Hubble is the Ultimate Multitasker: Discovering Asteroids While it’s Doing Other Observations

Some asteroids from within our Solar System have photobombed deep images of the Universe taken by the NASA/ESA Hubble Space Telescope. These asteroids reside, on average, only about 260 million kilometres from Earth — right around the corner in astronomical terms. Yet they've horned their way into this picture of thousands of galaxies scattered across space and time at inconceivably farther distances. This Hubble photo of a random patch of sky is part of the Frontier Fields survey. The colourful image contains thousands of galaxies, including massive yellowish ellipticals and majestic blue spirals. Much smaller, fragmentary blue galaxies are sprinkled throughout the field. The reddest objects are most likely the farthest galaxies, whose light has been stretched into the red part of the spectrum by the expansion of space. Intruding across the picture are asteroid trails that appear as curved or S-shaped streaks. Rather than leaving one long trail, the asteroids appear in multiple Hubble exposures that have been combined into one image. Of the 20 total asteroid sightings for this field, seven are unique objects. Of these seven asteroids, only two were earlier identified. The others were too faint to be seen previously. The trails look curved due to an observational effect called parallax. As Hubble orbits around Earth, an asteroid will appear to move along an arc with respect to the vastly more distant background stars and galaxies. The motion of Earth around the Sun, and the motion of the asteroids along their orbits, are other contributing factors to the apparent skewing of asteroid paths. All the asteroids were found manually, the majority by "blinking" consecutive exposures to capture apparent asteroid motion. Astronomers found a unique asteroid for every 10 to 20 hours of exposure time. The Frontier Fields program is a collaboration among several space telescopes and ground-based observatories to study six massive galaxy clusters and their effects. Using a diff

It looks like a poster of the famous Hubble Deep Field, marked with white streaks by a child, or put away carelessly and scratched in the process. But it’s not. The white streaks aren’t accidents; they’re the paths of asteroids.

Continue reading “Hubble is the Ultimate Multitasker: Discovering Asteroids While it’s Doing Other Observations”

Hubble Spots the Ghostly Light From Dead Galaxies

Hubble Frontier Fields observing programme, which is using the magnifying power of enormous galaxy clusters to peer deep into the distant Universe. Credit: NASA.

In a patch of sky 3.5 billion light-years away there are hazy elliptical galaxies, colorful spirals, blue arcs and distorted shapes seen clumping together. It’s the result of a vast cosmic collision that took place over the course of 350 million years.

The mess is a treasure trove of information for astronomers, allowing them to piece together the history of a cosmic pile-up of multiple galaxy clusters.

But now astronomers are digging through the nearby darkness. They’re eyeing the remnant stars that were cast adrift in intergalactic space. These stars should emit a faint glow known as intracluster light that — until now — has mostly remained a subject of speculation.

Mireia Montes and Ignacio Trujillo, both from the University of La Laguna, Spain, have used the Hubble Space Telescope to observe the aforementioned cluster, Abel 2744, in exquisite detail. The cluster has already earned the nickname Pandora’s Cluster for its violent past.

The team looked at both visible and near-infrared color images of the cluster, and then split these color images by brightness. This allowed Montes and Trujillo to pinpoint the color of the cluster’s faintest glow and therefore glean the ghost stars’ age, chemical content, and total mass.

Compared to stars within the cluster’s galaxies, the ghost stars emit bluer light and are therefore rich in heavier elements like oxygen, carbon, and nitrogen. So the scattered stars must be second- or third-generation stars enriched by previous supernovae. But they’re still between three and nine billion years younger than the stars within the cluster’s galaxies.

The team estimates that the combined light of about 100 billion outcast stars contributes approximately six percent of the cluster’s brightness.

But how did the stars get thrown from their respective galaxies in the first place? This new forensic evidence suggests that violent collisions tore apart between four and six Milky Way-size galaxies, scattering their stars into intergalactic space.

“The Hubble data revealing the ghost light are important steps forward in understanding the evolution of galaxy clusters,” said Trujillo in a news release. “It is also amazingly beautiful in that we found the telltale glow by utilizing Hubble’s unique capabilities.”

Abell 2744 is only one target in Hubble’s Frontier Fields program, which will map five more galaxy clusters in superb detail.

The results have been published in the Astrophysical Journal and are available online.