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The Astronomy & Astrology of Combustion

If you follow or study astrology at all, you will eventually encounter the concept of combustion. Let’s explore what it means for a planet to be combust.


Combustion is a form of syzygy, occurring when a planet is in relative alignment with the Earth and Sun. When this alignment happens, the light of the Sun blocks out the light of that planet. That planet can no longer be seen from Earth, and it is considered combust.

To illustrate, let’s take the example of Venus.

Below we have a two-dimensional, not-to-scale representation of the relative orbits of Venus around the Sun and the Sun around the Earth.

(Remember: because we are primarily interested in events here on Earth, we measure everything relative to ourselves. In order to accurately identify the position of other planets relative to Earth, it is vital that we acknowledge the astronomical realities of the cosmos i.e. the Earth orbits the Sun. However, for our purposes, the Sun is seen to orbit Earth.)

In the image below, Venus is combust at positions 2, 3 and 4, as well as 6, 7 and 8. Do you see the syzygy of these positions, the alignment of Earth, Sun and Venus?

So, what are we looking at? I have marked 8 positions of Venus in its orbit as seen from Earth.

  • Position 1: Venus is clearly visible in the East, early in the morning before sunrise.

  • Position 2: Venus approaches combustion, becoming difficult to see. The process of its disappearance is its “heliacal setting in the East.”

  • Position 3: Venus is combust and not visible, overcome by the light of the Sun.

  • Position 4: Venus approaches visibility once again, appearing just after sunset. The process of its reappearance is its “heliacal rising in the West.”

  • Position 5: Venus is clearly visible in the West, shining bright in the evening sky.

  • Position 6: Venus approaches combustion again, becoming difficult to see. The process of its disappearance on this side is its “heliacal setting in the West.”

  • Position 7: Venus is combust and not visible, overcome by the light of the Sun.

  • Position 8: Venus approaches visibility again, appearing just before sunrise. This process of this reappearance is its “heliacal rising in the East.”

This is how combustion happens astronomically, and explains why planets are sometimes bright in the sky and other times invisible.

Astronomically, Venus is not visible if it is within a 15 degree arc of the Sun.

Astrologically, Venus is considered combust if it is within a 10 degree arc of the Sun.

Each planet has a specifically defined range when it is considered combust. According to Parashara:

  • Mercury is combust within 17 degrees when direct; 12 degrees when retrograde.

  • Venus is combust within 10 degrees.

  • Mars is combust within 17 degrees.

  • Jupiter is combust within 11 degrees.

  • Saturn is combust within 15 degrees.

Note that only the two inner planets (Mercury and Venus) will operate as shown above.

The outer planets are only combust in positions 2, 3 and 4, when the Sun is between Earth and them. If they are in positions 6, 7 and 8, Earthlings must look in the opposite direction from the Sun to see them.

For a visual example of this, see the image below showing Saturn’s orbit (again, not even close to scale or proportion; simply a graphical demonstration of the principle).

This image also illustrates the concept of degrees of arc relative to the Sun. Clearly, Saturn is combust at 0 degrees and is not combust at 180 degrees from the Sun. Venus, however, is combust at both 0 and 180 degrees.

Make sense?


Now let’s discuss the astrological implications of combustion.

Combustion depletes the power of any given planet. Its light — the visible expression of its influence — is temporarily imperceptible to Earthlings. Out of sight, out of mind, is it not?

The Sun is, of course, the source of all light, life and power (heat) in the solar system. It grows our food, warms our bodies and lights our days. What a miraculous source of infinite generosity!

AND! The Sun is simultaneously capable of burning everything to the ground — scorching the soil and torching delicate skin with deadly force. Same source, same energy, different outcome.

Have you ever walked outside in the morning and felt enlivened by the invigorating sense of the Sun on your skin? Me too.

Have you ever spent a day doing nothing but lying in the Sun and afterwards been completely exhausted? Me too.

In order to reach Earth, the light of a combust planet must pass through the filter of the Sun. This filter reduces the quantity and quality of light that makes it through, and imprints a solar quality onto what does make it through.

Let’s use Venus as an example again. Venus is the Lover, associated with all things sensual, pleasurable, beautiful. You can imagine a combust Venus as being like a romantic suitor who starts out bright, dazzles you like a flash in the pan then just as quickly burns out, perhaps scalding you a bit with embarrassed resentment as you let the wind carry their ashes away.

That’s another quality of combustion — it can add a sharp edge to a planets energy, the way humans tend to get irritated and impatient when we’re hot and tired.

Combust planets are like a matchstick that’s already been lit. Have you ever tried to light a match whose tip is black not red? Me too. It doesn’t work, does it? How frustrating.

It’s like trying to lift weights after spending an hour in the sauna — there’s just no spark left in those soft, floppy muscles.

There are occasions when combustion is not completely depleting. A combust planet can actually borrow some of the Sun’s energy to amplify its own power and influence. This depends on the specific arrangement and relative rulership of the Sun and the combust planet. This is a more technical lesson best saved for a more in-depth class.

Concluding Questions

Okay for now. I’ll leave you with some questions to contemplate. Please leave a comment or reach out to me with your responses and let me know if you have any questions for me!

  • When have you experienced combustion in your own life?

  • Is there a particular occasion that jumps out? Or is it a frequent occurrence?

  • Do you have any combust planets in your chart? Which ones?

  • Can you think of any more similes/metaphors to describe combustion? (e.g. the matchstick or lifting weights after the sauna)

Let me know what you come up with!

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