Smaller Version of the Solar System Is Discovered
Astronomers said Wednesday that they had found a miniature version of our own solar system 5,000 light-years across the galaxy — the first planetary system that really looks like our own, with outer giant planets and room for smaller inner planets.
Their results are being published Friday in the journal Science. The discovery, they said, means that our solar system may be more typical of planetary systems across the universe than had been thought.
In the newly discovered system, a planet about two-thirds of the mass of Jupiter and another about 90 percent of the mass of Saturn are orbiting a reddish star at about half the distances that Jupiter and Saturn circle our own Sun. The star is about half the mass of the Sun.
Since 1995, around 250 planets outside the solar system, or exoplanets, have been discovered. But few of them are in systems that even faintly resemble our own. In many cases, giant Jupiter-like planets are whizzing around in orbits smaller than that of Mercury. But are these typical of the universe?
Almost all of those planets were discovered by the so-called wobble method, in which astronomers measure the gravitational tug of planets on their parent star as they whir around it. This technique is most sensitive to massive planets close to their stars.
The new discovery was made by a different technique that favors planets more distant from their star. It is based on a trick of Einsteinian gravity called microlensing. If, in the ceaseless shifting of the stars, two of them should become almost perfectly aligned with Earth, the gravity of the nearer star can bend and magnify the light from the more distant one, causing it to get much brighter for a few days.
If the alignment is perfect, any big planets attending the nearer star will get into the act, adding their own little boosts to the more distant starlight.
That is exactly what started happening on March 28, 2006, when a star 5,000 light-years away in the constellation Scorpius began to pass in front of one 21,000 light-years more distant, causing it to flash. That was picked up by the Optical Gravitational Lensing Experiment, or Ogle, a worldwide collaboration of observers who keep watch for such events.
Ogle in turn immediately issued a worldwide call for continuous observations of what is now officially known as OGLE-2006-BLG-109. The next 10 days, as Andrew P. Gould, a professor of mathematical and physical sciences at Ohio State said, were “extremely frenetic.”
Somewhat to the experimenters’ surprise, by clever manipulation they were able to dig out of the data not just the masses of the interloper star and its two planets, but also rough approximations of their orbits, confirming the similarity to our own system. David P. Bennett, an assistant professor of astrophysics at the University of Notre Dame, said, “This event has taught us that we were able to learn more about these planets than we thought possible.”
As a result, microlensing is poised to become a major new tool in the planet hunter’s arsenal, “a new flavor of the month,” Dr. Seager said.
Only six planets, including the new ones, have been discovered by microlensing so far, and the Scorpius event being reported Friday is the first in which the alignment of the stars was close enough for astronomers to detect more than one planet at once. Their success at doing just that on their first try bodes well for the future, astronomers say. source
My comment: Well ,slowly but surely we're getting there. And if that black hole fails to eat the Earth, we're going to find them :) Many speculations have been done about what will happen with Earth and its religions when we find out we're not alone and they are other sentient beings in our Universe. I won't speculate. I simply know that the new perspective always changes the old beliefs. Of course, for the moment we just discover new solar systems, new planets. We're far from any signs of life. But then if there's possibility, there will be an opportunity.
Lowering Odds of Multiple Births
In the complex, expensive and emotionally charged world of fertility treatment, doctors are sounding a call to arms to reverse the soaring rate of multiple births.
The doctors are responding to an unintended consequence of the success of in vitro fertilization — that it is often too successful. Since 1980, when the technique became available in the United States, the rate of twins in all births has climbed 70 percent, to 3.2 percent of births in 2004.
Much of the increase, experts say, is a result of in vitro treatment. The rate of triplets and higher-order multiples increased even more from 1980 to 1998. It is not that twins or triplets are undesirable, doctors say. But multiple pregnancies often lead to risky preterm births and other complications. With that in mind, fertility centers are trying to lower the odds of such pregnancies, even at a cost of slightly lower success rates.
In I.V.F., a woman is given ovulation-induction hormones to produce multiple eggs, which are retrieved, fertilized with her partner’s sperm and transferred back to her uterus. The more embryos transferred, the higher the likelihood of multiples.
To achieve the goal of a single healthy baby, clinics are focusing on transferring fewer embryos and on developing more sophisticated ways to identify the healthiest embryos with the greatest chance of success.
“We have been getting better at I.V.F. over the years, and as success rates go up, the number we transfer has to go down accordingly,” said Dr. Judy E. Stern, director of the human embryology and andrology lab at the Dartmouth-Hitchcock Medical Center in Lebanon, N.H. “Where three embryos used to work and give you mostly singletons, now we transfer two, because we’re making better embryos and more of them implant.”
The number of I.V.F. cycles in which four or more embryos were transferred has dropped sharply, to 21 percent in 2004 from 62 percent in 1996. Although the efforts have substantially lowered the rates of triplets born through in vitro fertilization, they have not made a dent in the twin rate. That is because many doctors and patients are reluctant to take the final step to ensure a single birth, a process called S.E.T., for single embryo transfer. From 1996 to 2004, the rate of such procedures rose modestly, to 8 percent from 6 percent.
The American Society of Reproductive Medicine now recommends that women younger than 35 with a good prognosis have just one embryo transferred. Women under 35 make up 44 percent of I.V.F. cycles.
In women older than 37, who have a higher incidence of embryos with chromosomal defects, three to five embryos are still recommended, depending on the woman’s age.
The main obstacle to single embryo transfer is its lower success rate. Some experts ask women to agree to two cycles, first transferring one fresh embryo while freezing the others. If the first transfer fails, doctors transfer a single frozen embryo, a much less costly and onerous procedure. That approach yields similar success rates to transferring two at once while drastically reducing twin rates.
With momentum building to transfer just one or two embryos, clinics focus on choosing the embryo most likely to succeed. Selecting embryos has traditionally been based on a visual examination of their morphology — shape, number of divisions and other physical factors. But morphology does not tell all, and many embryos that look great under the microscope have undetected chromosomal abnormalities like missing or extra chromosomes, called aneuploidy.
One method used to weed out unhealthy embryos is to leave the embryos in a Petri dish for five days, two more than usual, to allow more time for hidden chromosomal abnormalities to show up.
Other researchers are looking at the traits of women at high risk of having multiples. In research presented at the reproductive society’s annual meeting last October, Dr. Stern linked a higher number of oocytes, or eggs retrieved from ovaries, with higher rates of single and multiple pregnancies.
“This will change our practice,” she said. “If more oocytes are retrieved, we’ll want to transfer fewer embryos.”
Other experts are turning to preimplantation genetic screening to cull embryos without aneuploidy. The screening is used to select healthy embryos in families with histories of genetic diseases. Because one or two cells have to be removed for analysis, there is some concern that the process can damage embryos, lowering pregnancy rates.
Another screening, comparative genomic hybridization, can assess all 23 pairs of chromosomes, providing an 80 percent chance of a healthy embryo and a 60 percent chance of a live birth, says Dr. Geoffrey Sher, executive medical director of the Sher Institutes of Reproductive Medicine, a nationwide group of fertility centers.
But Dr. Sher, whose lab performs this procedure, has encountered the same obstacles as others. He has a very high twin rate, hovering around 60 percent, because although the technique yields a higher success rate, women are refusing to have just one embryo transferred.
Many women in fertility treatment say that they simply do not view having twins as a risky situation and that they are willing, if not eager, to have them to speed the completion of their family, to avoid the high costs of future I.V.F. cycles or to ensure that their child has a sibling, among other reasons.source
My comment: I like twins. I really do. So I find it sad that they want to decrease the rate of twins. But from the other hand, if it's more dangerous for the mother, they ought to try. Of course, the choice should remain. Because to some people that's the only possibility to have kids-and the more at once, the better .