1. Message from ancient universe
2. Old photos
of young galaxies
3. Hark! Dark energy!
On Mar. 1, French and Swiss scientists announced the
discovery of the most distant object ever located, at a distance
of (yow!) 13.23 billion light years. The galaxy is seen when the
universe was about
470 million years young, barely 3 percent of its current age. (Top
left): A near-infrared image of Abell 1835 IR1916 (circle in the
a galaxy cluster.
Top right: Detail of the ancient galaxy, still in the white circle.
Bottom: The detail region, seen in visible and infrared light. The galaxy is
invisible in visible light, but visible in infrared radiation (especially
the H-band) indicating a huge red-shift. This puff of photons came
from the most distant object ever seen. Photos: European
Two weeks ago, this galaxy (outlined in
white) was the furthest object on record, imaged when the universe
was just 750 million years old. The old gal is behind a cluster
of galaxies called Abell 2218, and appears several times due
to the focusing of the gravitational lens in Abell 2218. Photo:
J.P. Kneib and Richard Ellis, Advanced Camera for Surveys, Hubble
Looking long and hard into one of the darkest
parts of the sky, the Hubble telescope made this image of 10,000
galaxies, in this 13-day exposure. About 100 small, red galaxies
may date to 800 million years after the Big Bang. The nearest
galaxies -- the larger, brighter, well-defined spirals and ellipticals
-- thrived about 1 billion years ago, when the cosmos was 13
billion years old. Photo: NASA
If you're looking for the stuff of the universe, you better be
prepared to deal with invisible and unbelievable stuff. Dark energy
matters more than dark matter.
Scientists have just released photos of two astonishingly distant galaxies that burned in the first billion years of the universe. The ancient light traveled more than 13 billion light years, was focused by a gazillion-ton lens, and finally was scooped up in monster telescopes in Chile, and Hawaii.
Based on how the starlight was stretched by the Doppler effect, these galaxies must have been cooking within a few hundred million years of the Big Bang.
(Background blip: The Doppler effect happens when a source of sound or light is moving relative to an observer. When you're standing next to a highway and a semitrailer zooms past, the pitch of its engine suddenly drops when the sound waves start being stretched as the truck moves away from you. Same with the light of distant stars. A higher Doppler shift indicates a faster truck -- or star.)
If the results survive further scrutiny, the photos of these two galaxies would be the earliest direct evidence of conditions soon after the Big Bang. You remember: The mind-bogglingly huge explosion in which a, an, er, well, something really tiny, exploded and blossomed into everything there is -- or at least, the predecessor of everything that is?
What happened next is a bit murky: The first billion years of the universe are
a dark spot. Maybe there were no stars. Maybe there were stars, but their light
was blocked by immense clouds of hydrogen gas, and could not reach us across
the billions of light years and billions of time-years separating us from the
As some astronomers photograph early galaxies, others are desperately scrounging around for the bulk of the energy and matter in the universe.
You might think that by now we would have a rough idea of what's in the universe. True, except for two itsy-bitsy problems: dark matter, and dark energy.
About 30 years ago, astronomers realized the galaxies were spinning too fast: The mass of their stars would not make enough gravity to hold them together. Long ago, they should have spun to smithereens.
Astronomers cooked up "dark matter" as the source of gravity to prevent that unseemly outcome. Dark matter: Convenient jargon for "stuff we can't see"...
Since dark matter was s'posed to be way more common than the stuff we could see,
dark matter mattered. Now we hear of another trifling omission: Why did the
expansion of the universe start speeding up about 7 billion
years ago? Theunexpected action on the gas pedal (for 70 years, astronomers thought
gravity would be slowing the expansion ) has astronomers scrambling
for an explanation.
Meet "dark energy."
This illuminating name masks a pathetic inability to explain exactly why the universe would be expanding.
To skeptics, dark energy seems nothing more than a polite way of saying, "I
have no answer to your question about why the universe is expanding faster."
Dark energy: The cause of accelerating expansion.
Dark matter: The gravitational glue that holds galaxies together.
Visible matter and detectable light: The familiar atoms in beach sand and the
sun, and the radiation from our sun.
We'll return to dark energy, but first, what's new with old galaxies?