Neptune will reach opposition—on the opposite side of the sun in our sky—on September 23, 2025.
Neptune at opposition in 2025
When to see in 2025: Neptune is best visible around its September 23 opposition as it rises in the east at sunset and is visible all night. After opposition, Neptune disappears from the morning sky gradually as it rises and sets four minutes earlier each day. Three months after opposition, i.e., by the end of December 2025, Neptune is visible in the evening sky only as it sets at midnight.
How to identify: Neptune will be located very close to Saturn around its September 23 opposition. As Neptune shines beyond the limit of naked-eye visibility, it can’t be seen with the naked eye. You will need a medium-size telescope to see it.
Closest approach of Neptune in 2025: Neptune will be closest to Earth around its September 23 opposition, when Earth passes between the sun and Neptune. At its closest approach, Neptune will be 28.88 AU, or 4.32 billion kilometers, from Earth.
Brightness at opposition: At its September 23 opposition, Neptune will be brightest for 2025 and will shine with a magnitude of +7.8.
Disk size at opposition: At its September 23 opposition, Neptune will be largest in size for 2025 and will appear 2.4 arcseconds in diameter through a telescope.
Constellation at opposition: At its September 23 opposition, Neptune will be located in the zodiac constellation Pisces, the Fish.
What does “Neptune at opposition” mean?
Neptune reaches opposition when Earth passes between the sun and the 8th planet Neptune.
As the sun and Neptune are on opposite sides of the Earth during opposition, they appear on opposite sides, or 180° apart, in our sky.
As a result, Neptune rises in the east when the sun sets in the west, reaches its highest point in the sky at midnight when the sun is below your feet, and sets in the west when the sun rises in the east.
How often does Neptune reach opposition?
Neptune takes about 165 Earth years to orbit the sun once. So when our Earth makes one full orbit around the sun, Neptune travels 1/165 of the way around the sun. So to create Neptune’s opposition, our Earth would have to travel an extra 1/165 of the way in its orbit, which takes about (1/165)*365 = 2 days to travel.
That’s why Neptune reaches opposition once every 1 year and 2 days, or 367 days.
Neptune’s opposition dates
Here are the dates of Neptune’s opposition from 2025 to 2029, according to NASA:
| Date of opposition | Date of closest approach | Distance of closest approach (A.U.) |
|---|---|---|
| September 23, 2025 | September 23, 2025 | 28.88 |
| September 26, 2026 | September 25, 2026 | 28.88 |
| September 28, 2027 | September 28, 2027 | 28.87 |
| September 30, 2028 | September 29, 2028 | 28.86 |
| October 2, 2029 | October 2, 2029 | 28.86 |
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