by Dr Carol Davenport, Director of Think Physics, Northumbria University
After Jesus was born in Bethlehem in
Judea, during the time of King Herod, Magi from the east came to
Jerusalem and asked, ‘Where is the one who has been born king of the
Jews? We saw his star when it rose and have come to worship him.’ Matthew 2 v 1 – 2
Comets
One suggestion for the
star is that it was a comet. Comets are
giant balls of ice and rock that orbit the sun in a huge oval. At times they are very far away from the Sun,
but at other times their orbit brings them closer. As a comet approaches
the Sun it starts to heat up. The frozen
ice begins to melt and is blown away from the comet by the solar wind. This is the tail of the comet that we see
from Earth. If a very bright comet approached the Sun, then it would have been
visible from Earth for some time.
Ancient Chinese records have two possible sightings of comets at about
the right time, one which appeared in March, 5BC and one which appeared in
April, 4BC. However, in the ancient world comets were usually seem to be signs
of Doom, indications that bad things were about to happen. It is unlikely that they would be seen as heralding
the birth of a King.
Planets
Ancient astronomers
knew about two types of star – the fixed stars and the wandering stars. The fixed
stars appeared every night and stayed in the same position compared to each
other. The wandering stars moved about the sky, rising and setting in different
places. These are not actually stars,
but are the planets Mercury, Venus, Mars, Jupiter, Saturn. You can see these in the night sky without
using telescopes or binoculars. The reason that the planets appear to change
position in the sky is because they take different lengths of time to orbit the
sun. This means that we need to look in
different directions to see them. However, the behaviour and position of the
planets would have been known by the magi.
After
they had heard the king, they went on their way, and the star they had seen
when it rose went ahead of them until it stopped over the place where the child
was. When they say the star, they were
overjoyed. Matthew 2 v 9 – 10
Triple Conjunction
When two, or more,
planets appear close together in the night sky then this is known as a conjunction. Sometimes, when the Sun,
Earth, Jupiter and Saturn are in a certain alignment then a Triple Conjunction
can occur. This is when the two planets
appear close together in the sky three times in a short period.
The pictures show the different positions of Jupiter and
Saturn on three dates in 7 BC. This is
when they were in conjunction and would be seen near to each other in the sky. In between these dates, the planets were not
visible because they were in the sky at the same time as the Sun. The quote from Matthew suggests that for a while the star
wasn’t visible, but then it reappeared.
A triple conjunction would explain this. It takes the Earth one year to orbit round the sun, but it
takes Jupiter twelve (earth) years, and Saturn just under 30 (earth) years to
orbit the sun. This makes a triple conjunction
quite rare – they only occur once every nine hundred years. Although the triple conjunction could have been predicted,
the fact that they occur so rarely would have meant that the Magi would have
taken it to be a signal of something important happening.
Think Physics is a three year project based at Northumbria University. Our aim is to show students that studying science, particularly physics, opens doors to a wide range of interesting careers. We will be working with up to 30 partner schools (pre-school to post-16) from around the North East, focussing initially mainly on Newcastle, North Tyneside, Gateshead and Durham. We aim to interact with every child in our partner schools at least once, but hopefully more than once, during the project. As well as our partner schools, we will also be organising activities and workshops for other schools in the region. We will also be taking physics out to the wider public through collaborations between Think Physics and art galleries, festivals and other community organisations. The project is a partnership between the university and other organisations including the Institute of Physics, Kielder Observatory, Centre for Life, North Tyneside Learning Trust, Gateshead LA, Durham LA, North Tyneside LA, Durham LA, Solar Capture Technologies, and EDT. Funding for the project was given from the HEFCE catalyst fund.
Think Physics is a three year project based at Northumbria University. Our aim is to show students that studying science, particularly physics, opens doors to a wide range of interesting careers. We will be working with up to 30 partner schools (pre-school to post-16) from around the North East, focussing initially mainly on Newcastle, North Tyneside, Gateshead and Durham. We aim to interact with every child in our partner schools at least once, but hopefully more than once, during the project. As well as our partner schools, we will also be organising activities and workshops for other schools in the region. We will also be taking physics out to the wider public through collaborations between Think Physics and art galleries, festivals and other community organisations. The project is a partnership between the university and other organisations including the Institute of Physics, Kielder Observatory, Centre for Life, North Tyneside Learning Trust, Gateshead LA, Durham LA, North Tyneside LA, Durham LA, Solar Capture Technologies, and EDT. Funding for the project was given from the HEFCE catalyst fund.
@ThinkPhysicsNE
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