Artistic illustration of planet Neptune
Image 1: Artistic illustration of planet Neptune | © Unrevealed Files

Neptune is an ice giant, Dark, cold, and whipped by supersonic winds. It is the eighth and most distant planet in our solar system. Neptune is the only planet in our solar system not visible to the naked eye and the first predicted by mathematics before its discovery. NASA’s Voyager 2 spacecraft is the only one that has visited Neptune up close. Learn more read the full article

Ice giant Planet Neptune

Neptune is the eighth largest planet in our solar system. It is the fourth-largest planet in diameter and the third-largest planet of all the planets in the solar system. Neptune is 17 times the mass of the Earth, slightly higher than its nearest planet Uranus. Neptune is denser and smaller than Uranus, as its greater mass causes more gravitational compression of its atmosphere.

the European Southern Observatory developed unique laser-based methods to get clear and high-resolution images of Neptune from the surface of Earth
Image 2: The European Southern Observatory developed unique laser-based methods to get clear and high-resolution images of Neptune from the surface of Earth.
This image of the planet Neptune was obtained during the testing of the Narrow-Field adaptive optics mode of the MUSE/GALACSI instrument on ESO’s Very Large Telescope. The corrected image is sharper than a comparable image from the NASA/ESA Hubble Space Telescope.

Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 AU (4.5 billion km). It is named after the Roman god of the sea and has the celestial symbol ♆, a stylish version of the trident of the Roman god Neptune.

Neptune is not visible from the eye by the Earth and is the only planet in the solar system that has been found by mathematical prediction rather than empirical observation. Uranus’ unexpected change in its orbit prompted Alexis Bouvard that its orbit was subject to gravitational disturbances by an unknown planet.

Neptune was later spotted with a telescope on 23 September 1846. Within a fraction of the position predicted by Johann Gale to Urbain le Verrier. It soon discovered the largest moon, Triton.

However none of the remaining 13 moons of the planet were seen with binoculars until the 20th century. The planet’s distance from Earth gives it a very small size, making it challenging to study with Earth-based telescopes. Neptune was visited by Voyager 2 when he flew near the planet on 25 August 1989. The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics have recently allowed for additional detailed observations from afar.

Combined color and near-infrared image of Neptune, showing bands of methane in its atmosphere, and four of its moons, Proteus, Larissa, Galatea, and Despina
Credit: Hubble Space Telescope - frame from video on Hubblesite: STScI-2005-22
Image 3: Combined color and near-infrared image of Neptune, showing bands of methane in its atmosphere, and four of its moons, Proteus, Larissa, Galatea, and Despina
Credit: Hubble Space Telescope – frame from video on Hubblesite: STScI-2005-22

Like Jupiter and Saturn, Neptune’s atmosphere is composed primarily of hydrogen and helium, as well as traces of hydrocarbons and possibly nitrogen, although it has a higher proportion of “ions” such as water, ammonia, and methane. However, similar to Uranus, its interior is mainly composed of ions and rock. Uranus and Neptune are generally considered “ice giants” to emphasize this difference. Traces of methane in the outer regions for the appearance of the planet’s blue color.

Unlike the misty, relatively featureless environment of Uranus, Neptune (Neptune) environments have active and visible weather patterns. For example, at the time of the Vyzer 2 flyby in 1989, the planet had a Great Dark Spot compared to the Great Red Spot on Jupiter in the southern hemisphere. These weather patterns are driven by the strongest sustained winds of any planet in the solar system, with wind speeds exceeding 2,100 km / h (580 m / s, 1,300 mph). Due to its great distance from the Sun, Neptune’s outer atmosphere is one of the coldest places in the Solar System, with temperatures reaching 55 K (−218 ° C; −361 ° F) topped. The temperature at the center of the planet is about 5,400 K (5,100 ° C; 9,300 ° F). Neptune has a faint and fragmented ring system (labeled “arcs”), which was discovered in 1984, then later confirmed by Voyager 2.

Observations of Planet Neptune

Galileo Galilei
Image 4: Galileo Galilei

On 28 December 1612 and 27 January 1613 the earliest recorded observations were made through a telescope by Galileo. Galileo’s drawings contain plotted points that match up with what is now known to be the position of Neptune. On both occasions, Galileo seems to have mistaken Neptune for a fixed star when it appeared close—in conjunction—to Jupiter in the night sky; however, he is not credited with Neptune’s discovery. At his first observation in December 1612, Neptune was almost stationary in the sky because it had just turned retrograde that day. This apparent backward motion is created when Earth’s orbit takes it past an outer planet. Because Neptune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with Galileo’s small telescope. In 2009, a study suggested that Galileo was at least aware that the “star” he had observed had moved relative to the fixed stars.

Advertisement, continue reading

In 1821, Alexis Bouvard published astronomical tables of the orbit of Neptune’s neighbor Uranus. Subsequent observations revealed substantial deviations from the tables, leading Bouvard to hypothesize that an unknown body was perturbing the orbit through gravitational interaction. In 1843, John Couch Adams began work on the orbit of Uranus using the data he had. He requested extra data from Sir George Airy, the Astronomer Royal, who supplied it in February 1844. Adams continued to work in 1845–46 and produced several different estimates of a new planet.

Discovery Of Planet Neptune

Neptune was discovered by Johann Galle and Le Vernier in 1846 and in fact, its existence was predicted by John Couch Adams much earlier. It is the general belief that these distant planets were discoveries made for the first time in the history of mankind thanks to the invention of the telescope. 

Urbain Le Verrier
Image 5: Urbain Le Verrier

However, According to the epic Mahabharata (3100 BCE), Ancient Indian astronomers, planets were not visible to the naked eye were known to and that the planets mentioned as Sumeta, Syamet, and Teekshana could be a reference to the three distant planets Uranus, Neptune and Pluto. 

Maharshi Vyasa. 
Credit: Ramanarayanadatta astri Publisher: Gorakhpur Geeta Press
Image 6: Maharshi Vyasa. 
Credit: Ramanarayanadatta astri Publisher: Gorakhpur Geeta Press

The planet Sweta in the Citta Nakshatra (constellation) has been described by Mahabharata author Vyasa as being Greenish White and it has now been discovered to be the color of Uranus; the Bluish White of the planet Syamat is found to be the color of Neptune. Indian Scholars believe that the planet that Vyasa has referred to as Teekshana ‘troubling’ the Krittika constellation as Pluto discovered in 1930.  

“शुक्रहः प्रोस्थापदे पूर्वे समारुह्य विरोचते उत्तरे तु परिक्रम्य सहितः षमुदिक्ष्यते [१५-भीष्। ३]
स्यमोग्रहः प्रज्वलितः सधूम इव पावकः आऐन्द्रम् तेजस्वी णक्ष-तरं ज्येस्थां आक्रम्य तिष्ठति [ १६-भीष्। ३]”

Shukrahah Prosthapade Poorve Samaruhya Virochate Uttare tu Parikramya Sahitah Samudikshyate….[15-Bheeshma.3]
Syamograhah Prajwalitah Sadhooma iva Pavakah Aaindram Tejaswi Naksha- tram Jyesthaam Aakramya Tishthati…[16-Bheeshma.3]

Sage Vyasa mentions that a bluish-white (Syama) planet was in Jyeshtha and it was smoky (Sadhoom). Neelkantha calls it “Parigha” (circumference) in his commentary on Mahabharat, meaning that its orbit was almost of the circumference of our solar system. There is mention of mirrors and microscopic vision in Mahabharata (Shanti A. 15,308) as “Durbini” or “Durbin”. In ancient literature, Durbini (device used to see objects at far off distance, similar to binoculars) were mentioned. So, it means that lenses and telescopes were present at the time and they were used.


  1. Hamilton, Calvin J. (4 August 2001). “Neptune”. Views of the Solar System. Archived from the original on 15 July 2007. Accessed 13 August 2020.
  2. “Exploration | Neptune”NASA Solar System Exploration. Retrieved 3 February 2020. In 1989, NASA’s Voyager 2 became the first-and only-spacecraft to study Neptune up close.
  3. Podolak, M.; Weizman, A.; Marley, M. (December 1995). “Comparative models of Uranus and Neptune”. Planetary and Space Science43 (12): 1517–22. Bibcode:1995P&SS…43.1517P. DOI:10.1016/0032-0633(95)00061-5.
  4. Lunine, Jonathan I. (September 1993). “The Atmospheres of Uranus and Neptune”. Annual Review of Astronomy and Astrophysics31: 217–63. Bibcode:1993ARA&A..31..217L. DOI:10.1146/annurev.aa.31.090193.001245.
  5. Suomi, V.E.; Limaye, S.S.; Johnson, D.R. (1991). “High Winds of Neptune: A possible mechanism”. Science251 (4996): 929–32. Bibcode:1991Sci…251..929S. DOI:10.1126/science.251.4996.929. PMID 17847386.
  6. Hubbard, W.B. (1997). “Neptune’s Deep Chemistry”. Science275 (5304): 1279–80. DOI:10.1126/science.275.5304.1279. PMID 9064785.
  7. Wilford, John N. (10 June 1982). “Data Shows 2 Rings Circling Neptune”The New York TimesArchived from the original on 10 December 2008. Accessed 13 August 2020.
  8. Daily Mirror. (2017, December 1). Were Uranus, Neptune, and Pluto known to ancient Indians? Daily Mirror. Accessed 13 August 2020.

This Article was Published On: 20 August, 2019 And Last Modified On: 3 November, 2020