News – The latest star data from the Gaia space observatory has allowed astronauts for the first time to widely distribute a massive 3D atlas of binary stars within about 3,000 light-years on Earth – 1.3 million of them.
The one-of-a-kind atlas, created by Ph.D. psychologist Kareem El-Badry. a student from the University of California, Berkeley, should be a staple for those studying binary stars – which make up at least half of the constellations – and white dwarfs, exoplanets and stellar evolution, in general . Prior to Gaia, the last collection of nearby binary stars, collected using data from the now-dead Hipparcos satellite, included about 200 similar pairs.
“This is just a huge increase in sample size,” El-Badry said. “And it’s an increase in the types of evolutionary measures we find the binaries. In our sample, we only have 17,000 white dwarfs. This is a much larger census.”
White dwarfs are the final stages of most stars; the sun is likely to end up as a white dwarf in 5 billion years. The El-Badry atlas consists of 1,400 systems consisting of two white dwarfs and 16,000 binaries that include a white dwarf and another type of star
Most of the 2.6 million individual stars are still at the very beginning of life, however. Astronomers refer to them as mainline stars, because they accumulate online when plotted on a graph showing temperature versus brightness.
With such a large sample size, El-Badry said, it is possible to make demographics of these stellar pairs, asking questions such as: What is the distribution of the large ratios of the two stars in these binary systems? all? How is the separation or isolation spread?
El-Badry plans to focus in the future on the white dwarf binaries, as white dwarfs can be given a more accurate age than regular stars. Main series stars like the sun can look the same for billions, or even tens of billions, of years, while white dwarfs change – for one thing, they cool at a rate that is well explained. And since binary pairs are birthed at the same time, the age of the white dwarf tells astronomers the age of its predominant twin, or any planets around the stars.
“For a white dwarf, in general, it’s easy to tell how old he is – not just how old he became a white dwarf, but how old he is,” he said. “You can also measure their masses, because a white dwarf has a well-understood beauty-radius relationship.”
For example, El-Badry and colleagues recently used Gaia data to estimate the age of a Jupiter-sized gas giant that detected the TESS satellite around a pair of white-K dwarfs. That exoplanet, TOI-1259Ab, turned out to be about 4 billion years old, based on the age of the white dwarf.
“In this catalog, there are something like 15 systems like this: a star plus a planet in addition to a white dwarf,” he said, “and there are a few other hundred that are stars plus a planet and another star. These are two could be interesting because, in some cases, the other star will do something democratically on the planet. “
The new catalog of nearby binary stars has been approved for publication in the magazine Monthly notices from the Royal Astronomical Society.
El-Badry also collaborated with Jackie Faherty, a scientist and educator at the American Museum of Natural History in New York City, to create a video through the millions of binary stars around Earth, which represent a good piece of the whole Milky. Galaxy Way.
Binary stars
Until Gaia was launched by the European Space Agency in 2013 to measure the speed and movements of millions of nearby stars, the only way to find binaries was to look for nearby stars each other in the skies. This can be tricky, as stars that look very close to the Earth could be hundreds to thousands of light years apart, just sitting on the same line of the site.
Managing alignment requires a lot of observation time to ensure that both candidates are at the same speed and moving together. Because of the Earth’s motion around the sun, nearby stars appear to change position in the sky, and parallax can be used to work out how far away they are. The star’s movement across the sky, called a right motion, helps determine its speed.
Gaia continuously directs this tedious astrometry for all nearby stars in the sky, 24/7, from orbit at the Earth-Sun Lagrange point. The study of the most useful space telescope for stars is within about 3,000 light years on Earth, however, because beyond that, the parallax is usually too small to measure.
El-Badry first looked for binary stars in Gaia data after releasing the second round of star measurements in 2018, with the help of colleagues Hans-Walter Rix, director of the Max-Planck Institute for Astronomy there in Heidelberg, Germany, and Tyler Heintz, a graduate student at Boston University. They developed computer techniques to identify stars moving together through space and at the same distance from Earth. The device basically designs the movement of each star over thousands of years, based on its motion right today, and pulls out stars that are moving in the same direction. If they also turn out to be at the same parallax-based speed, they appear to be connected to each other, he said.
He and his colleagues focus exclusively on spacious binaries – those separated by a distance of 10 AU (celestial units) or more – that is, 10 or more times the distance between the Earth and the sun ( 93 million miles). Stars closer to that usually appear as a single point of light and require other spectroscopic techniques to differentiate whether they are true binaries.
To get the first crack at Gaia’s latest data, El-Badry woke up at 3 a.m. on the release date, Dec. 3 last year, and entered some 100 other astronauts from around the world on Zoom. It quickly ran pre-programmed queries on the data to extract the catalog information it needed to create the 3D map.
The first questions about 1.8 million binary applicants returned from Gaia’s catalog of 1.8 billion stars, so El-Badry first had to assess the likelihood that some of the pairs were at the same speed and move in similar directions just by chance, not because they are twins. He estimates that at least 1.3 million pairs had at least a 90% chance of being tied, and 1.1 million had a 99% chance of being tied.
“About half of the stars look like solar binaries, many of which are too close to separation, but we find that 25% of the stars have a binary companion similar to the sun at a separation greater than 30 AU, about the distance to Pluto, “he said.” The rotating peaks are at a separation of 30 or 50 AU. “
Some pairs are separated by as much as a parsec – 260,000 AU, or 3.26 light years – although most are within 1,000 AU apart.
One takeaway, he said, is that the new analysis confirms something examined in the 2018 data: Many binary star pairs are very similar in mass.
“One thing we’ve already found is cool – we found this out with Gaia DR2, but now we can better explore it with this sample – binaries like to be a pair of co. equal, “he said. “That’s pretty weird, because most of these are separated by hundreds or thousands of AUs, so they’re so far apart that, with conventional star formation theories, they should be random. But the data tells a different story: They know something about many of their companions. “
The effect, he said, is that they formed much closer together in a process that tended to equate their masses and then migrate from each other. probably due to interactions with other nearby stars.
The collection of binary stars allowed El-Badry to study the uncertainties reported in Gaia’s measurement of stellar position, which will help other researchers who use the data.
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