On Feb. 18, 1930, Clyde Tombaugh discovered Pluto, at that time classified as the ninth planet.

Trans-Neptunian objects (TNOs) are icy bodies that vary widely in size, from large dwarf planets like Pluto and Eris—each ...

For decades, we believed there were nine planets in our solar system—until Pluto was reclassified in 2006. But what if ...

These popular astronomy questions, answered by Astronomy magazine, will help you better understand our universe - and share ...

Take advantage of a special 6-7 planet alignment from Earth's perspective. Planets 'line up' in the skies over California in ...

For the first time, astronomers have imaged dozens of belts around nearby stars where comets and tiny pebbles within them are ...

Does our Solar System have 9 planets or only 8? Astronomers have gone back and forth on that a lot, with Pluto now being classified as a dwarf planet. However, out beyond Neptune there could be ...

In August 2006, the International Astronomical Union made the controversial, but correct, decision to demote Pluto from its ...

According to a recent YouGov poll, 35% of Americans think Pluto is not a planet. But they are all wrong—kind of. To get to the bottom of whether Pluto is a planet, I tracked down planetary scientist ...

(The last time all seven planets aligned was on April 8, 2024, during the total solar eclipse). Aug. 29, 2025: Six planets – Mercury, Venus, Jupiter, Saturn, Uranus and Neptune.

Here are some of this month’s highlights. As we discussed last month, late January and early February will provide a stage for a Planet Parade, with six planets lining up in the night sky.

Many models of the solar system’s formation suggest that Pluto formed much later than planets in the inner solar system, but if it did, it would have missed out on a lot of radioactive materials ...