Wednesday, December 28, 2011

Moving sand dunes

In several desert areas, the slow motion of sand dunes can be a challenge for modern human activities and a threat for the survival of ancient places or archaeological sites. However, several methods exist for surveying the dune fields and estimate their migration rate. Among these methods, the use of satellite images, in particular of those freely available on the World Wide Web, is a convenient resource for the planning of future human settlements and activities. More at

The barchans move. Note the dunes on the tracks.

Thursday, October 27, 2011

Giant Waterworld Around Naked Eye Star 

Giant Waterworld Confirmed Around Naked Eye Star - Technology Review
"55 Cancri A is a Sun-like star some 40 light years away. It has an apparent magnitude of about 6 and so is visible to the naked eye in the constellation of Cancer.
This star is unusual in that it is just one of a handful that are known to have at least 5 planets. The innermost of these planets--55 Cancri e--was discovered in 2004 and has since had plenty of attention from astronomers. Various groups have observed the the changes in radial velocity that it causes its parent star. This tells them about that it orbits its star every 18 hours and that its mass is about 8 times Earth's or about half Neptune's.""The innermost planet around 55 Cancri A is almost certainly an exotic waterworld with a radius about twice Earth's, say astronomers"

Friday, October 7, 2011

Eta Carinae's Homunculus

Homunculus Nebula is surrounding the star system Eta Carinae. The nebula is embedded within a much larger ionized hydrogen region, which is the Carina Nebula. Homunculus is believed to have been ejected in a huge outburst from Eta Carinae in 1841, so brightly to be visible from Earth. This massive explosion produced two polar lobes and an equatorial disc, moving outwards. Though Eta Carinae is quite away, approximately 7,500 light-years, it is possible to distinguish in the nebula, many structures with the size of about the diameter of our solar system. Knots, dust lanes and radial streaks appear quite clearly in many images.

At the, I am comparing the imaging of Homunculus Nebula, obtained by Hubble Space Telescope, and that from the Gemini South Telescope.
See also, A comment on Eta Carinae's Homunculus Nebula imaging.

Iris Nebula

Iris Nebula LBN 487 

From an image by Hewholooks, which is the user page of Hunter Wilson. Images may be seen at or on
Wikimedia at

Aurora boreale su Saturno

Un'aurora boreale su Saturno vista da Hubble

Dancing galaxies

Il Sole24ore propone una collezione di immagini con la danza delle galassie. Vedi

Tuesday, August 30, 2011

Europa, Ganymede and Callisto

Europa, Ganymede and Callisto in a surface comparison.
Images from NASA, JPL.
These are the icy surfaces of three of the Galileian Moons.

Friday, August 5, 2011

Collision may have shaped the Moon

"Differences between the near and far sides of the Moon could be the result of a collision between the Moon and a "Trojan" companion that occurred billions of years ago. That is the conclusion of geophysicists in the US and Switzerland who have done computer simulations on how the Moon would be affected by such a massive impact."
Trojan collision may have shaped the Moon -

Flowing water may exist on Mars

"Liquid water might exist on Mars today, according to a group of scientists in the US. Images from NASA's Mars Reconnaissance Orbiter (MRO) reveal that dark, narrow, finger-like structures follow slopes in certain regions of the southern hemisphere of the planet during its summer months."
Flowing water may exist on Mars -

Wednesday, August 3, 2011

Merowe Dam on the Nile

The artificial lake (reservoir) created by the Merowe Dam on the Nile has been photographed by the crew of the International Space Station. This image is recent, dating 5 October 2010. The dam is on the Nile near the Fourth Cataract, in that part of Nubia desert where the river Nile is creating the Great Bend, a contorted path through the bedrocks of Bayuda Massif. The satellite imagery of Google Maps, which is a few years old, shows the region, when the dam was under construction. Using Google, we see the Nile and river banks creating a fertile strip of land with many villages.

We can compare the region before and after the spill gates have been closed.
Comparison shows that the lake created itself through the paleochannes, the old dry riverbeds.


More at