You have to stay up pretty late this time of year to get a good look at a dark sky from around here. But waiting it out on a warm summer night to the music of the waves lapping the beach and the breeze gently rustling the dune grass and tree leaves—when the sky clears and the stars shine—brings some of the finest views of our corner of the universe.
By around midnight in the early summer, the constellation Lyra lies almost directly overhead. Lyra takes its name from the lyre, a musical instrument played in ancient Greece. You’ve probably seen an image of a lyre; a lyre is like a small harp, in about the same way as an accordion is a small church organ.
But the constellation Lyra doesn’t look too much like a musical instrument, at least not to most, nowadays. Maybe because most of us don’t see too many lyres in our everyday lives. Lyra looks more like a bow tie.
The brightest star in the constellation Lyra is Vega. Vega is the fifth brightest star visible from earth, and the third brightest star visible from the northern hemisphere mid latitudes. You can’t miss Vega and Lyra if you look straight up late at night in the summer.
Vega is one of the most thoroughly examined stars in the sky. Not only is it very bright—about 40 times brighter than the sun—, it is also nearby, at a distance of about 25 light years. Vega is also younger, hotter and bigger than the sun. Astronomers have determined that Vega is only about 4 or 5 hundred million years old—an infant, it seems, compared to the sun which is 4 or 5 billion years old—and that it is about 1.5 times hotter and a bit more than 2 times bigger than the sun.
Age, with stars, however, is a relative thing. It is believed that our sun is middle aged, in the sense that it will shine about as it does now for another 4 or 5 billion years. The same is true for Vega. Bigger, brighter stars don’t shine normally as long as smaller, dimmer stars; it is believed that Vega will shine about as it does now for another 4 or 5 hundred million years.
Vega and the sun share the same fate. At the end of their normal lives–what astronomers call their time on the Main Sequence, the distribution of normal stars–both will bloat into massive red giants, molt their outer layers, then collapse into brilliant-hot white dwarfs before gradually fading away.
Vega’s and the sun’s future are foretold by a faint nebula also in the constellation Lyra. Just about midway between the two stars that make up the side of the bowtie opposite Vega is an object commonly known as the Ring Nebula, or Messier 57, or just M57 for short.
M57 is a planetary nebula, and one of my long-time favorite telescope targets. Called a planetary nebula because it looks like a tiny round planet through a small telescope, M57 is actually a distant, dying, sun-like star.
The Ring Nebula
Image courtesy the Hubble Heritage website.
The Ring Nebula
M57 is about 2,300 light years away. What looks like a dim disk through a small telescope is revealed through larger telescopes to be a glowing, expanding ring of gas and dust–the material molted by a sun-like star as it rapidly transforms from a swollen red giant to a compact white dwarf.
All of this is for us to see high overhead on a warm summer night.
