According to recent popular science articles, there has been something of a revival of the traditional idea that our Milky Way is a 4-armed spiral galaxy, as opposed to having two spiral arms, as seen in the currently most popular rendition of our home Galaxy.
If you have never heard of the Herschels, then you are missing out on the most important astronomers of the 18 th and 19 th Century. William Herschel, discoverer of Uranus,
together with his able and dedicated sister Caroline and his erudite son John revealed the Milky Way and its diverse contents as never before.
This year, our eyes were once again redirected to our own Solar System for a just a few fleeting
minutes -- from the myriad wonders of our “seeable” Universe to a small space probe called New
Horizons that at 7:49 AM (EST) on July 14 th 2015 passed within 7,750 miles of little Pluto at a
record-breaking speed of 30,800 miles per hour (49,600 kilometers per hour).
We’ve all shown Saturn to someone, or perhaps have shared a clear view of a bright globular, say, M13, with someone who hasn’t seen such a thing before. In these and similar cases, the sheer beauty of the thing is the whole point; any impressive facts are secondary.
“It does not do harm to the mystery to know a little about it. For far more marvelous is the truth than any artists of the past imagined it. Why do the poets of the present not speak of it?” -- Richard Feynman (1918 – 1988)
For most of human history, the night sky demanded our attention. The shape-shifting Moon, wandering planets, pointillist stars, and occasional comet enchanted our sensibilities...
Spot naked-eye exoplanet host stars!
Want to see something new in the night sky? To date, more than 700 exoplanetary systems have been identified in...
By now, you have probably read or heard that our polluting ways have reached a critical point, where Earth is rapidly approaching total failure as a planet. Perhaps you have wondered how we humans could have managed to do so much damage in so little time.
Permanent settlements in space will require forms of localized government that are likely to differ from contemporary models of political order. This article thus asks a provocative question associated with the empirical record of human colonization and settlement in prior eras: What sort of authoritarian governance is most likely to form in human space settlements during the medium term?
The formula for collisional excitation of the atoms responsible for auroral emission can explain why green auroras from excited oxygen atoms can occur at relatively low altitudes, but red auroras from these same atoms are constrained to higher altitudes of lower density. The same formula also suggests much lower electron velocities (~100 km/s) than are required to excite the oxygen atoms to the required metastable levels for subsequent emission (~1000 km/s).
