A star is behaving strangely, getting brighter and brighter. A US research team digs up ancient data and makes an amazing discovery.
SEATTLE – University of Washington astronomers Anastasios Tzanidakis and James Davenport say they are interested in “unusual stars.” Then they received an automated warning from the “Gaia” mission of the European space agency Esa just right: data showed that the Star Gaia17bpp gradually brightened over two and a half years.
On Star that changes its brightness so much, makes experts sit up and take notice, because the behavior is unusual. But in the case of Gaia17bpp, a research team led by Tzanidakis and Davenport quickly determined that the star itself was not changing at all – something else must be responsible for the change in brightness.
Star becomes unusually bright – without changing itself
“Based on the data currently available, this star appears to have a slow-moving companion surrounded by a large disc of material,” Tzanidakis explains in one Message and clarifies the dimensions: “If this material were in the solar system, it would extend from the Sun to Earth’s orbit or beyond.”
In order to reach these conclusions, the research team had to do some detective work and first collect a large amount of data on the star Gaia17bpp. In addition to the data from the “Gaia” mission, which went back to 2014, information from the telescopes “Pan-Starrs1”, “Wise/Neowise” and the Zwicky Transient Facility was also included. This is how the researchers came up with data going back to 2010.
Star behaving strangely – research team suspects companion star
“Based on our analysis, the two stars orbit each other for an unusually long period of time — up to 1,000 years,” Tzanidakis found. He explains how unusual it is that his team noticed the star’s change in brightness at all: “The chance of observing this bright star as it eclipses its dusty companion is unique in a lifetime.”
The star Gaia17bpp has been dimmer than usual for almost seven years, according to data the research team has been sleuthing together. From 2012 to 2019, the companion star that passed in front of Gaia17bpp apparently blocked 98 percent of the light. What could be seen in the “Gaia” data as a brightening star was therefore actually the end of the occultation: the companion star released Gaia17bpp again, the light was able to penetrate unhindered into space again.
Is a small white dwarf star orbiting the star Gaia17bpp?
With the help of astronomical observations going back to the 1950s, Tzanidakis and Davenport were able to gain another important insight: “In 66 years of observations, we have found no other signs of a significant dimming of this star,” Tzanidakis describes the find. What the star Gaia17bpp’s dusty companion might look like is not entirely clear. Preliminary data suggest it could be a small but massive white dwarf star. It is also unclear where the dust came from.
In any case, Tzanidakis is happy about his team’s find: “It was a chance discovery,” emphasizes the astronomer. “If we were a few years late, we would have missed it.” However, the “oddity” could be much more common in space than experts previously thought, the research team says. The results of the study have not yet been published in a peer-reviewed journal, however presented at the 241st meeting of the American Astronomical Society in Seattle. (tab)
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