Jupiter's moon Ganymede casts a shadow over the planet's Great Red Spot. Image via Hubblesite.org
US space agency NASA’s Hubble Space Telescope is really getting into the swing of things this Halloween, with some intergalactic scare snaps beaming back down to Earth.
For scientists, staring into space is supposed to be a one-sided activity, but lately it seems our solar system has different ideas.
Only a couple of days ago, Hubble caught Jupiter sneaking a peek back at us, when the shadow of the Jovian moon Ganymede swept across the centre of the Great Red Spot — a giant storm on the planet.
This gave Jupiter the uncanny appearance of having a pupil in the centre of a 10,000 mile-diametre ‘eye.’ As yet, it hasn’t blinked, meaning it’s either a visual trick, or a monstrous eye that needs no moisture to see. We know what our money is on.
Then yesterday Hubble scientists reported on bachelor-like ghost stars, haunting the space in between different galaxies. Basically, when galaxies group together in massive clusters, some of them can be ripped apart by the gravitational pulls.
Hubble’s giant cosmic mosh pit
“It’s a giant cosmic mosh pit,” says Hubblesite.org. Astronomers monitoring Abell 2744 (an immense collection of nearly 500 galaxies nicknamed Pandora’s Cluster) have found evidence of galaxies torn apart long ago. The evidence is actually a phantom-like faint glow filling the space between the galaxies.
By observing the light from the orphaned stars, Hubble astronomers have assembled forensic evidence that suggests as many as six galaxies were torn to pieces inside the cluster over a stretch of 6bn years.
Computer modelling of the gravitational dynamics among galaxies in a cluster suggest that galaxies as big as our Milky Way are the likely candidates as the source of the stars.
“The doomed galaxies would have been pulled apart like taffy if they plunged through the centre of the galaxy cluster, where gravitational tidal forces are strongest.”
Astronomers have long hypothesised that the light from scattered stars should be detectable after such galaxies are disassembled. However, the predicted ‘intracluster’ glow of stars is very faint and was therefore a challenge to identify.
“The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters,” said Ignacio Trujillo of the Instituto de Astrofísica de Canarias (IAC), La Laguna, Tenerife, Spain, one of the researchers involved in this study of Abell 2744. “It is also amazingly beautiful in that we found the tell-tale glow by utilising Hubble’s unique capabilities.”
Ghost stars ripped from previous galaxies. Image via Hubblesite.org
