The last time the two planets appeared that close and formed was in 1623.
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But a triple conjunction is an astronomical event where two planets or a planet and a star meet each other three times in a short period.
On Thursday residents will be able to see the three distant worlds low on the eastern horizon.
Towards the south east of the eastern horizon, the planets will appear as small white dots just after 6am GMT.
Jupiter, the fifth planet from the sun, will be the bottom of the triangle, closest to the horizon, with Mercury above and to the right and Saturn the highest of the group and furthest right in the sky.
The planets will be visible until the end of the weekend.
Over the course of the week Mercury and Jupiter will appear to come closer together, before drifting apart again after Sunday.
The planets should be visible to the naked eye as bright spots of light, but may be viewed better when viewed through binoculars or a telescope.
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