Pluto: The 'Valence' Planet of Our Solar System

Image: Northern hemisphere of Pluto in true color, taken by NASA's New Horizons probe in 2015

Source: Wikipedia

Pluto is a dwarf planet in the Kuiper Belt, a region of icy bodies beyond the orbit of Neptune. It was discovered in 1930 by Clyde Tombaugh, and for many years it was considered to be the ninth planet in our solar system. However, in 2006, the International Astronomical Union (IAU) reclassified Pluto as a dwarf planet, along with Ceres, Eris, Haumea, and Makemake.

There are a few reasons why Pluto was demoted to dwarf planet status. First, it is much smaller than the other planets in our solar system. Pluto is only about half the size of Earth's moon, and it has a much lower mass. Second, Pluto's orbit is highly eccentric, meaning that it is much more elliptical than the orbits of the other planets. Third, Pluto shares its orbit with many other Kuiper Belt Objects (KBOs), which means that it is not the dominant object in its orbit.

Despite being demoted, Pluto is still a fascinating object. It has a complex surface, with mountains, craters, and even glaciers. It also has a thin atmosphere, and scientists believe that it may have a subsurface ocean.

In 2015, the New Horizons spacecraft flew by Pluto, providing us with our first close-up images of the dwarf planet. These images revealed a world that was even more amazing than we had imagined. Pluto has a heart-shaped region on its surface, as well as a variety of other features that have never been seen before.

Image: A detailed view of Tombaugh Regio; a constructed mosaic of monochrome images by New Horizons.

Image Source: A close-up view of Pluto

Why Pluto Was Originally Considered a Planet

Pluto was initially considered a planet because it met the criteria that were used to define a planet at the time. These criteria were:

• It had to orbit the Sun.

• It had to be massive enough that its gravity had cleared the neighborhood around its orbit.

Pluto met both of these criteria. It orbits the Sun, and it is massive enough that its gravity has cleared the neighborhood around its orbit of other objects. 

Now a ‘Dwarf’ planet

However, in 2006, the IAU redefined the term "planet" to exclude Pluto. The new definition of a planet is:

• It has to orbit the Sun.

• It has to be massive enough that its gravity has pulled it into a nearly round shape.

• It has to have cleared the neighborhood around its orbit.

Pluto does not meet the third criterion, because it shares its orbit with many other Kuiper Belt Objects. As a result, it was reclassified as a dwarf planet.

Life on Pluto

The dwarf planet is a frozen world with an average temperature of -228 degrees Celsius(-378 degrees Fahrenheit). However, scientists believe that there may be a subsurface ocean on Pluto. This ocean could be liquid because of the heat generated by Pluto's core. If there is an ocean on Pluto, it could potentially support life.

Image: Atmosphere of Pluto

Image: Pluto's subsurface ocean is located below hundreds of miles of ice and rock

In the meantime, Pluto continues to be a source of fascination and wonder. It is a reminder that there is still much that we don't know about the universe around us. And it is a reminder that even the smallest and most seemingly insignificant objects can hold great mysteries.

Sources:

• Pluto - Wikipedia

• The IAU's Definition of a Planet

• New Horizons: The Pluto Mission

 Astronomy: The Oldest Scientific Discipline

Introduction

Astronomy is the oldest of the natural sciences. Humans have been studying the stars and planets for centuries, and astronomy has played an important role in the development of human culture.

History of Astronomy

The first astronomers were likely early humans who gazed up at the night sky and wondered about the stars. They may have used the stars to track the seasons, to navigate, or to tell stories.

Image source: A bison figure depicted in the Lascaux Shaft Scene.

As civilizations developed, astronomy became more sophisticated. The ancient Egyptians, Babylonians, Greeks, and Chinese all made significant contributions to astronomy. They developed calendars, mapped the stars, and even calculated the orbits of planets. The people of that time made use of stone circles that, when discovered by researchers, were proof that the Egyptians could mark time and even predict when the floods would come. They also even invented a way to use stars visible at night to figure out the time at night.

Image source: Why And How Did The Ancient Egyptians Use Astronomy? (astronomerguide.com)

A Babylonian tablet recording Halley's comet in 164 BC

Image source: Babylonian astronomy - Wikipedia

Picture of George Trebizond's Latin translation of Claudius Ptolemy's Almagest (ca. 1451)

Image source: Greek Astronomy - World History Encyclopedia

The Dunhuang map from the Tang dynasty ( schools were distinguished with different colors: white, black, and yellow for the stars of Wu Xian, Gan De, and Shi Shen respectively. The whole set of star maps contains 1,300 stars.

Image source: Chinese astronomy - Wikipedia

The invention of the telescope in the 17th century revolutionized astronomy. Telescopes allowed astronomers to see objects in space that were invisible to the naked eye. This led to a new era of discovery, as astronomers began to study the planets, stars, and galaxies in unprecedented detail.

Image source: Modern Telescopes for star gazing

Modern Astronomy

Today, astronomy is a thriving scientific discipline. Astronomers use potent telescopes and other instruments to study the universe in all its vastness. They are working to understand the formation and evolution of stars and galaxies, the nature of dark matter and dark energy, and the possibility of life beyond Earth.

Image: Andromeda Galaxy

Conclusion

Astronomy is a fascinating and rewarding field of study. It offers us a glimpse into the vastness of the universe and the origins of our planet. It also challenges us to consider our place in the universe and our relationship to the cosmos.

As the oldest scientific discipline, astronomy has transcended time, culture, and boundaries to illuminate the mysteries of the universe. It has not only propelled humanity's scientific progress but also kindled our innate curiosity and thirst for knowledge. From ancient stargazers to modern-day astronomers, the pursuit of understanding our cosmic surroundings remains an enduring quest. Let us continue to gaze upward, for in the boundless expanse of the cosmos, there are endless wonders yet to be unveiled.

Whether we look to the skies for scientific discovery, personal contemplation, or simply to experience a moment of cosmic awe, astronomy will forever be an integral part of the human journey.