| Sep 19, 2024 |
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(Nanowerk Information) Astronomers research stars by trying on the totally different colors of sunshine they emit – colors they seize and analyze utilizing spectroscopy. Now a workforce led by Université de Montréal’s Étienne Artigau has developed a method that makes use of a star’s spectrum to chart variations in its temperature to the closest tenth of a level Celsius, over a spread of time scales.
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“By tracking a star’s temperature, we can learn a lot about it, such as its rotation period, its stellar activity, its magnetic field,” defined Artigau, an astrophysicist at UdeM’s Trottier Institute for Analysis on Exoplanets (IREx). “Such detailed knowledge is also essential for finding and studying a star’s planets.”
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In an article printed in The Astronomical Journal (“Measuring sub-Kelvin variations in stellar temperature with high-resolution spectroscopy”), Artigau and his workforce display the method’s effectiveness and flexibility utilizing observations of 4 very totally different stars made with the Canada-France-Hawaii Telescope in Hawaii and the European Southern Observatory (ESO) 3.6-m telescope in La Silla, Chile.
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| A star’s temperature is much from uniform; it varies each throughout the star’s floor and over time. Now an revolutionary method developed by Université de Montréal’s Étienne Artigau and his workforce makes it attainable to trace these adjustments with unprecedented precision. (Picture: Benoit Gougeon, UdeM)
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The scientists first turned their consideration to stellar spectra to enhance exoplanet detection utilizing radial velocity. This methodology measures slight oscillations in a star generated by the gravitational pull of an orbiting planet. The better the oscillations, the bigger the planet.
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But it surely’s onerous to detect very small oscillations and due to this fact low-mass planets. To beat this drawback, Artigau and his workforce developed a method exploiting the radial velocity methodology that analyzes a star’s full spectrum and never just some parts, as beforehand accomplished with this methodology.
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This makes it attainable to detect planets as small because the Earth orbiting round small stars. Artigau then got here up with the thought of utilizing an analogous technique to detect not solely variations in a star’s oscillations but in addition in its temperature.
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Distinguishing between stars and their planets
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Temperature measurements are important within the seek for exoplanets, that are principally noticed not directly by intently monitoring their star. Lately, astronomers have confronted a significant hurdle: easy methods to distinguish between the observable results of a star and its planets.
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This can be a drawback in each the seek for exoplanets utilizing radial velocity and the research of their atmospheres utilizing transit spectroscopy.
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“It’s very difficult to confirm the existence of an exoplanet or to study its atmosphere without precise knowledge of the host star’s properties and how they vary over time,” defined Charles Cadieux, a doctoral scholar at IREx who contributed to the research.
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“This new technique gives us an invaluable tool for ensuring that our knowledge of exoplanets is solid and for advancing our characterization of their properties.”
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A star’s floor temperature is a fundamental property that astronomers depend on as a result of it may be used to find out the star’s luminosity and chemical composition. At finest, a star’s actual temperature will be identified to an accuracy of about 20 levels Celsius.
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Nevertheless, the brand new method measures not actual temperatures however temperature variation over time, which it could actually decide with outstanding precision.
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“We can’t tell whether a star is 5,000 or 5,020 degrees Celsius, but we can determine if it has increased or decreased by a degree, even a fraction of a degree – no-one’s ever done this before,” stated Artigau.
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“It’s a challenge to detect such minute temperature changes in the human body, so imagine what it’s like for a gaseous ball with a temperature in the thousands located dozens of light-years away!”
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To display that their method works, the researchers used observations taken with the SPIRou spectrograph within the Canada-France-Hawaii Telescope and the HARPS spectrograph within the ESO’s 3.6-m telescope.
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Within the knowledge captured by these two telescopes for 4 small stars within the photo voltaic neighbourhood, the workforce might clearly see temperature variation, which they attributed to both the star’s rotation or to occasions at its floor or within the surrounding setting.
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The brand new method made it attainable to measure massive variations in temperature. For the star AU Microscopii, identified for its excessive stellar exercise, the workforce recorded variations of virtually 40 levels Celsius.
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With this method, they have been in a position to measure not solely very speedy adjustments in temperature related to brief rotation durations of some days, equivalent to these AU Microscopii and Epsilon Eridani, but in addition these occurring over for much longer durations of time, a tough feat for ground-based telescopes.
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“We were able to measure changes of a few degrees or less occurring over very long periods, such as those associated with the rotation of Barnard’s star, a very quiet star that takes five months to complete a full rotation,” defined Artigau. “Before, we would have had to use the Hubble Space Telescope to measure such a subtle and slow variation.”
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The brand new method additionally made it attainable to detect very advantageous temperature adjustments on the floor of the celebrities. For instance, the workforce detected delicate temperature adjustments in star HD 189733 coinciding with the orbit of its exoplanet HD 189733 b, a large “hot Jupiter” planet.
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The UdeM researchers level out that the method works not solely with SPIRou and HARPS, however with any spectrograph working within the seen or infrared vary.
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The revolutionary method will likely be straight relevant to observations from NIRPS, a spectrograph put in final yr within the ESO telescope in Chili. In line with the researchers, it could even be attainable to make use of this method with space-based devices, such because the James Webb Area Telescope.
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“The power and versatility of this technique means we can exploit existing data from numerous observatories to detect variations that were previously far too small to be perceived, even on very long timescales,” stated Artigau.
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“This opens up new horizons in our study of the stars, their activity and their planets.”
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