 |
| Credits: NASA, ESA, CSA, STScI |
With its first image of Neptune, NASA's James Webb Space Telescope demonstrates its capabilities closer to home. In addition to providing the clearest view of the distant planet's rings in more than 30 years, Webb's cameras shed new light on the ice giant.
The planet's rings, some of which have not been seen since NASA's Voyager 2 was the first spacecraft to observe Neptune during its 1989 flyby, are the most striking feature of Webb's new image. The fainter dust bands of Neptune are clearly visible in the Webb image, in addition to a few bright, narrow rings.
According to Heidi Hammel, a specialist in the Neptune system and an interdisciplinary Webb scientist, "It has been three decades since we last saw these faint, dusty rings, and this is the first time we’ve seen them in the infrared. "These extremely faint rings can be detected so close to Neptune thanks to Webb's extremely stable and precise image quality.
 |
| Credits: NASA, ESA, CSA, STScI |
Since its discovery in 1846, researchers have been captivated by Neptune. Neptune orbits in a remote, dark part of the outer solar system, 30 times further from the Sun than Earth. High noon on Neptune is comparable to a dim twilight on Earth because the Sun is so small and faint at that extreme distance.
The chemical composition of this planet's interior makes it an ice giant. Neptune has a significantly higher proportion of heavier elements than hydrogen and helium when compared to the gas giants Jupiter and Saturn. Small amounts of gaseous methane are to blame for Neptune's distinctive blue appearance in visible wavelength Hubble Space Telescope images.
Neptune does not appear blue to Webb because it is imaged by Webb's Near-Infrared Camera (NIRCam) in the near-infrared range of 0.6 to 5 microns. Except for high-altitude clouds, the planet is actually quite dark at these near-infrared wavelengths because the methane gas absorbs red and infrared light so strongly.These methane-ice clouds stand out as bright spots and streaks because they reflect sunlight before it is taken up by methane gas.Over time, these rapidly changing cloud features have been recorded in images from other observatories, such as the W.M. Keck Observatory and the Hubble Space Telescope.
A subtler visual sign of the global atmospheric circulation that powers Neptune's winds and storms could be a thin bright line that encircles the planet's equator.Because it warms at the equator as it descends, the atmosphere glows in the infrared more than the cooler gases that surround it.
The northern pole of Neptune, depicted at the top of this image, is obscured by the planet's 164-year orbit, but the Webb images hint at an intriguing brightness there.Webb's view shows a known vortex at the southern pole, but for the first time he shows that it is surrounded by a continuous band of high-latitude clouds.
Webb also took seven of the 14 known moons of Neptune. This Webb portrait of Neptune is dominated by a very bright point of light with the diffraction spikes that are characteristic of many of Webb's images, but this is not a star. Rather, this is Triton, Neptune's unusually large moon.
Triton reflects an average of 70% of the sunlight that hits it because it is covered in a frozen sheen of nitrogen that has been compressed. Methane absorption at these near-infrared wavelengths darkens the planet's atmosphere, making it stand out significantly from Neptune in this image. Astronomers have speculated that Triton was initially a Kuiper belt object that was gravitationally captured by Neptune due to its unusual backward (retrograde) orbit around Neptune. In the coming year, additional Webb studies of Triton and Neptune are planned.
The most important space science observatory in the world is the James Webb Space Telescope. Webb will investigate the enigmatic structures and origins of our universe and our place in it, as well as look beyond our solar system to worlds orbiting other stars. The European Space Agency (ESA) and the Canadian Space Agency are NASA's partners in the international Webb program.
0 Comments