Tuesday, August 21, 2012

The Sun, surprisingly, is as round as it can be: UH researchers

Even the Earth bulges a little as it spins, but the Sun...the Sun is nearly perfectly round.

Rounder than almost anything else--and that's a surprise.

(Image: An photo of the sun, showing sunspots, taken by the Solar Dynamics Observatory. Credit: NASA.)

University of Hawai`i scientists were among those who recently conducted state-of-the-art measurements using a device called the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory satellite.

They found that it is amazingly round. The sun spins, an activity that tends to widen objects at the equator and flatten them between the poles. But not Ol’ Sol. 

The solar research team on this project includes Jeff Kuhn and Isabelle Scholl of the Institute for Astronomy, University of Hawaii at Manoa, Rock Bush  of Stanford University, and Marcelo Emilio, of the Universidade Estadual de Ponta Grossa, Brazil. They reported their findings in the August 16, 2012, Science Express in an article entitled The Precise Solar Shape and Its Variability. The abstract is here.

First, the measurement. They found that if you shrank the Sun to a ball one meter across, then the distance measured through the poles would be only 17 millionths of a meter less than the distance measured at right angles to the poles, through the equator—the equatorial diameter. A sheet of paper is five or six times thicker than that. Most human hair is significantly thicker.

Our Sun spins fully every 28 days and it ought to flatten more than that, according to predictions based on that rotation. With all the sunspots and moving plasma and other stuff, you might also think there would be lots of variance in its shape. 

There isn’t.

"For years we've believed our fluctuating measurements were telling us that the sun varies, but these new results say something different. While just about everything else in the sun changes along with its 11-year sunspot cycle, the shape doesn't,” lead author Kuhn said.

In fact, the sunspot cycle seems to have no role, the authors say. It is “completely unaffected by the solar cycle variability seen on its surface.”

Their best guess: subsurface forces like solar magnetism may be having a much more powerful impact than anyone predicted. The sun's massive gravity, along with other subsurface forces, may counteract the effects of its spin, and keep it in a rounder shape.

This work was supported by NASA grants to Stanford University and the University of Hawaii.
More about the Solar Dynamics Observatory here and here.   

The University of Hawai`i press release on the discovery is here.

© Jan TenBruggencate 2012

Sunday, August 19, 2012

Invasive fish ta`ape maintains diversity by fast invasion

It seemed to make so much sense back then—if native species aren't doing well, just bring in stronger competitors rather than figuring out why the locals aren't thriving.

(Image: The introduced snapper, Lutjanus kasmira, commonly known as taʻape. Credit: Keoki Stender)

It happened in forestry, bringing in alien trees to reforest the Islands, rather than figuring out why the native forests were ravaged.

And it happened in fisheries, when the Hawai`i Territorial Division of Fish and Game determined, around the time of statehood, to supplement the islands' existing nearshore marine species with three alien reef fishes, Lutjanus fulvus (blacktail snapper or to‘au), Cephalopholis argus (blue-spotted grouper or roi) and Lutjanus kasmira (bluestriped snapper or ta‘ape).

What's been the result? A couple of them have done so well that organizations sponsor targeted fishing tournaments to try to reduce their impact on the reefs and the native species.

A group of scientists from the Hawai`i Institute of Marine Biology has studied the genetics of the three species to learn what happened to them as they settled in to their new Hawaiian home. The researchers are Michelle Gaither, Robert Toonen, and Brian Bowen.

They were released on O`ahu and Hawai`i Islands, but quickly spread to all the Main Hawaiian Islands, and the ta`ape traveled more than 1,000 miles right up the Northwestern Hawaiian Islands chain to Midway Atoll. Roi thus far has made it to French Frigate Shoals. Only to`au remains in the main islands.

The researchers found that the fast-spreading ta`ape maintained its genetic diversity—a diversity similar to that found in the ta`ape of its source islands in Fresh Polynesia. But the slower-spreading species, particularly the to`au, lost much of their genetic diversity.

It suggests that fast growth itself may play a role in protecting diversity of invasive species, they write.

We now have a better idea of why some species are more successful invaders than others. The faster a species becomes established in its new environment, the faster it finds food and begins to reproduce, the more likely it is to maintain the genetic diversity that is so important to its long term success as an alien species,” said Gaither, in a press release.

For more information the Hawai`i Institute of Marine Biology work in the Northwestern Hawaiian Islands, see www.hawaii.edu/himb/nwhi/. The abstract from their paper in is here: www.ncbi.nlm.nih.gov/pubmed/22874747. The publication is Proc Biol Sci. 2012 Aug 8.

© Jan TenBruggencate 2012

Friday, August 10, 2012

Nihoa millerbirds repopulate Laysan Island, redux

Researchers leave today (Aug. 10, 2012) for Nihoa Island to collect native Nihoa millerbirds, to help repopulate the species on Laysan Island.

(Image: It’s not easy working on remote islands. Here, a team transfers captured millerbirds from Nihoa to a waiting small boat during the first Laysan repopulation effort. Credit: USFWS Pacific.)

Millerbirds became extinct on Laysan, in the Northwestern Hawaiian Islands, after introduced rabbits destroyed the island’s vegetation a century ago. The rabbits have long since been removed, and Fish and Wildlife Service teams have been working for two decades to restore some of the native vegetation there.

Meanwhile, the endangered millerbird has been vulnerable, since its only population in the world has been on that single, tiny, volcanic island from which it gets its name. 

Nihoa lies 150 miles to the west of Kaua`i, and is the easternmost island of the 1,000-mile long Papahānaumokuākea Marine National Monument , which encompasses the Northwestern Hawaiian Islands.

Researchers last year made the first transfer of the birds from rocky Nihoa Island, where they still thrive, to sandy Laysan, which lies 650 miles to the west. Those birds have done well. Twenty-four were moved onto Laysan Sept. 10, 2011, and they have already produced 17 young.

This translocation is a project of the U.S. Fish and Wildlife Service (FWS), American Bird Conservancy (ABC), and other organizations. It takes place entirely within the Hawaiian Islands National Wildlife Refuge and Papahānaumokuākea Marine National Monument and World Heritage site.

Much of what is known about Nihoa millerbirds was discovered by pioneering zoologist Sheila Conant, a University of Hawai`i professor who studied them extensively starting in the 1980s. She continues to be involved.

(Image: Nihoa millerbird, which will help create a new population of millerbirds on Laysan. Credit: Robby Kohley via U.S. Fish and Wildlife Service.) 
“The reproductive success of the first group of birds moved to Laysan is very encouraging and demonstrates that Laysan is quite a hospitable island for millerbirds from Nihoa,” she said. “This second translocation will provide this tiny, new population with the best chance of flourishing. The reestablishment of millerbirds on Laysan is an extraordinary and long-needed step in the species’ recovery.”

The project hopes to capture another 26 birds to bring the total number of transferred millerbirds to 50. A biologist will overwinter on Laysan to monitor the birds.

Habitat restoration and restoring species to their former habitats is a rare conservation event, but it has shown considerable success with birds like the Hawaiian goose or nene, once not present but which is now thriving on Kaua`i. In another example, during the past decade, Laysan ducks have been restored to Midway Atoll, and they appear to be responding well to the new habitat.

“This type of restoration work is sorely needed for other Hawaiian birds,” Conant said.

© Jan TenBruggencate 2012