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Tour Guide Cheat Sheet

If the Sun (1.4 million km diameter) were shrunk to the diameter of the 26m dish, Earth would be the size of a basketball and the Moon about the size of a tennis ball. On this scale, Earth would be 2.6 km away (roughly Cambridge) and the Moon would be 6.5m from the Earth. You can fit all the planets into the space between the Earth and the Moon.

Jupiter is 11 times the diameter of the Earth so would be about 2.4m across on this scale.

Active Galactic Nuclei

There are millions of galaxies in the Universe. All the big ones - including our own Milky Way - have huge black holes at their centres. These are between a million and a billion times heavier than the Sun, which itself weighs 2 million million million million million kilograms! Black holes are supposed to be black, but actually regions immediately surrounding them are the brightest things in the Universe. Black holes suck matter up (physicists call this “accretion”), and the friction during this accretion process makes regions just outside the black hole event horizon glow white hot. We call these regions Active Galactic Nuclei (AGN).

During the accretion, AGN also eject jets of plasma (which consists of electrons moving at close to the speed of light, spiralling around magnetic field lines). These jets are the most powerful outbursts in the Universe, and we can see them with radio telescopes. Because they are so bright, we can observe AGN to huge cosmic distances and use them to study how the Universe has evolved. AGN also allow us to probe extreme physics - for example, whether the laws of physics as we know them still work in regions of really strong gravity or magnetic fields. Often this work is done using the technique of very long baseline interferometry, where signals from telescopes separated by thousands of kilometres are combined to create a much larger virtual telescope; this huge virtual telescope can then peer into the very inner regions of AGN, where the strongest gravity and magnetic fields are found.

AGN eject jets of plasma (which consists of electrons moving at close to the speed of light, spiralling around magnetic field lines). These jets are the most powerful outbursts in the Universe, and we can see them with radio telescopes. Because they are so bright, we can observe AGN to huge cosmic distances and use them to study how the Universe has evolved. Because AGN are so extreme, they allow us to probe extreme physics - for example, whether the laws of physics as we know them still work in regions of really strong gravity or magnetic fields. Often this work is done using the technique of very long baseline interferometry, where signals from telescopes separated by thousands of kilometres are combined to create a much larger virtual telescope; this huge virtual telescope can then peer into the very inner regions of AGN, where the strongest gravity and magnetic fields are found.

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Page last modified on November 16, 2017, at 09:31 PM