How much stars are there

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Transcript How many stars are there? How many stars are there in the night sky? And how many animals know how to fly? How much ice cream do I eat in a week? And how many years does it take to learn Greek? How much of the planet is covered in snow?

So, many astronomers estimate the number of stars in a galaxy based on its mass — which has its own difficulties, since dark matter and galactic rotation must be filtered out before making an estimate. Missions such as the Gaia mission, a European Space Agency space probe that launched in , may provide further answers. Gaia aims to precisely map about 1 billion stars in the Milky Way.

It builds on the previous Hipparchus mission, which precisely located , stars and also mapped 1 million stars to a lesser precision. Thanks to missions like these, we are one step closer to providing a more reliable estimate to that question asked so often: 'How many stars are there in the universe? Even if we narrow down the definition to the "observable" universe — what we can see — estimating the number of stars within it requires knowing just how big the universe is.

The first complication is that the universe itself is expanding, and the second complication is that space-time can curve. To take a simple example, light from the objects farthest away from us would take approximately So the radius of the observable universe should be Or should it? A relativist would use a device such as a meter stick, measuring the distance along that device and then extending it as long as needed.

This produces a different answer, which some sources define as 48 billion light-years in radius. Sources vary on this number, however.