dark energy

"Think of a rubber band. When you pull on it, it pulls back. It is attempting to retract. When you try to make it smaller, it will push outward. It will try and expand. This rubber band is the universe. Because the positive energy is trying to expand the universe, the negative energy is pulling it back in, and vice versa."



Newborn stars peek out from beneath their natal blanket of dust in this dynamic image of the Rho Ophiuchi dark cloud from NASA's Spitzer Space Telescope. Called "Rho Oph" by astronomers, it's one of the closest star-forming regions to our own solar system. Located near the constellations Scorpius and Ophiuchus, the nebula is about 407 light years away from Earth. Rho Oph is made up of a large main cloud of molecular hydrogen, a key molecule allowing new stars to form from cold cosmic gas, with two long streamers trailing off in different directions. Recent studies reveal more than 300 young stellar objects within the large central cloud. Their median age is only 300,000 years, very young compared to some of the universe's oldest stars, which are more than 12 billion years old. The colors in this image reflect the relative temperatures and evolutionary states of the various stars. The youngest stars are surrounded by dusty disks of gas from which they, and their potential planetary systems, are forming. These young disk systems show up as red in this image. Some of these young stellar objects are surrounded by their own compact nebulae. More evolved stars, which have shed their natal material, are blue.

Image Credit: NASA/JPL-Caltech/Harvard-Smithsonian CfA

Gravitational lensing.

A massive cluster of yellowish galaxies, seemingly caught in a red and blue spider web of eerily distorted background galaxies, makes for a spellbinding picture from NASA's Hubble Space Telescope. To make this image, Hubble peered straight through the center of one of the most massive galaxy clusters known, called Abell 1689.

The gravity of the cluster's stars, plus dark matter, acts as a 2-million-light-year-wide "lens" in space. This "gravitational lens" bends and magnifies the light of the galaxies located far behind it. Some of the faintest arcs in this image are background galaxies over 13 billion light-years away.

The most prominent lensing effect is the long blue arc, just above, and to the left of, centre.

The picture is an exquisite demonstration of Albert Einstein's prediction that gravity warps space and distorts beams of light. The image is a composite of visible-light and near-infrared exposures taken in June 2002.

CREDIT: NASA, N. Benitez (JHU), T. Broadhurst (Racah Institute of Physics/The Hebrew University), H. Ford (JHU), M. Clampin (STScI),G. Hartig (STScI), G. Illingworth (UCO/Lick Observatory), the ACS Science Team and ESA