Planetary Opposition 2024: Best Time to See Planets
Astronomical opposition is the best time to observe most of the Solar System planets and other celestial bodies. They appear at their largest and brightest state in the night sky. For not to miss any spectacular opposition, use the Sky Tonight astronomy app. Find out more about oppositions and get the best dates to see planets and asteroids.
Contents
- What does opposition mean in astronomy?
- September 29, 2024: asteroid Massalia at opposition
- Planetary oppositions
- Upcoming planetary oppositions 2024-2025
- Other upcoming oppositions
- F.A.Q.
- Bottom line
What does opposition mean in astronomy?
Astronomical opposition means that a planet is located on the opposite side of the Earth from the Sun. From our perspective, it means a planet at opposition is precisely 180 degrees from the Sun in the sky — so, when the Sun sets in the west, a planet appears in the east. In addition to planets, an opposition can be reached by comets, asteroids, and some other Solar System objects. A well-known example of opposition is a Full Moon. During this event, the lunar disk is opposed to the Sun, therefore fully lit by the star’s light.
September 29, 2024: asteroid Massalia at opposition
On September 29, the asteroid 20 Massalia will reach opposition. This is the time when it is at its largest and brightest in the sky. It will have a magnitude of 9.2 and will be visible through a small telescope. Search for Massalia in the constellation Pisces at around midnight local time – this is when it reaches its highest point in the night sky. To locate the asteroid, use the astronomy app Sky Tonight.
Planetary oppositions
What planets can be seen at opposition from the Earth?
Since an opposition can only occur when the Earth is between the Sun and another celestial body, this event happens for the planets further from the Sun than the Earth. These are Mars, Jupiter, Saturn, Uranus, and Neptune.
The planets’ oppositions occur roughly every year when the Earth reaches the proper configuration with them relative to the Sun. The only exception here is Mars. The Red Planet’s orbit and orbital speed are similar to the Earth’s, so the Earth “outraces” Mars only about every 27 months. That’s why Mars oppositions occur only once in about two-three years. Mercury and Venus are located inside the Earth’s orbit, so we’ll never see them at opposition.
How to find a planet at opposition?
To find a planet at opposition, look in the opposite direction from the sunset. The planet will be well-placed for a few weeks around the exact moment of opposition. So, check a forecast for your location, find a date close to the opposition when the skies are clear, and get outside to observe the bright planet.
You can easily locate and identify a planet using a stargazing app like Sky Tonight:
- To locate your desired planet, use the app's search function. Tap the magnifier icon in the bottom-left corner of the main screen and type the object’s name in the search bar. Tap the blue target button next to the matching result, and then tap the blue compass button in the lower right corner of the screen. Move your device in the direction of the white arrow until you see the planet on the screen. This is the direction in which you will find the planet in the real sky above you.
- To identify any bright dot in the sky, launch the app and point your device at the sky. On the app’s interactive sky map, you’ll see what celestial objects are in that direction. You can tap the object to learn its name and tap its name for more information.
At opposition, you can spot most of the planets with the naked eye, but you’ll see them even better through a pair of binoculars or a telescope. For instance, with a small 4-inch telescope, you should be able to observe Saturn’s rings, including the Cassini Division between them.
Why are planetary oppositions interesting?
Opposition is the best time to observe a planet or another celestial body. At that time, objects are fully illuminated by the Sun and shine brightly in the sky. Moreover, planetary oppositions occur near a planet’s closest approach to the Earth, when a planet appears at its biggest. Mars experiences the most striking size change because it’s the closest superior planet to the Earth. Most importantly, an opposition gives us plenty of time for stargazing! A celestial object is seen through the night and well-placed in the midnight sky. It is no coincidence that asteroids and other faint Solar System objects are often discovered at their opposition.
Upcoming planetary oppositions 2024-2025
The complete calendar of all the planetary and other celestial events is available in the stargazing app Sky Tonight.
September 20, 2024: Neptune opposition
Neptune will reach opposition on September 20, 2024, at 22:43 GMT (September 20, 18:43 p.m. EDT). The planet will shine with a magnitude of 7.8 in the constellation Pisces. You can spot Neptune right after sunset, rising in the opposite direction of the Sun. It will reach its highest point around midnight and remain visible until dawn. However, even at its brightest, Neptune may be challenging to see without a telescope. So, grab one if you want to enjoy a clear view of this distant planet.
January 16, 2025: Mars opposition
Mars will reach opposition on January 16, 2025, at 01:17 GMT (January 15, 20225, at 8:17 p.m. ET). This is the most anticipated planetary opposition of all, as Mars oppositions occur only once in 2–3 years. Other planets that can be in opposition (Jupiter, Saturn, Uranus, and Neptune) reach it about every year.
During the opposition, Mars will shine with a magnitude of -1.4 in the constellation Gemini. It will be easily visible to the naked eye. To explore the planet's surface, such as ice caps and brighter and darker areas, use a telescope of at least 50x magnification.
The planet will be in the sky throughout the night, reaching its highest point around midnight. In addition to Mars, you may spot 5 other planets if you start watching at sunset. This is commonly called a planetary parade – you can learn more about it in our dedicated article. To complete the view, the brightest Gemini star Pollux will be shining close to Mars.
Other upcoming oppositions
Not only planets but also comets, asteroids, and other Solar System bodies can reach opposition. Such events are more challenging to spot, so they are more for experienced astronomers. Opposition is also the best time for asteroid hunters. If you want to discover a new asteroid, it’s better to look at night in the direction opposite to the Sun, and maybe you’ll get lucky!
Asteroids in opposition
- September 29, 2024: 20 Massalia (mag 9.2), constellation Pisces.
- October 7, 2024: 39 Laetitia (mag 9.1), constellation Cetus.
- November 13, 2024: 11 Parthenope (mag 9.8), constellation Taurus.
- December 13, 2024: 15 Eunomia (mag 8.2), constellation Auriga.
Dwarf planets in opposition
- October 2, 2024: 120347 Salacia (mag 20.8), constellation Pegasus.
- October 17, 2024: 136199 Eris (mag 18.6), constellation Cetus.
- November 21, 2024: 90377 Sedna (mag 20.7), constellation Taurus.
F.A.Q.
What planets are in opposition now?
Saturn is the next planet to reach opposition on September 8, at 04:27 GMT (00:27 a.m. EDT). Learn more about the planet in our dedicated article.
How often do planetary oppositions occur?
A planetary opposition occurs when the Earth passes between the Sun and a planet. It happens every year for the superior planets. The only exception is the Martian opposition. Since the planet is very close to the Earth and its orbit and orbital speed are similar to the Earth’s, our planet manages to pass between Mars and the Sun only every 27 months, so we get one Martian opposition in about two-three years.
How long does an opposition last?
A planet is said to be “at opposition” at the exact moment of time, but the period of opposition lasts for a few weeks. You can observe the planet on any convenient date around that time. It will rise on the opposite side to the Sun right after sunset, reach the highest point at midnight, and set at dawn.
What is the opposite of opposition in astronomy?
The opposite of opposition in astronomy is a conjunction. During the conjunction of a planet and the Sun, the planet is at the closest distance from the Sun in the sky. It’s the most difficult time to observe the planet because the Sun hinders the view. But there are other astronomical conjunctions that don’t involve the Sun: for instance, planetary conjunctions and lunar-planetary conjunctions. They are quite interesting to observe!
Bottom line
Opposition is the best time to observe planets because they shine at their biggest and brightest, visible all night through. The good news is that you don’t need to catch the exact moment of opposition to enjoy the view. Get a stargazing app like Sky Tonight to easily find a planet in the sky, choose a convenient time, go away from the city lights and observe planetary oppositions in full beauty!
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