05 November 2018

Mercury in the evening Sky

In the evening sky, low in the horizon, if we carefully look we can find the smallest planet in our solar system. After sunset, in a place where there are no obstruction like buildings or trees, in this unobstructed view of the western horizon we can spot planet mercury. Since mercury orbits close to the sun we can only find the planets close to the horizon in evening or morning skies.

During its orbit around the sun there are two favorable points where we can observe the planet. This is the maximum separation of angle between Sun and planet. This point of maximum separation is called Greatest elongation. For planet mercury this greatest elongation angle is between 18 degrees to 28 degrees. This is the reason why most people miss the planet, since it is so close to horizon.

On November 6th the planet will reach greatest elongation giving us a good opportunity to catch a glimpse of this planet with naked eye, binoculars and telescopes. The angle for this elongation is 23 degrees, this means just after sunset the planet will be 23degrees above western horizon.

Spot planet after sunset in western sky.

The planet will be at a magnitude of -0.2, although it is bright the drawback is that it is immersed in twilight making it difficult to spot but as twilight fades its easy to spot.

With a telescope we can see the gibbous phase of mercury with an angular size of 6min of arc. The planet will be in half phase on 11th of November and from there on the illuminated side of mercury will start decreasing. This is a nice time to see and enjoy and also understand the phases and orbit of mercury. Since the planet is coming closer to earth the angular size will keep increasing and it will be 9mins of arc before the planet sinks into the glare of the sun and then reach inferior conjunction on 27th of November.

Clear Skies.

26 July 2018

July Total Lunar Eclipse

There are very few astronomical events for which we need not leave our house, or have telescopes, filters or worry about light pollution. One such event is Lunar eclipse, an astronomical event that can be seen from where we live and without any optical aid or equipment.  

This time on 27th July the eclipse happens when moon is high in the sky so no worries of buildings and trees blocking the view.  

Here are the times of the eclipse. Moon will enter Penumbral shadow at 10:45pm on 27th July this is hard to notice as the change in brightness is very less. Moon will start entering the Umbral shadow at 11:55pm, partial eclipse phase, from here we easily see the change in brightness. Moon will be completely inside Umbral shadow from 1:00am, here we say Moon is in total eclipse phase.

 The totality will end at 2:44am when Moon will start becoming brighter. As moon comes out of totality we can see partial eclipse phase as some portion of Moon will be in dark and other will be in brightness. Moon will come out of Partial phase at 3:45am. The Moon will come out of Penumbral shadow at 4:48am.

We urge you watch this amazing celestial show which is viable from all our India

30 January 2018

Watch Lunar Eclipse at Planetarium, Bangalore

Jawaharlal Nehru Planetarium is organizing Lunar Eclipse viewing at planetarium campus, Bangalore. Interested public can visit planetarium and enjoy the eclipse and get questions answered about eclipse and astronomy.

The event is from 6:15pm to 8:45pm on January 31st. 2018. Association of Bangalore Amateur Astronomers (A.B.A.A) members will also be there to help public understand and enjoy the eclipse.

03 January 2018

Earth and Sun Closest

Sun so close yet so cold...Yes Today Sun and earth will be closest to each other at a distance of 14,70,99,586 km. This point of any object closest to Sun is called Perihelion. The reason for the cold in northern hemisphere is due to the orientation of earth's axis and as you can see in the illustration, the Sun is moved to southern hemisphere where they are experiencing Summer now. 

Since earth's orbit is almost circular, at farthest point from Sun which occurs on July 6th the distance will be 15,20,96,155 km. This farthest point from Sun is called Aphelion. The angular size of the Sun which we measure in degrees at perihelion is 0.542018074degrees. And as we know the orbit is almost circular the difference in angular diameter of Sun from Perihelion to Aphelion is very small. At Aphelion the angular diameter is 0.5243709741degrees. 

 If we compare this to Mercury, the perihelion distance is 46,000,000 and this gives the angular diameter of Sun Seen from Mercury at 1.73434325degrees. The Aphelion distance of Mercury is 69,820,000 and this gives the angular diameter of Sun as seen from Mercury at 1.14247784degrees, almost half a degree difference. You can compare this to earth and Sun.