Hernandez and Cristhian Stuani.

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WASHINGTON Zapatillas Vans SK8 Hi Slim Negras Gum , July 25 (Xinhua) -- Large comets that take more than 200 years to make one revolution around the Sun are more common in the universe than previously thought, a new study conducted by the U.S. space agency NASA said Tuesday.

Based on observations by the agency's WISE spacecraft, the study found that the number of long-period comets measuring at least one kilometer across is about seven times more than had been predicted previously.

"Because they spend most of their time far from our area of the solar system, many 'long-period comets' will never approach the Sun in a person's lifetime," NASA said in a statement.

"In fact Zapatillas Vans SK8 Hi Reissue España Negras , those that travel inward from the Oort Cloud -- a group of icy bodies beginning roughly 186 billion miles (300 billion kilometers) away from the Sun -- can have periods of thousands or even millions of years," it said.

The existence of so many more long-period comets than predicted suggests that more of them have likely impacted planets, delivering icy materials from the outer reaches of the solar system, the study said.

The new study also found that long-period comets have a mean nucleus size of 2.1 kilometers in diameter, roughly twice as large as "Jupiter family comets Zapatillas Vans Sk8 Hi Lite Negras Blancas Comprar ," whose orbits are shaped by Jupiter's gravity and have periods of less than 20 years.

The results reinforced the idea that comets that pass by the Sun more often tend to be smaller than those spending much more time away from the Sun, NASA said.

That is because Jupiter family comets get more heat exposure, which causes volatile substances like water to sublimate and drag away other material from the comet's surface as well.

Previously, astronomers had no good way of measuring the sizes of long-period comets because a comet has a "coma," a cloud of gas and dust that appears hazy in images and obscures the cometary nucleus.

But by using the WISE data showing the infrared glow of this coma Zapatillas Mujer Vans Old Skool Blancas Verdes España , scientists were able to "subtract" the coma from the overall comet and estimate the nucleus sizes of these comets.

The data came from 2010 WISE observations of 95 Jupiter family comets and 56 long-period comets. The observations were carried out during the spacecraft's primary mission before it was renamed NEOWISE and reactivated to target near-Earth objects.

The findings were published in the Astronomical Journal.

Chinese research vessel "Kexue" conducts operation in South China Sea

Rescue drill held in E China's Yichun

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Tourists view lotus flowers in N China

Chinese research vessel "Kexue" conducts operation in South China Sea

Amazing scenery of Barkol grassland in Xinjiang

Highlights of Int'l Aviation and Space Salon MAKS-2017 in Zhukovsky, Russia

People enjoy lotus flowers at Xihu Park

WASHINGTON, Aug. 8 (Xinhua) -- One of the two Americans who contracted Ebola in West Africa and are being treated in a U.S. hospital said Friday that he is "growing stronger every day" as he "wrestled with this terrible disease."

In a statement he wrote from an isolation room at Emory University Hospital in Atlanta, 33-year-old Kent Brantly said he is being provided with "the very best care possible" and expressed his "deep and sincere thanks to" those who have been praying for his recovery as well as for his colleague Nancy Writebol.

Brantly and 59-year-old Writebol were stricken with the Ebola virus while treating patients in Liberia last month. Both were brought back to the Atlanta hospital for treatment early this month.

He recalled that when Ebola spread into Liberia, his usual hospital work turned more and more toward treating the increasing number of Ebola patients.

"I held the hands of countless individuals as this terrible disease took their lives away from them Zapatillas Mujer Vans Old Skool Rosa Blancas España ," the doctor said. "I witnessed the horror firsthand, and I can still remember every face and name."

Then on a Wednesday morning in July, he started feeling ill and immediately isolated himself, Brantly said. Three days later, he was confirmed being infected with the disease. "When the result was positive Zapatillas Vans Old Skool Blancas Verdes Baratas , I remember a deep sense of peace that was beyond all understanding," he recalled in the statement released by Samaritan 's Purse, the aid group he worked for.

Meanwhile, Writebol is also recovering. Her husband told U.S. media Friday that she is well enough to ask for Starbucks coffee.

Both Brantly and Writebol have received an experimental drug never tested in humans. U.S. health officials warned that it's too early to tell if the treatment is helpful, harmful or doesn't have any impact. There is no known cure for Ebola so far.

RIO DE JANEIRO Comprar Zapatillas Vans Old Skool Leather Zip Blancas Baratas , May 31 (Xinhua) -- Liverpool striker Luis Suarez is lined up in Uruguay's final 23-man squad for the World Cup, the Uruguay Football Association (AUF) said Saturday.

Suarez was a doubt after injuring himself in team training and is

currently doing rehabilitation following arthroscopic surgery on the

mensicus in his left knee.

But coach Oscar Tabarez named Suarez as one of his final 23 for

Brazil, alongside forwards Edinson Cavani, Diego Forlan, Abel

Hernandez and Cristhian Stuani.

Suarez Zapatillas Vans Old Skool Pro Negras Baratas , who enjoyed a brilliant season with Liverpool in the

Premier League, faces a race against time to be fit for Uruguay's

first match with Costa Rica on June 14.

Uruguay also face Italy and England in World Cup Group D.

NAIROBI, Aug. 17 (Xinhua) -- Former Kenyan international boxer on Thursday decried the falling standards of the game in the East African nation, saying the former boxing powerhouse ought to go back to the drawing board to arrest the decline.

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