 218th meeting of the American Astronomical Society. The map was created using data from the Two-Micron All-Sky Survey.
   The ESA spacecraft "Gaia" provides distance estimates by determining the parallax of a billion stars and is mapping the Milky Way with four planned releases of maps in 2022.
  
  Section::::See also.
  
  BULLET::::- Baade's Window
  
  BULLET::::- Galactic astronomy
  
  BULLET::::- Galactic Center GeV Excess
  
  BULLET::::- List of galaxies
  
  BULLET::::- Oort constants
  
  Section::::External links.
  
  BULLET::::- Milky Way – 3D Map
  
  BULLET::::- Milky Way – Basic plan map – Includes spiral arms and Orion spur
  
  BULLET::::- Milky Way – IRAS (infrared) survey – wikisky.org
  
  BULLET::::- Milky Way – H-Alpha survey – wikisky.org
  
  BULLET::::- Milky Way – MultiWavelength – Images and VRML models (NASA)
   Numerical descriptions of point sources (stars, planets, asteroids) and extended sources (galaxies, nebulae) were cataloged by automated computer programs to an average limiting magnitude of about 14. More than 300 million point sources and 1 million extended sources were cataloged. In November 2003, a team of scientists announced the discovery of the Canis Major Dwarf Galaxy, at that time the closest known satellite galaxy to the Milky Way, based on analysis of 2MASS stellar data.
   Direct measurements are simple, but very difficult. One just has to measure the total incoming power, and determine the contribution of each sky background component. The measurement has to be repeated in many directions to determine the contribution of the foregrounds. After the removal of all other components the remaining power – if it is the same constant value in any direction – is the CIB at that specific wavelength. In practice, one needs an instrument which is able to perform absolute photometry, i.e. it has some mechanism to fully block incoming light for an accurate zero level determination (cold shutter). Since the instrument parts, including the shutter, have non-zero temperatures and emit in the infrared, this is a very difficult task.
   There are a host of spacecraft that observe the Sun and interplanetary space. One of the latest to explore the Sun, from nearer than ever before, is the Parker Solar Probe launched in 2018. Solar observations, such as during a Solar eclipse, allow observation of the Sun's Corona. While various types of space observatories also provide data on the Sun and its influences. The study of other Stars can also allow insights indirectly.
   A third sub-project, HATPI, is currently under construction and will survey most of the night sky seen from its location in Chile.
  
  Section::::Missions.:KELT.
   Another reference frame is provided by the cosmic microwave background (CMB). The Milky Way is moving at with respect to the photons of the CMB, toward 10.5 right ascension, −24° declination (J2000 epoch, near the center of Hydra). This motion is observed by satellites such as the Cosmic Background Explorer (COBE) and the Wilkinson Microwave Anisotropy Probe (WMAP) as a dipole contribution to the CMB, as photons in equilibrium in the CMB frame get blue-shifted in the direction of the motion and red-shifted in the opposite direction.
  
  Section::::Etymology and mythology.
   The first project to describe the shape of the Milky Way and the position of the Sun was undertaken by William Herschel in 1785 by counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the Solar System close to the center. Using a refined approach, Kapteyn in 1920 arrived at the picture of a small (diameter about 15 kiloparsecs) ellipsoid galaxy with the Sun close to the center. A different method by Harlow Shapley based on the cataloguing of globular clusters led to a radically different picture: a flat disk with diameter approximately 70 kiloparsecs and the Sun far from the center. Both analyses failed to take into account the absorption of light by interstellar dust present in the galactic plane, but after Robert Julius Trumpler quantified this effect in 1930 by studying open clusters, the present picture of our host galaxy, the Milky Way, emerged.
   WISPR is designed to study the electron density and velocity structure of the corona. The instrument field of view is planned to extend from 13 to 108 degrees away from the Sun, and does not directly image the Sun; the area of interest is a very wide field extending away from the Sun.
  
  WISPR includes two separate telescopes, each with a radiation-hardened CMOS imager with resolution of 2,000×2,000 pixels. The CMOS sensors are an active pixel sensor type of detector.
   Earth's rotation about its axis causes the fixed stars to apparently move across the sky in a way that depends on the observer's geographic latitude. The time when a given fixed star transits the observer's meridian depends on the geographic longitude.
  
  To find the Sun's position for a given location at a given time, one may therefore proceed in three steps as follows:
  
  BULLET::::1. calculate the Sun's position in the ecliptic coordinate system,
  
  BULLET::::2. convert to the equatorial coordinate system, and
  
  BULLET::::3. convert to the horizontal coordinate system, for the observer's local time and location.
   To understand the magnetic field and activity of stars, studies of the Sun are not sufficient. Therefore, studies of other stars are necessary. Periodic changes in brightness have long been observed in stars which indicate cooler or brighter starspots on the surface. These spots are larger than the ones on the Sun, covering up to 20% of the star. Spots with similar size as the ones on the Sun would hardly give rise to changes in intensity. In order to understand the magnetic field structure of a star, it is not enough to know that spots exist because their location and extent are also important.
   The third method is best for moonless and clear nights, as it uses two faint "clouds" in the Southern Sky. These are marked in astronomy books as the Large and Small Magellanic Clouds. These "clouds" are actually dwarf galaxies near the Milky Way. Make an equilateral triangle, the third point of which is the south celestial pole.
  
  Section::::Finding the south celestial pole.:Method four: Sirius and Canopus.
   For example, the center of the Milky Way Galaxy is very bright in far infrared images because the dense concentration of stars there heats the surrounding dust and causes it to emit radiation in this part of the spectrum. Disregarding the center of our own galaxy, the brightest far infrared object in the sky is the galaxy M82, which radiates as much far infrared light from its central region as all of the stars in the Milky Way combined. This is due to the dust at the center of M82 being heated by an unknown source.
  
  Section::::Applications.:Human body detection.
   The Solar System orbits within the Milky Way, a barred spiral galaxy that is a prominent member of the Local Group of galaxies. It is a rotating mass of gas, dust, stars and other objects, held together by mutual gravitational attraction. As the Earth is located within the dusty outer arms, there are large portions of the Milky Way that are obscured from view.
   Parker Solar Probe
  
  Parker Solar Probe (previously Solar Probe, Solar Probe Plus, or Solar Probe+, abbreviated PSP) is a NASA robotic spacecraft launched in 2018, with the mission of repeatedly probing and making observations of the outer corona of the Sun. It will approach to within 9.86 solar radii (6.9 million kilometers or 4.3 million miles) from the center of the Sun and by 2025 will travel, at closest approach, as fast as , or 0.064% the speed of light.
   On 12 September 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."
  
  Section::::Mission progress.:Data releases.
   BULLET::::- WISPR, is double solar telescope on the Parker Solar Probe designed to image the corona close to the Sun from space
  
  Section::::Other types of observation.
  
  Most solar observatories observe optically at visible, UV, and near infrared wavelengths, but other solar phenomena can be observed — albeit not from the Earth's surface due to the absorption of the atmosphere:
  
  BULLET::::- Solar X-ray astronomy, observations of the Sun in x-rays
  
  BULLET::::- Multi-spectral solar telescope array (MSSTA), a rocket launched payload of UV telescopes in the 1990s
  
  BULLET::::- Leoncito Astronomical Complex operated a submillimeter wavelength solar telescope.
   Kelle Cruz
  
  Kelle Cruz is an astrophysicist who specializes in studying brown dwarfs. She currently works as an associate professor at Hunter College in New York City. With her study of brown dwarfs, Cruz hopes to better understand planets outside the Solar System and map out the universe, saying, "I hope that what I’m doing in our little bit of the galaxy is similar to what the explorers did by discovering and mapping the New World and North America."
  
  Section::::Further reading.
   For observers on extrasolar planets, the constellations would differ depending on the distances involved. The view of outer space of exoplanets can be extrapolated from open source software such as Celestia or Stellarium, and it appears that due to parallax, distant stars change their position less than nearby ones. For alien observers, the Sun would be visible to the naked human eye only at distances below 20 – 27 parsec (60–90 ly). If the Sun were to be observed from another star, it would always appear on the opposite coordinates in the sky. Thus an observer located near a star with RA at 4 hr and declination −10 would see the Sun located at RA: 16 hr, dec: +10. A consequence of observing the universe from other stars is that stars that may appear bright in our own sky may appear dimmer in other skies and vice versa.
  
presuppositions: Can't make an image of the galaxy when you are inside of it. We can't view the galaxy that we're in.
corrections: You can make an image when you are inside similar to how you can draw the walls when you are inside.  We can view the galaxy that we're in by mapping it out.
raw_presuppositions: Can't make an image of the galaxy when you are inside of it. We can't view the galaxy that we're in.
raw_corrections: You can make an image when you are inside similar to how you can draw the walls when you are inside.  We can view the galaxy that we're in by mapping it out.