BoPlanets is a virtual planetarium, which shows the
positions of the planets in the sun system relative to an observing planet,
which can be selected out of the planets and the sun. The planets can be shown
in various views. In the ecliptic view the Cartesian coordinates, in the
equatorial view right ascension and declination, in the horizontal view azimuth
and altitude of the planets relative to an observing planet are displayed. In
the horizontal view the position of the observer on the observing planet can be
selected out of a list of locations or directly by its longitude and latitude.
A list of rise, transit and set times of a planet,
as seen by an observer on the observing planet, may be generated. Times were
given as GMT date&time or as local date× at the observer's location on the
observing planet.
You may have a look to the epicycles of the planets, when
the earth was seen as the centre of the planet system. Or you may observe the
course of the sun as seen from the mercury, where the sun seems to go backwards
and then forwards again. You may change some of the orbital parameters to see
the effect on the orbital of the planet.
You can let the planets moving by single steps or let them
run continuously. You may vary the step size to let the planets run faster or
you can ask for the static and dynamic orbital parameters of a planet.
If there are questions, suggestions or bugs in the
software then do not hesitate to email to
In the future there may be software updates of BoPlanets.
You may download a new release from:
- http://sourceforge.net/projects/bo-planets/
BoPlanets requires Java run time
environment release jre1.6. If this release is not yet installed
download it from
http://java.sun.com/javase/downloads/index.jsp and install it in <java
install dir>. Add the following directory to the system environment variable
"path":
- <java install dir>jre1.6.0_13/bin
Extract the downloaded zip file to an
installation directory. Open a DOS window and navigate to this installation
directory. BoPlanets will be started by:
- java -jar BoPlanets.jar
- preferred on windows systems: javaw -jar
BoPlanets.jar (or by BoPlanets.bat)
- open Appl-BoPlanets.html in a browser to start
BoPlanets as an applet. First enable the browser to run applets.
The form Select Planets will appear. Select the
observing planet, from which the other planets should be observed. Choose
the planets to be observed. Clicking the start button will open the
main form with the logarithmic ecliptic view of the planets.
The main form consists of the following
elements:
- a menu bar with the menus File, Views, Options,
Orbital Parameters, Rise&Transit&Set and Help
- the images of the selected planets and at the last
position the observer
- a control panel
- the drawing panel showing the movement of the
planets in different views
The menu Views contains the following menu items:
- Ecliptical View: shows the planets at their Cartesian
coordinates of the ecliptic system
- Logarithmic Ecliptical View: as Ecliptical View, but
with logarithmic scaling of the radius vector
- Equatorial View: shows the planets in the equatorial
plan of the observer with right ascension and declination of the planet
above the equatorial plane
- Horizontal View: shows the planets in the horizontal
system of an observer on the observing planet. The location of an observer
is given by geographical longitude and latitude.
- Location (if Horizontal View is selected): select the location of the observer on the observing planet
The menu Options consists of menu items
by which the actual view may be modified.
- in ecliptical (and logarithmic) view the plane to
be shown can be set to x-y, x-z or y-z plane.
- if "show radius vector" is selected, the vector
from the origin to the planet is drawn
- "run forwards" selects the direction of time
forwards; "run backwards" backwards.
- "run step wise":if selected and after the Draw Panel
was left mouse-clicked, the planets move one step.
If the left mouse was pressed in the Draw Panel, the
planets are moving continously till the left mouse is released.
- "run continuously": if selected the planets are moving
continuously till option "run step wise" is selected or the menu item
"stop" of the context menu in planets panel is clicked.
(s. 8. Draw Panel)
Selecting this menu will show the orbital
parameters of the planet, selected in a combo box. In a first table static
and dynamic, but non-editable parameters are displayed. In a second table
static, editable parameters are shown.
By clicking a parameter in the second table it can be modified. Editing
must be terminated by the Enter-key or by clicking another parameter. The
modifications will be effective by clicking the apply-button.
The following parameters can be edited:
- numerical excentricity: valid values [0, 0.9]
- inclination of the orbital plane vs. ecliptic:
valid values [-180, 180]
- argument of perihelion : valid values [-180, 180]
- longitude of ascending node vs. x-axis of the
ecliptic: valid values [-180, 180]
If a non-valid value was entered, a beep sounds and
the focus stays on the last edited cell.
(since release V1.1)
Clicking this menu opens a panel, by
which the times of rise, upper transit and set of a selectable planet are
determined as seen from a location on the observing planet.
Elements of the panel:
- observer: name of the observing planet
- location of the observer: geographical longitude
and latitude, number of time zone and time zone offset in [days]
hours[: minutes]
- a button to browse for named locations
- planet, for which rise, transit and set times are
to be determined.
- Date&Time: date× will be given as GMT
date&time or local date&time
- Start date: the date (as GMT or local date), from
which on the first transit is looked for.
- No of transits: the number of consecutive transits to
be determined
- define rise/set altitude: the altitude of the
planet's centre relative to
the horizon, which
defines rise or set.
- 0°: center at the horizon
- -0.56°: center below the horizon due to atmospheric light refraction on the earth as observing planet
- -6°: center below the horizon, civilian twilight
- -12°: center below the horizon, nautical twilight
- -18°: center below the horizon, astronomical twilight
- text area of the resulting records. Each record
consists of the date× of rise, upper transit and set of the planet.
The azimuth is added to rise and set time, the altitude to the transit
time.
Rise and set occur, when the centre of the planet
reaches the altitude of the rise/set defining altitude relatively to the
horizon of the observer's location. This definition is applied for all objects of the
solar system including the sun. Another definition of the sun's rise and set
does not consider the centre of the sun, but the upper limb of the sun disk,
reaching or leaving the horizon. Using this definition results in rise/set
times being approximately 2 minutes earlier/later compared with the
centre-based times. Applying the twilight definition is meaningful only for the
sun observed by a planet with an atmosphere. The refraction angle of the earth is -0.56 degrees.
Refraction angles of other planets are not known.
The control panel consists of the following elements:
- step size: the size of the time steps, the planets
are moving in earth days. Editing must be terminated by the Ok-Button.
- elapsed msecs: the elapsed time in milliseconds for 365
steps in continuous mode
- a slider, which changes the speed of the moving
planets. (to left: slower, to right: faster)
- date and GMT-time
- in horizontal view the local date and time at the
observing location for the time zone of its location. The given time
zone TZ of a location is its number between -12 and + 12. The time offset
to GMT time is TZ * (duration of a sun day in hours)/24.
This panel shows the positions of the
planets in different views. Clicking this panel with the right mouse opens a context menu with:
- clear screen: clear the screen and show the actual
position
- start planets: start the planets, if the run mode
was set to continuous
- stop planets: stops the movement of the planets
Clicking the left mouse starts the movement of the
planets, in run mode 'step wise' as long as the mouse is released.
The orbital elements (also known as
osculating elements )define the orbital plane of a planet relative to the
ecliptic.
The elements of the picture below:
- vernal equinox of a planet:
The point at which the planet intersects its equatorial plane
in ascending direction.
The vernal equinox of the earth is the x-axis of the ecliptic.
Rotating the line of planet's vernal equinox by the
negative obliquity results in the planet's rotation axis.
- a: big half axis of the planet's ellipse
- e: numerical excentricity:
distance of the sun from the center of the ellipse= a*e
- line of nodes of a planet:
intersection of the orbital plane with the ecliptic
- Ώ: longitude of ascending node
- ω: argument of perihelion
- ωve: argument of planet's vernal equinox
- ν: true anomaly
- E: excentric anomaly:
the position of a planet on a ellipse is defined by the corresponding
position on a circle with radius equal to the big semi axis of the ellipse.
The projection of the vector of this position on the semi axis of the ellipse equals the
projection of the radius vector of the position on the ellipse.
The angle of this vector and the big semi axis at the center of the ellipse
is the excentric anomaly.
- Altitude:
the angle of an object above the horizontal plane of an observer
- Ascending node:
position, where a planet crosses the ecliptic
in ascending direction (north)
- Astronomical unit AU:
mean distance earth-sun, 149,598 Mio km
- Azimuth:
the angle of an object on the observer’s horizontal plane, measured vs. south (east: negative; west: positive)
- Declination:
the angle of an object above the equatorial plane
of the observing planet
- Descending node:
position, where a planet crosses the ecliptic
in descending direction (south)
- Ecliptic:
the reference plane of the planet system.
The x-axis is given by the line sun to the earth, when the earth is at the
position of its ascending vernal eqinox).
- Equatorial plane:
the plane parallel to the equator of a planet
- VernalEquinox:
The point at which a planet intersects its equatorial plane
in ascending direction.
The line to this position is the x-axis of planet's equatorial system.
- GMT date&Time:
the date and time of the Greenwich
meridian, given in date&time of the earth.
- Greenwich meridian:
the meridian with geographical longitude 0°.
As conventon for other planets than earth this meridian is defined as that
one, for which the sun passes its lowest altitude at 2001-Jan-1, 0:0hr.
For the sun as observer the 0-meridian is defined as that one with
Greenwich mean sidereal time GMST=0 at 2001-Jan-1, 0:0hr.
- Greenwich Mean Sidereal Time (GMST):
- the angle of the Greenwich meridian vs. the planet's
vernal equinox in degrees.
When the sun passes its position with the lowest altitude (anti-cumulation),
then GMST=Right Ascension of the planet in planet's fixed heliocentric equatorial system.
- Horizontal plane:
tangential plane at the observation point on a planet given by
geographical longitude and latitude
- Latitude:
angular position on a planet measured vs. equator (north: positive, south: negative)
- Local date&time:
the date&time of the local time
zone=GMT date&time + time zone * (duration of the planets sun day)/24
- Local Mean Sidereal Time (LMST) of a location on a planet with a given longitude:
the angle of the meridian with the given
longitude vs. the planet's vernal equinox. LMST=GMST + longitude
- Location of an observer:
given by longitude and latitude of
the position on the observing planet.
If a location on an observing planet
other than the earth is identified by the name of a city, this location has
the same longitude and latitude as this city on the earth.
- Longitude:
angular position on a planet vs. Greenwich Meridian (east: positive, west: negative)
- Obliquity:
inclination of the orbital plane vs. planet's equatorial plane.
- Orbit:
movement of the planet in it's plane
- Orbital (Keplerian) elements of a planet:
(s. Orbital Elements):
- Major axis:
big semi axis of the ellipse in astronomical units (AU)
- Numerical excentricity:
e= (distance of the sun from
the centre)/major axis
- Inclination:
inclination of the orbital plane versus ecliptic
- Longitude of ascending node:
angle between vernal equinox of aries and the position of the planet crossing the ecliptic from south to north
- Argument of perihelion:
angle on the planet’s orbit between the ascending node and the perihelion
- Orbital period:
time to rotate once around the sun
- Perihelion:
the position of the planet with minimum distance to the sun
- Right ascension:
angle of the position of an object vs. the vernal equinox
in the fixed equatorial system of an observing planet.
- Rise of a planet:
coming from below horizon the centre
of the planet reaches the rise defining altitude relatively to the horizontal
plane of an observer on the observing planet. This is valid for the sun
also.
- Rise/Set defining altitude:
The center of the planet is below the horizon
0°, -0.56° (due to atmospheric
light refraction of the earth), -6 °(civilian twilight), -12° (nautical
twilight) or -18° (astronomical twilight). The only objects of the solar
system, which produce twilight, are the sun and the moon.
- Set of a planet:
coming from above horizon the center
of the planet reaches the set defining altitude relatively to the horizontal
plane of an observer on the observing planet. This is valid for the sun
also.
- Sidereal day:
time to rotate 360 degrees around the axis of rotation (earth: 0.9972 *24 h)
- Sun day:
time to rotate once to the same position of the sun (earth: 24 h)
- Time zone of a location on the observing planet:
there are 24 time zones. The Greenwich meridian has time zone 0, east of
Greenwich meridian time zone >0, west of Greenwich time zone <0. The
difference of time offsets of of two adjacent time zones amounts to duration
of the planets sun day/24.
- vernal equinox:
The point at which the planet intersects its equatorial plane
in ascending direction.
BoPlanets: Copyright (c) Bernd Ostermann 2007;
eMail: ostermann.bernd@arcor.de
IMPORTANT:
THE SOFTWARE IS PROVIDED "AS IT IS",
WITHOUT WARRANTY
OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT
LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE
OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.