The Earth is closest to the Sun – at its Perihelion – about 2 weeks after the December solstice (figure 1).
Figure 1: Perihelion.
Earth orbits the Sun in an elliptical path, which means that there is 1 point of the path when the Sun is at its closest to the Earth and 1 point when it is furthest away.
The shape of this path varies due to gravitational influences of other planetary objects, particularly the Moon.
Approximately every 100 000 years, Earth's orbital path changes from being nearly circular to elliptical. The difference of the Earth’s orbital shape from a perfect circle is known as its eccentricity. An eccentricity value of 0 is a circular orbit, while values between 0 and 1 describe an elliptical orbit.
Perihelion in Wales is Thursday, 3 January 2019, 05:19 GMT.
Quadrantids Meteor Shower (figure 2): This will reach maximum rate of activity on the 3rd and 4th however, the shower is expected to be visible between the 1st and 6th.
Providing viewing conditions are good (dark skies) it should be possible to view approximately 25 meteors per hour. There could be a maximum peak rate of 60 per hour.
The Quadrantids are associated with asteroid 2003 EH1 (figure 3).The asteroid has a 5.5 year orbit around the Sun.
The shower gets its name from the former constellation Quadrans Muralis which is now part of Boötes.
Figure 2: Quadrantids radiant.
Figure 3: Orbit of EH1. AU = Astronomical Unit (Earth-Sun distance).
On 21st January there will be a total lunar eclipse (figure 4 & 5), also known as a blood moon, visible from the UK in the very early hours of the morning. The last total lunar eclipse was on 27 July 2018.
In the UK it will be possible to see every part of the eclipse as long as you are willing to stay up all night! The Moon will start to enter the Earth’s shadow just after 2:30am GMT and the maximum eclipse will occur just before 5:15am. The entire eclipse lasts for more than five hours, ending at 7:48am.
Figure 4: 'Blood Moon'
The colour of the Moon during totality will depend on the global state of dust in the Earth’s atmosphere – sometimes red or possible virtually invisible.
Dust in the atmosphere blocks out the higher frequency blue light waves, but the longer wavelength of red light comes through.
A Lunar eclipse occurs when the Moon passes directly behind the Earth and into its shadow. This occurs only when the Sun, Earth and Moon are exactly or very closely aligned (syzygy).
Figure 5: Total Lunar eclipse.
WARNING: Never attempt to view through binoculars, telescope or any optical aid an object close to the Sun. Also, never attempt to view the Sun unaided, doing so may result in immediate and permanent blindness. Always use astronomical approved viewing equipment.
The Stellarium software will assist greatly in locating objects in the sky.
A very happy New Year to all sky watchers.
Nuclear Fusion & Astrophysics.