Short "Offtopic" Explanation

2013 May 14
Galaxy Collisions: Simulation vs Observations

* Images Credit: NASA, ESA
http://www.esa.int/
http://www.nasa.gov/;
* Visualization: Frank Summers (STScI)
http://www.stsci.edu/;
* Simulation: Chris Mihos (CWRU) & Lars Hernquist (Harvard)
https://astronomy.case.edu/ .

Explanation:
What happens when two galaxies collide? Although it may take over a billion years, such titanic clashes are quite common. Since galaxies are mostly empty space, no internal stars are likely to themselves collide. Rather the gravitation of each galaxy will distort or destroy the other galaxy, and the galaxies may eventually merge to form a single larger galaxy. Expansive gas and dust clouds collide and trigger waves of star formation that complete even during the interaction process. Pictured above is a computer simulation of two large spiral galaxies colliding, interspersed with real still images taken by the Hubble Space Telescope. Our own Milky Way Galaxy has absorbed several smaller galaxies during its existence and is even projected to merge with the larger neighboring Andromeda galaxy in a few billion years.

https://apod.nasa.gov/apod/ap130514.html

#space #galaxy #astrophotography #photography #science #astronomy #nature #NASA

2025 June 30

NGC 4651: The Umbrella Galaxy
* Image Credit: Rabeea Alkuwari & Anas Almajed
https://www.instagram.com/bolahdan/
https://www.instagram.com/anas_almajed/

Explanation:
It's raining stars. What appears to be a giant cosmic umbrella is now known to be a tidal stream of stars stripped from a small satellite galaxy. The main galaxy, spiral galaxy NGC 4651, is about the size of our Milky Way, while its stellar parasol appears to extend some 100 thousand light-years above this galaxy's bright disk. A small galaxy was likely torn apart by repeated encounters as it swept back and forth on eccentric orbits through NGC 4651. The remaining stars will surely fall back and become part of a combined larger galaxy over the next few million years. The featured deep image was captured in long exposures from Saudi Arabia. The Umbrella Galaxy lies about 50 million light-years distant toward the well-groomed northern constellation of Berenice's Hair (Coma Berenices).
https://www.instagram.com/anas_almajed/https://www.instagram.com/anas_almajed/
https://en.wikipedia.org/wiki/NGC_4651

https://en.wikipedia.org/wiki/Satellite_galaxy
https://en.wikipedia.org/wiki/Orbital_eccentricity#/media/File:Animation_of_Orbital_eccentricity.gif

https://apod.nasa.gov/apod/ap130514.html
https://apod.nasa.gov/apod/ap120604.html

https://apod.nasa.gov/apod/ap250630.html

#space #galaxy #astrophotography #photography #science #astronomy #nature #NASA

April 6, 2011

Dry Ice on Mars
by Melody

On Mars the seasonal polar caps are composed of dry ice (carbon dioxide). In the springtime as the sun shines on the ice, it turns from solid to gas and causes erosion of the surface. Dry ice goes directly from solid to vapor, unlike water ice which melts into liquid when it gets warm.

On Mars the seasonal polar caps are composed of dry ice (carbon dioxide). In the springtime as the sun shines on the ice, it turns from solid to gas and causes erosion of the surface. I enjoy the incredible diversity of forms that the erosion takes, and am studying the factors that give us "spiders", "caterpillars", or "starbursts", all colloquial words for what we rigorously name "araneiform" terrain.

This particular example shows eroded channels filled with bright ice, in contrast to the muted red of the underlying ground. In the summer the ice will disappear into the atmosphere, and we will see just the channels of ghostly spiders carved in the surface. This is truly Martian terrain - this type of erosion does not take place anywhere naturally on earth because our climate is too warm.

Credit:
NASA/JPL/University of Arizona

#space #mars #astrophotography #photography #science #astronomy #nature #NASA