It’s fun to imagine what the sky would look like if you could plop yourself on a planet around another star. We’ve only scratched the surface, yet in fewer than 20 years, astronomers have discovered more than 750 new planets beyond those in our own solar system.
While I’d love to see a double sunrise and sunset like the fictional Luke Skywalker on the planet Tatooine, one of my favorite places to imagine a radically different sky from Earth’s is inside massive balls of stars called globular clusters. We know of about 150 in the Milky Way galaxy. Most are tens of thousands of light years away in the direction of the center of the galaxy in the constellation Sagittarius. Globulars are tightly bound by the gravity of their many stars into spherical shapes resembling hoards of bees.
Most globular clusters contain several hundred thousand stars, but a really big one like Omega Centauri (visible from the southern U.S.) tops out around 10 million. Star densities inside the clusters are much higher than in the sun’s neighborhood. The closest star system to our sun, Alpha Centauri, is 4.3 light years away or some 25 trillion miles. Within the densely packed core of some globulars, star densities are phenomenal – up to 1000 stars stuffed into a cube 3 light years on a side.
While so many stars whizzing about make it difficult for planets around stars to remain in stable orbits, we can safely assume planets are still possible. Think of the view on clear night. The sky from Earth contains at best a dozen bright first magnitude stars on a given night, all considerably fainter than Jupiter and Venus. Inside a globular, where stars are only tenths of a light year apart, there would be thousands of stars as bright as Venus and Jupiter. You could easily walk around (or dogsled) at night without the need of a moon to find your way. Some lucky life form must witness bejeweled nights in at least one of the many globulars that dot our skies. My feeble attempt above only hints at what we might imagine.
Because globulars are arrayed in a spherical cloud centered on the core of the Milky Way, they only begin to populate our evening sky as spring turns into summer and Sagittarius makes its appearance in the east. There are several out right now – the vanguard as it were – that you can spot in binoculars. And if you have a telescope, especially from 6-inches and up, you’ll can experience for yourself how fantastically starry-rich these objects are.
One of the best in the northern sky is named M3, the 3rd entry in a catalog of deep sky objects compiled by 18th century French astronomer Charles Messier. It’s located in the constellation Canes Venatici the Hunting Dogs below the handle of the Big Dipper. The cluster is 33,900 light years away, spans some 200 light years and contains half a million stars.
To find it, face northeast around 9:30 – 10 p.m. local time and locate brilliant Arcturus by following the arc of the Big Dipper’s Handle. The cluster is located not quite halfway from Arcturus to Cor Caroli, an easy-to-see star to the right of the Handle.
In binoculars look for a fuzzy 6th magnitude blob with a brighter core just to the left or north of a 6th magnitude star. You can use the more detailed map below to pinpoint M3′s location. M3 is easy to see in typical binoculars from suburban and rural areas. Take your imagination for a ride the next clear night.