Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Brighter Neptune suggests a planetary change of seasons

16.05.2003


A progressive increase in the brightness of the planet Neptune suggests that, like Earth, the distant planet has seasons.


A time series of images of the planet Neptune taken by the Hubble Space Telescope illustrate increasing cloudiness that is a hallmark of seasonal change. The growing bands of clouds in the southern hemisphere of the planet suggest seasonal change. Because the planet takes about 165 years to orbit the sun, the seasons on Neptune last more than 40 years.
Image credit: L. Sromovsky, P.Fry (University of Wisconsin), and NASA



Observations of Neptune made during a six-year period with NASA’s Hubble Space Telescope by a group of scientists from the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory (JPL) show that the planet is exhibiting a significant increase in brightness. The changes, observed mostly in the planet’s southern hemisphere, show a distinct increase in the amount and brightness of the banded cloud features that are a distinctive feature of the planet.

"Neptune’s cloud bands have been getting wider and brighter," says Lawrence A. Sromovsky, a senior scientist at UW-Madison’s Space Science and Engineering Center and a leading authority on Neptune’s atmosphere. "This change seems to be a response to seasonal variations in sunlight, like the seasonal changes we see on Earth."


The findings are reported in the current issue (May 2003) of Icarus, a leading planetary science journal.

Neptune, the eighth planet from the sun, is known for its weird and violent weather. It has massive storm systems and ferocious winds that sometimes gust to 900 miles per hour, but the new Hubble observations are the first to suggest that the planet undergoes a change of seasons.

Using Hubble, the Wisconsin team made three sets of observations of Neptune. In 1996, 1998 and 2002, they obtained observations of a full rotation of the planet. The images showed progressively brighter bands of clouds encircling the planet’s southern hemisphere. The findings are consistent with observations made by G.W. Lockwood at the Lowell Observatory, which show that Neptune has been gradually getting brighter since 1980.

"In 2002 images, Neptune is clearly brighter than it was in 1996 and 1998," Sromovsky says, "and is dramatically brighter at near infrared wavelengths. The greatly increased cloud activity in 2002 continues a trend first noticed in 1998."

Like the Earth, Neptune would have four seasons: "Each hemisphere would have a warm summer and a cold winter, with spring and fall being transitional seasons, which may or may not have specific dynamical features," the Wisconsin scientist explains.

Unlike the Earth, however, the seasons of Neptune last for decades, not months. A single season on the planet, which takes almost 165 years to orbit the sun, can last more than 40 years. If what scientists are observing is truly seasonal change, the planet will continue to brighten for another 20 years.

Also like Earth, Neptune spins on an axis that is tilted at an angle toward the sun. The tilt of the Earth, at a 23.5-degree inclination, is the phenomenon responsible for the change of seasons. As the Earth spins on its axis and orbits the sun during the course of a year, the planet is exposed to patterns of solar radiation that mark the seasons. Similarly, Neptune is inclined at a 29-degree angle and the northern and southern hemispheres alternate in their positions relative to the sun.

What is remarkable, according to Sromovsky, is that Neptune exhibits any evidence of seasonal change at all, given that the sun, as viewed from the planet, is 900 times dimmer than the sun as seen from the Earth. The amount of solar energy a hemisphere receives at a given time is what determines the season.

"When the sun deposits heat energy into an atmosphere, it forces a response. In the hemisphere getting the most sunlight, we would expect heating, which in turn could force rising motions, condensation and increased cloud cover," Sromovsky notes.

Bolstering the idea that the Hubble images are revealing a real increase in Neptune’s cloud cover consistent with seasonal change is the apparent absence of change in the planet’s low latitudes near its equator.

"Neptune’s nearly constant brightness at low latitudes gives us confidence that what we are seeing is indeed seasonal change, as those changes would be minimal near the equator and most evident at high latitudes where the seasons tend to be more pronounced."

Despite the new insights into Neptune, the planet remains an enigma, says Sromovsky. While Neptune has an internal heat source that may also contribute to the planet’s apparent seasonal variations and blustery weather, when that is combined with the amount of solar radiation the planet receives, the total is so small that it is hard to understand the dynamic nature of Neptune’s atmosphere.

There seems, Sromovsky says, to be a "trivial amount of energy available to run the machine that is Neptune’s atmosphere. It must be a well-lubricated machine that can create a lot of weather with very little friction."

In addition to Sromovsky, authors of the Icarus paper include Patrick M. Fry and Sanjay S. Limaye, both of UW-Madison’s Space Science and Engineering Center, and Kevin H. Baines of NASA’s Jet Propulsion Laboratory in Pasadena, Calif.


Terry Devitt, 608-262-8282, trdevitt@wisc.edu

CONTACT: Lawrence Sromovsky, 608-263-6785, lsromovsky@ssec.wisc.edu.

Lawrence Sromovsky | EurekAlert!
Further information:
http://www.wisc.edu/

More articles from Physics and Astronomy:

nachricht New quantum liquid crystals may play role in future of computers
21.04.2017 | California Institute of Technology

nachricht Light rays from a supernova bent by the curvature of space-time around a galaxy
21.04.2017 | Stockholm University

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Making lightweight construction suitable for series production

More and more automobile companies are focusing on body parts made of carbon fiber reinforced plastics (CFRP). However, manufacturing and repair costs must be further reduced in order to make CFRP more economical in use. Together with the Volkswagen AG and five other partners in the project HolQueSt 3D, the Laser Zentrum Hannover e.V. (LZH) has developed laser processes for the automatic trimming, drilling and repair of three-dimensional components.

Automated manufacturing processes are the basis for ultimately establishing the series production of CFRP components. In the project HolQueSt 3D, the LZH has...

Im Focus: Wonder material? Novel nanotube structure strengthens thin films for flexible electronics

Reflecting the structure of composites found in nature and the ancient world, researchers at the University of Illinois at Urbana-Champaign have synthesized thin carbon nanotube (CNT) textiles that exhibit both high electrical conductivity and a level of toughness that is about fifty times higher than copper films, currently used in electronics.

"The structural robustness of thin metal films has significant importance for the reliable operation of smart skin and flexible electronics including...

Im Focus: Deep inside Galaxy M87

The nearby, giant radio galaxy M87 hosts a supermassive black hole (BH) and is well-known for its bright jet dominating the spectrum over ten orders of magnitude in frequency. Due to its proximity, jet prominence, and the large black hole mass, M87 is the best laboratory for investigating the formation, acceleration, and collimation of relativistic jets. A research team led by Silke Britzen from the Max Planck Institute for Radio Astronomy in Bonn, Germany, has found strong indication for turbulent processes connecting the accretion disk and the jet of that galaxy providing insights into the longstanding problem of the origin of astrophysical jets.

Supermassive black holes form some of the most enigmatic phenomena in astrophysics. Their enormous energy output is supposed to be generated by the...

Im Focus: A Quantum Low Pass for Photons

Physicists in Garching observe novel quantum effect that limits the number of emitted photons.

The probability to find a certain number of photons inside a laser pulse usually corresponds to a classical distribution of independent events, the so-called...

Im Focus: Microprocessors based on a layer of just three atoms

Microprocessors based on atomically thin materials hold the promise of the evolution of traditional processors as well as new applications in the field of flexible electronics. Now, a TU Wien research team led by Thomas Müller has made a breakthrough in this field as part of an ongoing research project.

Two-dimensional materials, or 2D materials for short, are extremely versatile, although – or often more precisely because – they are made up of just one or a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Expert meeting “Health Business Connect” will connect international medical technology companies

20.04.2017 | Event News

Wenn der Computer das Gehirn austrickst

18.04.2017 | Event News

7th International Conference on Crystalline Silicon Photovoltaics in Freiburg on April 3-5, 2017

03.04.2017 | Event News

 
Latest News

Molecular libraries for organic light-emitting diodes

24.04.2017 | Life Sciences

Research sheds new light on forces that threaten sensitive coastlines

24.04.2017 | Earth Sciences

Making lightweight construction suitable for series production

24.04.2017 | Machine Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>