Hubble images reveal Neptune's 'lost' inner moon

Naiad is the encircled point of light just to the left of Neptune.

Neptune's tiny, innermost moon, Naiad, has now been seen for the first time since it was discovered by Voyager's cameras in 1989.

Dr. Mark Showalter, a senior research scientist at the SETI Institute in Mountain View, California, announced the result today in Denver, Colorado, at the annual meeting of the Division for Planetary Sciences of the American Astronomical Society.

He and collaborators Dr. Jack Lissauer of the NASA Ames Research Center, Dr. Imke de Pater of UC Berkeley, and Robert French of the SETI Institute, also released a dramatic new image of Neptune's puzzling rings and ring-arcs, which were first imaged by Voyager.

Mark Showalter

"Naiad has been an elusive target ever since Voyager left the Neptune system," said Dr. Showalter. From Earth, Neptune is 2 million times brighter than Naiad, andthetwo are separated by only one arcsecond.

"This is equivalent to the width of a human hair from 50 feet away," noted collaborator Lissauer. The team of astronomers needed to develop new techniques to suppress Neptune's glare.

Naiad was finally revealed, moving across a sequence of eight images taken during December 2004.

Strangely, Naiad appears to have veered significantly off course. The astronomers are puzzled by the fact that Naiad is now far ahead of its predicted orbital position.

They wonder whether gravitational interactions with one of Neptune's other moons may have caused it to speed up, although the details remain mysterious.

Further observations will be needed in order to understand Naiad's motion.

In addition to its moons, Neptune hosts a family faint rings and ring-arcs. The arcs have been changing slowly in the years since their discovery.

Whereas Voyager saw a set of four closely-spaced arcs, the leading two arcs have been fading away, and are completely absent from the newest images.

The trailing arcs, however, are essentially unchanged. This system of arcs is probably confined by the gravitational effects of the nearby moon Galatea, but the reason for the long-term changes is unknown.

Dr. de Pater has also been following the ongoing evolution of the arcs from the 10-meter W. M. Keck telescope in Hawaii.

ESA's SOHO Archive is now online

The SOHO science archive is the first in a series of new generation scientific archives being developed and implemented by the Science Archives and Virtual Observatory Team at the European Space Astronomy Centre in Spain.

These archives will contribute to preserving the legacy of ESA's science missions by conserving and providing access to data from all of these missions.

Access to data from the ESA-NASA SOHO mission has just become easier with the launch of a new SOHO science archive with enhanced capabilities for searching and visualising the vast SOHO data archive. This is the first in a new generation of science archives under development at ESA's European Space Astronomy Centre.

Since operations began in 1995 the Solar and Heliospheric Observatory (SOHO) has been transmitting data from its twelve scientific instruments back to Earth at a rate of 1 Gigabyte per day.

Analysis of this data has resulted in ground-breaking scientific results which have included the first images of a star's convection zone and the structure of sunspots below the photosphere; the most precise measurements of the temperature structure, interior rotation, and gas flow in the solar interior; the discovery of new dynamic phenomena such as coronal waves and solar tornadoes, and the discovery of more than 1600 comets.

The recently launched ESA SOHO Science Archive allows for seamless access to the complete archive of science data sets from the 12 instruments as soon as the data are processed.