The solar system had nine planets. Maybe he's still doing it? Here's the latest space news today

Some of us remember August 24, 2006 as if it were yesterday. That was the day Pluto was expelled from the exclusive "Planetary Club".

Even famous astronomers known for their public character stumbled upon mostly unapologetic explanations. It was a missed opportunity. What was badly advertised as a demotion was actually the discovery of exciting new organs in our solar system, the first of which was Pluto.

The good news is that astronomers have better media support now, and there is a lot of amazing science to catch. Let's dwell on what you may have missed.

Return to shocking demotion

Pluto's fate was almost certainly decided on the day Iris was discovered in 2005. Like Pluto, Iris orbits on the outskirts of our solar system. Although its radius is smaller than Pluto's, it has a greater mass.

Astronomers have concluded that the discovery of objects like Pluto and Iris will only become more common when our telescopes become more powerful. They were right. Today there are five known dwarf planets in the solar system.

The conditions for what is classified as a "planet" as opposed to a "dwarf planet" were determined by the International Astronomical Union. In short, Pluto was not targeted in 2006. It did not meet the three criteria for a complete planet:

It must orbit a star (in our solar system it will be the sun)

It must be large enough that gravity forced it to take a spherical shape

It must be large enough that its gravity can remove any other objects of the same size close to its orbit.

The third criterion was the fall of Pluto. He did not clear the area next to him of other things.

Is our solar system destined to contain only eight planets? Not necessarily. There may be another one waiting to be found.

Is there a ninth planet?

With the discovery of new and distant dwarf planets, astronomers eventually realized that the movements of dwarf planets around the sun were not entirely logical. We can use complex simulations in supercomputers to model how gravitational reactions occur in a complex environment like our solar system.

In 2016, astronomers Konstantin Batijin and Mike Brown of the California Institute of Technology concluded — after modeling dwarf planets and their observed trajectories — that mathematically there must be a ninth planet. Their models determined that the mass of this planet should be about ten times that of Earth, located about 90 billion kilometers from the sun (about 15 times farther than Pluto). It's a very bold claim, and some are still skeptical.

One might assume that it is easy to determine whether such a planet exists or not. Just point the telescope at where you think it is and look, right? If we could see galaxies billions of light-years away, shouldn't we be able to detect the ninth planet in our solar system? Well, the problem is how bright this theoretical planet is. The best estimates indicate that it is located at the maximum depth of the largest telescopes on Earth. In other words, it can be 600 times fainter than Pluto.

But that doesn't stop us from looking. In 2021, a team using the Atacama Cosmology Telescope published the results of their search for the motion of a ninth planet on the outskirts of the solar system.

While they could not confirm his existence, they submitted ten candidates for further follow-up. Perhaps only a few years away from knowing what lies on the outskirts of our planetary neighborhood.

Finding exoplanets

Although we have telescopes that can detect galaxies from the early years of the universe, we still can't easily image planets just outside our solar system, also called exoplanets.

The reason can be found in basic physics. Planets emit very faint red wavelengths of light, so we can only see them clearly when they reflect the light of their star. The farther away the planet is from its star, the harder it is to see.

Astronomers knew they had to find other ways to search for planets in foreign star systems. Before Pluto's reclassification, they had already discovered the first exoplanet, 51 Pegasi B, using the radial velocity method.

So astronomers came up with another way to find exoplanets: the method of transit. When Mercury or Venus passes in front of the sun, they block a small amount of sunlight. Using powerful telescopes, we can look for this phenomenon in distant star systems as well.

We do this via the Kepler Space Telescope and the Exoplanet Survey Transit Satellite (TESS). Both have observed tens of thousands of stars and discovered thousands of new planets, dozens of them roughly the same size as Earth. But these observatories can only tell us the size of the planet and its distance from its star. They can't tell us if the planet hosts life. And for this we need the James Webb Space Telescope.

Looking for life

The James Webb Space Telescope (JWST) has just finished its first and a half year of science. Among his many achievements is the discovery of particles in the atmospheres of exoplanets, an achievement made possible by the method of transit.

One of these exoplanets, WASP-17, is also known as "hot Jupiter." It appears to have been snatched from a page in a science fiction novel, with evidence of quartz nanocrystals in its clouds.

The field of planetary studies is developing and 2024 seems promising. Perhaps the James Webb Space Telescope will finally produce signs of the presence of water vapor in the atmosphere of an exoplanet. Who knows, we might have a ninth planet that surprises us all, to fill the void left by Pluto.

Stay tuned for exciting science to come.