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Asteroids help scientists to measure distant stars – ScienceDaily

Looking up at the clear night sky, you will see many stars. Sometimes it is almost reachable, or at least seems to burn short rockets. However, the star closest to the earth, which does not rely on the sun, is more than four light years away from a distance of 25 trillion miles.

There are over 100 billion stars in our galaxy. We have learned a lot, but because the size is too far, the measured size is relatively small. The size of a star is important information that opens up many other riddles about information. Several methods have been used to measure the size of stars, but there are limitations.

But an international team, including researchers at the University of Delaware, have found a new way to determine the size of stars. Their method utilizes the unique features of the VERITAS (Very Energetic Radiation Imaging Telescope Array System) at the Fred Lawrence Whipple Observatory in Arizona and draws asteroids that pass in the right place and time.

Using this technique, Tarek Hassan of Deutsches Elektronen-Synchrotron (DESY) and 23 colleges and research institutions led by Michael Daniel of the Smithsonian Astrophysical Observatory have found that the diameter of a huge star is 2,674 light years away. 700 light years away like the sun – the smallest stars ever measured in the night sky. The study was reported in the journal on Monday, April 15. Natural Astronomy.

Resize stars

"Knowing the size of stars is generally important," said Jamie Holder, an associate professor of UD physics and astronomy and co-author of the study. "It tells us how big and how hot a star was born, how long it would shine, and how it would eventually die."

However, almost all the stars in the sky are too far away to be able to accurately measure with the best optical telescopes.

"You can not solve the same image as a star," Holder said. "The telescope will have a purge."

To overcome this limitation, scientists use the optical phenomenon called diffraction to measure the star diameter. When an object passes in front of a star, an event called "occultation" can calculate the size of the star using light shadows and surrounding patterns.

In this pilot study, the object passing in front of the star was an asteroid. It is possible that the space remains from the time the planet was formed about 4.6 billion years ago.

Asteroids travel at an average speed of 15 miles per second and are added to your team's achievements. In general, the VERITAS telescope will see faint blue light generated by high-energy cosmic particles and gamma rays as they race through the Earth's atmosphere. The telescope does not produce the best optical image, but it is very sensitive to rapid light changes, including starlight, thanks to the huge mirror surface painted in hexagon, like the eye of a fly. Holder was involved in the construction and commissioning of the telescope in 2006 and all the optical sensor modules of the four telescopes were assembled in the UD.

Ph.D. students make pioneering observations.

On February 22, 2018, using four large VERITAS telescopes, the team was able to clearly detect the diffraction pattern of the 60 km (37 miles) asteroid TYC 5517-227-1 passed by Imprinetta. UD doctoral student Tyler Williamson was there for observation.

"Since we made this kind of measurement for the first time, we had to spend a lot of time preparing and correctly following the procedure," Williamson, one of three scientists that night, said. "The occult itself takes only a few seconds, but we estimate the state before and after the event by taking the telescope to the front of the star for about 15 minutes, knowing what it looked like without blocking it."

Usually, when a crew brings in data, you can see what the computer is collecting in real time, but there is no way to see this transient. They simply had to wait for the telescope.

"At first we may see occult in our position." "The most recent estimate that we entered at night was that the shadow was about 50% likely to be thrown over our observatory, because the asteroid was small and uncertain about its size and trajectory, it was impossible to tell.

The crew took the data and emailed it to the project 's chief investigator late at night.

"The next afternoon, I woke up to PI's e-mail and reminded me of a brilliant conspiracy that looked sharp," Williamson said. "We were all very excited and as observers we were very happy to be part of the result."

With the VERITAS telescope, the team was able to take 300 snapshots per second. This data allowed us to reconstruct the brightness profile of the diffraction pattern with a high degree of accuracy and calculated the star's angle or apparent diameter per 0.125 milliseconds. Scientists have classified the star as a star of the red giant, with its distance being 2,674 light years, the actual diameter of the star being 11 times the sun.

According to Holder, this star is about 200 million times more distant than the sun. But it is within the galaxy of the galaxy. This is about 100,000 light years in the Milky Way.

The researchers repeated their feats three months later on May 22, 2018 when the asteroid Penelope, 88 kilometers in diameter, occulted star TYC 278-748-1. As a result of the measurement, the angle of 0.094 milliseconds and the actual diameter of 2.17 times of our sun – the smallest star was measured directly.

However, "small" is relative. "This star is G-dwarf, about twice the size of the sun, about 700 times farther from us than our closest star," Holder said.

The new technology provides astronomers 10 times better resolution than the standard method based on lunar elimination, but it is twice as big as size measurements using interferometry techniques, and Holder says the team is working to improve it for more accurate accuracy "He said.

"Asteroids go to Earth every day," Holder said. "Veritas is preparing to increase observations and broaden the scope of observations, and we are building data for a whole new population of stars."

The UD team's work was supported by the National Science Foundation.

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