Jupiter’s moon Europa continues to be a source of wonder and scientific intrigue. As one of the four Galilean Moons (so-named because of their founder, Galileo Galilee), Europa is one of Jupiter’s largest satellites and is considered one of the best bets for finding extraterrestrial life in the Solar System. And recently, it joined its cousins (Io and Callisto) in passing in front of a star.
This type of rare event (a stellar occultation) allows astronomers to conduct unique observations of a celestial body. In Europa’s case, the occultation took place in 2017 and allowed astronomers to make more precise measurements of Europa’s size, its position relative to Jupiter, and its true shape. All this was made possible by the ESA’s Gaia Observatory, which let astronomers know exactly when and where to look for the moon.
Despite the many advancements made in the field of astronomy, astronomers still struggle to get an accurate assessment of the Milky Way Galaxy. Because we are embedded in its disk, it is much more difficult to assess its size, structure, and extent – unlike galaxies located millions (or billions) of light-years away. Luckily, thanks to improved instruments and tireless efforts, progress is being made all the time.
For instance, a team of astronomers recently combined the latest data obtained by the ESA’s Gaia observatory with the infrared and optical observations of other telescopes to start mapping the bar-shaped collection of stars at the center of our Milky Way. This constitutes the first time in history that astronomers have been able to make direct measurements of this barred structure.
During the early 1990s, NASA’sPioneer 10 and 11 probes became the first robotic missions to venture beyond Neptune. In 2012 and 2018, the Voyager 1 and 2 missions went even farther by crossing the heliopause and entering interstellar space. Eventually, these probes may reach another star system, where their special cargo (the Pioneer Plaques and the Golden Records) could find their way into the hands of another species.
Which raises an important question: where might these spacecraft eventually wander? To address this, Coryn Bailer-Jones of the Max Planck Institute for Astronomy and Davide Farnocchia of NASA’s Jet Propulsion Laboratory recently conducted a study that examined which star systems the Voyager and Pioneer probes will likely encounter as they drift through the Milky Way over the next few million years…
Our understanding of the universe, and of the Milky Way, is built on an edifice of individual pieces of knowledge, all related to each other. But each of those pieces is only so accurate. The more accurate we can make one of the pieces of knowledge, the more accurate our understanding of the whole thing is.
The age of stars is one such piece. For years, astronomers have used a method of determining the age of stars that has a 10% to 20% margin of error. Now, a team of scientists from Embry-Riddle Aeronautical University has developed a new technique to determine the age of stars with a margin of error of only 3% to 5%.
About fifty years ago, astronomers predicted what the ultimate fate of our Sun will be. According to the theory, the Sun will exhaust its hydrogen fuel billions of years from now and expand to become a Red Giant, followed by it shedding it’s outer layers and becoming a white dwarf. After a few more billion years of cooling, the interior will crystallize and become solid.
Until recently, astronomers had little evidence to back up this theory. But thanks to the ESA’s Gaia Observatory, astronomers are now able to observe hundreds of thousands of white dwarf stars with immense precision – gauging their distance, brightness and color. This in turn has allowed them to study what the future holds for our Sun when it is no longer the warm, yellow star that we know and love today.
In December of 2013, the European Space Agency (ESA) launched the Gaia mission. Since that time, this space observatory has been busy observing over 1 billion astronomical objects in our galaxy and beyond – including stars, planets, comets, asteroids, quasars, etc. – all for the sake of creating the largest and most precise 3D space catalog ever made.
The ESA has also issued two data releases since then, both of which have led to some groundbreaking discoveries. The latest comes from the Leiden Observatory, where a team of astronomers used Gaia data to track what they thought were high-velocity stars being kicked out of the Milky Way, but which actually appeared to be moving into our galaxy.
In all this time, the question of ‘Oumuamua’s origin has remained unanswered. Beyond theorizing that it came from the direction of the Lyra Constellation, possibly from the Vega system, there have been no definitive answers. Luckily, an international team led by researchers from the Max Planck Institute for Astronomy (MPIA) have tracked ‘Oumuamua and narrowed down its point of origin to four possible star systems.
In December of 2013, the European Space Agency (ESA) launched the Gaia mission, a space observatory designed to measure the positions of movements of celestial bodies. Over the course of its five-year mission, this observatory has been studying a total of 1 billion objects – including distant stars, planets, comets, asteroids, quasars, etc. – for the sake of creating the largest and most precise 3D space catalog ever made.
Ever since the first exoplanet was confirmed in 1992, astronomers have found thousands of worlds beyond our Solar System. With more and more discoveries happening all the time, the focus of exoplanet research has begun to slowly shift from exoplanet discovery to exoplanet characterization. Essentially, scientists are now looking to determine the composition of exoplanets to determine whether or not they could support life.
In 2013, the European Space Agency (ESA) deployed the Gaia mission, a space observatory designed to measure the positions of movements of celestial bodies. For the past four years, Gaia has been studying distant stars, planets, comets, asteroids, quasars and other astronomical objects, and the data it has acquired will be used to construct the largest and most precise 3D space catalog ever made, totaling 1 billion objects.
The second release of Gaia data, which took place on April 25th, 2018, has already resulted in a number of impressive discoveries. The latest was made by an international team of scientists who identified 13,928 white dwarfs within 100 parsecs (326 light-years) of the Sun, many of which were formed through mergers. This is the first time that white dwarf stars have been directly detected within the Solar neighborhood.
Basically, white dwarfs are what become of the majority of stars (with masses less than 8 Solar masses) once they exit the main sequence phase of their lives. This consists of a star exhausting its hydrogen fuel and expanding to several times its size (entering its Red Giant Branch Phase). These stars then blow off their external layers (a supernova) and leaving behind a white dwarf remnant.
By studying them, astronomers can learn far more about the life cycle of stars and how they evolve. As Dr. Kilic explained to Universe Today via email:
“[W]e’re basically doing Galactic archaeology when we study nearby white dwarfs. They tell us about the ages and star formation histories of the Galactic disk and halo. More importantly, white dwarfs explode as a Type Ia supernova when they reach 1.4 times the mass of the Sun. We use these supernovae to study the shape of the Universe and conclude that the expansion of the universe is accelerating. However, we have not yet found the progenitor systems of these supernovae. One of the channels to form Type Ia supernovae is through mergers of white dwarfs. Hence, the direct detection of merged white dwarfs is important for understanding the frequency of these white dwarf mergers.”
However, until recently only a few hundred white stars have been found within the local galactic neighborhood (500 within a 40 parsec radius). In addition, astronomers were only able to obtain accurate parallax (distance) measurements for about half of these. But thanks to the Gaia data, the number of white dwarfs systems that astronomers are able to study has increased exponentially.
“Gaia provided distance measurements,” said Kilic. “We can now create complete samples of white dwarfs within a given volume. For example, prior to Gaia, we only knew about 100 white dwarfs within 20 parsecs of the Sun. With Gaia Data Release 2, we identified more than 13,000 white dwarfs within 100 parsecs of the Sun. The difference in numbers is amazing!”
The Gaia data was also helpful in determining the nature of these white dwarf systems and how they formed. As they indicate in their study, previous research has shown that the majority of white dwarf stars in our local galaxy (roughly 56%) are the product of single-star evolution, whereas 7 to 23% were the product of mergers between binaries. The remainder were white dwarf binaries, or binaries with one white dwarf and a main sequence star.
Using the Gaia data – which included the color and distribution data of thousands of white dwarf stars within ~326 light-years of the Sun – the team was able to determine how massive these stars are. This, in turn, provided vital clues as to how they formed, which indicated that mergers were far more common than previous studies suggested. As Kilic explained:
“Massive white dwarfs tend to be smaller, which means that they are also fainter (since they have a smaller surface area). Since Gaia gave us a complete sample of white dwarfs within 100 parsecs of the Sun, for the first time, we were able to derive the magnitude distribution (hence the mass distribution) of thousands of white dwarfs and find a large fraction of massive white dwarfs. We see that the number of massive white dwarfs is significantly higher than expected from single star evolution. Therefore, we concluded that many of these massive white dwarfs actually formed through mergers in previously binary systems.”
From this, the team was able to assemble the first reliable Hertzsprung-Russell Diagram for nearby field white dwarf stars, as well as estimates on how often white dwarf binaries merge. As Kilic indicated, this could have significant implications for other areas of astronomical study.
“Based on the frequency of these single white dwarfs that formed through mergers, we can estimate how many white dwarf mergers occur on average and with what mass distribution,” he said. “We can then infer the rate of Type Ia supernovae from these mergers and see if it’s enough to explain part or all of the Ia supernova explosions. This is an ongoing area of research and I’m sure we will some results on these very soon.”
These findings are yet another gem to come from the second Gaia data release, which has proven to be a treasure trove for astronomers. The third release of Gaia data is scheduled to take place in late 2020, with the final catalog being published in the 2020s. Meanwhile, an extension has already been approved for the Gaia mission, which will now remain in operation until the end of 2020 (to be confirmed at the end of this year).