Término del glosario: Unidad Astronómica
Descripción: Una unidad astronómica (UA) es una unidad de distancia equivalente a 149,597,870.7 kilómetros (km) exactos. Esta es la distancia media entre la Tierra y el Sol, que era una definición anterior de la UA. La UA se utiliza a menudo para medir distancias en el Sistema Solar y en otros sistemas planetarios o estelares. Por ejemplo, Neptuno orbita a unas 30 UA del Sol.
Términos relacionados:
Ver este término en otros idiomas
Estado del término y la definición: La definición original de este término en inglés ha sido aprobada por unastrónomo o astrónoma investigadora y un docente La traducción de este término y su definición aún están pendientes de aprobación
El Glosario multilingüe de la OAE es un proyecto de la Oficina de Astronomía para la Educación de la UAI (OAE) en colaboración con la Oficina de Divulgación de Astronomía de la UAI (OAO). Los términos y definiciones fueron seleccionados, redactados y revisados gracias al esfuerzo colectivo de la OAE, los Centros y Nodos de la OAE, los Coordinadores Nacionales de Educación Astronómica (NAECs) y otros voluntarios. Puedes encontrar una lista completa de créditos aquí. Todos los términos del glosario y sus definiciones se publican bajo la licencia Creative Commons CC BY-4.0 y deben atribuirse a la "IAU OAE".
Si detectas algún error de contenido o de traducción en este término del glosario o en ladefinición, ponte en contacto con nosotros.
En otros idiomas
- Árabe: الوحدة الفلكية
- Alemán: Astronomische Einheit
- Inglés: Astronomical Unit
- Francés: Unité astronomique
- Hindi: खगोलीय इकाई (AU)
- Italiano: Unità astronomica
- Japonés: 天文単位 (enlace externo)
- Coreano: 천문단위
- Maratí: खगोलशास्त्रीय एकक
- Portugués de Brasil: Unidade astronômica
- Chino simplificado: 天文单位
- Chino tradicional: 天文單位
Diagramas relacionados
Astronomical Unit
Pie de foto: An astronomical unit (AU) is a convenient unit of distance equal to exactly 149,597,870.7 kilometers (km). This is approximately the average distance between the Earth and the Sun, which was a previous definition of the AU. The AU is often used to measure distances in the Solar System and in other planetary or stellar systems.
Crédito: Danielle Futselaar/IAU OAE
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) íconos
Annual Parallax
Pie de foto: Distance determination has historically been a challenge for astronomy. One of the primary ways to measure distance is to use annual parallax. The Earth orbits around the Sun over the course of a year meaning that it moves from one side of the Sun (shown here as position A) to the other side of the Sun (position B) over the course of six months. It then moves back to its original position over the remaining six months. This movement subtly changes the perspective an observer on Earth sees the night sky from. This is similar to the change in viewing perspective you may get when viewing a scene from your left eye and then your right eye. The change of viewing perspective causes nearby objects to shift in position in your vision. The annual motion of the Earth around the Sun changes the perspective of the observer enough to shift the observed positions of celestial objects. How big this effect is depends on the distance to the celestial object. Nearby stars will have bigger shifts in observed position than more distant stars.
The positional shift is known as the trigonometric or annual parallax (which we will call α here) and is defined as the shift in position of a star compared to what an observer at the center of the Solar System (the Sun) would see. In this diagram we see the star viewed from perspectives six months apart (positions A and B). When observed from position A the star’s shift in position will be α while when observed at position B it will be –α. Thus the relative difference in the stars position between being observed at position A and position B will be 2α.
The size of the trigonometric or annual parallax in arcseconds is approximately 1 divided by the distance in parsecs. An arcsecond (often represented by a ″ symbol) is the angular diameter a one-metre-long stick would have when viewed from 206 km away. A parsec (often abbreviated to pc) is 3.26 light years or 30.86 trillion kilometres. This is 206,265 astronomical units (the typical distance between the Earth and the Sun). No other star is closer than 1 pc to the Sun so all stars in the sky have trigonometric parallaxes less than one arcsecond.
While trigonometric parallaxes have long been used to measure the distances to objects in our Solar System or nearby stars, recent advances have pushed the boundaries of these distance measures further. The Gaia satellite has pushed the boundaries of parallax measurements to over a thousand parsecs. Arrays of radio telescopes can also very accurately measure the positions of very distant objects and thus their trigonometric parallax.
Note the Earth and Sun are not to scale here and the Earth’s axial tilt is not accurately represented.
Crédito: Aneta Margraf/IAU OAE
License: CC-BY-4.0 Creative Commons Reconocimiento 4.0 Internacional (CC BY 4.0) íconos
