WEBVTT

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Planets around other stars.

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More than six thousand planets around other stars, in the copy of NASA's catalogue this map carries, each drawn as a mark at its star.

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Most were found by the dip in a star's light as a planet crosses in front of it, the rest mostly by the wobble a planet gives its star.

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The nearest one.

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Proxima b goes round the nearest star to the Sun, four light-years away, once every eleven days.

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Nobody has seen it: it was found by the wobble it gives its star.

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Seven worlds round a small red star.

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TRAPPIST-1 is a cool red star forty light-years away, a little bigger than Jupiter.

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Seven planets about the size of the Earth go round it, and all seven were found as they crossed in front of it.

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TRAPPIST-1 e.

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A year here lasts six days.

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It is nine tenths as wide as the Earth and seven tenths as heavy, and at its closest its neighbour d would look as wide in its sky as the Moon is in ours.

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TRAPPIST-1 b.

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The innermost, 1.7 million kilometres from its star, over thirty times closer than Mercury is to the Sun.

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Its year is a day and a half, and it is a tenth wider than the Earth.

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TRAPPIST-1 c.

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The second out, round its star in just under two and a half days.

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Like b it is a little wider than the Earth and about a third heavier.

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TRAPPIST-1 d.

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Four days a year, and the smallest but one: four fifths of the Earth's width and less than two fifths of its mass.

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TRAPPIST-1 f.

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Nine days a year, and the nearest of the seven to the Earth's own size and mass, a few per cent over on both.

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TRAPPIST-1 h.

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The outermost and the smallest, three quarters of the Earth's width.

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A year here is nineteen days, and b goes round twelve times in one of them.

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All of it inside Mercury's orbit.

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The dashed ring is the size of Mercury's orbit round our Sun, drawn here for scale.

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It is six times wider than the orbit of h: every one of these worlds is closer to its star than Mercury is to ours.

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The Sun, from one light-year.

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From here the whole Solar System is smaller than a pixel.

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Light from the Sun takes a year to reach this spot; Voyager 1, the fastest thing we have sent out of the Solar System, would take about eighteen thousand.

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Proxima Centauri.

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The nearest star to the Sun, a dim red one an eighth of the Sun's mass.

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It has at least one planet.

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Every star you can see with your eyes at night is farther away than this one.

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Sirius.

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The brightest star in our sky, eight and a half light-years out and twenty-five times as bright as the Sun.

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The light reaching your eye tonight left it eight and a half years ago.

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The Pleiades.

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Over a thousand young stars, a hundred million years old, about four hundred and twenty-five light-years away.

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Their light left when Shakespeare was alive.

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The centre of the galaxy.

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Twenty-seven thousand light-years from home, a black hole of four million Suns that the whole Milky Way turns around.

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The disc, bar and arms drawn around you are a model built from measurements; the stars are the measured part.

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The Milky Way.

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Our galaxy, about ninety thousand light-years across, seen from sixty thousand light-years above its disc, a view nobody has had.

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The shape is an illustration of what has been measured.

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Andromeda.

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The nearest big galaxy, two and a half million light-years away and coming our way.

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Its light left when the first humans were learning to use tools.