Pushy black holes stop elliptical galaxies from forming stars

Multi-wavelength view of the elliptical galaxy NGC 5044. Credit: Digitised Sky Survey /NASA Chandra /Southern Observatory for Astrophysical Research/Very Large Array. 

Contradicting past theories, cold gas has been found in abundance in some elliptical galaxies—showing that there must be some other explanation why these types of galaxies don't form new stars.

Astronomers believe that the jets from supermassive black holes in these galaxies' center must push around the gas and prevent stars from forming.

Researchers spotted the gas for the first time using old data from the recently retired Herschel space observatory, which was able to peer well into the infrared—where it spotted carbon ions and oxygen atoms.

This find stands against the previous belief that these galaxies were "red and dead", referring to their physical appearance and the fact that they form no new stars.

"We looked at eight giant elliptical galaxies that nobody had looked at with Herschel before and we were delighted to find that, contrary to previous belief, six out of eight abound with cold gas", stated Norbert Werner, a researcher at Stanford University in California who led the study.

"These galaxies are red, but with the giant black holes pumping in their hearts, they are definitely not dead," added Werner.

Previously, scientists thought that the galaxies got rid of their cold gas or had used it all up during a burst of earlier star formation.

With cold gas found in the majority of the sample, researchers then used other observatories to try to find warmer gas up to tens of millions of Kelvin (or Fahrenheit or Celsius).

NGC 1399, an elliptical galaxy about 65 million light years from Earth. Credit: NASA, Chandra

X-ray information from NASA's Chandra X-ray Observatory revealed that there is hot gas cooling in six of the eight galaxies, but not in the remaining two of the sample.

"This is consistent with theoretical expectations: once cooled, the hot gas would become the warm and cold gas that are observed at longer wavelengths.

However, in these galaxies the cooling process somehow stopped, and the cold gas failed to condense and form stars," the European Space Agency stated.

"While the six galaxies with plenty of cold gas harbour moderately active black holes at their centres," ESA added, "the other two show a marked difference."

"In the two galaxies without cold gas, the central black holes are accreting matter at frenzied pace, as confirmed by radio observations showing powerful jets of highly energetic particles that stem from their cores."

More information: N. Werner, J. B. R. Oonk, M. Sun, P. E. J. Nulsen, S. W. Allen, R. E. A. Canning, A. Simionescu, A. Hoffer, T. Connor, M. Donahue, A. C. Edge, A. C. Fabian, A. von der Linden, C. S. Reynolds, and M. Ruszkowski. "The origin of cold gas in giant elliptical galaxies and its role in fuelling radio-mode AGN feedback." MNRAS first published online February 24, 2014 DOI: 10.1093/mnras/stu006

Spider Silk Skin can Stop a bullet

Dutch artist Jalila Essaïdi and cell biologist Abdoelwaheb El Ghalbzouri have blended spider silk with human skin to produce material that is three times stronger than kevlar.

In the first clip, the bioengineered skin cushions a bullet fired at half speed. But its resistance has its limits: when shot at a full speed of 329 m/s, the bullet pierces the material and travels through it. The same tests were also performed with piglet skin, human skin and human skin fused with regular silkworm silk, which were all penetrated by bullets of both speeds.

An international team worked together to create the new material. First, transgenic goats and silkworms equipped to produce spider-silk proteins spun out the raw material at the synthetic biology lab at Utah State University. The cocoons were then shipped to South Korea, where they were reeled into thread, before being woven into fabric in Germany. The modified silk was then wedged between bioengineered skin cells developed by biochemist Abdoelwaheb El Ghalbzouri at the Leiden University Medical Center in the Netherlands. After five weeks of incubation, the hybrid skin was ready for target practice.

In addition to exploring the material artistically, Essaïdi is also looking into practical uses, such as skin transplants. Spider silk is already being developed by other teams for high-tech applications, which range from artificial corneas to brain implants.

For more about spider silk spin-offs, check out our full-length feature: "Stretching spider silk to its high-tech limits". Or you might also like to find out about the science behind a lavish golden spider-silk cape, currently on display at the Victoria and Albert Museum in London.

Indonesian militants call for sharia law to stop HIV

Jakarta (AFP) Nov 29, 2009 - Several hundred hardline Muslim protestors staged rallies in Indonesia Sunday to urge the government to prevent the spread of HIV by implementing Islamic law.

Ahead of World AIDS Day on December 1, members of the Hizbut Tahrir group took to the streets in several cities including Jakarta, Solo, Yogyakarta and Makassar.

"We urge everybody to support the application of sharia in an Islamic caliphate so that, God willing, all of us will be free from the HIV/AIDS threat," Hizbut spokeswoman Febrianti Abassuni said in a statement. In the capital, more than 200 female demonstrators urged the government to close down brothels and ban condoms, which they said encouraged "free sex and unhealthy behaviour".

One banner read: "Prostitutes, drug users and homosexuals are the agents of immorality." Around 270,000 Indonesians are estimated to be infected with HIV, and AIDS has claimed about 8,700 lives in the Muslim-majority nation of 228 million people, according to the UNAIDS agency.