by Surendra Yadav
An old guest of Earth is coming again for a visit. Comet named 46P or Wirtanen is going to visit the Earth again after it was last seen in July, 2013. It is expected to visit the earth at closest approach of 11.5 million km from the Earth on 16th December, 2018. People on the Earth are ready to give cordial welcome to this guest. Affected by another friend of this comet which is Jupiter, this comet changes its period of orbit around the Sun. This time, it has visited the Earth after almost 5.4 years with an inclination of 11.7 degree from the ecliptic plane. The brightness of this comet is expected to peak up to 3 magnitude which will be brightest closest approach for next 20 years. People on the earth won’t be able to see this comet as bright as it will appear this time for the next 20 years!
Carl A. Wirtanen discovered this comet in the cold month of January, 17 in the year 1948, 13 days before the death of Mahatma Gandhi. Wirtanen detected the faint image of this object of 17 magnitude on a photographic plate.
In the beginning of December, this wonderer object will be near the border line of constellation Cetus and Eridanus at a declination of around -20 degrees. On the evening of 15 December, it will pass almost midway between Hyades and Pleiades star clusters. If your telescope or binoculars has not been used for long time then it is the best time to take out your telescope or binocular for gazing the night sky and look at this comet. During its journey, 46P will pass within some few degrees to the south and east of Capella-brilliant shining yellow star at the nights 22nd and 23rd December. After that it will give farewell to our Earth!
Though the brightness of this comet is expect to be of 3 magnitude, but observer excitement might get hindered. Visibility of this comet will strongly depends on the site from which observer is observing this comet. If the site for observation is polluted then even if someone observe this comet with good telescope under dark sky, they may still find difficulty in looking to this comet. The reason behind this problem is the large angular size (nearly the apparent size of the moon) of this comet due to which its light spread in large area. This comet appears to be more condensed at the centre. This observation will also be intervened by moon which will lightens up the sky in the first half of the night during the mid-December.
If you are under perfectly dark clear sky and free from pollution then you may also be able to see this object with the naked eye and you may not need any special instrument or device to see it.