Class AstroUtils

java.lang.Object
gaiasky.util.coord.AstroUtils
public class AstroUtils extends Object
Astronomical utilities. Contains functions to convert Julian dates, reference systems, and more.

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final long
    J2000_MS
    Milliseconds of J2000 in the scale of Instant.
    static final double
    JD_J2000
    Julian date of reference epoch J2000 = JD2451544.5 = 2000-01-01T00:00:00Z.
    static final double
    JD_J2010
    Julian date of reference epoch J2010 = JD2455197.5 = 2010-01-01T00:00:00Z.
    static final double
    JD_J2015
    Julian date of reference epoch J2015.0 = JD2457023.5 = 2015-01-01T00:00:00Z.
    static final double
    JD_J2015_5
    Julian date of reference epoch J2015.5 = JD2457206.125 = 2015-01-01T00:00:00Z.
    static final double
    JD_TO_Y
    Julian days per year.

  • Constructor Summary

    Constructors
    Constructor
    Description
    AstroUtils()
     

  • Method Summary

    Modifier and Type
    Method
    Description
    static double
    absoluteMagnitudeToPseudoSize(double absMag)
    Computes the pseudo-size of a star from the absolute magnitude.
    static double
    absoluteToApparentMagnitude(double distPc, double absMag)
    Converts an absolute magnitude to an apparent magnitude at the given distance in parsecs.
    static double
    apparentToAbsoluteMagnitude(double distPc, double appMag)
    Converts an apparent magnitude to an absolute magnitude given the distance in parsecs.
    static long[]
    getCalendarDay(double julianDate)
    Gets the Gregorian calendar quantities given the Julian date.
    static long[]
    getDayQuantities(double dayFraction)
    Deprecated.
    Not used anymore.
    static double
    getDaysSince(Instant date, double epoch_jd)
    Returns the elapsed days since the given julian date jd until the given date.
    static double
    getDaysSinceJ2000(Instant date)
    Returns the elapsed days since the epoch J2000 until the given date.
    static double
    getJulianDate(double refEpoch)
    Get julian date from a double reference epoch, as a Gregorian calendar year plus fraction.
    static double
    getJulianDate(Instant instant)
    Gets the Julian date from a given Instant.
    static double
    getJulianDateCache(Instant instant)
    Gets the Julian Date for the given Instant.
    static double
    getJulianDateUTC(int year, int month, int day, int hour, int min, int sec, int nanos)
    Computes the Julian Date (JD) for a given date and time with nanosecond precision, using either the Julian or Gregorian calendar depending on the date.
    static double
    getJulianDayNumberBook(int year, int month, int day)
    Deprecated.
    This does not work well!
    static double
    getJulianDayNumberGregorian(int year, int month, int day)
    Determine Julian day number from Gregorian calendar date.
    static double
    getJulianDayNumberJulianCalendar(int year, int month, int day)
    Returns the Julian day number of a date in the Julian calendar.
    static double
    getMsSince(Instant date, double epoch_jd)
    Returns the elapsed milliseconds since the given julian date jd until the given date.
    static String
    getSpectralType(float tEff)
    Get the spectral type from the effective temperature for main sequence stars.
    static double
    getSunLongitude(Instant date)
    Returns the Sun's ecliptic longitude in degrees for the given time.
    static boolean
    isLeapYearGregorian(int year)
    Is a given year in the Gregorian calendar a leap year ?
    static Instant
    julianDateToInstant(double jd)
     
    static double
    obliquity(double julianDate)
    Returns the obliquity of the ecliptic (inclination of the Earth's axis of rotation) for a given date, in degrees
    static void
    plutoEclipticCoordinates(Instant date, Vector3Q out)
    Spherical ecliptic coordinates of Pluto at the given date.
    static double
    T(double julianDate)
    Time T measured in Julian centuries from the Epoch J2000.0.
    static double
    tau(double julianDate)
     

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • JD_TO_Y

      public static final double JD_TO_Y
      Julian days per year.
      See Also:

    • JD_J2000

      public static final double JD_J2000
      Julian date of reference epoch J2000 = JD2451544.5 = 2000-01-01T00:00:00Z.

    • JD_J2010

      public static final double JD_J2010
      Julian date of reference epoch J2010 = JD2455197.5 = 2010-01-01T00:00:00Z.

    • JD_J2015

      public static final double JD_J2015
      Julian date of reference epoch J2015.0 = JD2457023.5 = 2015-01-01T00:00:00Z.

    • JD_J2015_5

      public static final double JD_J2015_5
      Julian date of reference epoch J2015.5 = JD2457206.125 = 2015-01-01T00:00:00Z.

    • J2000_MS

      public static final long J2000_MS
      Milliseconds of J2000 in the scale of Instant. This is the number of milliseconds elapsed since 1970-01-01T00:00:00Z (UTC) until 2000-01-01T00:00:00Z (UTC).

  • Constructor Details

    • AstroUtils

      public AstroUtils()

  • Method Details

    • getJulianDate

      public static double getJulianDate(double refEpoch)
      Get julian date from a double reference epoch, as a Gregorian calendar year plus fraction.
      Parameters:
      refEpoch - The reference epoch as a Gregorian calendar year.
      Returns:
      The julian date.

    • getSunLongitude

      public static double getSunLongitude(Instant date)
      Returns the Sun's ecliptic longitude in degrees for the given time. Caches the last Sun's longitude for future use.
      Parameters:
      date - The time for which the longitude must be calculated.
      Returns:
      The Sun's longitude in [deg].

    • getJulianDateUTC

      public static double getJulianDateUTC(int year, int month, int day, int hour, int min, int sec, int nanos)
      Computes the Julian Date (JD) for a given date and time with nanosecond precision, using either the Julian or Gregorian calendar depending on the date.

      The calendar transition is determined by comparing the input against a predefined gregorianSwitch Instant, after which the Gregorian calendar is used. The input quantities are assumed to be in UTC.

      Parameters:
      year - the year component of the date
      month - the month component of the date (1 = January, ..., 12 = December)
      day - the day of the month (1-31)
      hour - the hour of the day (0–23)
      min - the minute of the hour (0–59)
      sec - the second of the minute (0–59)
      nanos - the nanosecond of the second (0–999,999,999)
      Returns:
      the Julian Date corresponding to the given date and time
      Throws:
      DateTimeException - if the date-time values are invalid

    • getJulianDateCache

      public static double getJulianDateCache(Instant instant)
      Gets the Julian Date for the given Instant. It uses a cache.
      Parameters:
      instant - The date.
      Returns:
      The Julian Date.

    • getJulianDate

      public static double getJulianDate(Instant instant)
      Gets the Julian date from a given Instant. Instants are by definition in UTC.
      Parameters:
      instant - The instant.
      Returns:
      The Julian date.

    • getDaysSinceJ2000

      public static double getDaysSinceJ2000(Instant date)
      Returns the elapsed days since the epoch J2000 until the given date. Can be negative.
      Parameters:
      date - The date.
      Returns:
      The elapsed days.

    • getMsSince

      public static double getMsSince(Instant date, double epoch_jd)
      Returns the elapsed milliseconds since the given julian date jd until the given date. Can be negative.
      Parameters:
      date - The date.
      epoch_jd - The reference epoch in julian days.
      Returns:
      The elapsed milliseconds.

    • getDaysSince

      public static double getDaysSince(Instant date, double epoch_jd)
      Returns the elapsed days since the given julian date jd until the given date. Can be negative.
      Parameters:
      date - The date.
      epoch_jd - The reference epoch in julian days.
      Returns:
      The elapsed days

    • getCalendarDay

      public static long[] getCalendarDay(double julianDate)
      Gets the Gregorian calendar quantities given the Julian date.
      Parameters:
      julianDate - The Julian date.
      Returns:
      Vector with [year, month, day, hour, min, sec, nanos].

    • getJulianDayNumberBook

      @Deprecated public static double getJulianDayNumberBook(int year, int month, int day)
      Deprecated.
      This does not work well!
      Returns the Julian day number. Uses the method shown in "Astronomical Algorithms" by Jean Meeus.
      Parameters:
      year - The year
      month - The month in [1:12]
      day - The day in the month, starting at 1
      Returns:
      The Julian date

    • getJulianDayNumberJulianCalendar

      public static double getJulianDayNumberJulianCalendar(int year, int month, int day)
      Returns the Julian day number of a date in the Julian calendar. Uses Wikipedia's algorithm.
      Parameters:
      year - The year
      month - The month in [1:12]
      day - The day in the month, starting at 1
      Returns:
      The Julian date
      See Also:

    • isLeapYearGregorian

      public static boolean isLeapYearGregorian(int year)
      Is a given year in the Gregorian calendar a leap year ?
      Parameters:
      year - The year.
      Returns:
      Whether the year in the Gregorian calendar is a leap year.

    • getJulianDayNumberGregorian

      public static double getJulianDayNumberGregorian(int year, int month, int day)
      Determine Julian day number from Gregorian calendar date.
      Parameters:
      year - The year.
      month - The month.
      day - The day.
      Returns:
      The julian day number.

    • julianDateToInstant

      public static Instant julianDateToInstant(double jd)

    • getDayQuantities

      @Deprecated public static long[] getDayQuantities(double dayFraction)
      Deprecated.
      Not used anymore.
      Gets the day quantities from the day fraction
      Parameters:
      dayFraction - The day fraction.
      Returns:
      [hours, minutes, seconds, nanos].

    • obliquity

      public static double obliquity(double julianDate)
      Returns the obliquity of the ecliptic (inclination of the Earth's axis of rotation) for a given date, in degrees
      Returns:
      The obliquity in degrees

    • T

      public static double T(double julianDate)
      Time T measured in Julian centuries from the Epoch J2000.0.
      Parameters:
      julianDate - The julian date.
      Returns:
      The time in julian centuries.

    • tau

      public static double tau(double julianDate)

    • apparentToAbsoluteMagnitude

      public static double apparentToAbsoluteMagnitude(double distPc, double appMag)
      Converts an apparent magnitude to an absolute magnitude given the distance in parsecs.
      Parameters:
      distPc - The distance to the star in parsecs.
      appMag - The apparent magnitude.
      Returns:
      The absolute magnitude.

    • absoluteToApparentMagnitude

      public static double absoluteToApparentMagnitude(double distPc, double absMag)
      Converts an absolute magnitude to an apparent magnitude at the given distance in parsecs.
      Parameters:
      distPc - The distance to the star in parsecs.
      absMag - The absolute magnitude.
      Returns:
      The apparent magnitude at the given distance.

    • absoluteMagnitudeToPseudoSize

      public static double absoluteMagnitudeToPseudoSize(double absMag)
      Computes the pseudo-size of a star from the absolute magnitude.
      Parameters:
      absMag - The absolute magnitude of the star.
      Returns:
      The pseudo-size of this star, mainly used for rendering purposes. It has no physical meaning and has no relation to the actual physical size of the star.

    • getSpectralType

      public static String getSpectralType(float tEff)
      Get the spectral type from the effective temperature for main sequence stars. More info: see here.

    • plutoEclipticCoordinates

      public static void plutoEclipticCoordinates(Instant date, Vector3Q out)
      Spherical ecliptic coordinates of Pluto at the given date.
      Parameters:
      date - The date.
      out - The out vector with [lambda, beta, r] in radians and kilometres.