[SN Today] from [ScienceNews]
[SN Today]
Galaxies that go the distance
First results from revamped Hubble identify distant starlit bodies and pose a cosmic puzzle
By Ron Cowen
Web edition : Wednesday, September 16th, 2009
Just days after NASA released the first cosmic dreamscapes taken by the newly refurbished Hubble Space Telescope (SN: 9/26/09, p. 7) three teams of astronomers have used the rejuvenated observatory to find what appears to be a bounty of the most distant galaxies known.
Analyses of infrared images of these galaxies captured in late August and early September with the newly installed Wide Field Camera 3 suggest there were fewer bright galaxies early in cosmic history and those galaxies formed stars at an unexpectedly low rate.
Because the researchers do not yet have measurements of the wavelengths that make up the starlight from these galaxies, they do not directly know how far away the galaxies lie. But the starlit bodies’ colors suggest that about 16 reside roughly 12.9 billion light-years from Earth and another five or so sit even further, a record-breaking 13.1 billion light-years away.
“We are looking back 13 billion years and seeing galaxies just 600 to 700 million years after the Big Bang, when the Universe was like a 4-year-old,” says Garth Illingworth of the University of California, Santa Cruz, a member of one of the discovery teams.
The galaxies all lie within a small patch of the southern sky, called the Hubble Ultra Deep Field, that has already been imaged by Hubble and a slew of other telescopes.
It’s the new camera’s greater sensitivity, as well as its larger field of view, that has enabled scientists to rapidly find what appear to be extremely remote galaxies, says Richard Ellis of Caltech in Pasadena, a coauthor of two of four papers that the three teams recently posted online at arXiv.org.
“This is a golden moment,” Ellis says. “All the groups independently analyzed the data with different software and broadly speaking, we’re all in agreement.”
A team that includes Illingworth and Rychard Bouwens, also of UC-Santa Cruz, posted its findings on September 11. Ross McLure and James Dunlop of the University of Edinburgh in Scotland, along with Ellis and their colleagues, posted their report on September 15. A team led by Andrew Bunker of the University of Oxford in England, again including Ellis, also posted an analysis of the new Hubble data on September 15.
The researchers all find a marked downturn in the number of bright galaxies as the telescope peers farther away and thus further back in time. That decrease in the galactic population is expected from current models of galaxy formation, comments Harry Ferguson of the Space Telescope Science Institute in Baltimore, who was not a member of any of the teams.
The findings “appear to show that galaxy formation is just starting at these [early times],” comments Simon White of the Max Planck Institute for Astrophysics in Garching, Germany.
Because the Hubble Ultra Deep Field is tiny — one one-hundred-fiftieth the apparent area of the full moon on the sky — and because the Wide Field Camera 3 has only just begun taking pictures, it is difficult to know how representative the findings are of the rest of the universe at these early cosmic times, Ferguson and Ellis both caution.
Ellis notes that the new findings also hint at a puzzle. His team estimates that the distant galaxies, which are too tiny to be clearly resolved by Hubble, are making stars at a puny rate. In some cases, that rate is as low as the mass equivalent of 0.0025 suns per year. According to current models, that rate couldn’t have generated enough ultraviolet starlight for a critical milestone in the evolution of the universe — the wrenching apart of neutral hydrogen atoms into their subatomic constituents.
About 400,000 years after the Big Bang, the cosmos had cooled sufficiently for protons and electrons to recombine into atoms. But the universe has long been reionized, with hydrogen atoms once again split into protons and electrons. Many astronomers have assumed that ultraviolet light from the first galaxies did the splitting.
This is not yet an astronomical crisis, Ellis says. It may be that the first stars were more efficient than expected at producing ultraviolet radiation. Another possibility is that ultraviolet light more easily escaped these early galaxies than it did from later galaxies.
Another possibility, comments White, is that “there might be enough undetected very small galaxies to do the job.”
New data is just starting to pour in that may solve this and other cosmic riddles, Ellis says. “This is a very exciting time.”
[SN Today]
Monkeys get full color vision
Males with red-green colorblindness can distinguish the hues after gene therapy, study suggests
By Tina Hesman Saey
Web edition : Wednesday, September 16th, 2009
Two male squirrel monkeys now see the world in a whole new way — in full color.
Female squirrel monkeys can see in color, but male squirrel monkeys are normally red-green colorblind because they lack pigments in the retina that detect those wavelengths of light. Now, researchers have performed gene therapy that allowed two male squirrel monkeys named Sam and Dalton to produce proteins that detect red light. As soon as the red-light-harvesting protein was made in the monkeys’ eyes, the animals were able to discriminate between red and green spots in color vision tests, Jay Neitz of the University of Washington in Seattle and his collaborators report online September 17 in Nature.
The experiment wasn’t supposed to work, Neitz says. People born with cataracts don’t develop nerve connections that help the brain make sense of messages sent by the eye. If the defect isn’t corrected early, these people remain essentially blind even if their eyes return to full function later. Because there was no reason to assume color vision was different from other types of vision, the team had assumed it would not be possible to reverse the deficit in an adult animal.
Neitz polled experts in the vision field on whether they thought producing photoreceptors in colorblind adult monkeys could give color vision. “Every single person said, ‘absolutely not.’” But the researchers decided to move forward with the experiment to see if they could get the pigment protein to be made in the eye.
Male monkeys lacking the red photoreceptor protein were given injections of a virus carrying a gene for the protein. Levels of the protein slowly rose in some retinal cells. After 20 weeks, Neitz and his colleagues started to see differences in the way Sam and Dalton performed on daily color vision tests. Around that time, protein production levels peaked and the monkeys have maintained stable color vision for two years since treatment.
In the tests, monkeys were shown a panel with a patch of colored dots on a background of gray dots. If the monkeys press the area with the colored dots, the animals get a grape juice reward. Even colorblind monkeys guess correctly about a third of the time, Neitz says.
“Sometimes they get on a streak, so those first couple of days when they were on a streak, we tried not to get too excited,” he says. “But by the end of the week it became clear that this was not random chance.”
Sam and Dalton could consistently pick out red, green, blue and yellow dots from the gray background and discriminate between the colors. Before the gene therapy, they could only discriminate yellow and blue. The speed at which the monkeys learned the new colors indicates that no brain rewiring was required for the feat, unlike that needed to restore other types of vision such as distinguishing objects.
The achievement is causing a stir among vision scientists and may have implications for understanding the evolution of color vision, says Bevil Conway, a neuroscientist at Wellesley College in Massachusetts.
“Somehow the brains of these monkeys are already wired to decode these color signals,” Conway says. That fact raises the possibility that “the evolution of color vision may have required just one genetic switch.”
But, Conway says, there is an important disclaimer. “We have no idea if this would work in humans or that it would be a delightful experience for the people post-surgery.” People who have surgery to repair sight lost in childhood often report that their new vision is confusing and disorienting, he says. Adding color could prove to be similar.
Other scientists who originally thought color vision couldn’t be generated in adult animals are impressed by Neitz’s achievement.
“They certainly have added some color vision,” says Gerald Jacobs, a neuroscientist at the University of California, Santa Barbara. “I find the measurements compelling.”
Still, the monkeys’ actual sensation of color — what it looks like to them — remains a mystery.
“The achievement is technically amazing and conceptually very cool,” says Melissa Saenz, a neuroscientist at Caltech in Pasadena, Calif. But even though the monkeys can discriminate some new wavelengths of light, “there's no evidence that the monkeys perceive a new dimension of color,” she says. For example, the monkeys may now perceive red and green as different shades of yellow and blue, colors the animals already knew.
“If it doesn't involve experiencing new sensations of color, it would not dramatically change the experience of colorblind people if the treatment were applicable to humans,” Saenz says.
[SN Today]
Galaxies that go the distance
First results from revamped Hubble identify distant starlit bodies and pose a cosmic puzzle
By Ron Cowen
Web edition : Wednesday, September 16th, 2009
Just days after NASA released the first cosmic dreamscapes taken by the newly refurbished Hubble Space Telescope (SN: 9/26/09, p. 7) three teams of astronomers have used the rejuvenated observatory to find what appears to be a bounty of the most distant galaxies known.
Analyses of infrared images of these galaxies captured in late August and early September with the newly installed Wide Field Camera 3 suggest there were fewer bright galaxies early in cosmic history and those galaxies formed stars at an unexpectedly low rate.
Because the researchers do not yet have measurements of the wavelengths that make up the starlight from these galaxies, they do not directly know how far away the galaxies lie. But the starlit bodies’ colors suggest that about 16 reside roughly 12.9 billion light-years from Earth and another five or so sit even further, a record-breaking 13.1 billion light-years away.
“We are looking back 13 billion years and seeing galaxies just 600 to 700 million years after the Big Bang, when the Universe was like a 4-year-old,” says Garth Illingworth of the University of California, Santa Cruz, a member of one of the discovery teams.
The galaxies all lie within a small patch of the southern sky, called the Hubble Ultra Deep Field, that has already been imaged by Hubble and a slew of other telescopes.
It’s the new camera’s greater sensitivity, as well as its larger field of view, that has enabled scientists to rapidly find what appear to be extremely remote galaxies, says Richard Ellis of Caltech in Pasadena, a coauthor of two of four papers that the three teams recently posted online at arXiv.org.
“This is a golden moment,” Ellis says. “All the groups independently analyzed the data with different software and broadly speaking, we’re all in agreement.”
A team that includes Illingworth and Rychard Bouwens, also of UC-Santa Cruz, posted its findings on September 11. Ross McLure and James Dunlop of the University of Edinburgh in Scotland, along with Ellis and their colleagues, posted their report on September 15. A team led by Andrew Bunker of the University of Oxford in England, again including Ellis, also posted an analysis of the new Hubble data on September 15.
The researchers all find a marked downturn in the number of bright galaxies as the telescope peers farther away and thus further back in time. That decrease in the galactic population is expected from current models of galaxy formation, comments Harry Ferguson of the Space Telescope Science Institute in Baltimore, who was not a member of any of the teams.
The findings “appear to show that galaxy formation is just starting at these [early times],” comments Simon White of the Max Planck Institute for Astrophysics in Garching, Germany.
Because the Hubble Ultra Deep Field is tiny — one one-hundred-fiftieth the apparent area of the full moon on the sky — and because the Wide Field Camera 3 has only just begun taking pictures, it is difficult to know how representative the findings are of the rest of the universe at these early cosmic times, Ferguson and Ellis both caution.
Ellis notes that the new findings also hint at a puzzle. His team estimates that the distant galaxies, which are too tiny to be clearly resolved by Hubble, are making stars at a puny rate. In some cases, that rate is as low as the mass equivalent of 0.0025 suns per year. According to current models, that rate couldn’t have generated enough ultraviolet starlight for a critical milestone in the evolution of the universe — the wrenching apart of neutral hydrogen atoms into their subatomic constituents.
About 400,000 years after the Big Bang, the cosmos had cooled sufficiently for protons and electrons to recombine into atoms. But the universe has long been reionized, with hydrogen atoms once again split into protons and electrons. Many astronomers have assumed that ultraviolet light from the first galaxies did the splitting.
This is not yet an astronomical crisis, Ellis says. It may be that the first stars were more efficient than expected at producing ultraviolet radiation. Another possibility is that ultraviolet light more easily escaped these early galaxies than it did from later galaxies.
Another possibility, comments White, is that “there might be enough undetected very small galaxies to do the job.”
New data is just starting to pour in that may solve this and other cosmic riddles, Ellis says. “This is a very exciting time.”
[SN Today]
Monkeys get full color vision
Males with red-green colorblindness can distinguish the hues after gene therapy, study suggests
By Tina Hesman Saey
Web edition : Wednesday, September 16th, 2009
Two male squirrel monkeys now see the world in a whole new way — in full color.
Female squirrel monkeys can see in color, but male squirrel monkeys are normally red-green colorblind because they lack pigments in the retina that detect those wavelengths of light. Now, researchers have performed gene therapy that allowed two male squirrel monkeys named Sam and Dalton to produce proteins that detect red light. As soon as the red-light-harvesting protein was made in the monkeys’ eyes, the animals were able to discriminate between red and green spots in color vision tests, Jay Neitz of the University of Washington in Seattle and his collaborators report online September 17 in Nature.
The experiment wasn’t supposed to work, Neitz says. People born with cataracts don’t develop nerve connections that help the brain make sense of messages sent by the eye. If the defect isn’t corrected early, these people remain essentially blind even if their eyes return to full function later. Because there was no reason to assume color vision was different from other types of vision, the team had assumed it would not be possible to reverse the deficit in an adult animal.
Neitz polled experts in the vision field on whether they thought producing photoreceptors in colorblind adult monkeys could give color vision. “Every single person said, ‘absolutely not.’” But the researchers decided to move forward with the experiment to see if they could get the pigment protein to be made in the eye.
Male monkeys lacking the red photoreceptor protein were given injections of a virus carrying a gene for the protein. Levels of the protein slowly rose in some retinal cells. After 20 weeks, Neitz and his colleagues started to see differences in the way Sam and Dalton performed on daily color vision tests. Around that time, protein production levels peaked and the monkeys have maintained stable color vision for two years since treatment.
In the tests, monkeys were shown a panel with a patch of colored dots on a background of gray dots. If the monkeys press the area with the colored dots, the animals get a grape juice reward. Even colorblind monkeys guess correctly about a third of the time, Neitz says.
“Sometimes they get on a streak, so those first couple of days when they were on a streak, we tried not to get too excited,” he says. “But by the end of the week it became clear that this was not random chance.”
Sam and Dalton could consistently pick out red, green, blue and yellow dots from the gray background and discriminate between the colors. Before the gene therapy, they could only discriminate yellow and blue. The speed at which the monkeys learned the new colors indicates that no brain rewiring was required for the feat, unlike that needed to restore other types of vision such as distinguishing objects.
The achievement is causing a stir among vision scientists and may have implications for understanding the evolution of color vision, says Bevil Conway, a neuroscientist at Wellesley College in Massachusetts.
“Somehow the brains of these monkeys are already wired to decode these color signals,” Conway says. That fact raises the possibility that “the evolution of color vision may have required just one genetic switch.”
But, Conway says, there is an important disclaimer. “We have no idea if this would work in humans or that it would be a delightful experience for the people post-surgery.” People who have surgery to repair sight lost in childhood often report that their new vision is confusing and disorienting, he says. Adding color could prove to be similar.
Other scientists who originally thought color vision couldn’t be generated in adult animals are impressed by Neitz’s achievement.
“They certainly have added some color vision,” says Gerald Jacobs, a neuroscientist at the University of California, Santa Barbara. “I find the measurements compelling.”
Still, the monkeys’ actual sensation of color — what it looks like to them — remains a mystery.
“The achievement is technically amazing and conceptually very cool,” says Melissa Saenz, a neuroscientist at Caltech in Pasadena, Calif. But even though the monkeys can discriminate some new wavelengths of light, “there's no evidence that the monkeys perceive a new dimension of color,” she says. For example, the monkeys may now perceive red and green as different shades of yellow and blue, colors the animals already knew.
“If it doesn't involve experiencing new sensations of color, it would not dramatically change the experience of colorblind people if the treatment were applicable to humans,” Saenz says.
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