Is the Solar System still home to nine planets? Catch up on the latest space updates.

Is the Solar System still home to nine planets? Catch up on the latest space updates.

August 24, 2006, is a day that many of us remember vividly. It was the day when Pluto was removed from the list of planets in our Solar System.

As an 11-year-old, I (Sara) can still recall the passionate protest my classmates and I staged during lunch break, chanting “Pluto is a planet.” At the time, I was outraged and inconsolable. However, as I’ve grown older, I have come to accept that Pluto is not a planet.

Similarly, my colleague Rebecca also remembers the re-designation of Pluto to dwarf status. What bothered her was not the scientific reclassification itself, but rather how it was communicated to the public. She felt that astronomers missed an opportunity to explain that this was not a demotion, but rather the discovery of new members of our Solar System, with Pluto being the first.

Fortunately, astronomers now have better media support, and there is a wealth of exciting science to catch up on. Let’s take a look at what you might have missed.

Pluto’s demotion was not a surprise given the discovery of Eris in 2005. Eris, like Pluto, orbits in the outer regions of our Solar System. Although it is smaller than Pluto in terms of radius, it has more mass. This discovery led astronomers to realize that there would likely be more objects like Pluto and Eris as our telescopes improved. Today, we know of five dwarf planets in our Solar System.

The criteria for classifying a celestial body as a planet were established by the International Astronomical Union. Unfortunately, Pluto did not meet all three criteria: it must orbit a star (in our case, the Sun), it must be spherical due to gravity, and it must have cleared its orbit of other objects. It was this third criterion that led to Pluto’s downfall.

But does this mean our Solar System will only have eight planets? Not necessarily. There may be a ninth planet waiting to be discovered.

In 2016, astronomers Konstantin Batygin and Mike Brown from the California Institute of Technology proposed the existence of a ninth planet based on their simulations of the motions of dwarf planets. According to their calculations, this planet would be about ten times the mass of Earth and located about 90 billion kilometers away from the Sun, much farther than Pluto. However, the search for this theoretical planet is challenging due to its faintness and the vastness of our Solar System.

While we continue to search for the ninth planet, astronomers have also made significant progress in finding exoplanets, planets outside of our Solar System. Directly imaging these planets is difficult due to their dimness, so astronomers have developed methods like the radial velocity method and the transit method to detect them. Telescopes like Kepler and TESS have discovered thousands of exoplanets, some of which are similar in size to Earth.

However, these observatories can only provide information about a planet’s size and distance from its star. To determine if a planet could support life, we need telescopes like the James Webb Space Telescope (JWST). The JWST has already made remarkable discoveries, including detecting molecules in the atmospheres of exoplanets. While we have found planets with interesting characteristics like quartz nanocrystals and signs of methane and carbon dioxide, the search for water vapor, a crucial ingredient for life, continues.

As we look forward to the future of planetary studies, we can anticipate exciting developments in 2024. Perhaps the JWST will finally detect water vapor in an exoplanet’s atmosphere. And who knows, we may even be surprised by the discovery of a ninth planet, filling the void left by Pluto.

So stay tuned for more fascinating science to come as we continue to explore the mysteries of our Solar System and beyond.

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