| Sep 19, 2024 |
|
|
|
(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 spread of time scales.
|
|
“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.”
|
|
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.
|
|
| A star’s temperature is much from uniform; it varies each throughout the star’s floor and over time. Now an progressive 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)
|
|
The scientists first turned their consideration to stellar spectra to enhance exoplanet detection utilizing radial velocity. This technique measures slight oscillations in a star generated by the gravitational pull of an orbiting planet. The larger the oscillations, the bigger the planet.
|
|
However it’s exhausting to detect very small oscillations and subsequently low-mass planets. To beat this drawback, Artigau and his crew developed a method exploiting the radial velocity technique that analyzes a star’s full spectrum and never just some parts, as beforehand performed with this technique.
|
|
This makes it doable to detect planets as small because the Earth orbiting round small stars. Artigau then got here up with the concept of utilizing an identical technique to detect not solely variations in a star’s oscillations but additionally in its temperature.
|
Distinguishing between stars and their planets
|
|
Temperature measurements are vital within the seek for exoplanets, that are principally noticed not directly by intently monitoring their star. In recent times, astronomers have confronted a serious hurdle: how one can distinguish between the observable results of a star and its planets.
|
|
This can be a drawback in each the seek for exoplanets utilizing radial velocity and the research of their atmospheres utilizing transit spectroscopy.
|
|
“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 pupil at IREx who contributed to the research.
|
|
“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.”
|
|
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 actual temperature may be recognized to an accuracy of about 20 levels Celsius.
|
|
Nonetheless, the brand new method measures not actual temperatures however temperature variation over time, which it might probably decide with outstanding precision.
|
|
“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,” mentioned Artigau.
|
|
“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!”
|
|
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.
|
|
Within the information 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.
|
|
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 just about 40 levels Celsius.
|
|
With this method, they had been in a position to measure not solely very fast modifications in temperature related to quick rotation durations of some days, comparable to these AU Microscopii and Epsilon Eridani, but additionally these occurring over for much longer durations of time, a tough feat for ground-based telescopes.
|
|
“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.”
|
|
The brand new method additionally made it doable to detect very nice temperature modifications on the floor of the celebs. For instance, the crew detected refined temperature modifications in star HD 189733 coinciding with the orbit of its exoplanet HD 189733 b, an enormous “hot Jupiter” planet.
|
|
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.
|
|
The progressive method will likely be immediately relevant to observations from NIRPS, a spectrograph put in final 12 months within the ESO telescope in Chili. In accordance with the researchers, it could even be doable to make use of this method with space-based devices, such because the James Webb Area Telescope.
|
|
“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,” mentioned Artigau.
|
|
“This opens up new horizons in our study of the stars, their activity and their planets.”
|
