Saturn’s F ring bisects the grandest globular cluster of them all, Omega Centauri, in this photo taken by Cassini on March 29 this year. Hi-res image. Credit: NASA/JPL/SSI
WOW! This photo appeared on NASA’s Jet Propulsion Lab site yesterday and my jaw dropped when I saw it. It was taken by the Saturn Cassini probe of the globular cluster Omega Centauri sparkling 16,000 light away in the distance behind Saturn’s outer F ring. Look closely at the rings where the slice through the cluster. The ring material, which consists primarily of chunks of ice, is sparse enough that many stars shine right through it. Early space and science fiction artists like Chesley Bonestell would paint imaginary scenes from other planets to help us imagine the unearthy vistas our solar system might offer. Isn’t it crazy cool that we now get a near daily dose of the real thing? Photos like these offer us viewpoints no one even imagined. We’ll always need those artists to help us see and understand what’s out there, but it’s nice when it’s supplemented now and again by the real thing.
Powdery with stars, Omega Centauri is easily visible with the naked eye from southern skies. Omega Centauri is the biggest globular cluster in the Milky Way and second biggest among all the globulars in the 50 or so galaxies in our neighborhood called the Local Group. #1 goes to cluster G1 in the Andromeda galaxy. Gigantic hi-res image. Credit: ESO
It’s visible during the spring months in the constellation Centaurus if you live in the southern U.S. I’ve seen it several times from Arizona, where it looks like a fat, fuzzy star with the naked eye. Omega was known in antiquity but cataloged as a star. It wasn’t until English astronomer John Herschel pointed a good telescope at it in the 1830s that we learned it was a cluster. And what a heap of stars it is. Omega contains contains up to 10 million stars in a densely-packed ball 230 light years across. Suns in the core are packed tight as a crowded subway car; their average distance from one another is just a third of a light year. The sky as viewed from a planet orbiting a star in the cluster’s center would be 100 times brighter than Earth’s night sky and filled with hundreds of Venus lookalikes.
The Hubble Space Telescope took this picture of the core of Omega Centauri which is crowded with stars and may harbor a black hole. Credit: NASA/ESA
Omega is 10 times bigger than the average globular cluster and contains muliple generations of stars, something very unusual in almost all other globulars in the Milky Way, which were formed in one fell swoop billions of years ago from large clouds of hydrogen gas. These peculiarities lead astronomers to suspect that Omega is more likely the core of a small galaxy that was pulled toward and eventually merged with our galaxy. Its outer stars and gas stripped away, it now mimics a globular but on a much larger scale. Recent observations indicate there may even be a black hole in Omega’s core whipping around stars at the cluster’s center at speeds much higher than expected. This is yet another galactic trait.
Sunspots are plentiful in the 1089 group as seen in this photo taken this morning. Details: 540mm at f/10, 1/5000 second exposure at ISO 50 with solar filter. Photo: Bob King
I looked at the sun this morning and saw that sunspot group 1089 is still growing quickly. It now looks like a healthy bed of sunflowers just over the sun’s east limb. I refer you to the SOHO (Solar Heliospheric Observatory) page for additional photos. Tomorrow we’ll look at a star almost 300 times the size of the sun.
Clear skies by you tonight? Check out the waxing gibbous moon and Antares in Scorpius the Scorpion. They’ll be near one another all evening and make a pretty sight. Created with Stellarium