new data clouds cosmic distance measurements - precision laser distance measurement

by:UMeasure     2019-10-28
new data clouds cosmic distance measurements  -  precision laser distance measurement
Maggie mckaya's new measurement of the distance of the plei star cluster raises doubts about the reliability of one of the most widely used databases in astronomy, reigniting a 7-
Controversy over how the distance of the universe is determined for a year.
Valeri Makarov of the California Institute of Technology says this is a key issue;
"The distance we know from astronomical objects is based on several open clusters closest to each other.
Like the onsen Star, The Open Star Group is a loose Star Group.
Measuring astronomical distances is not simple.
For example, bright objects in the distance look the same as dim objects nearby.
So astronomers set up a step. by-
Step system, which starts with using several independent methods to accurately determine the distance to nearby objects-open clusters.
They then use these measurements to define a more distant cosmic scale, and so on.
The traditional measurement method puts plei star under 430 light
Give or take a dozen lights in a few years-years.
These are derived by comparing the graphs of color and brightness of some stars and similar graphs from closer Hyades clusters, the distances of which are known from simple geometric measurements.
But things became more complicated in 1997.
That spring, according to data from the European Space Agency's Hipparcos satellite, a huge database of more than 100,000 stars was released.
It uses parallax to calculate the distance, I. e.
Following our orbit around the Sun, observe a target at points far apart and measure the angle between them with a million seconds accuracy.
Astronomers immediately noticed that the distance of about a dozen open clusters was 20 different from traditional data.
The distance from Hipparcos to the star is about 385 light years lower.
"The issue has been very controversial since the beginning, and Hipparcos claims that system errors can't be that big," said Bohdan Paczynski of Princeton University, New Jersey . ".
"Others claim that if Hipparcos are correct, this will require significant modifications to our understanding of the cluster of stars and stars.
The best way to solve this debate is to measure the distance very accurately, but with a completely different approach, that's what this latest work has done.
"This long study was conducted by NASA's California Jet Propulsion Laboratory, astronomers pan Xiaopei and two colleagues.
For ten years, they used a link telescope called an interference meter to monitor a bright double star in the plei cluster.
They decide how often the stars surround each other and how far the stars are in the sky.
The inherent brightness of the stars gives an estimate of their mass, and they insert all this information into a simple equation to derive a cluster distance of about 440 light. years.
"This paper does not fully address this debate, but rather sets out strong reasons against Hipparcos," said Paczynski . ".
But he said another team might have evidence to verify Pan's results by the end of 2004.
Pan told New Scientist and Cologne that this study confirms that the traditional method of estimating distance is good;
"Hipparcos is good too, but only 1 million seconds.
"Paczynski agreed with colon cancer.
"In this case, they try to stretch the instrument beyond its capacity.
"This is because all the controversial star groups are too far away from the satellite to be accurately measured using one star.
So, the average distance from dozens of stars in each cluster.
Normally, this will work, Paczynski says, but some unknown errors are involved.
"I don't think it's an instrument error," said Makarov, who was involved in writing the Hipparcos database . ".
In his view, it depends on the formula for reducing the data and publishing possible solutions.
This may be important because Hipparcos may keep the best distance data for the rest of the time
ESA's Gaia and NASA's new generation of astrometric tasks, such as space interference measurement missions, will rise in the next decade.
This will be 1000 times more accurate than Hipparcos.
Magazine reference and colon; Nature (vol 427, p 326)
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