Earth-Sun Vector, Ecliptic to Equatorial Coordinates

In summary, The JPL Horizons website provides the earth-sun vector in the default reference plane "ecliptic and mean equinox of reference epoch" for an astrophysics project in Python. To convert this vector into equatorial coordinates, the reference plane can be changed to "Earth mean equator and equinox of reference epoch". To convert from equatorial to ecliptic coordinates, a simple rotation about the x-axis by the obliquity of the ecliptic at the epoch time is needed. The tilt of the ecliptic relative to the celestial equator is 23.44 degrees or 84381.448 arc seconds.
  • #1
science.girl
103
0
I'm writing some code in Python for an astrophysics project, and I need some help. The JPL Horizons website gives the earth-sun vector in the default reference plane "ecliptic and mean equinox of reference epoch". I need to convert this vector (3 vectors, actually, reproduced below) into equatorial coordinates.

R1 = vector(-1.578367764168768E-02,1.016223492126721E+00,-2.062339622509254E-05)
R2 = vector(-1.340151802889625E-01,1.007749050898379E+00,-2.428725690505359E-05)
R3 = vector(-3.319485124441679E-01,9.608466316506223E-01,-1.853950030885721E-05)

Now, I have two questions. Will changing the reference plane to "Earth mean equator and equinox of reference epoch" convert the given vectors to equatorial coordinates?

Could someone explain how to convert these vectors from equatorial to ecliptic (either mathematically or in Python)?
 
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  • #2
By the way, feel free to assume the tilt of the ecliptic relative to the celestial equator is e=23.44 degrees.
 
  • #3
It's a simple rotation about the x-axis by the obliquity of the ecliptic at the epoch time, 12:00 UT on January 1, 2000. Rather than 23.44 degrees you would be better of using 84381.448 arc seconds.
 
  • #4
D H said:
It's a simple rotation about the x-axis by the obliquity of the ecliptic at the epoch time, 12:00 UT on January 1, 2000. Rather than 23.44 degrees you would be better of using 84381.448 arc seconds.

Thank you for the clarification!
 

What is the Earth-Sun Vector?

The Earth-Sun Vector refers to the imaginary line connecting the center of the Earth to the center of the Sun. It is used in astronomy to understand the relative position and movement of the Earth and the Sun in space.

What are Ecliptic Coordinates?

Ecliptic Coordinates are a type of celestial coordinate system that is based on the position of the Earth in its orbit around the Sun. It is used to locate objects in the sky and to track their movement relative to the Earth's orbit.

What are Equatorial Coordinates?

Equatorial Coordinates are a type of celestial coordinate system that is based on the Earth's rotational axis. It is used to locate objects in the sky and to track their movement relative to the Earth's rotation.

How are Ecliptic and Equatorial Coordinates related?

Ecliptic and Equatorial Coordinates are related through the concept of precession. Precession is the slow, continuous change in the orientation of the Earth's axis, which causes the celestial coordinate systems to change over time. As a result, the ecliptic and equatorial coordinate systems are not fixed and constantly shift in relation to each other.

Why are Ecliptic and Equatorial Coordinates important in astronomy?

Ecliptic and Equatorial Coordinates are important in astronomy because they provide a standardized way to locate and track objects in the sky. By using these coordinate systems, astronomers can accurately communicate the position of celestial objects and make observations and measurements that help us better understand the universe.

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