June 16, 2024

Maybe There’s No Way to Tell if Habitable Planets Orbit Proxima Centauri… Yet!

Our closest outstanding neighbor is Proxima Centauri, an M-type (red dwarf) star located over 4.24 light-years away (part of the Alpha Centauri trinary system). In 2016, the huge neighborhood was amazed to learn that an Earth-like planet orbited within this stars circumsolar habitable zone (HZ). In addition to being the closest exoplanet to Earth, Proxima b was likewise thought about the most appealing place to search for extraterrestrial life for a time.
Sadly, the scientific community has actually been divided on whether life might even be possible on this world. All of these research studies show that this question can not be answered until astronomers identify Proxima bs environment, preferably by observing it as it passes in front (aka. transited) of its host star. But in a new NASA-supported study, a team led by astrophysicists at the University of Chicago identified that this is a not likely possibility.

The study that explains their findings, which will appear soon in Frontiers in Astronomy and Space Sciences, was led by Emily A. Gilbert, a Graduate Student with the University of Chicagos Department of Astronomy and Astrophysics. She was joined by researchers from The Adler Planetarium, the Center for Space Science and Technology (University of Maryland), and the Exoplanets and Stellar Astrophysics Laboratory at the NASA Goddard Space Flight Center.
TOI 1338 b is a circumbinary planet orbiting its two stars. It was discovered by TESS. Credit: NASAs Goddard Space Flight Center/Chris Smith
Individuals accountable for the discovery were Guillem Anglada-Escudé and a group of astronomers from the Pale Red Dot campaign. Utilizing the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph on the ESO 3.6-metre telescope at the ESOs La Silla Observatory, the team validated the presence of Proxima b using a technique referred to as Doppler Spectroscopy (aka. the Radial Velocity Method).
This technique consists of observing the spectra of stars for indications of “wobble,” where the star is moving more detailed and farther away from Earth. This is triggered by the gravitational influence of worlds that orbit the star, the degree of which is utilized to infer the mass of the worlds. When it comes to Proxima b, astronomers acquired a minimum mass quote of 1.24 and an optimal quote of 2.06 Earth masses.
Its existence was validated again in 2020 using the ESOs Very Large Telescope (VLT) and its Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) instrument– the followers to the HARPS spectrograph. While most exoplanets to date have actually been discovered using the Transit Method (aka. Transit Photometry), this was considered unwise for a star like Proxima Centauri, which is a low-mass and less brilliant M-type (red dwarf) star.
As Gilbert and her colleagues suggest in their study, this has actually not avoided various astronomical research groups from attempting to detect planets transitting in front of Proxima Centauri. For instance. Prof. Kipping and his coworkers from the Cool Worlds Laboratory at Columbia University observed Proxima Centauri for 43.5 days in between 2014-15 utilizing the Canadian Space Agencys Microvariability and Oscillation of Stars (MOST) satellite.
An artists rendition of the Transiting Exoplanet Survey Satellite (TESS). Credit: NASAs Goddard Space Flight
In 2016, 2 research study teams individually observed Proxima Centauri for signs of transits utilizing the Las Campanas Observatory in Chile and the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. Both studies discovered proof of possible transits however were unable to confirm them. In 2018-19, a worldwide group released a two-part research study concerning hundreds of observations made between 2006 and 2017 from observatories all throughout Earth. In both the original and the follow-up research study, the authors showed that no transits were observed.
For the sake of their study, Gilbert and her group depended on information collected by the Transiting Exoplanet Survey Satellite (TESS), the successor to the Kepler Space Telescope. Utilizing a novel set of algorithms, the group examined 2 observation campaigns TESS made of Proxima Centauri– from Apr. 23rd– Jun. 18th, 2019, and from Apr. 29th to May 26th, 2021– for signs of Proxima b transiting.
They also included an algorithm that modeled Proxima Centauris outstanding activity, which releases white light flares 2 to 3 times a day or more (a few of which are really effective). In fact, in a 2016 study co-authored by David Kipping, it was recommended that flares may so control Proxima Centauri that time-series observations of its light curve might be mostly considered a superposition of many flares. As Gilbert and her associates suggest in their research study, this has always made looking for signals of planetary transits really hard with Proxima Centauri:
” Here we take a different approach, we identify the flares utilizing a customized algorithm, design the flares using a template, subtract these flares from the information, and then carry out the transit search. We then inject transits into the light curve to evaluate our level of sensitivity to transiting worlds.”
Stellar flares might threaten life on red dwarf worlds. Credit: NASA/ESA/D. Gamer (STScI).
One might ask the concern, why do astronomers continue looking for transits? The response is easy: if Proxima b were to transit in front of its sun, astronomers might obtain transmission spectroscopy from the light going through its environment. This would permit them to discern the existence of chemical signatures and constrain the worlds atmospheric composition, consisting of prospective biomarkers.
The group utilized two various planet search algorithms to find planetary transit signals in the TESS information as a next step. Initially, they used the Transit Least Squares (TLS) established by Michael Hippke and René Heller (Sonneberg Observatory and Max Planck Institute for Solar System Research, respectively). Second, they employed the Quasiperiodic Automated Transit Search (QATS) by Hubble Fellow Joshua A. Carter and Eric Agol– of the Harvard Smithsonian Center for Astrophysics (CfA) and the University of Washington.
Gilbert and her team still discovered no proof of transits in the information. To be sure, they injected synthetic transiting world signals into the TESS data to determine what circumstances a transiting planet could be detected.
This is disappointing news for exoplanet scientists, as it verifies that the only method we can characterize Proxima b is to send out a real mission there. In this regard, jobs such as Breakthrough Starshot and other “light sail” ideas would require to happen before scientists might determine if our closest exoplanet neighbor is ideal for life. It may also be possible to straight image Proxima b in the near future utilizing next-generation telescopes.
Artists impression of a synchronised transit of 3 planets in front of Kepler-11, as observed by NASAs Kepler spacecraft on Aug. 26th, 2010. Credit: NASA/Tim Pyle.
This consists of the James Webb Space Telescope, which is arranged to launch on Dec. 18th, and the Nancy Grace Roman Space Telescope, which will follow in 2027. Ground-based observatories like the ESOs Extremely Large Telescope (ELT) and the Carnegie Institute of Sciences Giant Magellan Telescope (GMT) will likewise be able to conduct direct imaging research studies using their large mirrors, spectrographs, coronographs, and adaptive optics.
These and other observatories will also benefit from next-generation maker knowing techniques (like the one established by Gilbert and her coworkers). Accounting for the level of stellar activity will allow astronomers to tease exoplanet signatures from all the background noise with higher precision. As they conclude in their research study:.
” With the continuous TESS objective along with planned missions like Plato supplying long baseline, high-precision observations, this method may be exceptionally important for discovering little planets orbiting active host stars. There are many low-mass active neighboring stars, and the approaches we have actually provided here are could substantially enhance our level of sensitivity to small planets transiting these stars.”.
More Reading: arXiv.
Like this: Like Loading …

Transit Photometry), this was considered not practical for a star like Proxima Centauri, which is a low-mass and less intense M-type (red dwarf) star.
As Gilbert and her colleagues show in their study, this has actually not avoided various astronomical research study groups from attempting to identify worlds transitting in front of Proxima Centauri. In 2016, two research teams separately observed Proxima Centauri for indications of transits utilizing the Las Campanas Observatory in Chile and the Bright Star Survey Telescope at the Zhongshan Station in Antarctica. We then inject transits into the light curve to test our level of sensitivity to transiting worlds.”
To be sure, they injected artificial transiting planet signals into the TESS data to identify what scenarios a transiting planet might be spotted.