NASA's Space Place: Why did it take so long to discover Uranus?

A carefully trained eye in perfect conditions can spot the dim light of Uranus without a telescope. Despite this fact, it wasn’t officially discovered until 1781—thousands of years after the other visible planets were documented. Part of the problem was not finding it, but correctly identifying it. Read all about it in the Space Place’s latest column:

The Space Place is a NASA educational website about space and Earth sciences and technologies. It targets upper-elementary-aged-children.

NASA's Space Place in a SNAP! - Tectonic Forces

NASA Space Place in a SNAP!

NASA's Space Place in a SNAP! is a series of quick, narrated tours of animated infographics that illustrate key science concepts. Not only are they fun and entertaining on their own, they also come with a downloadable poster and a transcript of the video, making for a cross-disciplinary learning experience. There was once a time when you could take a stroll from North or South America to Africa no problem. There was no ocean to get in the way, because all of Earth’s continents were stuck together in one massive supercontinent called Pangea. How is this possible?

NASA's Space Place: Droughts, Floods and the Earth's Gravity, by the GRACE of NASA

NASA's Space Place

By Dr. Ethan Siegel  --  When you think about gravitation here on Earth, you very likely think about how constant it is, at 9.8 m/s2 (32 ft/s2). Only, that's not quite right. Depending on how thick the Earth's crust is, whether you're slightly closer to or farther from the Earth's center, or what the density of the material beneath you is, you'll experience slight variations in Earth's gravity as large as 0.2%, something you'd need to account for if you were a pendulum-clock-maker.

NASA's Space Place: The Invisible Shield of our Sun

NASA's Space Place

By Dr. Ethan Siegel - Whether you look at the planets within our solar system, the stars within our galaxy or the galaxies spread throughout the universe, it's striking how empty outer space truly is. Even though the largest concentrations of mass are separated by huge distances, interstellar space isn't empty: it's filled with dilute amounts of gas, dust, radiation and ionized plasma.

NASA's Space Place: A Glorious Gravitational Lens

NASA's Space Place

By Dr. Ethan Siegel  --  As we look at the universe on larger and larger scales, from stars to galaxies to groups to the largest galaxy clusters, we become able to perceive objects that are significantly farther away. But as we consider these larger classes of objects, they don't merely emit increased amounts of light, but they also contain increased amounts of mass. Under the best of circumstances, these gravitational clumps can open up a window to the distant universe well beyond what any astronomer could hope to see otherwise.

NASA's Space Place: The Hottest Planet in the Solar System

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By Dr. Ethan Siegel  --  When you think about the four rocky planets in our Solar System—Mercury, Venus, Earth and Mars—you probably think about them in that exact order: sorted by their distance from the Sun. It wouldn't surprise you all that much to learn that the surface of Mercury reaches daytime temperatures of up to 800 °F (430 °C), while the surface of Mars never gets hotter than 70 °F (20 °C) during summer at the equator.

NASA's Space Place: The Power of the Sun's Engines

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By Dr. Ethan Siegel  --  Here on Earth, the sun provides us with the vast majority of our energy, striking the top of the atmosphere with up to 1,000 Watts of power per square meter, albeit highly dependent on the sunlight's angle-of-incidence. But remember that the sun is a whopping 150 million kilometers away, and sends an equal amount of radiation in all directions; the Earth-facing direction is nothing special. Even considering sunspots, solar flares, and long-and-short term variations in solar irradiance, the sun's energy output is always constant to about one-part-in-1,000.