from us. Intrinsically, it shines about 25 times brighter than our sun. But a beacon from a distant lighthouse might appear nearly as bright as the streetlamp despite its greater distance. Take the well-known Summer Triangle, which this week stands directly over our heads at around 8:30 p.m. local daylight time. Its member stars — Deneb,, and Altair — are at very unequal distances from us, making it a rather good example of how misleading the two-dimensional"vault" illusion can be.
The closest of the three is Altair, which is 16.7 light-years away, followed by Vega, at 25 light-years; but Deneb is enormously farther, at 1,400 light-years. Despite the fact that we are seeing the latter star by light that started its journey around the time the Vikings invaded Ireland, it still manages to rank as a star of the first magnitude since it is a brilliant blue supergiant, more than 100,000 times brighter than the sun.
And for all our science and technology, how do we stand against the first ancient sentry on that watchtower who thought to measure the heavens?