The sky at the moment of the discovery of Pluto

Pluto’s discovery chart

Lowell Observatory, Flagstaff, Arizona · 18 February 1930 · 16:00

Tropical zodiac, Placidus houses

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The Pluto discovery’s reading
The Pluto discovery’s reading

The hidden planet, found

18 February 1930 · 4:00 pm · Lowell Observatory, Flagstaff, Arizona

☉ Aquarius · ☽ Scorpio · ↑ Leo

Clyde Tombaugh discovered Pluto at Lowell Observatory in Flagstaff, Arizona, at 4:00 PM Mountain Standard Time on 18 February 1930, which was 23:00 UTC. Tombaugh found it with the comparator, studying photographic plates taken on 23 and 29 January. The sky of that afternoon has an Aquarius Sun, a Scorpio Moon and Leo rising, and Pluto itself was in Cancer in the 12th house, the part of a chart that astrology keeps for what lies out of sight.

At the moment of its own discovery, Pluto sat at 17° Cancer in the 12th house, the house of the unseen. In a chart the 12th is the slice of sky just above the eastern horizon, and it's read as the inward, private room: solitude, intuition, the work that happens where nobody is watching. That's a gentle picture for a world too faint for any eye, picked out by patience at a comparator rather than by a glance upward. Pluto was moving retrograde at the time, and Cancer is the sign of home and belonging, which makes this a warm first portrait for the planet this site is named after.

The Sun, Mercury and Mars were all in Aquarius on the afternoon Pluto was found, the sign of science, the future and the idea nobody saw coming. The Sun had reached 29°34', its final degree, less than half a degree from Pisces. Mercury, the planet of observation and notes, sits in the 7th house a tenth of a degree from the Descendant, the point opposite the rising sign that rules what we meet face to face. It's a neat image for an afternoon of comparing one plate with another. Mars makes an easy sextile to Uranus, the planet of discovery, and Uranus also forms an exact square with Saturn: careful method and sudden breakthrough, working on the same problem.

Leo was rising at 3° over Flagstaff, a sign that loves to shine and be seen, and Leo holds the horizon across the whole quarter hour either side of 4:00 PM. The Moon is in Scorpio, the sign modern astrology pairs with Pluto, sitting in the 4th house of roots and foundations: a Moon that rewards depth and the patient search for what lies beneath. Jupiter in Gemini, in the 11th house of shared aims, makes an easy trine to Mars, and Venus has just stepped into Pisces beside the Sun.

WaterAirEarthFire
Air40%

Air moves between people: ideas, conversation and the curiosity that connects one thing to another.

It blows strongest of the four here, so you understand the world by talking it through.

It shows in who you are at your centre, how you think and talk, how you go after things and where luck and growth come easily.

☉Sun in Aquarius☿Mercury in Aquarius♂Mars in Aquarius♃Jupiter in Gemini
The Pluto discovery’s elements

Mostly air, with water next

Tap an element in the picture or on the bar to see which planets feed it. The Sun, Moon and rising sign count extra.

1♆23☽45♄6☿♂7☉♀8♅910♃11♇12AC
House 7 · Aquarius

The Other

partnership · contracts · counterpart☿ ♂

Mercury and Mars sit here.

The Pluto discovery’s houses

The planets gather at the top of the sky

A wintergreen, or teaberry: each leaf is one of twelve houses, a part of life, and each berry is a planet. Hover or tap a leaf or berry to see what’s there, or tap a pattern to light up its leaves.

The Pluto discovery’s crystal

Clear Quartz

An air stone · clarity, focus, amplification

The all-purpose amplifier — it sharpens intention and pairs well with any other stone.

Clear quartz is silicon dioxide in its purest form, one of the most common minerals in the Earth’s crust. Large, water-clear crystals come from Brazil, Madagascar, the Alps and the hills around Hot Springs, Arkansas. The ancient Greeks believed it was ice frozen so hard it could never thaw, and the word crystal comes from their name for it.

Clear quartz is hard enough to carry loose, though it will scratch softer stones it shares a bag with. Keep spheres out of direct sunlight, since a clear ball can focus the sun and scorch whatever sits behind it.

Gift Clear Quartzat Paradise Found

Where the time comes from

When
18 February 1930, 23:00 UTC
Where
Lowell Observatory, Flagstaff, Arizona
Time from
Clyde Tombaugh's handwritten note on the envelope of discovery plate 171, in the Lowell Observatory Archives: “On Feb 18, 1930 at 4:00 PM (Mt. Standard Civil Time) planet X (Pluto) was discovered – using the comparator.” Source
Note
Tombaugh wrote a round 4:00 PM months afterwards, so treat it as give or take a quarter of an hour. The images being compared were photographed on 23 and 29 January 1930.

Questions

What time was Pluto discovered?

At 4:00 PM Mountain Standard Time on 18 February 1930, which is 23:00 UTC. Clyde Tombaugh wrote the time on the envelope of discovery plate 171, now in the Lowell Observatory Archives. The note was written as a round figure months afterwards, so give or take a quarter of an hour; Leo stays rising across that whole range. By 4:45 PM the find had been made known to C.O. Lampland, then V.M. Slipher and E.C. Slipher.

What sign was the Sun in when Pluto was discovered?

Aquarius, at 29°34', in the 8th house. Mercury and Mars were in Aquarius too.

Where was Pluto in its own discovery chart?

At 17°45' Cancer, in the 12th house, moving retrograde. You can read more about what Pluto's sign means in the Pluto sign guide.

More famous moments

Pluto Garden

What did the sky look like when you arrived?

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Planet by planet

Where each planet stood at that moment, and what it stands for. Tap one to find it in the sky.

The twelve houses

Each house is an area of life, fixed to the horizon where you were born. A planet in a house tells you where its energy goes.

Below the horizon the private, inward houses

  1. 1Selfidentity, body, doorway
  2. 2Resourcesvalue, money, what you holdNeptune in Virgo
  3. 3Voicespeech, siblings, daily mind
  4. 4Rootshome, ancestry, inner foundationMoon in Scorpio
  5. 5Playcreativity, romance, children
  6. 6Workroutine, service, body, craftSaturn in CapricornLilith in Aquarius

Above the horizon where a life turns outward

  1. 7The Otherpartnership, contracts, counterpartMercury in AquariusMars in Aquarius
  2. 8The Sharedintimacy, taboo, transformationSun in AquariusVenus in Pisces
  3. 9Horizonphilosophy, meaning, the long journeyUranus in Aries
  4. 10Vocationpublic face, calling, authorityNorth Node in Taurus
  5. 11Tribecommunity, allies, hopes for the futureJupiter in Gemini
  6. 12The Hiddendreams, solitude, the unconsciousPluto in Cancer

The four angles

Ascendant the eastern horizon
Leo rising3°33′ Leo
Midheaven the top of the sky
Aries Midheaven23°14′ Aries
Descendant the western horizon
Aquarius setting3°33′ Aquarius
Imum Coeli beneath your feet
Libra IC23°14′ Libra

The chart, drawn flat

The same sky the way astrologers read it: as the traditional wheel, or as an orrery with Earth at the centre.

♈︎ARIES♉︎TAURUS♊︎GEMINI♋︎CANCER♌︎LEO♍︎VIRGO♎︎LIBRA♏︎SCORPIO♐︎SAGITTARIUS♑︎CAPRICORN♒︎AQUARIUS♓︎PISCESASCMCDSCIC☉︎29°☽︎13°☿︎3°♀︎2°♂︎9°♃︎6°♄︎8°♅︎9°♆︎2°♇︎17°☊︎6°⚸︎0°

Bright lines: the four angles where your local sky met the zodiac. Warm lines between planets: conjunctions and oppositions. Dashed: squares and sextiles. The zodiac is spaced evenly; each planet’s house is listed with it above.

☉︎Sun29°34′ AQU
☽︎Moon13°14′ SCO
☿︎Mercury3°36′ AQU
♀︎Venus2°32′ PIS
♂︎Mars9°27′ AQU
♃︎Jupiter6°55′ GEM
♄︎Saturn8°57′ CAP
♅︎Uranus9°05′ ARI
♆︎Neptune2°16′ VIR ℞
♇︎Pluto17°45′ CAN ℞
☊︎North Node6°20′ TAU ℞
⚸︎Lilith0°28′ AQU

Your chart as text