Planetary Opposition 2023: Jupiter, Uranus, and Other Planets At Their Brightest
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. In December 2023, the asteroid Vesta will be the brightest celestial object to reach opposition. Find out more about oppositions and get the best dates to see planets and asteroids.
- What does opposition mean in astronomy?
- December 21, 2023: Asteroid 4 Vesta at opposition
- Planetary oppositions
- Upcoming planetary oppositions
- Other upcoming oppositions
- 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.
December 21, 2023: Asteroid 4 Vesta at opposition
On December 21, at 21:34 GMT (04:34 p.m. EST), asteroid 4 Vesta will reach opposition. It’s the best time to observe the asteroid because it will appear at its largest and brightest state in the sky. It will shine in the constellation Orion with a magnitude of 6.4. You won’t be able to observe the asteroid with the naked eye, but you can see it with a small telescope or a pair of binoculars. A large telescope will help you see the asteroid’s oval shape. The best time to view Vesta is at midnight local time when the asteroid reaches its highest point in the night sky.
Vesta is the second-largest object in the Main Asteroid Belt after the dwarf planet Ceres and the brightest asteroid in the Solar System. It has a very bright surface and can sometimes even be seen with the naked eye (although you will need a perfectly dark sky and eagle eyes to spot it).
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
The complete calendar of all the planetary and other celestial events is available in the stargazing app Sky Tonight.
September 8, 2024: Saturn opposition
On September 8, 2024, at 04:27 GMT (00:27 a.m. EDT), Saturn will reach opposition. The Ringed Planet will shine at its brightest with a magnitude of 0.6. To the naked eye, it will look like a yellowish dot; with a pair of binoculars, you may spot Saturn’s oval shape. And you’ll need at least a small 4-inch telescope to see the famous planet’s rings. Look for Saturn in the constellation Aquarius.
For a few days around the opposition, the observers may notice an unusual brightening of Saturn’s rings – known as the Seeliger Effect. During opposition, the Sun shines directly at Saturn from our vantage point, so the planet and its rings’ particles are fully illuminated and cast no shadows. Moreover, the sunlight interacts with the particles in the planet’s rings and reflects many times, making the rings look even brighter.
September 21, 2024: Neptune opposition
Neptune will reach opposition on September 21, 2024, at 00:08 GMT (September 20, 08:08 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.
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
- Nov 5, 2023: 18 Melpomene (mag 8.2), constellation Eridanus.
- Dec 18, 2023: 37 Fides (mag 9.8), constellation Auriga.
- Dec 21, 2023: 4 Vesta (mag 6.6), constellation Orion.
- Dec 22, 2023: 9 Metis (mag 8.4), constellation Gemini.
- Dec 28, 2023: 5 Astraea (mag 9.4), constellation Orion.
- Jan 20, 2024: 354 Eleonora (mag 9.5), constellation Canis Minor.
- Mar 3, 2024: 3 Juno (mag 8.6), constellation Leo.
- Mar 12, 2024: 23 Thalia (mag 9.7), constellation Leo.
- Apr 8, 2024: 532 Herculina (mag 9.1), constellation Bootes.
- May 17, 2024: 2 Pallas (mag 9.0), constellation Hercules.
- June 3, 2024: 43 Ariadne (mag 9.1), constellation Ophiuchus.
- June 28, 2024: 42 Isis (mag 9.4), constellation Sagittarius.
Dwarf planets in opposition
- Nov 22, 2023: 90377 Sedna (mag 20.8), constellation Taurus.
- Mar 30, 2024: 136472 Makemake (mag 17.1), constellation Coma Berenices.
- Apr 21, 2024: 136108 Haumea (mag 17.3), constellation Bootes.
- July 6, 2024: 1 Ceres (mag 7.3), constellation Sagittarius.
- July 23, 2024: 134340 Pluto (mag 15.0), constellation Capricornus.
What planets are in opposition now?
Jupiter is the next planet to reach opposition on November 3, at 10:44 GMT (06:44 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!
Opposition is the best time to observe planets because they shine at their biggest and brightest, visible all night through. The next planet to reach opposition is Jupiter on November 3, 2023. 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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