Tiny Moon Neptune Spotted by Hubble May Have Broken Larger Moon – ScienceDaily

After several years of analysis, a team of planetary scientists using NASA's Hubble Space Telescope finally offered an explanation for the mysterious moon surrounding Neptune that she discovered with Hubble in 2013.

The small moon, named Hippocamp, is exceptionally close to a much larger moon called Neptunian called Proteus. Normally, a moon like Proteus should have gravitationally swept or swallowed the smaller moon while clearing its orbital trajectory.

So why does the little moon exist? Hippocamp is probably a chipped piece of the largest moon resulting from a collision with a comet billions of years ago. The tiny moon, which is only 34 kilometers long, represents 1 / 1000th of the Proteus mass (260 miles) [about 418 kilometers] through).

"The first thing we realized was that you would not expect to find such a small moon next to Neptune's biggest inner moon," said Mark Showalter of SETI Institute of Mountain View, California. "In the distant past, given the slow migration of the great moon to the outside, Proteus was once the place where Hippocamp is now located."

This scenario is corroborated by Voyager 2 images from 1989 that show a crater of significant impact on Proteus, large enough to have broken the moon. "In 1989, we thought the crater was the end of history," Showalter said. "With Hubble, we now know that a small piece of Proteus has been left and we see it today under the name of Hippocamp." The orbits of the two moons are now separated by 12,500 km.

Neptune's satellite system has a violent and tortured history. Several billion years ago, Neptune captured the great Triton moon from the Kuiper Belt, a vast region of frozen and rocky objects beyond the orbit of Neptune. The severity of Triton would have torn Neptune's original satellite system. Triton settled in a circular orbit and the debris from the broken Neptunian moons came together to form a second generation of natural satellites. However, the comet bombardment continued to do damage, which resulted in the birth of Hippocamp, which could be considered a third-generation satellite.

"According to estimates of comet populations, we know that other moons of the outer solar system have been affected by comets, broken and re-accrued repeatedly," said Jack Lissauer of the center of NASA's Ames research in Silicon Valley California, on new research. "This pair of satellites provides a dramatic illustration of the fact that moons are sometimes separated by comets."

Hippocamp is a half-fish half-fish of Greek mythology. The scientific name of the hippocampus is Hippocampus, also the name of an important part of the human brain. The rules of the International Astronomical Union require that the moons of Neptune bear the name of the Greek and Roman mythology of the underwater world.

The team of astronomers in this study consists of M. Showalter (SETI Institute, Mountain View, California), I. de Pater (University of California, Berkeley, California) and J. Lissauer (NASA Ames Research Center). , Silicon Valley, California) and R. French (SETI Institute, Mountain View, California).

The document will appear in the February 21 issue of the scientific journal Nature.

The Hubble Space Telescope is an international cooperation project between NASA and ESA (European Space Agency). NASA's Goddard Space Flight Center in Greenbelt, Maryland, operates the telescope. The Space Telescope Scientific Institute (STScI) in Baltimore, Maryland, conducts Hubble's scientific activities. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Washington, D.C.