Astronomy
A photo on Naiad from Voyager 2 in 1989, courtesy of NASA

Naiad, Neptune’s moon was lost and then found again by SETI



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A photo on Naiad from Voyager 2 in 1989, courtesy of NASA
Keith Ziegman's image for:
"Naiad, Neptune's moon was lost and then found again by SETI"
Caption: A photo on Naiad from Voyager 2 in 1989, courtesy of NASA
Location: 
Image by: Voyager 2
©  http://solarsystem.nasa.gov/planets/profile.cfm?Object=Nep_Naiad

Naiad, a tiny moon of Neptune was lost and had not been seen for over twenty years. The elongated-shaped moon was originally discovered in September, 1989 by the Voyager 2 spacecraft. Since 1989 all attempts to view the tiny moon have been unsuccessful.

The problem with trying to view the moon is that it is the innermost moon of Neptune. According to Dr. Mark Showalter of the SETI Institute, Neptune is two million times brighter than Naiad and only separated by one arcsecond. “It is equivalent to the width of a human hair at fifty feet”, noted Dr. Jack Lissauer of the NASA Ames Research Center. 

The SETI Institute stated the Naiad was finally revealed by moving across a sequence of eight images from the Hubble space telescope taken during December 2004. In viewing the moon the scientists noted the moon is off course. Naiad has sped up and is far ahead of its predicted orbital position. Further observation will be required to understand Naiad’s motion. 

According to NASA information page about Naiad, the moon was originally discovered to be in a decaying orbit and may eventually crash into Neptune or be torn apart by the planetary rings.

NASA’s information page states, Naiad (Nye-ed) was named after a type of nymph which took care of springs, streams and brooks in Greek mythology and was originally designated S/1989 N6. The moon is 62 miles or 100 kilometers wide and orbits Neptune every seven hours and six minutes. Naiad travels at about 43,000 kph or 27,000 mph, with an orbit size of 48,227 km or 29,967 miles. 

Naiad was most likely formed from fragments from Neptune’s original satellites, which were smashed up by perturbation caused by Triton or Triton smashed into them allowing Triton to be captured by Neptune. It is probable Naiad has not been modified by any internal geological processes since its formation.

Here are some other interesting facts about Naiad. Naiad is one of eleven moons of Neptune. The surface gravity of Naiad is only 0.012 m/s2 compared to Earth’s surface gravity of 9.8 m/s2; meaning if an object was dropped while standing on the surface of Naiad, the object would travel at 0.012 meters per second squared or 0.026 mph per second squared. In contrast, dropping an object on Earth would travel at 9.8 meters per second squared or 21.9 mph/s2.  

Naiad is one of four innermost moons: Thalassa, Despina, and Galatea, all of which orbit very close to Neptune inside the planetary rings and very little is known about them.    

The escape velocity of Naiad is only 101 kph or about 63 mph.  Which means one would only have to reach the speed noted to lift off of the surface of Naiad.

Naiad’s density is listed as 1.3 grams per cubic centimeter compared to Earth’s 5.5 g/cm3, which means Naiad is probably not made up of heavy elements. In fact Neptune’s density is only slightly higher listed as 1.64 g/cm3 but is however considered a gas giant like Jupiter and Saturn.

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More about this author: Keith Ziegman

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ARTICLE SOURCES AND CITATIONS
  • InfoBoxCallToAction ActionArrowhttp://www.seti.org/seti-institute/press-release/archival-hubble-images-reveal-neptunes-lost-inner-moon
  • InfoBoxCallToAction ActionArrowhttp://www.merriam-webster.com/dictionary/surface%20gravity
  • InfoBoxCallToAction ActionArrowhttp://hyperphysics.phy-astr.gsu.edu/hbase/vesc.html
  • InfoBoxCallToAction ActionArrowhttp://starchild.gsfc.nasa.gov/docs/StarChild/teachers/densities.html