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Circumstellar Dust Disks in Taurus-Auriga: The Submillimeter Perspective

Written by Sean M. Andrews and Jonathan P. Williams, Institute for Astronomy, University of Hawaii
Jun 12, 2005 at 04:49 PM
We present a sensitive, multiwavelength submillimeter continuum survey of 153 young stellar objects in the Taurus-Auriga star formation region. The submillimeter detection rate is 61% to a completeness limit of <10mJy ({tex}3-\large\sigma{/tex}) at 850 µm. The inferred circumstellar disk masses are log-normally distributed with a mean mass of {tex}~5\times10^{-3}M\odot{/tex} and a large dispersion (0.5 dex). Roughly one third of the submillimeter sources have disk masses larger than the minimal nebula from which the solar system formed. The median disk to star mass ratio is 0.5%. The empirical behavior of the submillimeter continuum is best described as {tex}F_v\propto v^{2.0\pm 0.5}{/tex} between 350 µm and 1.3 mm, which we argue is due to the combined effects of the fraction of optically thick emission and a flatter frequency behavior of the opacity compared to the interstellar medium. This latter effect could be due to a substantial population of large dust grains, which presumably would have grown through collisional agglomeration. In this sample, the only stellar property that is correlated with the outer disk is the presence of a companion. We find evidence for significant decreases in submillimeter flux densities, disk masses, and submillimeter continuum slopes along the canonical infrared spectral energy distribution evolution sequence for young stellar objects. The fraction of objects detected in the submillimeter is essentially identical to the fraction with excess nearinfrared emission, suggesting that dust in the inner and outer disk are removed nearly simultaneously. (0) Comments posted about this in the forum
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MIT ESD Professors Receive NASA Funding for Interplanetary Supply-Chain Management Research

Written by Everything Science

Jun 05, 2005 at 12:05 AM

CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 18, 2005--The National Aeronautics & Astronautics Administration (NASA) has awarded two ESD professors funding to conduct research to support its new vision for human and robotic space exploration. (http://exploration.nasa.gov).

Interplanetary Supply Chain Management and Logistics Architectures (Graphic: Business Wire)

David Simchi-Levi, Professor of Civil and Environmental Engineering and Engineering Systems and Olivier de Weck, Robert N. Noyce Career Development Assistant Professor of Aeronautics and Astronautics and Engineering Systems will lead the "Interplanetary Supply-chain Management & Logistics Architectures" project, in partnership with the Jet Propulsion Laboratory, Payload Systems Inc. and United Space Alliance, LLC. Its purpose is to create a framework for analysis and strategic planning of the future interplanetary supply-chain.

The interplanetary supply-chain encompasses the transfer of goods and associated information from terrestrial suppliers to launch sites, the integration of payloads onto launch vehicles and launch to Low Earth Orbit (LEO), the in-space transfer of payloads from LEO to the Moon and Mars as well as planetary surface logistics.

Although there are a vast number of scientific principles and techniques that have been developed since World-War-II to improve the effectiveness and efficiency of supply-chain management (SCM) in the private and military sectors on Earth, the potential benefits of this body-of-knowledge are currently only poorly understood in the context of space exploration.

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Written by Everything Science

Jun 04, 2005 at 11:49 PM

ATLANTA--(BUSINESS WIRE)--June 3, 2005--Two whale sharks took a 60-hour ride on a UPS plane this week to arrive Friday at their new home at the Georgia Aquarium here. Whale sharks are known as the largest fish on earth.

Special Delivery -- Georgia Aquarium specialists secure a whale shark off the coast of Taiwan, Wednesday, June 1st. Two of the animals were transported by UPS aboard a B-747 aircraft for delivery to the Atlanta-based aquarium. The animals are known as the largest fish on earth, and will reside in the soon-to-be-opened Georgia Aquarium.

The fish were flown more than 8,000 miles on a UPS B-747 freighter from Taipei, Taiwan, through Anchorage to Atlanta. The two sharks each are about 13 feet in length and together weigh nearly 2,200 pounds.

The movement of the whale sharks is believed to be the first in history for this species. The name "whale" has been applied to the fish because of its huge size, but they are fish and not mammals. The whale shark can reach up to 45-to-50 feet in length.

The movement presented a number of logistics challenges, including the re-configuration of the plane's interior, custom tanks with a highly advanced marine life support system, and marine animal doctors traveling aboard. Special hoisting equipment also was required at each end of the journey. The full capacity of the B-747 was required because the fish, their special tanks and water weighed a combined 54,000 pounds.

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Gender bending bumblebees

Written by Everything Science

Jun 04, 2005 at 09:40 AM

Researchers at the University of Southampton’s School of Biological Sciences have discovered that inbreeding in threatened bumblebee species results in female worker bees changing sex.

Many bumblebee species have become rare in recent years, and their last populations are confined to nature reserves, which effectively act as islands amidst a sea of intensively farmed land. In small, isolated bumblebee populations where there are very few individuals, relatives may mate with each other.

Now the Southampton researchers have discovered that this inbreeding has significant consequences. They have studied a number of species, including the Moss Carder Bee (Bombus muscorum), at various sites across the UK, from the Hebrides in Scotland to Dungeness on the Kent coast.

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Humans went out of Africa for shellfish

Written by Everything Science

May 16, 2005 at 08:27 PM

The lure of a seafood diet may explain why early humans came out of Africa, according to research by the universities of Leeds and Glasgow published in Science this week.

Early modern humans in East Africa survived on an inland diet based on big game but by 70,000 years ago their diet had changed to a coastal one consisting largely of shellfish. However, dramatic climate change seems likely to have reduced the Red Sea's shellfish stocks. New DNA evidence suggests their taste for life beside the sea caused them to set off from Africa to find new, better fishing grounds.

The international project shows – contrary to previous thinking – that early modern humans spread across the Red Sea from the Horn of Africa, along the tropical coast of the Indian Ocean towards the Pacific, in just a few thousand years.

Leeds biologist Dr Martin Richards said: "What’s more, those early settlers were the ancestors of all non-Africans alive today - including modern Europeans, whose ancestors splintered off from the small group of pioneers somewhere around the Persian Gulf."

Re: Humans went out of Africa for shellfish
Retrospector May 21st, 2005 - 2:57 AM

I've followed this business for a long time. The debate goes on and on centering on two main theories-the "recently out of Africa" idea and the idea that modern humans evolved worldwide in a diverse multiregional fashion following much earlier migrations from Africa. Here's a short aricle from the National Geographic site.

http://news.nationalgeographic.com/news/2001/01/0111origins.html

Quote

Opposition to this theory comes from multiregionalists, anthropologists who see modern man arising from "a process of change within a species," said one of the theory’s architects, Milford Wolpoff.

Multiregionalists see modern humans arising from these changes in Africa, Eurasia, and Australia. The species that evolved, they say, gained traits held by all modern humans but remained racially diverse because of geographical adaptations and the distances between populations.

The modern traits were shared species-wide through interbreeding, maintains Wolpoff.

"The [Homo sapiens’] genes spread widely and were successful," he explained.

Wolpoff also argues for a much earlier date for the evolution of Homo sapiens than Out of Africa theorists postulate.

"There’s only been one species for a long time," he said.

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