| Sep 19, 2024 |
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(Nanowerk Information) Astronomers research stars by wanting on the totally different colors of sunshine they emit – colors they seize and analyze utilizing spectroscopy. Now a crew 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 variety of time scales.
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“By monitoring a star’s temperature, we are able to be taught quite a bit about it, resembling its rotation interval, its stellar exercise, its magnetic subject,” defined Artigau, an astrophysicist at UdeM’s Trottier Institute for Analysis on Exoplanets (IREx). “Such detailed data can also be important for locating and learning a star’s planets.”
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In an article revealed in The Astronomical Journal (“Measuring sub-Kelvin variations in stellar temperature with high-resolution spectroscopy”), Artigau and his crew exhibit 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 crew makes it doable to trace these modifications 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 higher the oscillations, the bigger the planet.
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But it surely’s laborious to detect very small oscillations and due to this fact low-mass planets. To beat this drawback, Artigau and his crew developed a method exploiting the radial velocity methodology that analyzes a star’s full spectrum and never only a few parts, as beforehand carried out with this methodology.
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This makes it doable to detect planets as small because the Earth orbiting round small stars. Artigau then got here up with the thought of utilizing the same technique to detect not solely variations in a star’s oscillations but additionally in its temperature.
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Distinguishing between stars and their planets
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Temperature measurements are essential within the seek for exoplanets, that are principally noticed not directly by carefully monitoring their star. Lately, astronomers have confronted a serious hurdle: the right way to distinguish between the observable results of a star and its planets.
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It is 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 troublesome to substantiate the existence of an exoplanet or to check its ambiance with out exact data of the host star’s properties and the way they differ over time,” defined Charles Cadieux, a doctoral pupil at IREx who contributed to the research.
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“This new method provides us a useful software for making certain that our data of exoplanets is stable and for advancing our characterization of their properties.”
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A star’s floor temperature is a primary property that astronomers depend on as a result of it may be used to find out the star’s luminosity and chemical composition. At greatest, a star’s precise temperature might be recognized to an accuracy of about 20 levels Celsius.
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Nevertheless, the brand new method measures not precise temperatures however temperature variation over time, which it could possibly decide with outstanding precision.
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“We are able to’t inform whether or not a star is 5,000 or 5,020 levels Celsius, however we are able to decide if it has elevated or decreased by a level, even a fraction of a level – no-one’s ever carried out this earlier than,” mentioned Artigau.
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“It’s a problem to detect such minute temperature modifications within the human physique, so think about what it’s like for a gaseous ball with a temperature within the hundreds situated dozens of light-years away!”
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To exhibit 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 crew may 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 doable to measure giant variations in temperature. For the star AU Microscopii, recognized for its excessive stellar exercise, the crew 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 fast modifications in temperature related to quick rotation intervals of some days, resembling these AU Microscopii and Epsilon Eridani, but additionally these occurring over for much longer intervals of time, a troublesome feat for ground-based telescopes.
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“We have been in a position to measure modifications of some levels or much less occurring over very lengthy intervals, resembling these related to the rotation of Barnard’s star, a really quiet star that takes 5 months to finish a full rotation,” defined Artigau. “Earlier than, we might have had to make use of the Hubble Area Telescope to measure such a refined and sluggish variation.”
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The brand new method additionally made it doable to detect very advantageous temperature modifications on the floor of the celebrities. For instance, the crew detected refined temperature modifications in star HD 189733 coinciding with the orbit of its exoplanet HD 189733 b, a large “scorching 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 shall be instantly relevant to observations from NIRPS, a spectrograph put in final 12 months within the ESO telescope in Chili. In response to the researchers, it could even be doable to make use of this method with space-based devices, such because the James Webb Area Telescope.
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“The ability and flexibility of this method means we are able to exploit present knowledge from quite a few observatories to detect variations that have been beforehand far too small to be perceived, even on very lengthy timescales,” mentioned Artigau.
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“This opens up new horizons in our research of the celebrities, their exercise and their planets.”
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