Conjunctions
Planets passing close together on the sky, and the dates each one disappears into the Sun's glare and comes back out the other side.
Times are UTC throughout, because an instant is the same everywhere and a local rendering would hide which day an event actually falls on for you. Nothing here knows or asks where you are. Every computed instant carries an uncertainty, and most of those are measurements rather than estimates: every build checks the lunar phases against NASA's own published table, the equinoxes, solstices and Earth's apsides against the US Naval Observatory's, and the planetary positions the remaining events are derived from against JPL Horizons. The Moon's perigee and apogee are the one family with no external table to check against, and their cards say so.
20 events
Venus at inferior conjunction
ComputedVenus passes between Earth and the Sun and is not observable. It moves from the evening sky into the morning sky around this date.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury at inferior conjunction
ComputedMercury passes between Earth and the Sun and is not observable. It moves from the evening sky into the morning sky around this date.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mars and Jupiter in conjunction
ComputedThe two planets pass 1.2° apart — about 2 full-Moon widths — and are easily taken in at a glance.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 1.19°
- Elongation from the Sun
- 88° west (morning sky)
- Mars magnitude
- 0.7
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Mercury at superior conjunction
ComputedMercury passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury at inferior conjunction
ComputedMercury passes between Earth and the Sun and is not observable. It moves from the evening sky into the morning sky around this date.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Neptune at conjunction with the Sun
ComputedNeptune passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mars and Jupiter in conjunction
ComputedThe two planets pass 4.3° apart — about 9 full-Moon widths — and are easily taken in at a glance.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 4.26°
- Elongation from the Sun
- 131° east (evening sky)
- Mars magnitude
- -0.4
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Saturn at conjunction with the Sun
ComputedSaturn passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury and Saturn in conjunction
ComputedThe two planets pass 0.6° apart — about 1 full-Moon widths — but only 10° from the Sun, so they sit low in bright twilight and are hard to catch. Wait until the Sun is fully below the horizon.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 0.57°
- Elongation from the Sun
- 10° west (morning sky)
- Mercury magnitude
- -1.1
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Mercury at superior conjunction
ComputedMercury passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Venus and Saturn in conjunction
ComputedThe two planets pass 0.6° apart — about 1 full-Moon widths — and are easily taken in at a glance.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 0.60°
- Elongation from the Sun
- 26° west (morning sky)
- Venus magnitude
- -3.9
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Uranus at conjunction with the Sun
ComputedUranus passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury at inferior conjunction
ComputedMercury passes between Earth and the Sun and is not observable. It moves from the evening sky into the morning sky around this date.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury and Venus in conjunction
ComputedThe two planets pass 4.6° apart — about 9 full-Moon widths — but only 12° from the Sun, so they sit low in bright twilight and are hard to catch. Wait until the Sun is fully below the horizon.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 4.56°
- Elongation from the Sun
- 12° west (morning sky)
- Mercury magnitude
- 3.1
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Mercury and Venus in conjunction
ComputedThe two planets pass 0.5° apart, but only 2° from the Sun: this one is NOT observable, and you must not sweep the area with binoculars or a telescope looking for it. It is a real alignment, not a sight.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 0.51°
- Elongation from the Sun
- 2° west (morning sky)
- Mercury magnitude
- -1.9
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Mercury at superior conjunction
ComputedMercury passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Venus at superior conjunction
ComputedVenus passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Mercury and Jupiter in conjunction
ComputedThe two planets pass 0.6° apart — about 1 full-Moon widths — but only 9° from the Sun, so they sit low in bright twilight and are hard to catch. Wait until the Sun is fully below the horizon.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 0.62°
- Elongation from the Sun
- 9° east (evening sky)
- Mercury magnitude
- -1.1
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Venus and Jupiter in conjunction
ComputedThe two planets pass 0.5° apart, but only 4° from the Sun: this one is NOT observable, and you must not sweep the area with binoculars or a telescope looking for it. It is a real alignment, not a sight.
How exact: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
- Closest separation
- 0.49°
- Elongation from the Sun
- 4° east (evening sky)
- Venus magnitude
- -3.9
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: A minimum of the apparent angular separation of the two planets, located by bisecting the derivative after a daily scan of the geocentric positions. (planet-pair-minimum-separation, version 1.0.0)
Uncertainty: The separation is good to about ten arcminutes — each position is checked against JPL Horizons on every build and agrees to under five — and the instant to a few hours. The pair looks equally close for a night either side.
Where it applies: The separation is geocentric; from the ground it changes by a fraction of a degree with your position, and whether the pair is above the horizon at that hour depends on where you are.
Jupiter at conjunction with the Sun
ComputedJupiter passes behind the Sun as seen from Earth and is not observable for some weeks either side.
How exact: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where this date comes from
Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
Method: The instant the planet's geocentric ecliptic longitude equals the Sun's, both referred to the mean equinox of date; the geocentric distance separates an inferior conjunction from a superior one. (planet-solar-longitude-conjunction, version 1.0.0)
Uncertainty: Within a few hours, from planetary positions checked against JPL Horizons on every build to under five arcminutes.
Where it applies: Not observable from anywhere: the planet is in the same direction as the Sun. Never attempt to look.
Four kinds of date
- Computed
- Derived on this platform from published position series. The algorithm and its version are recorded, and the stated uncertainty is the real one.
- Published prediction
- Taken from an authority's own published prediction. AsteriaStar reproduces it and links the document; it does not recompute it.
- Annual forecast
- Recurs every year at approximately the same point in Earth's orbit. The date shown is the expected one; the exact hour and the strength vary from year to year.
- Planned
- A date somebody intends to meet. Planned dates move, often by months. The timestamp of the last confirmation is shown so you can judge how much the date is worth.
Take this away as a calendar file: subscribe or download the next year of events, or read it as JSON from the Open Data API. Both carry the basis, the method or source, and the uncertainty for every entry.