NightHemisphere
is a two-dimensional GeoGraphics primitive that represents the half of the Earth currently in darkness.
NightHemisphere[datespec]
represents the night half of the Earth for the specified date.
Details and Options
- datespec can be a DateObject or a string that resolves to a date.
- A date without explicit time zone is assumed to use $TimeZone.
- The NightHemisphere[…] primitive can be used in maps of solar system bodies other than Earth, such as planets and many of their moons.
- The option ReferenceAltitude specifies how to define the terminator line, separating the day and night parts of the Earth. Possible values include:
-
Automatic upper limb of the Sun crosses zero altitude alt center of the Sun crosses numeric altitude alt {alt,limb} the given limb of the Sun crosses numeric altitude alt "Civil" the center of the Sun has altitude –6 degrees "Nautical" the center of the Sun has altitude –12 degrees "Astronomical" the center of the Sun has altitude –18 degrees - The reference altitude angle alt can be given as a Quantity angle or as a numeric expression interpreted in angular degrees.
- Possible values for the limb of the Sun include:
-
"UpperLimb" upper limb of the Sun "Center" central point of the Sun "LowerLimb" lower limb of the Sun limb numeric value between –1 (lower limb) and 1 (upper limb)
Examples
open all close allBasic Examples (2)
Shade the part of the Earth currently at nighttime:
GeoGraphics[NightHemisphere[]]Show the unilluminated part of the Earth on the next June solstice, using red lines to denote the Arctic and Antarctic Circles:
FindAstroEvent["JuneSolstice"]GeoGraphics[{NightHemisphere[%], Red, GeoPath["ArcticCircle"], GeoPath["AntarcticCircle"]}]GeoGraphics[{NightHemisphere[%%], Red, GeoPath["ArcticCircle"], GeoPath["AntarcticCircle"]}, GeoProjection -> "Bonne"]Scope (6)
NightHemisphere[] gives a plot for the current date and time:
GeoGraphics[NightHemisphere[]]Using Now explicitly gives the same result:
GeoGraphics[NightHemisphere[Now]]Illustrate changes in the unilluminated hemisphere at different times of day and year:
GeoGraphics[Table[{GeoStyling[Opacity[0.2], Hue[n / 12]], NightHemisphere[DateObject[{2014, n, 1, 2n, 0, 0}]]}, {n, 1, 12}]]Specify dates in other formats:
GeoGraphics[NightHemisphere["31 December 2000"]]GeoGraphics[NightHemisphere[Tomorrow]]NightHemisphere can be used to simulate the phase of the Moon on a given date:
date = DateObject[{2026, 1, 9, 0, 0, 0}];GeoGraphics[{GeoStyling[Opacity[.7]], NightHemisphere[date]}, GeoModel -> "Moon", GeoProjection -> "Orthographic", Background -> Black, GeoGridRangePadding -> 0.1]Compare to the icon representation provided by MoonPhase for the same date:
MoonPhase[date, "Icon"]Show the phase of Mars on a given date, as observed from the center of the Earth:
date = DateObject[{2026, 11, 1, 0, 0, 0}];GeoGraphics[{GeoStyling[Opacity[.7]], NightHemisphere[date]}, GeoModel -> "Mars", GeoProjection -> "Orthographic", GeoCenter -> AstroSubpoint["Earth", {"Mars", date}], Background -> Black, GeoGridRangePadding -> 0.1]Show an iconic form of the phase of Venus on a given date:
date = DateObject[{2026, 8, 1, 0, 0, 0}]GeoGraphics[{GeoStyling[Black], NightHemisphere[date]}, GeoModel -> "Venus", GeoProjection -> "Orthographic", GeoBackground -> White, GeoCenter -> AstroSubpoint["Earth", {"Venus", date}], Background -> Gray, GeoGridRangePadding -> 0.1]Options (1)
ReferenceAltitude (1)
By default, NightHemisphere corresponds to the part of the Earth for which the Sun is below the horizon:
GeoGraphics[NightHemisphere[]]Show the parts of the Earth not including the areas of civil, nautical and astronomical twilight:
nightHemispheres = {
NightHemisphere[],
NightHemisphere[ReferenceAltitude -> "Civil"],
NightHemisphere[ReferenceAltitude -> "Nautical"],
NightHemisphere[ReferenceAltitude -> "Astronomical"]
};GeoGraphics[nightHemispheres]Their meaning is clearer in a world map using the "Orthographic" projection:
Manipulate[GeoGraphics[nightHemispheres, GeoProjection -> "Orthographic", GeoCenter -> {lat, lon}], {{lat, 0}, -90, 90}, {{lon, 0}, -180, 180}, SaveDefinitions -> True]
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Properties & Relations (2)
The terminator line separates the day and night hemispheres:
GeoGraphics[{GeoStyling[Opacity[0.5], Yellow], DayHemisphere[], GeoStyling[Opacity[0.5], Black], NightHemisphere[], Red, DayNightTerminator[]}]For a spherical model of the Earth, the night hemisphere is a geo disk:
sun = AstroSubpoint["Sun"]d = GeoDistance[sun, GeoAntipode[sun]] / 2GeoGraphics[{NightHemisphere[], GeoStyling[Opacity[0.3], Red], GeoDisk[GeoAntipode[sun], d]}, GeoRange -> "World"]The true night hemisphere and approximate darkness geo disk differ slightly when using an ellipsoidal model of the Earth:
GeoGraphics[{NightHemisphere[], GeoStyling[Opacity[0.3], Red], GeoDisk[GeoAntipode[sun], d]}, GeoCenter -> GeoDestination[GeoAntipode[sun], {d, 90}], GeoRange -> Quantity[20, "Miles"], Frame -> True]Interactive Examples (1)
Full synodic month of Moon phases as observed from the center of the Earth:
Manipulate[
GeoGraphics[{GeoStyling[Opacity[.7]], NightHemisphere[date]}, GeoModel -> "Moon", GeoProjection -> "Orthographic", Background -> Black, GeoCenter -> AstroSubpoint["Earth", {"Moon", date}], PlotRange -> AstroDistance["Moon", Dated["Earth", date]] / Quantity[350000, "Kilometers"]],
{date, Now, Now + Quantity[1, "SynodicMonths"], Quantity[1, "Seconds"]}, SaveDefinitions -> True
]Text
Wolfram Research (2014), NightHemisphere, Wolfram Language function, https://reference.wolfram.com/language/ref/NightHemisphere.html (updated 2026).
CMS
Wolfram Language. 2014. "NightHemisphere." Wolfram Language & System Documentation Center. Wolfram Research. Last Modified 2026. https://reference.wolfram.com/language/ref/NightHemisphere.html.
APA
Wolfram Language. (2014). NightHemisphere. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/NightHemisphere.html