Planets by the Billions

New calculations suggest that there may be as many as 60 billion habitable planets just in our own Milk Way galaxy, maybe more. At least 100 of these planets may be as close as 30 light-years away.

Researchers at the European Southern Observatory (ESO) carefully sampled 102 red dwarf stars in the southern skies. Red dwarfs are very common in our galaxy. Based on observations and calculations, the ESO team estimates that approximately 40% of the red dwarf stars are orbited by planets. What’s more, these planets are in what astronomers call the “habitable zone,” meaning they are neither too close nor too far from their sun. In particular, it means that the temperature may be right for liquid water to exist on the planet’s surface.

The ESO project is the work of an international team using observations with the HARPS spectrograph on the 3.6-metre telescope at ESO's La Silla Observatory in Chile. It is published in the March 28 issue of Astronomy & Astrophysics.

Caption: This artist's impression shows a sunset seen from the super-Earth Gliese 667 Cc. The brightest star in the sky is the red dwarf Gliese 667 C, which is part of a triple star system. The other two more distant stars, Gliese 667 A and B appear in the sky also to the right. Astronomers have estimated that there are tens of billions of such rocky worlds orbiting faint red dwarf stars in the Milky Way alone. Credit: ESO/L. Calçada. Usage Restrictions: None

"Our new observations with HARPS mean that about 40% of all red dwarf stars have a super-Earth orbiting in the habitable zone where liquid water can exist on the surface of the planet," says Xavier Bonfils in a press release issued by ESO.

"Because red dwarfs are so common — there are about 160 billion of them in the Milky Way — this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone," according to Bonfils.

"The habitable zone around a red dwarf, where the temperature is suitable for liquid water to exist on the surface, is much closer to the star than the Earth is to the Sun," says Stephane Udry, another member of the ESO team.

Red dwarfs, however, may pose a special challenge to life. According to Udry, "Red dwarfs are known to be subject to stellar eruptions or flares, which may bathe the planet in X-rays or ultraviolet radiation, and which may make life there less likely." In the more technical language of the scientific publication, “The main difference from earth are a significantly higher mass and a different stellar environment, which potentially can have caused divergent evolutions.”

All the more tantalizing, of course. As one of the ESO scientists puts it, "Now that we know that there are many super-Earths around nearby red dwarfs we need to identify more of them using both HARPS and future instruments. Some of these planets are expected to pass in front of their parent star as they orbit — this will open up the exciting possibility of studying the planet's atmosphere and searching for signs of life," concludes Xavier Delfosse.

The article, "The HARPS search for southern extra-solar planets XXXI. The M-dwarf sample", by Bonfils et al. appears in Astronomy & Astrophysics on March 28.

Stem Cell Update: Important Research Breakthrough

Another important step has just been taken toward achieving the medical promise of stem cell research. For the first time, researchers at the Max Planck Institute for Molecular Biomedicine in Münster, Germany, have reprogrammed skin cells directly into multipotent stem cells.

Over the past five years, stem cell researchers have learned how to induce or reprogram skin cells to become pluripotent stem cells—cells capable of becoming any type of cell in the body. The result: induced pluripotent stem cells or iPSCs. Scientists have also discovered how to reprogram cells to become precursor or progenitor cells. Precursor cells have a much narrower range of potential for development. They are able to become one very specific type of cell in the body.

Expanding on previous work, the latest breakthrough achieves a kind of “goldilocks” or just-right level. Working with mice, the team led by Hans Schöler discovered how to reprogram fully differentiated skin cells into neuronal stem cells (NSC)s. Unlike pluripotent cells, NSCs are far more suitable for clinical use. And now, with this breakthrough, the Max Plank Institute team has learned how to reprogram or induce NSCs or iNSCs.

And unlike precursor or progenitor cells, iNSCs are capable of multiplying and diffentiating once they are implanted. When researchers implanted their iNSCs into mouse brains, iNSCs generated new cells that began to take on some of the characteristics of ordinary developing brain cells.

Caption: This is an immunofluorescence microscopy image of the induced neural stem cells (iNSCs) using antibodies against two neural stem cell markers SSEA1 (red color) and Olig2 (green color). Credit: MPI for Molecular Biomedicine

The field of stem cell research has faced many obstacles, some moral and some medical. The main moral objection is that the prime source of human pluripotent cells is the human embryo, and many object to the destruction of the embryo for medical purposes. One of the medical challenges is that implanted cells are likely to be rejected by the immune system, much as transplanted organs are rejected unless immunosuppressant drugs are given.

Unless, of course, the source of the cells is from the patient’s own body. That’s why this achievement is important. If this technique can be applied to human cells—and there’s no reason to think it can’t—then someday it may be possible to take a small sample of cells from a patient’s skin, convert them to iNSCs, and then implant them in the patient’s brain to repair damage from disease or injury.

Not only does the iNSC discovery use the patient’s own cells as the source. It also by-passes the pluripotent stage. That fact should help researchers avoid creating cancer or other problems.

According to Schöler, "pluripotent stem cells exhibit such a high degree of plasticity that under the wrong circumstances they may form tumours instead of regenerating a tissue or an organ."

"Our research shows that reprogramming somatic cells does not require passing through a pluripotent stage," Schöler said in a press release issued by the Max Plank Institute. "Thanks to this new approach, tissue regeneration is becoming a more streamlined—and safer—process."

The article, "Direct Reprogramming of Fibroblasts into Neural Stem Cells by Defined Factors," appears in the March 22 issue of Cell Stem Cell.

Space Age View of Stone Age Settlements

Thousands of early human settlements have been located using computers and satellite images, according to a paper published on March 19 in the Proceedings of the National Academy of Sciences.

Researchers used computers to analyze satellite images of a 23,000 square kilometer region in the Upper Khabur Basin of northeastern Syria. The finding? They believe they can identify 14,312 possible sites of human settlements dating back eight thousand years. The region, a relatively small 100 miles square, was nearly 3% occupied at various points over the intervening millennia.

Harvard archeologist Jason Ur collaborated with MIT researcher Bjoern Menze to develop a system that identified settlements based on a several factors. Old sites tend to leave mounds that show distinctive shapes and colors from the collapse of building materials such as mud bricks.

“With these computer science techniques, however, we can immediately come up with an enormous map which is methodologically very interesting, but which also shows the staggering amount of human occupation over the last 7,000 or 8,000 years,” Ur said in a press release issued by Harvard.

"What's more, anyone who comes back to this area for any future survey would already know where to go," he continued. "There's no need to do this sort of initial reconnaissance to find sites. This allows you to do targeted work, so it maximizes the time we have on the ground."

The article, “Mapping patterns of long-term settlement in Northern Mesopotamia at a large scale,” appears in the March 19 issue of PNAS.

Red Deer People? Really?

Did our human family tree just grow a new branch? That seems to be the tentative conclusion reported today in the online journal, PLoS ONE.

A first analysis of human remains from two caves in southwest China has prompted researchers to make some astounding claims: These "Red Deer People" are not anatomically modern humans (AMH). Their remains date from 14,500 to 11,500 years ago, far more recent than anything similar ever found on the mainland of Asia. They shared their territory with modern humans just at the time when early agriculture was being developed. And—even more puzzling—they shared anatomical features with modern and archaic humans.

Caption: An artist's reconstruction of fossils from two caves in southwest China have revealed a previously unknown Stone Age people and give a rare glimpse of a recent stage of human evolution with startling implications for the early peopling of Asia. The fossils are of a people with a highly unusual mix of archaic and modern anatomical features and are the youngest of their kind ever found in mainland East Asia. Dated to just 14,500 to 11,500 years old.

Credit: Art copyright by Peter Schouten Usage Restrictions: Image may be used in association with initial news media reports - otherwise seek permission from Peter Schouten: info@studioschouten.com.au

Who were they? The international team of researchers speak of these early humans as the “Red-Deer People,” named for extinct species of deer they hunted and for the Maludong or “Red Deer Cave” where some of the remains were discovered. The team was led by Professor Darren Curnoe of the University of New South Wales and Professor Ji Xueping of the Yunnan Institute of Cultural Relics and Archeology.

But researchers hesitate to draw any conclusions about species. "These new fossils might be of a previously unknown species, one that survived until the very end of the Ice Age around 11,000 years ago," says Professor Curnoe in a press release issued by UNSW. "Alternatively, they might represent a very early and previously unknown migration of modern humans out of Africa, a population who may not have contributed genetically to living people."

Although the remains were first discovered in 1979, they remained encased in rock until 2009. While the researchers have been able to compare anatomical features with modern and archaic human remains, they have not been able to extract DNA from the samples. According to the paper, “our ongoing attempts to extract DNA from a specimen from Maludong have so far proven unsuccessful owing to a lack of recoverable genetic material.”

"The discovery of the red-deer people opens the next chapter in the human evolutionary story – the Asian chapter – and it's a story that's just beginning to be told," says Professor Curnoe.

The paper is entitled "Human Remains from the Pleistocene-Holocene Transition of Southwest China Suggest a Complex Evolutionary History for East Asians" and appears in the March 14, 2012 issue of PLoS ONE.