what is rahu ketu peyarchi?

the tamil term for the nodes changing sign. it is treated as a notable event because it only happens once every eighteen months, and the whole axis moves at once.

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rahu and ketu move backwards, and always take two houses

every other transit moves one house at a time. the nodes always move two, they are always exactly opposite, and they walk the zodiac in reverse. here is the mechanism, counted from ur moon, with the eclipse seasons and the nodal return.

OCTOBER 4, 2026 · 11 MIN READ

every other transit moves one house at a time. this one always moves two, and they are always opposite each other.

rahu and ketu are the two ends of a single axis. they are permanently 180 degrees apart, they travel backwards through the zodiac, and they change sign about every eighteen months. so a nodal transit is never a single event. it is a pull in one house and a loosening in the one directly across from it, running at the same time, for a year and a half.

here is the whole mechanism: why they move backwards, what the eighteen month unit can honestly describe, where the eclipse seasons come from, and what actually happens at the nodal return.

the short version

rahu and ketu are the two points where the moon's path crosses the sun's. they are maths, not rock.
they are always exactly opposite, so they always transit two opposite houses at once.
they move retrograde, backwards through the signs, which is why rahu goes from mesha into meena and not into vrishabha.
about eighteen months per sign, and a full circuit in 18.6 years.
eclipses happen only near them. that is the whole reason eclipse seasons arrive twice a year.
the nodal return lands at roughly 18 or 19, 37, and 55 or 56, and the reversal at roughly 9, 28 and 46.
counted from ur moon sign, as with all gochar, which means about a twelfth of the planet is in it with u.

quick facts

What they are: The lunar nodes. The two intersections of the Moon's orbital plane with the ecliptic.
Rahu: The north or ascending node, where the Moon crosses to the north of the Sun's path.
Ketu: The south or descending node, always 180 degrees from Rahu.
Direction: Retrograde. Backwards through the zodiac, effectively always.
Speed: About 18 months per sign. A full circuit takes 18.6 years.
Counted from: The natal Moon sign, as with all classical gochar.
Favourable houses: 3, 6 and 11 from the Moon, the same short list Saturn gets.
Eclipses: Only occur when the Sun and Moon are near the nodes. Roughly every 173 days.

the axis, not the planet

Rahu and Ketu are the two points where the Moon's orbit crosses the plane of the Sun's apparent path. They are not physical bodies. They are the intersections of two circles, and that is why they are always exactly opposite each other.

the moon's orbit is tilted about five degrees to the ecliptic. two tilted circles that share a centre cross in exactly two places, and those two places are on opposite sides. that is the whole geometry, and every strange thing about the nodes falls out of it.

they are always opposite, because two circles cannot cross in three places. they have no brightness, because there is nothing there to light. and they are the only points in the sky where the sun and moon can line up exactly, which is why eclipses are theirs and nobody else's.

the tradition arrived at the same fact from the other end. the old story gives rahu a head and ketu a body, one creature cut in half and left in two pieces that can never be reunited. that is a description of an axis. it is also a better piece of writing than most modern astronomy gets.

why they move backwards

The Moon's orbital plane slowly wobbles, and that wobble drags the crossing points backwards through the zodiac. So Rahu moves from Aries into Pisces, not into Taurus, and the whole axis walks the signs in reverse.

this catches people out constantly. every other graha moves forward through the signs and occasionally appears to loop back for a few weeks. the nodes do the opposite: backwards is their normal state, all the time.

so if rahu is in kumbha now, its next sign is makara. if u are tracking a nodal transit through ur own houses, count down, not up.

there is a small technical fork worth knowing. the mean node is the smoothed average position and it retrogrades without exception. the true node is the actual instantaneous crossing point, and it wobbles enough to pause and creep forward for a few days at a time. most vedic software uses the mean node, and the difference between the two is typically under two degrees. it matters at a sign boundary and almost nowhere else.

eighteen months, and what that can describe

The nodes take about 18 months to cross a sign and 18.6 years to complete a circuit. That puts them between Jupiter at a year per sign and Saturn at two and a half, which is the range where a transit can describe a chapter rather than a mood.

graha	per sign	full circuit	what it can describe
Moon	~2.25 days	~27 days	a mood
Mars	~45 days	~2 years	a burst of effort
Jupiter	~1 year	~12 years	a year with a direction
Rahu and Ketu	~18 months	18.6 years	two houses under pressure at once
Saturn	~2.5 years	~29.5 years	a chapter, and what it costs

eighteen months is long enough that u can look back at it as a period rather than a week. it is also short enough that two of them fit inside one sade sati, which is a useful sense of scale.

two houses at once

Because the nodes are always opposite, a nodal transit always activates a pair of houses: 1 and 7, or 2 and 8, or 3 and 9, and so on. Rahu's house is where the appetite goes. Ketu's house is where the interest quietly drains out.

this is the part that makes nodal transits recognisable when they happen. it is rarely "everything is intense". it is usually "i cannot stop thinking about this one area, and this other one has gone strangely flat", and the two areas turn out to be exactly opposite each other on the chart.

the axis	rahu pulls toward	ketu empties out
1 and 7	urself, ur own image, ur own project	the partnership, the other side of the table
2 and 8	earning it, holding it, naming a price	other people's money and the things u inherited
3 and 9	skill, nerve, the thing u are practising	the belief u were handed and no longer argue for
4 and 10	home, roots, the place u sleep	the job title, the public record
5 and 11	making something, romance, the risk	the network, the group, the income stream
6 and 12	work, routine, the daily grind	retreat, sleep, the cost of being unavailable

counted from ur moon sign, as with everything in classical gochar. the nodes get the same short favourable list saturn does: 3, 6 and 11. everywhere else is read as work.

and the same two refinements apply. vedha can cancel the result outright, and ashtakavarga bindus adjust it to ur own chart. a nodal transit read without either is a claim about a twelfth of the population.

where eclipse season comes from

An eclipse needs the Sun, the Moon and the Earth in a straight line, which can only happen when the Sun and Moon are near a node. So eclipses arrive in the pair of signs the nodal axis currently occupies, roughly every 173 days.

this is the single best argument that the nodes were being tracked as real long before anybody called them astrology. u cannot predict an eclipse without knowing where the crossing points are, and india was predicting eclipses a very long time ago.

it also explains the shape of an eclipse year. two eclipse seasons, about six months apart, both landing in the signs the axis is sitting in. when the axis changes sign, the eclipses change sign with it, and they walk backwards through the zodiac at the same 18.6 year pace.

what the tradition does with that is a separate question, and it is a more cautious one than the internet suggests. sutak is a set of observances, not a prediction, and the vedic position on watching an eclipse is closer to "do less today" than to "something will happen to u".

the nodal return, and the reversal

The nodes come back to their birth position every 18.6 years, so a nodal return lands around ages 18 to 19, 37, and 55 to 56. Halfway between, at roughly 9, 28 and 46, the axis is flipped: Rahu is sitting where Ketu was born.

the return is read as the axis asking the same question it asked at birth, with an adult on the other side of it. the reversal is read as the more uncomfortable of the two, because the house that has spent ur whole life being the one u avoid is now the one being pulled at.

age	what the axis is doing
~9	first reversal. rarely noticed, and not meant to be
~18 to 19	first return. lands on top of every other thing happening at eighteen
~28	second reversal. arrives next to the first saturn return, which is why that stretch is loud
~37	second return. the one people actually describe as a turn
~46	third reversal
~55 to 56	third return, and it overlaps the second saturn return

notice how many of these land on top of each other. 28 and 56 have both a nodal reversal and a saturn return in them, which is a decent structural explanation for why those two ages get talked about more than 33 or 44 do.

how to actually read one

Find where the nodes are now, count the house from your Moon sign, and read the pair rather than the single house. Then check it against your dasha, because a transit describes conditions and the dasha is what decides whether anything comes of them.

four steps, in the order a practitioner would actually use them.

	step	why
1	find ur moon sign	gochar is counted from it, and it needs no birth time
2	count rahu's house from there	ketu's is automatically the seventh from it
3	read the pair as one sentence	the pull and the drain are the same event
4	check the running dasha	a rahu or ketu dasha under a nodal transit is the case worth reading

that last row is the one most transit content skips. the nodes run 18 years of vimshottari between them, rahu for 18 and ketu for 7. a nodal transit landing while the matching dasha is running is a genuinely different reading from the same transit landing in the middle of a venus period, and the tradition puts the dasha first every time.

if all of that sounds like more counting than u want to do on a sunday, that is roughly why we built the app. it does the counting and then says the answer in a sentence.

myths, one at a time

Rahu and Ketu are planets.

They are the two points where the Moon's orbit crosses the ecliptic. No body, no light, and that is not a downgrade: eclipses are theirs precisely because of it.

A Rahu transit brings bad luck.

It describes a house getting an appetite. Whether that is useful depends on the house, the chart under it, and the dasha running. It applies to a twelfth of the planet at once.

The nodes move forward like the other grahas.

They move backwards through the zodiac, effectively always. Any transit piece that walks them forward has every date in it wrong.

Ketu is the bad one.

Ketu is the end of the axis where interest drains out. It is read as a release rather than a loss, and it is also the node the tradition associates with knowing something without being taught it.

You should fear an eclipse in your sign.

An eclipse lands in the sign the axis occupies, which is a twelfth of everyone. Sutak is a set of observances, not a forecast.

Kaal sarp dosha is a transit.

It is a natal pattern: every graha hemmed between the nodes at birth. It has nothing to do with where the nodes are today. We took that one apart here.

faq

how long does rahu stay in one sign?

about eighteen months, and ketu is in the opposite sign for exactly the same stretch. a full circuit of the zodiac takes 18.6 years.

why do rahu and ketu move backwards?

because the moon's orbital plane slowly wobbles, and that drags the two crossing points backwards through the zodiac. so rahu goes from mesha into meena, not into vrishabha.

are rahu and ketu always opposite?

yes, exactly 180 degrees apart, always. they are the two intersections of two tilted circles, and two circles cannot cross in three places.

which houses are good for a rahu transit?

counted from ur moon sign, the classical favourable houses for both nodes are the 3rd, 6th and 11th. that is the same short list saturn gets.

what is the rahu ketu transit called in sanskrit?

rahu ketu peyarchi in tamil usage, or simply the nodal gochar. peyarchi means the change of sign, and it is treated as a notable event because it only happens every eighteen months.

what is a nodal return?

transiting rahu coming back to the sign or degree it occupied at ur birth. it happens roughly every 18.6 years, so around ages 18 to 19, 37, and 55 to 56.

why do eclipses only happen near rahu and ketu?

an eclipse needs the sun, moon and earth in a line, and the only places the moon's path meets the sun's are the two nodes. so eclipses arrive in whichever pair of signs the axis currently occupies.

what is the difference between the mean node and the true node?

the mean node is the smoothed average position, which always retrogrades. the true node is the actual instantaneous crossing point, which wobbles and can creep forward for a few days. most vedic software uses the mean node and the gap is usually under two degrees.

does a rahu transit affect everyone with my moon sign?

the cohort reading does, and that is about a twelfth of everyone alive. vedha can cancel it and ashtakavarga bindus adjust it to ur chart, which is where a shared reading starts becoming ur own.

is the rahu transit worse than sade sati?

they are different instruments. sade sati is saturn spending seven and a half years across three houses from ur moon. a nodal transit is eighteen months across a pair of opposite houses, and it repeats far more often.

what happens when rahu transits my natal moon?

it is one of the more watched positions, read as the mind getting loud and hungry about whatever that house covers. it happens roughly once every 18.6 years and lasts about eighteen months.

do rahu and ketu have a dasha as well as a transit?

yes, and that is the more important of the two. rahu runs eighteen years of vimshottari and ketu runs seven. a nodal transit landing while a nodal dasha is running is the case actually worth reading closely.