Archive for October 3rd, 2006

Supernova 80% Younger Than Thought

Science, Uncategorized | Posted by Chris Parker
Oct 03 2006

 

10/01/2006

The age of a supernova remnant has dropped from 10,000 years to less than 2,000 years.

According to a news item on Space.com, the object RCW 86 in Centaurus has been linked to sightings by the Chinese in 185 AD, making it the oldest supernova recorded by man, taking place 1821 years ago.

But astronomers thought this supernova remnant was 10,000 years old. How could the earlier age estimates be so far off? The article explains:

The new age estimate matches the supernova spotted in 185 AD. But this calculation means the remnant is 8,000 years younger than previously thought. The astronomers said the difference can be attributed to the irregular shape of the remnant’s expanding bubble. Stellar wind from the progenitor star pushed some of the remnant’s gases in a certain direction, forming a dense pile.

“The idea for RCW 86 is that in some regions the shock has hit this piled-up material. In those regions the shock will start moving slower,” [Jacco] Vink [U of Utrecht] said. And in other regions, the shock wave is much speedier.

X-ray measurements from the Chandra X-ray Observatory were used in making the new age determination based on outflow speeds of the gas. The new estimate was about 2,000 years, within the range of the event in 185 AD.

One of the captions in the article was “Shell Shocked,” but it was not clear if this referred to the supernova remnant or to the astronomers finding out how wrong they had been. In this case, we had an observation to calibrate a dating method, and the result was drastically lower than predicted from theory. There are many other things in space and time that cannot be so calibrated. The parameter to watch in dating methods is the observation-to-assumption ratio.

Source: CreationEvolutionHeadlines

Ancient Hair Dye Used Nanotechnology

Science, Sophistication of Ancestors, Uncategorized | Posted by Chris Parker
Oct 03 2006

Anna Salleh

ABC Science Online

2 October 2006

ABC Science Online   Photo: Since ancient times, people have dyed their grey hair black (Image: iStockphoto

A 2000-year-old recipe for hair dye shows Ancient Greeks and Romans used nanotechnology to permanently colour grey hair black, say experts.Dr Philippe Walter of the French state museum agency’s Centre for Research and Restoration and colleagues report their findings online in the journal Nano Letters.

The researchers made up a batch of dye according to a recipe used since Greco-Roman times, which includes a mixture of lead oxide and slaked lime.They soaked 50 milligrams of blond human hair in the dye for three days, then studied the hair closely.

The hair turned progressively black and when the researchers took cross-sections of hair and studied it under the microscope they found nanocrystals of lead sulfide inside the hair shaft. The lead in the lead oxide had reacted with sulfur from the amino acids found in hair keratins, the scientists say, giving the black colour.

They say the 5 nanometre lead sulfide crystals look very much like lead sulfide quantum dots that are made today by advanced materials science methods.

The researchers say their discovery might help develop new mineral-based nanomaterials.Dr Ivan Kempson, a materials scientist and research fellow at the University of South Australia, is impressed with the research. “It’s the highest resolution and most detailed study of the incorporation of a metal like lead into hair,” he says.Kempson says the findings are interesting for his own work, which looks at how hair takes up metals from the environment.

But he says it is not yet clear how the sulfur in the keratin is made available to interact with the lead in the hair.

Kempson says the research is also of interest to the cosmetics industry in developing hair dyes.

“If you know how they penetrate the hair and how they react within the hair then you can develop better cosmetic products,” he says.

The research team includes a member from L’Oréal cosmetics company.