How many planets are there in the solar system?

List of 8 official planets

In order from closest to the Sun, the 8 main planets of the Solar System are:

Mercury

Venus

Earth

Mars

Jupiter

Saturn

Uranus

Neptune

Each planet has its own unique characteristics in terms of size, atmosphere, orbit, and environmental conditions. But they all have one thing in common: they are officially recognized as planets by the International Astronomical Union (IAU).

Illustration photo.

Pluto: The "Demoted" Planet

For nearly 76 years, Pluto was recognized as the ninth planet of the Solar System since its discovery in 1930. However, in 2006, the IAU issued an official definition of the concept of “planet” – and Pluto did not meet the criteria.

To be recognized as a planet, a celestial body must:

Orbiting the Sun.

Has a nearly circular shape due to its own gravity.

Clear the space around its orbit, meaning it doesn't share its orbit with similar objects.

Pluto fails the third criterion, because there are many other small bodies in the Kuiper Belt region where it is located. Therefore, Pluto is "demoted" to dwarf planet status - in the same group as objects such as Eris, Haumea and Makemake.

Reaction from scientists and the public

The removal of Pluto from the list of planets has caused quite a bit of controversy among astronomers and the general public. Many people still have feelings for the “little planet” that was a part of their childhood. However, from a scientific perspective, this decision helps create a clearer and more consistent standard for classifying celestial bodies.

Goodbye Pluto, but it's not the end

Although no longer an official planet, Pluto is still an incredibly interesting celestial body. In 2015, the New Horizons spacecraft flew by Pluto, sending back precious images and data that revealed an icy world with a thin atmosphere and impressive ice mountains.

Meanwhile, astronomers continue to search for undiscovered planets at the far edges of the solar system – there may even be a true “Planet Nine” beyond Neptune.

Conclusion: The Solar System – a miniature universe full of fluctuations

From 9 planets to 8, from Pluto being “demoted” to endless debates, the Solar System has always been a living testament to the constant change of science. And although Pluto is no longer a planet by definition, it is still an indispensable part of the wonderful story of the universe that we are discovering every day.

Thanh Lam (t/h)

Source: https://doanhnghiepvn.vn/cong-nghe/he-mat-troi-co-bao-nhieu-hanh-tinh/20250415111119086