Pluto, an object which was once known as a planet

Many people ask me why Astronomers classified Pluto from planet to dwarf planet category? Last few years the voices demanding for the planet status to Pluto has weakens. But it is very interesting question people still wondered that what was the necessity of classifying Pluto. Debate for the status of Pluto as a planet was not recent ones. Astronomers has taken doubt time to time on Pluto as new observations came since its discovery. We will see that how Pluto became a dwarf planet. But, before that let me tell you a short story of Pluto's discovery. It's a fascinating story. The search for Pluto began before Clyde Tombaugh, the discoverer, was even born. It began with the Percival Lowell who during his lime time was best known for his work for a Mars planet.

Percival Lowell

Lowell believed that Mars had intelligent life. He thought there were canals on Mars that the Martians had built. He suffered a lot of ridicule from other astronomers for believing such fantasies. Lowell in the 1890 had actually founded an entire observatory to study planet Mars which still exist to this day in Arizona, United states. 

In order to get even with other astronomers who were ridiculing him for his work on Mars, he wanted to discover a new planet in the solar system. He called this hypothetical planet, a Planet X. He thought that if he could predict the location of another planet, and then find that planet, he would attain the prestige that had eluded him in all his work on Mars. 

He began his calculations, using observations of the motion of planet Neptune. He was hoping to see deviations in that planet's motion around the sun that would signal the gravitational effect of more distant planet on the orbit of planet Neptune. Unfortunately, Lowell died in 1916, before Planet X was ever found. Lowell observatory had to stop their search for planet X because of many reasons. 

Clyde Tombaugh

But then in 1929, Lowell observatory hired a young man from Kansas (U.S.), Clyde Tombaugh. Clyde Tombaugh was only 22 at that time. He was very skilled observer from the beginning of  his young age only. He implemented a search for the Planet X. Tombaugh started taking photographs of sky in night time from telescope and in day timings he used to check those photographs. He was checking any movement of object in these series of photographic plates taken from same sky region with regular interval of days. It was laborious work to check these photographic plates. During his search he found several objects like asteroids and comets. 

on February 18, 1930 he saw an object moved which was not seen before. It took many days for the confirmation then they came to conclusion that it is a planet. The discovery of this Planet X was inspired by Percival Lowell and Clyde Tombaugh's hard work which he put into searching millions of stars to find this tiny, faint object in distance space.

Telescope which was used to search Pluto, Source;sciencephotolibrary

The Lowell observatory team were allowed to name it, because the had discovered it. They put a public request for suggesting interesting name for this newly find object. They settled on PLUTO, a name suggested by an eleven year old school girl from Oxford, England (it wasn't named after the Disney's famous character, but the roman god of the underworld). It was perfect name for this distance world after the Roman god of underworld and its two initial letters PL were initials for Percival Lowell.

The solar system now counted nine planets in it.

Since its discovery astronomers could see very little of this distance world. Very less was known about Pluto for long time. Astronomers weren't sure about Pluto's mass and size until the discovery of its largest moon, Charon in 1978. By knowing its mass which is 0.0021 Earths, they could more accurately gauge its size. The most accurate measurement currently gives the size of the Pluto is 2400 km which is smaller than earths moon. Pluto's moon also showed that it is not rotating around Pluto, but these two object rotate around the common center of mass which is located outside of the Pluto. Astronomers thought its not what planet shows with their moons. They suggested its more like the binary planet system.

Pluto and Charon rotating around common center of mass

Pluto is tiny, but it was considered lager than anything else beyond the orbit of Neptune. Over the last few decades, powerful new ground and space based observatories have completely changed previous understanding of the outer Solar System. Instead of being the only planet in its region, like the rest of the solar system, Pluto and its moons are now known to be just a larger example of a collection of objects called the Kuiper Belt. This region extends from the orbit of Neptune to outer region of solar system up to 55 astronomical units. (1 Astronomical Unit is a distance between Earth and Sun).

Astronomers estimate that there are at least 70,000 icy objects with the same composition of Pluto. Astronomers again asks what Pluto should be called a planet or not a planet?

Astronomer's nervousness, Pluto's data was not indicating it as a planet

Astronomers had been turning up with larger and larger objects in the Kuiper Belt. Object Makemake, discovered by Caltech astronomers team was only little smaller than the Pluto. There are several other Kuiper Belt objects in that same classification. Caltech team discovered another object further than the orbit of Pluto. It was same size of the Pluto even some believed it was bigger than Pluto. officially named 2003 UB313, the object later designated as Eris. Since, its discovery, astronomers have determined that Eris size is approximately 2,600 km. It also has approximately 25%  more massive than Pluto. 

With Eris being larger, made of the same ice/rock mixture and more massive than Pluto, the concept that we have nine planets in the solar system began to fall apart. What is Eris? a planet or Kuiper Belt object. What is Pluto then? Astronomers decided they must take decision about the planet at the 26th general assembly of International Astronomical Union. It was held from August 14 to August 25, 2006 in Prague, Czech Republic.

26th General Assembly of IAU in 2006, voting for Pluto

Astronomers from the various association were given the opportunity to vote on the definition of planets. One version of the definition would have actually boosted the number of planets to twelve. Pluto was still a planet and so were Eris and even Ceres, which had been thought of as the largest asteroid. A different proposal kept the total at nine, defining the planets as just the familiar ones we know without any scientific rationale, and a third would drop the number of planet down to eight and Pluto would be out of the planet club. In the end, astronomer voted for the controversial decision of categorize Pluto (and Eris) to newly created classification of "Dwarf Planet". They put some rule for an object to known as planet.

For an object to be a planet, it needs to meet these three requirements defined by IAU

It need to be in orbit around the Sun - Yes, so may be Pluto is planet

It need to have enough gravity to pull itself into spherical shape -Pluto is still planet

In needs to have "clear neighborhood" of its orbit - Uh ohw... according to this its status is in trouble

What does "clear neighborhood" means? As planet form, they become the dominant gravitational body in their orbit in the solar system. As they interact with other, smaller objects, they either consume them, or sling them away with their gravity. Pluto is only 0.07 times the mass of the other objects in its orbit. The Earth, in comparison, has 1.7 million times the mass of the other objects in its orbit.

Any object that doesn't meet this third criterion is considered a dwarf planet. And so, Pluto is a dwarf planet. There are still many objects with similar size and mass to Pluto jostling around in its orbit. And until Pluto crashes into many of them and gains mass, it will remain a dwarf planet. Eris suffers from the same problem.

Even though Pluto is a dwarf planet, and no longer officially a planet, it will still be fascinating target for study. It will help us to understand the outer region of our solar system. NASA sent their New Horizon spacecraft to just look at planet Pluto. New Horizon passed by Pluto in July 2015 and transmitted first ever pictures of this dwarf planet and its moon Charon. From these pictures astronomers now know much about Pluto. We will see about this mission some other time.

New Horizon flyby Pluto in 2015 

Many people still asks what is the necessity of classifying Pluto or any other object in this category? Yes their is necessity for such categorization. Because, science is the systematic study of the universe. We tried to understand and define things/events/phenomenon around us. For the ages there were not a single definition available for the objects called planets. The only way to define them was they were wanderers across the earth's sky. In the beginning years of astronomy these objects were few, because of limitations of human eyes. When telescopes enhances our vision we began to start see many of them. Then the need pf classification came up with our new observations. It was very necessary to define these new objects for our better understanding of solar system. Now, with new definition or criteria we can study and understand our solar system as well as extra-solar system objects too.

references and images for this article are taken from universe today, space.com, gify and IAU websites.

Pictures from the Lunar Eclipse of the century

There were much talk about this Lunar eclipse because it was very special for this century. It was the longest total lunar eclipse of the century. Eclipses happens in June, July, August and September are usually depends upon the mercy of monsoon clouds. I remember many eclipses which washes in the Monsoon clouds. I have never witnessed Total Solar Eclipse. Shadow of the moon on earth surface is very small so it could visible from small geographical belt. On 22 July I was in that shadow belt, but monsoon clouds covered this show on that day. 

This time also I was feeling that, there are chances of happening this events under clouds only. From entire day sky was covering with thick clouds of monsoon. But, astronomy is full of surprises you never expect what will happen. This time when partial eclipse was going to start means around 11:45 pm I just peek out side and saw clouds were started getting clear and full moon appeared with bright red planet shining near to it. It was sudden. Then I immediately, take out my simple camera, DSLR camera. Binocular, camera stand, mobile and telescope. I just wanted to get ready with whatever came in my hand 😄. 

I got few good pictures from camera and did some telescopic observations. on the same day Mars was also in opposition to earth. Mars shining big brightly near to eclipsing moon. I took time to observe this red planet. It was very windy so mars detail was not visible clearly through telescope but if sky condition get settle in coming days then mars will be the great object to observe for next days. 

When moon moved into umbra of earth it turned into red. This time red color was bit darker from last 31 January eclipse. But it was great to see both Mars and Red Moon together. how many time we will get such opportunity. I struggle with my camera setting to capture this red pair. For an hour was awake. Then, clouds started gathering after giving good two and half hour of clear sky. I could see half of the eclipse part but it was great to observe and capture it. Here, are some clicks from the eclipse. 

The red pair of Planet Mars and eclipsed Moon

The night of the Blood Moon and the Red Planet

Night of 27th July is very special for the sky watchers. On this night two special events are going to happen. These two events are very rare to happen together. One is the longest total lunar eclipse of the 21st century and other is the opposition of planet mars. 

27th July Lunar eclipse is the longest eclipse of the twenty first century. Usually, total Lunar eclipses are longer because earth's shadow is very big at the point of lunar orbit. Earth's shadow size is approximately 2.6 times bigger than moons diameter. Even at the speed of  3,682 kilometer per hour moon takes much time to cross earth's shadow. Time of totality depends on the from which part of the shadow moon moves. Last lunar eclipse on 31 January 2018 moon passes from the southern part earth's umbral shadow. It's totality lasted for the 1 hour and 6 minutes. On 31 January moon was at perigee means nearest point to earth in its orbit. Moon was big and near to the earth so it could crosses earth's shadow comparatively fast. 

31 January 2018 Super moon Eclipse, photo taken by me 

On 27th July moon will be at apogee, means it will be at farthest point from earth in orbit so its size will be comparatively small. At this time moon will be passing through the center part of the earth's shadow so it will take time for moon to cross earth's shadow. Moon will be eclipsed for the 1 hour and 43 minutes. This is the duration of totality only. Entire Lunar eclipse is much longer. There are some stages are involved in lunar eclipse which help us to understand path of the moon through earth's shadow. 

Lunar eclipse happens when moon passes through earth's shadow but earth forms two kind of shadows one is Umbra this is center part of shadow which is dark and there is another shadow around umbra which is called Penumbra. Penumbra is the lighter than umbra. When Lunar eclipse happens moon first touches the outer portion of the penumbra this is the beginning of the penumbral eclipse. Next stage moon touches earth's dark shadow umbra this the beginning of partial eclipse. From here onward one can see earth's shadow traveling on the moon's surface. Naked eyes feels that its moving slowly but though telescope one can see the speed of earth's shadow when it gradually gulps moons surface features. After that moon totally goes into earth's umbra and it starts showing red color because some light from sun passes through the earth's atmosphere and fall on moons surface. Redness of eclipsed moon depend upon the activity of the earth's atmosphere. 

Different stages of Total Lunar Eclipse

Then there is a stage called as maximum eclipse this is the middle of the eclipse. After maximum eclipse moon starts traveling to the other end of shadow and touches inner edge of umbra shadow this is the end of total eclipse and again partial eclipse start. Moon start moving out of the umbra and enters in penumbra here, partial eclipse ends. In the last stage moon travels through penumbra and then come out entirely from earth's shadow.

27 July 2018, Eclipse timings for Indian Sky watchers are as follows 

Penumbral Eclipse will start at 10:44 pm IST (Indian standard time)
Umbral Eclipse will be start at 11:54 pm IST
Totality will start at 1:00 am IST on 28 July
Maximum eclipse at 1:52 am IST
Totality ends at 2:43 am IST
Partial eclipse ends at 3:49 am IST
Penumbral eclipse ends at 4:58 am IST

Total Duration of eclipse is 6 hours and 13 minutes 
Total duration of totality is 1 hour and 43 minutes

Animation of total lunar eclipse stages of 27th July 2018, Timings are given in Universal standard we can add Indian zone time of 5:30 hrs to get Indian timings, Sours: earthsky.org

Many people do not find Lunar eclipse exciting as solar eclipse. Might be because of their long duration but lunar eclipses have significance in many ways. Lunar eclipse at ancient times gave opportunity to figure out earth's shape and its size. Nowadays also one can measure size of earth by measuring earth's shadow size on lunar surface. If you don't want to do any measuring just see earth's curve shadow and imagine how people find out its spherical shape.

With the Total Lunar Eclipse, the red planet Mars is aligning opposition with Earth on the same day and coming close to earth. On this day we will get opportunity to see eclipsed blood moon with red planet Mars. They will be near to each other during eclipse. So, do not miss the opportunity to see these two red celestial objects on 27 July night.

Eclipse moon and red planet mars can be observe near to each other, Source: Stellarium 

Planets, Opposition and Retrograde motion

Last year season of sky watching went without any visible planet in evening sky. So, last year I spent nights watching deep sky objects like star clusters, Galaxies and nebulae. These objects are interesting and have importance in sky watching. But with telescope in hand anyone would like to watch planets. There are seven planets in our sky and in these seven planets we can observe five without help of any optical aid. These five planets are very interesting. If you have any small telescope you can observe changes on them. Mercury and Venus shows phases like Moon. On mars surface you can observe changes like dust storms and shrinking and expansion of polar cap. Jupiter shows very dynamic features on its gaseous surface. Saturn with its beautiful ring display magnificent sight in telescope.

Last year we missed them from our evening and night sky. But from last some months they are making their presence in our sky again. From Last few months Venus is stunningly bright in west horizon after sunset. In may month Jupiter was in opposition and then on 27 June Saturn was in opposition. At the end of this month on 27 July Mars is also going to be in opposition. So month by month they are making their presence and some of them are also getting closer to earth on opposition in their orbit.

Opposition is very interesting alignment of planets and it's also provide great opportunity for sky observers to see planets. At this position planets come at exactly opposite to Sun and Earth in their orbit. When planet comes at this position they rise at sunset and set at sunrise which means they stay maximum time in earth's sky. In case of Jupiter you observe its maximum surface as its day is only of 10 hours. At opposition planets reflects maximum light so appear bright at this position. Opposition is condition at which planets comes directly opposite side of Sun and Earth in their orbit. This condition applied to the Superior planets means planets beyond earth orbit like Mars, Jupiter, Saturn, Uranus and Neptune.

Different alignments of planets with respect to Earth

Different kind of alignment happen with the inferior planets which are located in between earth and sun which are Mercury and Venus. They never comes to opposition. In their case when they comes in between sun and earth its called as Inferior conjunction. At inferior conjunction if they come in plane of Sun and Earth we can see then travelling on Sun disc, its called as Transit. When they Go beyond Sun its called as superior conjunction and we can not see them as they are located exactly beyond Sun. In superior planets condition its called as conjunction. For seeing maximum part of inferior planet they must go far from sun in their orbits. This is called as planets elongation from sun. When they get maximum far from sun its called as planets Maximum or Greatest Elongation from sun. At this greatest elongation inferior planets visible in sky for more time before sunrise or after sunset. 

Unlike stars planets stays in motion constantly. Apart from these conditions planets also sometimes shows retrograde motion. Planets shows motions like direct which is their regular motion in sky which is toward east (there is daily motion of planet also in which they move from east to west, this happens due to earth's rotation on it axis). Sometimes they stop and start moving westward and again stops and then again picked their regular motion. Jupiter was in retrograde motion from 9th March and it ended on 11 July this month. Retrograde motion appears when Earth in her orbit passes other planets in their respected orbit. From earth, observer see that planet is moving backward which is east to west and then again start its direct motion which is west to east. Retrograde motion is long time motion. Planet keep moving in this motion for several days. Its very interesting to observe planets such motions. In 2003 Mars showed retrograde motion which I observed, it was great experience to observe planet moving background of stars. Mars was moving notably quick. Observing planet at different alignments and motions give clear picture that how all these planets with earth move around sun that what Copernicus and Galileo said. So, keep eye on planets for next few months.

Retrograde motion of planet Mars in 2003 as seen from Earth

Note:Images are taken from various internet sources