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Ever wonder about what lies between the stars? Learn all about the interstellar medium in this short video! Follow Evant Horizon for more astronomy posts!

The interstellar medium is the gas and dust between stars. Of its mass, this gas is composed of mainly hydrogen and helium with a touch of heavier elements. Highly dense regions of the ISM known as molecular clouds are directly responsible for the formation of stars.

Aurora from the ISS.

Photo credit: NASA

Wormholes

Also known as Einstein-Rosen Bridges are theoretically possible going by Einstein’s theory, and equations of general relativity. Basically wormholes take advantage of our 3 dimensional space and are able to “bend” it. Picture a sheet of paper; now put two circular holes on each end of that sheet of paper. Normally the quickest way to join one point to the other would be to draw a straight line between them. Now instead, you could fold the piece of paper so each hole is touching meaning that there is no longer any distance between them. This is an analogy of how a wormhole works except instead of a circular hole on a 2D plane, the entry and exit points of an Einstein-Rosen bridge can be visualised as spheres in a 3D space.

While the theory of general relativity allows the existence of wormholes, we have not yet found physical evidence. The first wormhole solution discovered was the Schwarzschild wormhole presented in the Schwarzschild metric describing an eternal black hole. However this is not stable enough and would collapse before anything could cross from one end to the other. Traversable wormholes could exist of there was a form of exotic matter with a negative energy to stabilise them.

The Casmir effect shows that quantum field theory allows the energy density in some space to be relatively lower than the ordinary vacuum of space. A lot of physicists (like Stephen Hawking) use this to argue that it is possible to stabilise a traversable wormhole. However there are no known natural processes that would cause a traversable wormhole to stabilise.

The quantum foam hypothesis can be used to suggest the spontaneous appearance of tiny black holes at the Planck scale. Stable versions of these tiny wormholes have been suggested as dark matter candidates. It is also possible that one of these wormholes opened into a previously empty space from another universe, held open by a cosmic string (1D string) with a negative mass then it could be inflated to a macroscopic size by cosmic inflation. Is it possible this happened at the start of the Big Bang?

The beautiful surface of Europa

To visualise the black hole in Interstellar, the VFX team collaborated with theoretical physicist Kip Thorne to solve the equations for propagation of light around a spinning black hole. The shape is due to way light is lensed (deflected) by the strong gravitational field of the black hole. The asymmetry is caused by the relativistic time dilation near the event horizon.

The top image shows the black hole in the movie. The bottom image is a more accurate visualisation taking into account Doppler and gravitational frequency shifts. This was considered too confusing for the audience. They also slowed the black hole’s spin down from that required to explain the time dilation experienced in the movie, to make the black hole appear less asymmetric.

The are releasing two papers on their work, the first of which is available in preprint on arXiv.

Today marks the 40th anniversary for the launch of the Viking 1 lander/orbiter to Mars in 1975, which set the stage - err, launch pads - for subsequent flyby, orbiter, lander, and rover missions. 

Although some of these missions are marked as “failed” attempts, an engineer or flight controller would dismiss this classification, as data from every mission parleyed information for the next. Failures? No. More like “growing pains” in our spacefaring adolescence. 

The year 2015 marks another noteworthy anniversary to which the Viking program laid the foundation for our curiosity and present trajectory for NASA’s #JourneyToMars. 

This wonderfully produced video from NASA’s Jet Propulsion Laboratory (JPL) conveys the breadth of vision and the excitement from, among every aspect of each robotic mission, successfully received data! 

Enjoy, and continue the journey with us as we work to preserve the legacy of the Viking program with The Viking Mars Missions Education and Preservation Project, the #FirstOnMars!