What is a Planet?
By: Flaka Ismaili November 9, 2022
It wasn’t until the 2006 that astronomers attending the IAU General Assembly in Prague agreed on a formal definition of the word. Venus has the most massive atmosphere of all the terrestrial planets. Its gaseous envelope is composed of more than 96 percent carbon dioxide and 3.5 percent molecular nitrogen.
When you reach out to them, you will need the page title, URL, and the date you accessed the resource. Mars is often dubbed the “Red Planet” because of the iron on its surface. It is the fourth planet from the Sun, located around 228 million km (142 million mi) away. Then the different types of planets followed by all the planets in order from the sun outward.
What makes Saturn more interesting is that it has the most moons in the solar system. The 82 known moons range in different sizes and compositions. However, some of its https://cryptolisting.org/blog/total-revenue-in-economics-definition-amp-formula moons have the potential for life, especially the ocean worlds of Enceladus and Titan. It lies at an average distance of about 58 million kilometers (36 million miles).
- Second, it must be big enough to have enough gravity to force it into a spherical shape .
- It has the least eccentric orbit of any planet, with a deviation from a perfect circle of only about 1 part in 150.
- Venus spins very slowly, taking about 243 Earth days to complete one rotation with respect to the stars—the length of its sidereal day.
- Before joining us, Daisy completed an editorial internship with the BBC Sky at Night Magazine and worked at the National Space Centre in Leicester, U.K., where she enjoyed communicating space science to the public.
I am fascinated by our quest to find Earth-sized exoplanets around small stars, and the big question of how stellar flares impact their habitability. Whenever I am not searching for new worlds, I enjoy exploring our own Earth, travelling, and the outdoors (scuba diving, rock climbing and hiking). The inner four planets closest to the sun — Mercury, Venus, Earth and Mars — are often called the “terrestrial planets” because their surfaces are rocky. Pluto also has a rocky, albeit frozen, surface but has never been grouped with the four terrestrials. Venus orbits the Sun at a mean distance of 108 million km (67 million miles), which is about 0.7 times Earth’s distance from the Sun.
Big planet or tiny star?
Its modern name comes from the Roman goddess of love and beauty (the Greek equivalent being Aphrodite), perhaps because of the planet’s luminous jewel-like appearance. The difficulty in seeing it notwithstanding, Mercury was known at least by Sumerian times, some 5,000 years ago. In Classical Greece it was called Apollo when it appeared as a morning star just before sunrise and Hermes, the Greek equivalent of the Roman god Mercury, when it appeared as an evening star just after sunset. Hermes was the swift messenger of the gods, and the planet’s name is thus likely a reference to its rapid motions relative to other objects in the sky. Even in more recent eras, many sky observers passed their entire lifetimes without ever seeing Mercury. Concurrent sea voyages provided practical proof that Earth is a globe, just as Galileo’s use of his newly invented telescope in the early 17th century soon showed various other planets to be globes as well.
- It got its name from Greek mythology’s primal god of the sky.
- The red planet got its name from the Roman god of war whose Greek equivalent is Ares.
- This process can take millions of years and is influenced by factors such as the protoplanetary disk’s composition, the budding planet’s distance from its star, and the presence of other objects within the disk.
- At first glance the surface of the planet looks similar to the cratered terrain of the Moon, an impression reinforced by the roughly comparable size of the two bodies.
- The gas giant is more than twice as massive as all the other planets combined, according to NASA.
Neptune is about 17 times as massive as Earth and has a rocky core. The collision is also thought to have knocked rock and ice into Uranus’ orbit. Methane in Uranus’ atmosphere gives the planet its blue-green tint. Asteroids are minor planets, and according to NASA there are approximately between 1.1 and 1.9 million asteroids in the main asteroid belt larger than 0.6 miles (1 km) in diameter and millions more smaller asteroids. Over its four-year mission, NASA’s MESSENGER spacecraft revealed incredible discoveries that challenged astronomers’ expectations.
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Earth and the rest of the solar system formed about 4.6 billion years ago from a huge, spinning cloud of gas and dust. Earth’s atmosphere is a blanket of gases enveloping Earth and retained by our planet’s gravity. Atmospheric gases include nitrogen, water vapor, oxygen, and carbon dioxide. Wanderersin the Night SkyAncient astronomers viewed the sky with nothing more powerful than their own eyes. These astronomers noticed a few lights in the sky that looked different from stars.
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Its near-surface environments are the only places in the universe known to harbour life. Planets play an indispensable role in enhancing our understanding of the universe. Analyzing their characteristics, compositions, and atmospheres can offer valuable insights into the formation and evolution of planetary systems across the cosmos. Furthermore, the quest for Earth-like exoplanets may finally help shed light on the age-old question of whether we are alone in the universe. Others think that it can only be a planet if it formed around a star.
Saturn
Jupiter and Saturn are sometimes called the gas giants, whereas the more distant Uranus and Neptune have been nicknamed the ice giants. For perspective, methane crystallizes at minus 296 Fahrenheit (minus 183 degrees Celsius), according to the U.S. The four large outer worlds — Jupiter, Saturn, Uranus and Neptune — are sometimes called the Jovian or “Jupiter-like” planets because of their enormous size relative to the terrestrial planets.
Europa and Enceladus, moons of Jupiter and Saturn respectively, are ice-covered rocky objects that scientists think may harbour life in the water beneath the surface. Some geological evidence points to the possibility of microorganisms on Mars. From the nearby rocky planets in our own solar system to the bizarre rogue worlds that lurk in deep space, there is a wealth of knowledge to be gained by studying these enigmatic objects. As we continue to explore our universe, the study of planets will undoubtedly unveil more about the cosmos, our place within it, and even the potential for life on other worlds. One of the primary goals of exoplanet research is to find potentially habitable worlds, or planets with conditions that could support life as we know it. This typically involves searching for Earth-like worlds within the habitable zones of their parent stars, where temperatures are just right for liquid water to exist.
It does not have an atmosphere, but only a thin exosphere. Mercury has been known for a long time because it is visible to the naked eye. Galileo Galilei made the first telescopic observation of this small planet in the 17th century.
