Astronomy in Northland
Christmas Star Visible after almost 800 years
Update - Mon 8:00am
Thanks to everyone who came over the weekend. Observing is a game of patience and was proven last night when the clouds covered the conjuction, however we did get to see many other features with our telescopes.
Tonight looks like a lost cause, there is a large cloud bank due to arrive late afternoon. If you do manage to get clear view west the planets will be at their closest tonight. For the next couple days the will be visible at sunset but getting lower so will be harder to catch.
Update - Sun 2:00pm
Cloud coming in from Tasman sea is burning off, if this continues there is a good chance of viewing again tonight. We will open the observatory from 8:45pm unless there is a significant change this afternoon.
Update - Sun 8:00am
Thanks to everyone who came and waited so patiently to view through the telescopes. Even though we had cloud right until sunset, a break appeared in the right place just as the right time and within 15 minutes the whole sky cleared for a perfect night of viewing.
Many requested another viewing opportunity tonight (Sunday) and I have just reviewed the satellite images which look promising. If the cloud banks continue on their current path we should have another outstanding night and the volunteers will open the observatory at 8:45pm again. Standby for another update by 2pm.
Update - Sat 7:30pm
Cloud overhead but satelitte image gives us hope that we will get a break around the optimal time of 9-10pm. Just got to take a chance on this folks, in 1623 people missed it as well
Update - Sat 1pm
A cloud bank is travelling South-West across the Tasman Sea this afternoon. Currently it looks like it will still give us a view of the conjunction at Sunset, but if we are clouded out we will attempt again on Sunday or Monday evening.
Join us at Planetarium North this Saturday (19th Dec) at 9pm to watch the sunset and the two stars emerge in the twilight. We will have every telescope and our big binoculars looking at them, and then as it gets darker we will take a look at Matariki, The Orion Nebula, and whatever else pops out.
Admission by donation, thanks for your support in 2020.
Just over two thousand years ago, three wise men set off on a journey that changed the course of history – and they did so after noticing a unique event in the heavens, which became known as the Christmas Star. This month, we can see a similarly rare planetary event, visible for the first time in 400 years, in the skies above New Zealand.
This year’s Christmas Star is created by what looks like Jupiter and Saturn merging. The two have been slowly coming together in the early-evening sky for the past few months, and they move closest to each other on December 21, our summer solstice (also known as the longest day).
Each planet takes different lengths of time to complete its orbit of the Sun: Earth does it in a year, while Jupiter takes 12 years and Saturn just over 29 years. Occasionally planets will ‘catch up’ to each other, and when viewed from Earth they appear to be coming together, or in conjunction.
Astronomers have been able to replicate the past movements of the planets to determine the source of the original Christmas Star story: it’s thought to be a rare triple conjunction of Jupiter, Saturn and Venus.
In fact, the solstice has also influenced Christmas as we know it today. In the northern hemisphere, December 21 is the date of the winter solstice (the shortest day). In Roman times, they marked this with Saturnalia, a long-running festival celebrating new life and the planting of crops.
Many elements of this festival influenced the development of Christmas and the New Year, when the Roman empire came under Christian rule a few centuries later. (Christmas was first celebrated in 336AD, under the rule of emperor Constantine.)
This year’s particular conjunction is rare because of how small the separation is between the two planets. A conjunction happens approximately every 20 years, but to the naked eye, the planets will still appear a finger-width (or two degrees) apart, because of the angle of the planet’s orbit around the sun. A conjunction so close that we can’t tell the planets apart with the naked eye (one-tenth of a degree) only happens roughly every 400 years.
To find the planets, look west just as the sun sets and note where the sun sinks below the horizon: it’s about 30 degrees south of west at the moment. Stretch the fingers of one hand apart. The distance between the tips of your index and little fingers is about 18 degrees when held at arm’s length. Measure one-and-a-half hand spans from the sunset position to the north, then measure one hand span up and you should see the two planets clearly.
You’ll need to be alert: the planets will sink below the horizon fairly quickly, so make sure you’re looking as the sun sets or in the 15 minutes afterwards. You don’t need to get away from city lights, but do make sure you go somewhere elevated that has a clear view of the western horizon.
While Jupiter is 10 times brighter than Saturn, we hope to see them both in our telescopes at Planetarium North. All going well, we will see the four biggest moons of Jupiter, the rings of Saturn and several of its moons as well.
This is an event not to be missed – the last time the planets were this close was in 1623. Even though Galileo had been using his telescope for a decade by then, that conjunction was too close to the Sun for anyone to observe.
The significance of heavenly bodies and their motion has shaped much of our culture and heritage since the first days of civilisation. Māori and Pacific people chose to celebrate the rising of Matariki during our winter solstice, remembering those who have passed and preparing for the year ahead. This month, as we head towards the summer solstice and the end of a long year, it’s a good time to look up and think of other turning points in our history, so long ago.