© NASA/New Horizons

134340 Pluto at opposition

Dominic Ford, Editor
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The sky at

Across much of the world 134340 Pluto will reach opposition, when it lies opposite to the Sun in the sky. Lying in the constellation Sagittarius, it will be visible for much of the night, reaching its highest point in the sky around midnight local time.

From Seattle however, it will not be readily observable since it will lie so far south that it will never rise more than 19° above the horizon.

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A close approach to the Earth

At around the same time that 134340 Pluto passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest.

This happens because when 134340 Pluto lies opposite to the Sun in the sky, the Earth passes between 134340 Pluto and the Sun. The solar system is lined up with 134340 Pluto and the Earth on the same side of the Sun, as shown by the configuration labelled perigee in the diagram below:


When a planet is at opposition, the solar system is aligned such that the planet lies on the same side of the Sun as the Earth. At this time, the planet makes its perigee, or closest approach to the Earth. Not drawn to scale.

In practice, however, 134340 Pluto orbits much further out in the solar system than the Earth – at an average distance from the Sun of 39.82 times that of the Earth, and so its brightness does not vary much as it cycles between opposition and solar conjunction.

Observing 134340 Pluto

At opposition, 134340 Pluto is visible for much of the night. When it lies opposite to the Sun in the sky, this means that it rises at around the time the Sun sets, and it sets at around the time the Sun rises. It reaches its highest point in the sky at around midnight local time.

But even when it is at its closest point to the Earth, 134340 Pluto is so distant from the Earth that it is not possible to distinguish it as more than a star-like point of light, even through a telescope.

A chart of the path of 134340 Pluto across the sky in 2021 can be found here, and a chart of its rising and setting times here.

At the moment of opposition, 134340 Pluto will lie at a distance of 33.31 AU, and reach a peak brightness of magnitude 14.9. Its celestial coordinates at the moment it passes opposition will be:

Object Right Ascension Declination Constellation Magnitude Angular Size
134340 Pluto 19h51m20s 22°34'S Sagittarius 14.9 0.0"

The coordinates above are given in J2000.0.

Over the weeks following its opposition, 134340 Pluto will reach its highest point in the sky four minutes earlier each night, gradually receding from the pre-dawn morning sky while remaining visible in the evening sky for a few months.

The sky on 17 July 2021
Sunrise
05:27
Sunset
21:03
Twilight ends
23:43
Twilight begins
02:51

7-day old moon
Waxing Gibbous

65%

7 days old

Planets
Rise Culm. Set
Mercury 04:13 12:07 20:00
Venus 08:07 15:18 22:29
Moon 14:05 19:39 01:00
Mars 07:52 15:05 22:18
Jupiter 22:35 03:44 08:52
Saturn 21:44 02:24 07:03
All times shown in PDT.

Source

The circumstances of this event were computed using the DE430 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).

This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.

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17 Jul 2021  –  134340 Pluto at opposition
20 Jul 2022  –  134340 Pluto at opposition
22 Jul 2023  –  134340 Pluto at opposition
23 Jul 2024  –  134340 Pluto at opposition

Image credit

© NASA/New Horizons

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