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The aim of this project is to provide users with a set of small generic routines useful above all in astronomical and astrophysical context, written in Julia.
Included are also translations of some
IDL Astronomy User's Library
procedures, which are released under terms of
BSD-2-Clause License.
AstroLib.jl's functions are not drop-in replacement of those procedures, Julia
standard data types are often used (e.g., DateTime
type instead of generic
string for dates) and the syntax may slightly differ. Refer to the
documentation of the functions for details.
Note: this project is a work-in-progress, only few procedures have been translated so far. In addition, function syntax may change from time to time. Check TODO.md out to see how you can help. Volunteers are welcome!
AstroLib.jl
is available for Julia 0.6 and later versions, and can be
installed with
Julia built-in package manager.
In a Julia session run the command
julia> Pkg.update()
julia> Pkg.add("AstroLib")
Older versions are also available for Julia 0.4 and 0.5.
Note that, in order to work, a few functions require external files, which are automatically downloaded when building the package. Should these files be missing for some reason, you will be able to load the package but some functions may not work properly. You can manually build the package with
julia> Pkg.build("AstroLib")
After installing the package, you can start using it with
using AstroLib
Many functions in AstroLib.jl
are compatible with
Measurements.jl
package, which
allows you to define quantities with uncertainty and propagate the error when
performing calculations according to
propagation of uncertainty rules.
For example:
using AstroLib, Measurements
mag2flux(12.54 ± 0.03)
# => 3.499451670283562e-14 ± 9.669342299577655e-16
AstroLib.jl
defines a new Observatory
type. This can be used to define a
new object holding information about an observing site. It is a
composite type
whose fields are
name
(AbstractString
type): the name of the sitelatitude
(Real
type): North-ward latitude of the site in degreeslongitude
(Real
type): East-ward longitude of the site in degreesaltitude
(Real
type): altitude of the site in meterstz
(Real
type): the number of hours of offset from UTC
The type constructor Observatory
can be used to create a new Observatory
object. Its syntax is
Observatory(name, lat, long, alt, tz)
name
should be a string; lat
, long
, and tz
should be anything that can
be converted to a floating number with ten
function; alt
should be a real
number.
A predefined list of some observing sites is provided with
AstroLib.observatories
constant. It is a dictionary whose keys are the
abbreviated names of the observatories. For example, you can access information
of the European Southern Observatory with
julia> obs = AstroLib.observatories["eso"]
Observatory: European Southern Observatory
latitude: -29.256666666666668°N
longitude: -70.73°E
altitude: 2347.0 m
time zone: UTC-4
julia> obs.longitude
-70.73
You can list all keys of the dictionary with
keys(AstroLib.observatories)
Feel free to contribute new sites or adjust information of already present ones.
The package provides Planet
type to hold information about Solar System
planets. Its fields are
-
Designation:
name
: the name
-
Physical characteristics:
radius
: mean radius in meterseqradius
: equatorial radius in meterspolradius
: polar radius in metersmass
: mass in kilogram
-
Orbital characteristics (epoch J2000):
ecc
: eccentricity of the orbitaxis
: semi-major axis of the orbit in metersperiod
: sidereal orbital period in seconds
The constructor has this syntax:
Planet(name, radius, eqradius, polradius, mass, ecc, axis, period)
The list of Solar System planets, from Mercury to Pluto, is available with
AstroLib.planets
dictionary. The keys of this dictionary are the lowercase
names of the planets. For example:
julia> AstroLib.planets["mercury"]
Planet: Mercury
mean radius: 2.4397e6 m
equatorial radius: 2.4397e6 m
polar radius: 2.4397e6 m
mass: 3.3011e23 kg
eccentricity: 0.20563069
semi-major axis: 5.790905e10 m
period: 5.790905e10 s
julia> AstroLib.planets["mars"].eqradius
3.3962e6
julia> AstroLib.planets["saturn"].mass
5.6834e25
Every function provided has detailed documentation that can be accessed at Julia REPL with
julia> ?FunctionName
or with
julia> @doc FunctionName
Full documentation of all functions can be accessed at https://astrolibjl.readthedocs.io/. There you can find the complete list of all functions provided by this library. You can also download the manual in PDF format from https://media.readthedocs.org/pdf/astrolibjl/latest/astrolibjl.pdf.
You can contribute to the project in number of ways. You can translate more routines from IDL Astronomy User's Library or provide brand-new functions and improve existing ones. Also bug reports are encouraged.
This is not the only effort to bundle astronomical functions written in Julia language. Other packages useful for more specific purposes are available at https://juliaastro.github.io/.
In addition, there are similar projects for Python (Python AstroLib) and R (Astronomy Users Library).
The AstroLib.jl package is licensed under the MIT "Expat" License. The original author is Mosè Giordano.