Inner Voyage of a Stranger

On this day in 1977 was launched the space probe Voyager 1.

Voyager 1 is a space probe launched by NASA on September 5, 1977. Part of the Voyager program to study the outer Solar System, Voyager 1 launched 16 days after its twin, Voyager 2. Having operated for 41 years as of September 5, 2018, the spacecraft still communicates with the Deep Space Network to receive routine commands and return data. At a distance of 142.31 astronomical units from the Sun as of June 4, 2018, it is the most distant man-made object from Earth.

The probe’s objectives included flybys of Jupiter, Saturn, and Saturn’s largest moon, Titan. While the spacecraft’s course could have been altered to include a Pluto encounter by forgoing the Titan flyby, exploration of the moon, which was known to have a substantial atmosphere, took priority. It studied the weather, magnetic fields and rings of the two planets and was the first probe to provide detailed images of their moons. (read more)

Wolf–Rayet star

Wolf–Rayet stars, often abbreviated as WR stars, are a rare heterogeneous set of stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon. The spectra indicate very high surface enhancement of heavy elements, depletion of hydrogen, and strong stellar winds. Their surface temperatures range from 30,000 K to around 200,000 K, hotter than almost all other stars.

Classic (or Population I) Wolf–Rayet stars are evolved, massive stars that have completely lost their outer hydrogen and are fusing helium or heavier elements in the core. A subset of the population I WR stars show hydrogen lines in their spectra and are known as WNh stars; they are young extremely massive stars still fusing hydrogen at the core, with helium and nitrogen exposed at the surface by strong mixing and radiation-driven mass loss. A separate group of stars with WR spectra are the central stars of planetary nebulae (CSPNe), post asymptotic giant branch stars that were similar to the Sun while on the main sequence, but have now ceased fusion and shed their atmospheres to reveal a bare carbon-oxygen core.