Herbig-Haro objects are small patches of nebulosity associated with newly-born stars, and are formed when gas ejected by young stars collides with clouds of gas and dust nearby at speeds of several hundred kilometres per second. Herbig-Haro objects are ubiquitous in star-forming regions, and several are often seen around a single star, aligned along its rotational axis. HH objects are transient phenomena, lasting only a few thousand years at most. They can evolve visibly over quite short timescales as they move rapidly away from their parent star into the gas clouds in interstellar space. Hubble Space Telescope observations reveal complex evolution of HH objects over a few years, as parts of them fade while others brighten as they collide with clumpy material in the interstellar medium. The objects were first observed in the late 19th century by Sherburne Wesley Burnham, but were not recognised as being a distinct type of emission nebula until the 1940s. The first astronomers to study them in detail were George Herbig and Guillermo Haro, after whom they have been named.

Read the rest of this article: http://en.wikipedia.org/wiki/Herbig-Haro_object

_______________________________ Today's selected anniversaries:

1865: Slavery in the United States was abolished when the Thirteenth Amendment to the Constitution was adopted. (http://en.wikipedia.org/wiki/Thirteenth_Amendment_to_the_United_States_Const...)

1961: Indonesia invaded Dutch New Guinea to annex West Papua on New Guinea. (http://en.wikipedia.org/wiki/Western_New_Guinea)

1966: Epimetheus, one of Saturn's natural satellites, was discovered, but was mistaken as Janus. It took 12 years to determine that they are two distinct objects sharing the same orbit. (http://en.wikipedia.org/wiki/Epimetheus_%28moon%29)

1987: The programming language Perl was released by Larry Wall. (http://en.wikipedia.org/wiki/Perl)

_____________________ Wikiquote of the day:

"It is better to die for an idea that will live, than to live for an idea that will die." -- Steve Biko (http://en.wikiquote.org/wiki/Steve_Biko)