<p><a href="http://ssd.jpl.nasa.gov/horizons.cgi#top" rel="nofollow noreferrer">Horizons Ephemeris generator</a> can give you a planet's position and velocity vectors at a specified time.</p>

<p>This is one set of possible options:</p>

<p><img src="https://i.sstatic.net/BFbfc.png" alt="enter image description here"></p>

<p>Clicking <strong>Generate Ephemeris</strong> on that page will give you position and velocity vectors:</p>

<p><img src="https://i.sstatic.net/h6kAv.png" alt="enter image description here"></p>

<p>Above the position and velocity vectors are the Julian date as well as the more conventional date.</p>

<p>Wikipedia can give the masses of the sun and planets.</p>

CC BY-SA 3.0
2014-05-13T07:20:40.933Z
2014-05-13T07:20:40.933Z
HopDavid
<p>I was able to get the Cartesian orbital vectors for all the major bodies from HORIZON at the J2000 epoch only.  I could extend the coverage forward thru time. It’s easy to get data overload doing this. My simulation is modeled using the Laws of Gravitation and Motion alone.  This gives results that are surprisingly close to those published.  Running the solar system backwards (by reversing the velocity vectors) has given me the initial vectors back to 1900.  This is all I needed and the results were close enough for my purposes.  I still have the CSV  files.</p>

<p>I have also have had all sorts of problems with the horizons interface.  For instance changing the date had no effect on the value of the vectors. i.e.: all specified start dates have the same values.  Lately, I have not been able to duplicate this feat.  There are obviously some serious problems with this interface, especially lately.</p>

<p>I know the data I got was correct because it correlates, perfectly, with published events, e.g.: the recent transit of Mercury.</p>

<p>I too am still looking for this type of data.</p>

CC BY-SA 3.0
2016-05-19T22:45:13.417Z
2016-05-19T22:45:13.417Z
Abe
<p>What language are you writing this simulation in? Is it 2D or 3D? Do you only need positions and velocities for our solar system planets?</p>

<p>I've done this exact thing (simulated the solar system in Fortran) and I didn't need exact initial positions, all I needed were initial radii (in AU from the Sun/centre of mass) and initial velocities. Use a random number generator to distribute the planets at random places along their orbits. In Fortran, this looked like:</p>

<pre><code>CALL RANDOM_NUMBER(randNum)
degrees = 2*3.141592653
theta(1:15) = degrees*randNum(1:15)
</code></pre>

<p>And there I have an array of 15 random radial positions. You can obtain initial velocities of our solar system's planets from any reputable resource.</p>

CC BY-SA 3.0
2014-05-13T01:33:14.280Z
Wouldn't this solution assume planets have circular orbits?
Isracg
CC BY-SA 3.0
2014-05-13T01:34:58.953Z
Yeah, it does, unfortunately. Luckily for us though, it's a reasonable assumption. Which planets are you attempting to simulate? It'd help a bit more if we knew more about your project's initial parameters and goals.
IronWaffleMan
CC BY-SA 3.0
2014-05-13T01:38:54.707Z
Well firstly I'm doing this in C# using OpenCL and OpenGL. I'm using the naive O(n^2) algorithm as this was the easiest to implement in OpenCL. At first I tried to simulate the milkyway-andromeda collision but this turned out to be really slow, so now I'm only trying to simulate our solar system in 2D.
Isracg
CC BY-SA 3.0
2014-05-13T01:44:43.417Z
OK, so... C# is suited far less for this kind of scientific computing than something like C/C++/Fortran. What are you using OpenCL/GL for? 
Simulating the solar system is far easier than the collision of billions of stars, yeah. For starters, unless you really care about it, you can ignore Mercury (it doesn't affect anything else). Are you simulating this to try to see how it reacts to instability, or some other end goal?
IronWaffleMan
CC BY-SA 3.0
2014-05-13T01:48:33.913Z
Well I'm most familiar with C# than Fortran, and I'm using OpenGL for visualization and OpenCL for parallelism My end goal is visualizing the planets orbits around the sun.
Isracg
CC BY-SA 3.0
2014-05-13T01:50:36.003Z
Ahh, well that makes sense. I've not actually done visualisation of my simulation's results (the results for me were a huge CSV file), so I'm afraid I can't help you much for that. It doesn't sound like you're after immense precision, so my answer regarding initial positions will work fine for you.
IronWaffleMan
CC BY-SA 3.0
2014-05-13T01:26:17.920Z
2014-05-13T01:26:17.920Z
IronWaffleMan
<p>As the title suggests, I'm in need of a set of data of our solar system. Similar to this <a href="http://bima.astro.umd.edu/nemo/archive/#iau25" rel="nofollow noreferrer">http://bima.astro.umd.edu/nemo/archive/#iau25</a>, but more specifically, the Dubinsky Milky Way-Andromeda data.</p>

<p>I'm creating a n-body simulation for school and can't seem the find any initial particle conditions that I could use to simulate our solar system in the software I'm developing. I need initial positions, velocity and mass. </p>

<p>Any idea where I could find this?</p>

<solar-system><software><n-body-simulations>
Where can I find a set of data of the initial conditions of our solar system?
Isracg
# Where can I find a set of data of the initial conditions of our solar system?

(Asked by: username_0 on 2014-05-13)

As the title suggests, I'm in need of a set of data of our solar system. Similar to this <http://bima.astro.umd.edu/nemo/archive/#iau25>, but more specifically, the Dubinsky Milky Way-Andromeda data.

I'm creating a n-body simulation for school and can't seem the find any initial particle conditions that I could use to simulate our solar system in the software I'm developing. I need initial positions, velocity and mass.

Any idea where I could find this?

**Tags:** solar-system, software, n-body-simulations

---

## 3 answers

### Answer by username_1 on 2014-05-13. Score: 4 | Accepted answer

[Horizons Ephemeris generator](http://ssd.jpl.nasa.gov/horizons.cgi#top) can give you a planet's position and velocity vectors at a specified time.

This is one set of possible options:

![enter image description here](https://i.sstatic.net/BFbfc.png)

Clicking **Generate Ephemeris** on that page will give you position and velocity vectors:

![enter image description here](https://i.sstatic.net/h6kAv.png)

Above the position and velocity vectors are the Julian date as well as the more conventional date.

Wikipedia can give the masses of the sun and planets.


---

### Answer by username_2 on 2016-05-19. Score: 2

I was able to get the Cartesian orbital vectors for all the major bodies from HORIZON at the J2000 epoch only. I could extend the coverage forward thru time. It’s easy to get data overload doing this. My simulation is modeled using the Laws of Gravitation and Motion alone. This gives results that are surprisingly close to those published. Running the solar system backwards (by reversing the velocity vectors) has given me the initial vectors back to 1900. This is all I needed and the results were close enough for my purposes. I still have the CSV files.

I have also have had all sorts of problems with the horizons interface. For instance changing the date had no effect on the value of the vectors. i.e.: all specified start dates have the same values. Lately, I have not been able to duplicate this feat. There are obviously some serious problems with this interface, especially lately.

I know the data I got was correct because it correlates, perfectly, with published events, e.g.: the recent transit of Mercury.

I too am still looking for this type of data.


---

### Answer by username_3 on 2014-05-13. Score: 0

What language are you writing this simulation in? Is it 2D or 3D? Do you only need positions and velocities for our solar system planets?
I've done this exact thing (simulated the solar system in Fortran) and I didn't need exact initial positions, all I needed were initial radii (in AU from the Sun/centre of mass) and initial velocities. Use a random number generator to distribute the planets at random places along their orbits. In Fortran, this looked like:
CALL RANDOM_NUMBER(randNum)
degrees = 2*3.141592653
theta(1:15) = degrees*randNum(1:15)

And there I have an array of 15 random radial positions. You can obtain initial velocities of our solar system's planets from any reputable resource.

> **Comments:**
> **username_0**: Wouldn't this solution assume planets have circular orbits?  
> **username_3**: Yeah, it does, unfortunately. Luckily for us though, it's a reasonable assumption. Which planets are you attempting to simulate? It'd help a bit more if we knew more about your project's initial parameters and goals.  
> **username_0**: Well firstly I'm doing this in C# using OpenCL and OpenGL. I'm using the naive O(n^2) algorithm as this was the easiest to implement in OpenCL. At first I tried to simulate the milkyway-andromeda collision but this turned out to be really slow, so now I'm only trying to simulate our solar system in 2D.  
> **username_3**: OK, so... C# is suited far less for this kind of scientific computing than something like C/C++/Fortran. What are you using OpenCL/GL for?  Simulating the solar system is far easier than the collision of billions of stars, yeah. For starters, unless you really care about it, you can ignore Mercury (it doesn't affect anything else). Are you simulating this to try to see how it reacts to instability, or some other end goal?  
> **username_0**: Well I'm most familiar with C# than Fortran, and I'm using OpenGL for visualization and OpenCL for parallelism My end goal is visualizing the planets orbits around the sun.  
> **username_3**: Ahh, well that makes sense. I've not actually done visualisation of my simulation's results (the results for me were a huge CSV file), so I'm afraid I can't help you much for that. It doesn't sound like you're after immense precision, so my answer regarding initial positions will work fine for you.  

---

