Solar eclipses on Pluto
Encyclopedia
Solar eclipses on Pluto
are caused when one of its four natural satellites – Charon
, Nix
, Hydra
, and P4 – passes in front of the Sun
, blocking its light.
An eclipse of the Sun on Pluto can occur only when one of the satellites' orbital node
s, the points where their orbits cross the dwarf planet
's ecliptic
, is lined up with the apparent position of the Sun as seen from Pluto. Since all three of its satellites orbit in the same plane, the times at which this is possible are the same for all three. Due to Pluto's steep axial tilt, this can only occur at two points in Pluto's orbit, centered around perihelion and aphelion.
Charon presents an angular diameter
of roughly 4 degrees of arc as seen from the surface of Pluto; the Sun appears much smaller, only 40 arcseconds to 1 arcminute. Charon's proximity further ensures that a large proportion of Pluto's surface can experience a total eclipse. Because Pluto always presents the same face towards Charon due to tidal locking, only the Charon-facing hemisphere can experience a total solar eclipse by Charon.
There are large uncertainties in the diameters of the three smaller moons, and as a result their apparent diameters (as seen from Pluto) are also uncertain. However, it is known that Nix's angular diameter is 3–9 minutes of arc, while Hydra's is 2–7 minutes. These are much larger than the Sun's angular diameter, so total solar eclipses are possible with these moons.
The period when eclipses were observed on Pluto was between February 1985 and October 1990. As seen from Earth
, Charon also transited
Pluto every orbit during this period. By measuring the change in brightness during these transit events, astronomers were able to measure the radius of both Pluto and Charon. Currently, telescopes, such as the Hubble Space Telescope
have high enough resolution that the radius can be measured directly.
The next period of time when solar eclipses can occur on Pluto will begin October 2103, peak in 2110, and end January 2117. During this period, solar eclipses will occur at some point on Pluto every orbit of Charon. The maximum duration of any solar eclipse by Charon as seen from Pluto during this period is about 90 minutes.
Pluto
Pluto, formal designation 134340 Pluto, is the second-most-massive known dwarf planet in the Solar System and the tenth-most-massive body observed directly orbiting the Sun...
are caused when one of its four natural satellites – Charon
Charon (moon)
Charon is the largest satellite of the dwarf planet Pluto. It was discovered in 1978 at the United States Naval Observatory Flagstaff Station. Following the 2005 discovery of two other natural satellites of Pluto , Charon may also be referred to as Pluto I...
, Nix
Nix (moon)
Nix is a natural satellite of Pluto. It was discovered along with Hydra in June 2005, and is to be visited along with Pluto by the New Horizons mission in July 2015.- Discovery :...
, Hydra
Hydra (moon)
Hydra is the second outermost known natural satellite of Pluto. It was discovered along with Nix in June 2005, and is to be visited along with Pluto by the New Horizons mission in July 2015.- Discovery :...
, and P4 – passes in front of the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, blocking its light.
An eclipse of the Sun on Pluto can occur only when one of the satellites' orbital node
Orbital node
An orbital node is one of the two points where an orbit crosses a plane of reference to which it is inclined. An orbit which is contained in the plane of reference has no nodes.-Planes of reference:...
s, the points where their orbits cross the dwarf planet
Dwarf planet
A dwarf planet, as defined by the International Astronomical Union , is a celestial body orbiting the Sun that is massive enough to be spherical as a result of its own gravity but has not cleared its neighboring region of planetesimals and is not a satellite...
's ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
, is lined up with the apparent position of the Sun as seen from Pluto. Since all three of its satellites orbit in the same plane, the times at which this is possible are the same for all three. Due to Pluto's steep axial tilt, this can only occur at two points in Pluto's orbit, centered around perihelion and aphelion.
Charon presents an angular diameter
Angular diameter
The angular diameter or apparent size of an object as seen from a given position is the “visual diameter” of the object measured as an angle. In the vision sciences it is called the visual angle. The visual diameter is the diameter of the perspective projection of the object on a plane through its...
of roughly 4 degrees of arc as seen from the surface of Pluto; the Sun appears much smaller, only 40 arcseconds to 1 arcminute. Charon's proximity further ensures that a large proportion of Pluto's surface can experience a total eclipse. Because Pluto always presents the same face towards Charon due to tidal locking, only the Charon-facing hemisphere can experience a total solar eclipse by Charon.
There are large uncertainties in the diameters of the three smaller moons, and as a result their apparent diameters (as seen from Pluto) are also uncertain. However, it is known that Nix's angular diameter is 3–9 minutes of arc, while Hydra's is 2–7 minutes. These are much larger than the Sun's angular diameter, so total solar eclipses are possible with these moons.
The period when eclipses were observed on Pluto was between February 1985 and October 1990. As seen from Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
, Charon also transited
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
Pluto every orbit during this period. By measuring the change in brightness during these transit events, astronomers were able to measure the radius of both Pluto and Charon. Currently, telescopes, such as the Hubble Space Telescope
Hubble Space Telescope
The Hubble Space Telescope is a space telescope that was carried into orbit by a Space Shuttle in 1990 and remains in operation. A 2.4 meter aperture telescope in low Earth orbit, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared...
have high enough resolution that the radius can be measured directly.
The next period of time when solar eclipses can occur on Pluto will begin October 2103, peak in 2110, and end January 2117. During this period, solar eclipses will occur at some point on Pluto every orbit of Charon. The maximum duration of any solar eclipse by Charon as seen from Pluto during this period is about 90 minutes.