Package gaiasky.util.coord

Class AstroUtils

java.lang.Object

gaiasky.util.coord.AstroUtils

public class AstroUtils
extends Object

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 double	getDayFraction(int hour, int min, int sec, int nanos)	Gets the day fraction from the day quantities.
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(int year, int month, int day, int hour, int min, int sec, int nanos, boolean gregorian)	Gets the Julian date number given the Gregorian calendar quantities.
static double	getJulianDate(Instant instant)
static double	getJulianDateCache(Instant instant)	Gets the Julian Date for the given 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 Vector3b	moonEclipticCoordinates(Instant date, Vector3d aux, Vector3b out)	Algorithm in "Astronomical Algorithms" book by Jean Meeus.
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, Vector3b out)	Spherical ecliptic coordinates of Pluto at the given date.
static Vector3d	properMotionsToCartesian(double muAlphaStar, double muDelta, double radVel, double ra, double dec, double distPc, Vector3d out)	Converts proper motions + radial velocity into a cartesian vector.
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 java.lang.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:

• Constant Field Values

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].

moonEclipticCoordinates

public static Vector3b moonEclipticCoordinates(Instant date,
 Vector3d aux,
 Vector3b out)

Algorithm in "Astronomical Algorithms" book by Jean Meeus. Returns a vector with the geocentric ecliptic longitude (λ) in radians, the ecliptic latitude (β) in radians and the distance in kilometers.

Parameters:

date - The instant date.

aux - Auxiliary double vector.

out - The out vector with geocentric [lambda, beta, r] in radians and kilometres.

Returns:

The out vector with geocentric [lambda, beta, r] in radians and kilometres.

plutoEclipticCoordinates

public static void plutoEclipticCoordinates(Instant date,
 Vector3b 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.

getJulianDate

public static double getJulianDate(int year,
 int month,
 int day,
 int hour,
 int min,
 int sec,
 int nanos,
 boolean gregorian)

Gets the Julian date number given the Gregorian calendar quantities.

Parameters:

gregorian - Whether to use the Gregorian or the Julian calendar.

Returns:

The julian date number.

getJulianDateCache

public static double getJulianDateCache(Instant instant)

Gets the Julian Date for the given date. It uses a cache.

Parameters:

instant - The date.

Returns:

The Julian Date.

getJulianDate

public static double getJulianDate(Instant instant)

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:

• http://en.wikipedia.org/wiki/Julian_day

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)

getDayFraction

public static double getDayFraction(int hour,
 int min,
 int sec,
 int nanos)

Gets the day fraction from the day quantities.

Parameters:

hour - The hour in 0-24

min - The minute in 0-1440

sec - The second in 0-86400

nanos - The nanoseconds

Returns:

The day fraction

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)

properMotionsToCartesian

public static Vector3d properMotionsToCartesian(double muAlphaStar,
 double muDelta,
 double radVel,
 double ra,
 double dec,
 double distPc,
 Vector3d out)

Converts proper motions + radial velocity into a cartesian vector. See this article.

Parameters:

muAlphaStar - Mu alpha star, in mas/yr.

muDelta - Mu delta, in mas/yr.

radVel - Radial velocity in km/s.

ra - Right ascension in radians.

dec - Declination in radians.

distPc - Distance in parsecs to the star.

Returns:

The proper motion vector in internal_units/year.

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.