“Is there a ninth planet in our solar system?”
Planet nine is the hypothetical planet that we believe may be hiding in the solar system. Its existence is assumed based on the witnessed gravitational influence on a group of small, very distant objects with elongated, clustered orbits.
However, due to how far away planet Nine would be from the sun, it's likely that it would reflect very little sunlight thus can evade telescopes.
In order to defined as a planet, it must meet three criteria:
1. It must orbit a star, and not another planet
2. It must be spherical
3. It must clear its orbit, meaning that when it orbits it can push all the smaller bodies out of it's way making in the primary gravitational force in that ring
Pluto, for example, didn't meet this third criteria meaning its not longer considered out ninth planet.
Learn more about this with our series “The Bright Night Sky”
For centuries, we have been looking up to the sky to understand the mysteries that surround us. The sky might hold the answers to some of our deepest questions such as where we came from. But what do we know so far?
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Prof. Sara Seager
Professor Sara Seager is a pioneer in vast world of exoplanets & the search for other life in the universe. In this Garden Talk, Sara will consider space science's biggest question: Are we alone in the universe?
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Dr Emma Chapman
400 million years after the Big Bang, the Universe was very different from what it appears today. At that time (around 13 billion years ago) the universe was dark and empty. But how can we know that? Is there a way to travel back in time?
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Dr. Harry Cliff
We are all surrounded by an unseen, invisible world; a world made of mysterious substances that we can’t see or touch: the Dark Universe. But if we can’t see it, touch it, or detect it, why do we think it is there?
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Dr Malena Rice
Our solar system has anomalies. Astronomers suggested the existence of a hidden giant planet as a plausible explanation. The problem is that we have never been able to see this planet. Is our math wrong or are we really missing something?
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