A new planet has been detected around Gliese 410, a star located 39 light-years from the Sun in the Leo constellation. This discovery was made using the SPIRou spectropolarimeter, installed on the Canada-France-Hawaii Telescope atop Maunakea, and the SOPHIE spectrograph at the Haute-Provence Observatory. Several members of IREx contributed to this discovery, published last week in the journal Astronomy & Astrophysics.
Étienne Artigau, a senior researcher at our Institute, agreed to answer our questions about this discovery.
IREx: Could you explain what is special about this discovery?
Étienne: Most stars near the Sun, known as the “solar neighborhood,” are low-mass stars, or red dwarfs. Gliese 410, also called DS Leonis, is such a star; it is about half the mass of the Sun. These stars are dimmer, and the planets orbiting them tend to be less massive than those around stars like the Sun. Planets comparable to Jupiter, for example, are rarely found. It is thus quite hard to detect them.
Thanks to observations over several years using two distinct instruments, the team, led by Andres Carmona from the University Grenoble Alpes, was able to reveal a periodic motion of Gliese 410 caused by the presence of a planet, Gliese 410 b.
IREx: What do we know about this planet?
Étienne: We measured its mass, which is at least about eight times that of Earth. It is, therefore, slightly lighter than Neptune, which is seventeen times Earth’s mass. Unfortunately, this planet does not transit its star; it does not pass in front of it. It was not possible to find a signal in the data from the TESS telescope. Consequently, its size remains unknown, and its exact nature is uncertain. It could be a rocky, dense planet, a gaseous planet, or something in between, like Uranus and Neptune.
We can, however, confirm that it orbits its star in six days, placing it very close to its star and receiving 20 times more heat than Earth receives from the Sun. Its equilibrium temperature could be around 300°C, making it extremely hot! This planet has no equivalent in our Solar System; it’s like having Neptune in Mercury’s orbit!
This planet likely also endures intense activity from its star: red dwarfs typically exhibit strong and frequent flares. Gliese 410 is relatively young (about 480 million years old), and SPIRou measurements confirm a magnetic field 100 times stronger than that of our Sun. Such phenomena can lead to the erosion (loss) of the planet’s atmosphere.
IREx: Are there other planets around this star?
Étienne: Two other planets might be present: one closer to the star, completing an orbit in about 3 days, and another farther out, with an orbital period of 19 days. Their existence still requires confirmation.
It’s important to note that detecting planets using the radial velocity method employed here is quite challenging. It’s common for planets to be announced and later refuted when, for example, it’s realized that the signal was due to stellar activity or Earth’s atmosphere.
Our teams conduct statistical tests to assign a confidence level to each detection, considered definitive beyond a certain threshold. In the case of Gliese 410 b, the discovery is compelling, especially since it’s observed in both SPIRou and SOPHIE data.
IREx: Why use these two instruments?
Étienne: SPIRou, a spectrograph operating in the infrared spectrum, is more sensitive to light from small stars than ordinary optical instruments. This makes it easier to detect planets around red dwarfs like Gliese 410. In other words, red dwarfs like Gliese 410 are brighter in this wavelength regime with this instrument allowing for the detection of planetary signals with high confidence. Its location on the Canada-France-Hawaii Telescope atop Maunakea is also advantageous: this mountain, of great significance to Native Hawaiians, offers unparalleled sky quality.
The second instrument, SOPHIE, is installed on the 193 cm telescope at the Haute-Provence Observatory. Operating in the visible spectrum, it has been in use for many years.
Combining observations from both instruments minimizes the possibility of false detections. This discovery was part of a survey initiated in 2018 utilizing these two instruments to discover more planetary systems around nearby red dwarfs.
IREx: What is your contribution and that of our Institute’s members?
Étienne: Together with Neil Cook, Charles Cadieux, and several members of our team, we’ve been working diligently for years to ensure astronomers worldwide can fully exploit observations made with SPIRou. One of our concerns is preventing contamination from Earth’s atmosphere from hindering the detection of small planets with this instrument. We’ve developed a new technique called LBL (for “line-by-line”), which maximizes the use of SPIRou and similar spectrographs, enabling the detection of even less massive planets using the radial velocity method. All these efforts contributed to revealing Gliese 410 b in SPIRou data.
Jonathan Gagné, a specialist in young stellar associations, helped reassess Gliese 410’s age, suggesting it might be one of the youngest stars in the solar neighborhood.
IREx: Why do you consider this discovery important?
Étienne: Detecting new planets is always exciting! If the other two planets are confirmed, this will be a relatively close planetary system with interactions to study.
Another interesting aspect is observing that all efforts to enhance SPIRou’s effectiveness are paying off, allowing us to unveil new planetary systems.
Finally, this discovery highlights the importance of small observatories in confirming the existence of exoplanets. The Observatoire de Haute-Provence, where SOPHIE is located, uses a telescope similar in size to that of the Mont-Mégantic Observatory (OMM). Our team is currently developing a new spectrograph, VROOMM, which should be installed at OMM in the coming years. It will be a major new tool for contributing to this type of discovery!
Note: This interview, inspired by a conversation with Étienne Artigau and a news piece written by Mélina Le Corre from CNRS, has been edited for clarity.
About the study
The article Characterizing planetary systems with SPIRou: Detection of a sub-Neptune in a 6-day period orbit around the M dwarf Gl 410 was led by Andres Carmona from Université Grenoble Alpes. The team includes 44 other co-authors from Europe, the United Kingdom, South America, the United States, and Canada, including Étienne Artigau, Neil J. Cook, Jonathan Gagné, Charles Cadieux, and René Doyon from IREx.
Links
Link to the CNRS news story
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