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Hubble precisely measures distance to globular star cluster

Astronomers using NASA's Hubble Space Telescope have for the first time precisely measured the distance to one of the oldest objects in the universe -- a collection of stars born shortly after the Big Bang

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nasa's hubble space telescope

Astronomers using NASA’s Hubble Space Telescope have for the first time precisely measured the distance to one of the oldest objects in the universe — a collection of stars born shortly after the Big Bang. This stellar assembly, a globular star cluster called “NGC 6397”, is one of the closest such clusters to Earth. The new measurement sets the cluster’s distance at 7,800 light-years away, with just a three per cent margin of error.

This new distance yardstick provides an independent estimate for the age of the universe, the US space agency said in a statement on Thursday. The new measurement will also help astronomers improve models of stellar evolution.

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Countless galaxies exist in the universe, each hiding secrets that humankind is yet to unearth. Pixabay

Star clusters are the key ingredient in stellar models because the stars in each grouping are at the same distance, have the same age, and have the same chemical composition. The new measurement uses straightforward trigonometry, the same method used by surveyors, and as old as classical Greek science. The research team calculated NGC 6397’s age at 13.4 billion years old. “The globular clusters are so old that if their ages and distances deduced from models are off by a little bit, they seem to be older than the age of the universe,” said Tom Brown of the Space Telescope Science Institute (STScI) in Baltimore, Maryland

The researchers say they could reach an accuracy of one per cent if they combine the Hubble distance measurement of NGC 6397 with the upcoming results obtained from the European Space Agency’s Gaia space observatory.

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“Getting to one per cent accuracy will nail this distance measurement forever,” Brown said. The findings appeared in The Astrophysical Journal Letters. IANS

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NASA Probe Makes New Discoveries on Asteroid Bennu

As a result, Bennu's rotation period is decreasing by about a second every 100 years, the scientists explained

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Asteroid
This Nov. 16, 2018, image provide by NASA shows the asteroid Bennu. NASA

NASA’s first asteroid-sampling mission OSIRIS-REx has observed particle plumes erupting from the surface of Bennu, an asteroid the size of the pyramid at Giza.

The Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) spacecraft, which began orbiting Bennu on December 31, first discovered the particle plumes on January 6, followed by additional particle plumes over the last two months.

While some of the particles were slow-moving, the others were found orbiting Bennu, like small satellites.

Bennu’s entire surface was also found to be rough and dense with boulders, contrary to the Earth-based observations, which showed a smooth surface with a few large boulders.

This means that the sample collection part of the mission will have to be adjusted to make sure that OSIRIS-REx can touch down and collect a sample, said NASA while presenting the discoveries at the 50th Lunar and Planetary Conference in Houston.

“The discovery of plumes is one of the biggest surprises of my scientific career,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson.

NASA
This artist’s rendering made available by NASA in July 2016 shows the mapping of the near-Earth asteroid Bennu by the OSIRIS-REx spacecraft. VOA

“And the rugged terrain went against all of our predictions. Bennu is already surprising us, and our exciting journey there is just getting started,” Lauretta added.

Further, the team observed a change in the spin rate of Bennu as a result of what is known as the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) effect.

The uneven heating and cooling of Bennu as it rotates in sunlight is causing the asteroid to increase its rotation speed.

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As a result, Bennu’s rotation period is decreasing by about a second every 100 years, the scientists explained.

OSIRIS-REx launched in 2016 to explore Bennu, the smallest body ever orbited by spacecraft, is expected to return a sample of the asteroid to Earth in 2023.

The findings will allow researchers to learn more about the origins of our solar system, the sources of water and organic molecules on Earth, the resources in near-Earth space, as well as improve our understanding of asteroids that could impact Earth. (IANS)