The ESA’s Gaia mission is our most accurate star-measuring spacecraft. It’s busy mapping the positions and radial velocities of one billion stars in the Milky Way. The mission’s goal is to create a representative map of the galaxy’s stellar population with unprecedented accuracy. The mission has released 3 sets of data since its inception, leading to many discoveries.
Now a team of astronomers has found an exoplanet with help from Gaia, an unintended result of the ambitious mission.
Most exoplanets are found using the transit method, where an exoplanet passes in front of its star and causes a dip in the light. But that method has its limitations, as every method does. The transit method is an indirect observation of an exoplanet. All observers see is the dip in starlight, not the planet itself, and while the dip provides important information, that information is limited.
Direct observations provide more information but are much more difficult. We’re only now getting telescopes powerful enough to observe exoplanets directly. The powerful James Webb Space Telescope directly imaged the exoplanet HIP 65426 b in 2022. Thanks to the JWST and the powerful ground-based telescopes that are nearing completion, astronomers are getting to a point where they can use both direct and indirect observations of exoplanets to learn more about them, at least in some instances.
This image shows the exoplanet HIP 65426 b in different bands of infrared light, as seen from the James Webb Space Telescope. This was the first exoplanet imaged by JWST. Credit: NASA/ESA/CSA, A Carter (UCSC), the ERS 1386 team, and A. Pagan (STScI).
In this new research, Gaia data played a central role, helped by data from the ESA’s now-defunct Hipparcos mission, Gaia’s predecessor. That data told astronomers where to point the Subaru Telescope on Mauna Kea, which provided direct observations and confirmation of the distant exoplanet.
Illustrations of the Gaia spacecraft (l), the Hipparcos spacecraft (m), and a photo of the Subaru Telescope (r). All three facilities contributed to the exoplanet discovery. Image Credits: ESA, ESA, NAOJ.
The team of astronomers that found the planet presented their results in a research article in the journal Science. The article is “Direct imaging and astrometric detection of a gas giant planet orbiting an accelerating star.” The lead author is Thayne Currie from the National Astronomical Observatory of Japan and the NASA Ames Research Center.
“This is sort of a test run for the kind of strategy we need to be able to image an Earth.”
Thayne Currie, NASA, NAOJ
Astronomers have only been able to observe about 20 exoplanets directly, and that’s out of over 5000 confirmed exoplanets. And the 20 all have two things in common: they orbit at a great distance from their stars, and they’re much more massive than Jupiter. With our current level of technology, those are the only exoplanets we can really see directly.
Scientists would like to find and study more of these planets because they’re rare. There’s nothing like them in our Solar System. But they need to know where to look, and that’s where this new method comes in. The Gaia and
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Starship gave us quite a show during the first flight test of a fully integrated Starship (S24) and Super Heavy rocket (B7) from Starbase in Texas.
On April 20, 2023 at 8:33 a.m. CT, Starship successfully lifted off from the orbital launch pad for the first time. The vehicle cleared the pad and beach as Starship climbed to an apogee of ~39 km over the Gulf of Mexico – the highest of any Starship to-date.
With a test like this, success comes from what we learn, and we learned a tremendous amount about the vehicle and ground systems today that will help us improve on future flights of Starship.
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This is the vehicle trajectory and mission control audio without any additional commentary. There may be very long periods of silence. For our full hosted webcast, visit
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When two black holes collide, they don’t smash into each other the way two stars might. A black hole is an intensely curved region of space that can be described by only its mass, rotation, and electric charge, so two black holes release violent gravitational ripples as merge into a single black hole. The new black hole continues to emit gravitational waves until it settles down into a simple rotating black hole. That settling down period is known as the ring down, and its pattern holds clues to some of the deepest mysteries of gravitational physics.
Gravitational wave observatories such as the Laser Interferometry Gravitational-Wave Observatory (LIGO) have mostly focused on the inspiral period of black hole mergers. This is the period where the two black holes orbit ever closer to each other, creating a rhythmic stream of strong gravitational waves. From this astronomers can determine the mass and rotation of the original black holes, as well as the mass and rotation of the merged black hole. The pattern of gravitational waves we observe is governed by Einstein’s general relativity equations, and by matching observation to theory we learn about black holes.
General relativity describes gravity extremely well. Of all the gravitational tests we’ve done, they all agree with general relativity. But Einstein’s theory doesn’t play well with the other extremely accurate physical theory, quantum mechanics. Because of this, physicists have proposed modifications to general relativity that are more compatible with quantum theory. Under these modified theories, there are subtle differences in the way merged black holes ring down, but observing those differences hasn’t been possible. But a couple of new studies show how we might be able to observe them in the next LIGO run.
The modified Teukolsky equation. Credit: Li, Dongjun, et al
In the first work, the team focused on what is known as the Teukolsky Equation. First proposed by Saul Teukolsky, the equations are an efficient way of analyzing gravitational waves. The equations only apply to classical general relativity, so the team developed a way to modify the equations for modified general relativity models. Since the solutions to both the Teukolsky and modified Teukolsky equations don’t require a massive supercomputer to solve, the team can compare black hole ring downs in various gravitational models.
The second work looks at how this would be done with LIGO data. Rather than focusing on general differences, this work focuses on what is known as the no-hair theorem. General relativity predicts that no matter how two black holes merge, the final merged black hole must be described by only mass, rotation, and charge. It can’t have any “hair”, or remnant features of the collision. In some modified versions of general relativity, black holes can have certain features, which would violate the no-hair theorem. In this second work, the authors show how this could be used to test general relativity against certain modified theories.
LIGO has just begun its latest observation run, so it will be a while before there is enough data to test. But we may soon have a new observational test of Einstein’s old theory, and we might just prove it isn’t the final theory of gravity after all.
Reference: Li, Dongjun, et al. “Perturbations of spinning black holes beyond General Relativity: Modified Teukolsky equation.” Physical Review X 13.2 (2022): 021029.
Reference: Ma, Sizheng, Ling Sun, and Yanbei Chen. “Black hole spectroscopy by mode cleaning.” Physical Review Letters 130.2 (2023): 141401.
The post When Black Holes Merge, They’ll Ring Like a Bell appeared first on Universe Today.
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