You stand on a mountaintop in Chile beside the new Vera C. Rubin Observatory (at last, a woman astronomer thus honored). You gaze wide-eyed at the night sky sprinkled with thousands of stars and an overarching milky-white glowing band.
Since you are wide-eyed your pupil is 8 mm in diameter. Then you peer through your 40 mm diameter binoculars and see so many more stars in every small patch of the Milky Way that you can believe there are billions of stars in our home galaxy. The binocular lenses are bigger than your pupil, so you see 25X fainter objects, including many other galaxies. Inside the Rubin Observatory the Large Synoptic Survey Telescope (LSST) is being completed. It will have a million times your eye’s light-gathering power.
Ancient Greeks called the Milky Way “galaxias kyklos” meaning milky circle, and a hundred years ago it was generally believed that the galaxy was the whole universe. In 1922 Henrietta Swan Leavitt, another brilliant woman astronomer, discovered that one type of star varies in brightness with a period, typically days, that depends on its luminosity. Measuring the period and the apparent brightness of a star she could calculate its distance.
Two years later Edwin Hubble studied variable stars in the Andromeda Nebula and used Leavitt’s method to measure how far away it is, proving that it is another galaxy. A “new star” or nova had been noticed there in 1885; in 1924 it became certain that the exploding star was briefly as bright as the whole galaxy – a supernova – and that many nebulae are galaxies. In 1054 Chinese astronomers recorded a very bright new star; its debris can still be seen as the Crab Nebula.
The Hubble Space Telescope photographed 5,500 galaxies within a spot on the sky that could be covered by a pinhead at arm’s length. The James Webb Space Telescope, launched on Christmas Day 2021, is even bigger and will begin observing this summer.
You enter the Rubin Observatory and see the LSST. In 2023 it will start scanning the whole sky every few days to spot anything that changes quickly, finding thousands of supernovae and near-Earth asteroids. Hundreds of alerts will be made available to the public. So, get some good binoculars and find a dark sky location. You may be the first to see a new supernova! In any case you can enjoy finding dozens of galaxies – and the Crab Nebula!
