Tag Archives: #reddwarf

Two Planets Around A Red Dwarf (Planetary Science)

Red dwarfs are the coolest kind of star. As such, they potentially allow liquid water to exist on planets that are quite close to them. In the search for habitable worlds beyond the borders of our solar system, this is a big advantage: the distance between an exoplanet and its star is a crucial factor for its detection. The closer the two are, the higher the chance that astronomers can detect the planet from Earth.

The SAINT-EX Observatory is a fully robotic facility hosting a 1-metre telescope based in Mexico. ©Institute of Astronomy, UNAM / E. Cadena

“But these stars are rather small and emit little light compared to most other stars, such as our Sun”, Brice-Olivier Demory, lead author of the study and Professor of Astrophysics at the University of Bern explains. These factors make them challenging to observe in detail. Without the proper instruments, any planets that might orbit them could easily be overlooked – especially terrestrial planets, like Earth, that are comparably small.

A dedicated telescope

One instrument, with which it is possible to study red dwarfs and their planets closely, is the Mexico-based SAINT-EX telescope, co-operated by the NCCR PlanetS. SAINT-EX is an acronym that stands for Search And characterIsatioN of Transiting EXoplanets. The project has been named in honor of Antoine de Saint-Exupéry (Saint-Ex), the famous writer, poet and aviator.

The SAINT-EX Observatory is a fully robotic facility hosting a 1-metre telescope. It is equipped with instrumentation specifically suited to enable high-precision detection of small planets orbiting cool stars. Now, this specialization pays off: earlier this year, the telescope was able to detect two exoplanets orbiting the star TOI-1266, located around 120 light years from Earth. The research, published recently in the journal Astronomy and Astrophysics, provides a first impression of their characteristics.

A peculiar pair

Compared to the planets in our solar system, TOI-1266 b and c are much closer to their star – it takes them only 11 and 19 days respectively to orbit it. However, as their host star is much cooler than the Sun, their temperatures are not very extreme: the outer planet has approximately the temperature of Venus (although it is 7 times closer to its star than Venus is to the Sun). The two planets are of similar density, possibly corresponding to a composition of about a half of rocky and metallic material and half water. This makes them about half as rocky as Earth or Venus but also far rockier than Uranus or Neptune.

In size, the planets clearly differ from each other. The inner planet, TOI-1266 b, measures up to a little under two-and-a-half times the Earth’s diameter. This makes it a so-called “sub-Neptune”. The outer planet, TOI-1266 c, is just over one-and-a-half times the size of our planet. Thus, it belongs to the category of “super-Earths”.

This places the two planets at the edges of the so-called radius-valley, as Brice-Olivier Demory explains: “Planets between about the radius of TOI-1266 b and c are quite rare, likely because of the effect of strong irradiation from the star, which can erode their atmospheres”. Yilen Gómez Maqueo Chew, SAINT-EX Project Coordinator and researcher at the National Autonomous University of Mexico adds: “Being able to study two different types of planets in the same system is a great opportunity to better understand how these different sized planets come to be”.

Good timing and help from the embassy

Having this opportunity, especially this year, is anything but a given. The scientists were fortunate enough to be able to complete their observations shortly before the Covid-19-related lockdown in Mexico. Shortly after the observations were made, the observatory had to be closed due to the consequences of the pandemic. This has not changed until today. The scientists hope to resume operations of SAINT-EX in the next few months and to target the next red dwarf and its potential planets. “Also, the Mexican Embassy in Bern was a great help in facilitating the discussions with the Mexican government and in providing continued support to the project”, says Demory.

SAINT-EX – Search and characterisation of exoplanets

SAINT-EX is an international collaboration which had its kick-off meeting in the National Astronomical Observatory in San Pedro Martir (MEX) in September of 2016. The project’s principal investigator is Prof. Brice-Olivier Demory, from the Center for Space and Habitability of the University of Bern in Switzerland and National Center of Competence in Research PlanetS; the project’s coordinator and leader in Mexico is Dr. Yilen Gomez Maqueo Chew from the Instituto de Astronomía of the Universidad Nacional Autonoma de Mexico (UNAM). Also, part of the project are Prof. Willy Benz from the National Center of Competence in Research PlanetS, Prof. François Bouchy from the University of Geneva in Switzerland, Dr. Michaël Gillon from the University of Liège in Belgium, Prof. Kevin Heng from the University of Bern in Switzerland, Prof. Didier Queloz from the University of Geneva, Switzerland, and Cambridge in the UK, and Dr. Laurence Sabin, also from Instituto de Astronomía de Astronomía in UNAM. SAINT-EX has been funded by the Swiss National Science Foundation and the Universities of Bern, Geneva, Liège and Cambridge as well as UNAM. SAINT-EX also received support from the National Council for Science and Technology (CONACYT) through the National Laboratories call for proposals for the National Astronomical Observatory of San Pedro Martir.

Bernese space exploration: With the world’s elite since the first moon landing

When the second man, “Buzz” Aldrin, stepped out of the lunar module on July 21, 1969, the first task he did was to set up the Bernese Solar Wind Composition experiment (SWC) also known as the “solar wind sail” by planting it in the ground of the moon, even before the American flag. This experiment, which was planned and the results analysed by Prof. Dr. Johannes Geiss and his team from the Physics Institute of the University of Bern, was the first great highlight in the history of Bernese space exploration. Ever since Bernese space exploration has been among the world’s elite. The numbers are impressive: 25 times were instruments flown into the upper atmosphere and ionosphere using rockets (1967-1993), 9 times into the stratosphere with balloon flights (1991-2008), over 30 instruments were flown on space probes, and with CHEOPS the University of Bern shares responsibility with ESA for a whole mission. The successful work of the Department of Space Research and Planetary Sciences (WP) from the Physics Institute of the University of Bern was consolidated by the foundation of a university competence center, the Center for Space and Habitability (CSH). The Swiss National Fund also awarded the University of Bern the National Center of Competence in Research (NCCR) PlanetS, which it manages together with the University of Geneva.

References: B.-O. Demory, F. J. Pozuelos, Y. Gómez Maqueo Chew, L. Sabin, R. Petrucci, U. Schroffenegger, S. L. Grimm, M. Sestovic, M. Gillon, J. McCormac, K. Barkaoui, W. Benz, A. Bieryla, F. Bouchy, A. Burdanov, K. A. Collins, J. de Wit, C. D. Dressing, L. J. Garcia, S. Giacalone, P. Guerra, J. Haldemann, K. Heng, E. Jehin, E. Jofré, S. R. Kane, J. Lillo-Box, V. Maigné, C. Mordasini, B. M. Morris, P. Niraula, D. Queloz, B. V. Rackham, A. B. Savel, A. Soubkiou, G. Srdoc, K. G. Stassun, A. H. M. J. Triaud, R. Zambelli, G. Ricker, D. W. Latham, S. Seager, J. N. Winn, J. M. Jenkins, T. Calvario-Velásquez, J. A. Franco Herrera, E. Colorado, E. O. Cadena Zepeda, L. Figueroa, A. M. Watson, E. E. Lugo-Ibarra, L. Carigi, G. Guisa, J. Herrera, G. Sierra Díaz, J. C. Suárez, D. Barrado, N. M. Batalha, Z. Benkhaldoun, A. Chontos, F. Dai, Z. Essack, M. Ghachoui, C. X. Huang, D. Huber, H. Isaacson, J. J. Lissauer, M. Morales-Calderón, P. Robertson, A. Roy, J. D. Twicken, A. Vanderburg and L. M. Weiss, “A super-Earth and a sub-Neptune orbiting the bright, quiet M3 dwarf TOI-1266”, A&A, 642 (2020) A49
DOI: https://doi.org/10.1051/0004-6361/202038616

Provided by University Of Bern

Indian Astronomers Detected 70 New Variable Stars (Astronomy)

Researchers have presented the first long-term photometric variability survey of the intermediate-age open cluster NGC 559. Time-series V band photometric observations on 40 nights taken over more than three years with three different telescopes are analyzed to search for variable stars in the cluster. They investigated the data for the periodicity analysis and revealed 70 variable stars including 67 periodic variables in the target field, all of them are newly discovered.

The finding chart for the 70 variable stars identified in the observed field of NGC 559 in the V band. The variables belonging to the cluster are shown with circles while variables belonging to the field population are shown by squares. Credit: Joshi et al., 2020.

Located at a distance of about 7,900 light years away from the Earth, NGC 559 is an open cluster estimated to be around 224 million years old. Previous observations of NGC 559 have identified 542 member stars and found that the cluster has a reddening at a level of 0.82 mag, and that its radius containing half the members is about 4.86 arcmin.

In the new study, study detected 70 new variable stars, out of which 67 are periodic variables with periodicities ranging from three hours to 41 days. The vast majority of the newfound periodic variables have periods below one day and most of them have relatively small amplitude of variability down to 0.02 mag level.

Their membership analysis of the periodic variables revealed that 30 of them belong to the cluster, with estimated masses between 1.72 and 3.6 solar masses, and remaining 37 are identified as field variables. Out of the 67 periodic variables, 48 are short-period (P<1 day) variables and 19 are long-period (P>1 day) variables. The variable stars have periodicity between 3 hours to 41 days and their brightness ranges from V = 10.9 to 19.3 mag.

The periodic variables belonging to the cluster are then classified into different variability types on the basis of observational properties such as shape of the light curves, periods, amplitudes, as well as their positions in the Hertzsprung-Russell (H-R) diagram. As a result, researchers identified one Algol type eclipsing binary, one possible blue straggler star, 3 slowly pulsating B type stars, 5 rotational variables, 11 non-pulsating variables, 2 FKCOM variables and remaining 7 are characterized as miscellaneous variables. They also identified three Eclipsing Binary stars (EBs) belonging to the field star population. The PHOEBE package is used to analyse the light curve of all four EBs in order to determine the parameters of the binary systems such as masses, temperatures and radii.

References: Yogesh C. Joshi, Ancy Anna John, Jayanand Maurya, Alaxendra Panchal, Brijesh Kumar, Santosh Joshi, “Variable stars in the field of intermediate-age open cluster NGC 559”, pp. 1-15, 2020. arXiv:2009.06997 [astro-ph.SR] arxiv.org/abs/2009.06997 link: https://arxiv.org/abs/2009.06997

Astronomers Find Warm Jupiter Orbiting Cool Red Dwarf (Astronomy)

Using a combination of available TESS photometry; high-precision, near-infrared spectroscopy with the Habitable-zone Planet Finder; and speckle and adaptive optics imaging astronomers confirmed the planetary nature of a warm Jupiter transiting the early M dwarf TOI-1899.

TOI-1899b warm jupiter exoplanet around red dwarf. Credit: Hitendra Prakash

TOI-1899 is an M0-type star located 419 light-years away in the constellation of Cygnus.

Also known as TIC 172370679 and 2MASS 19574239+4008357, the star has a temperature of 3,652 degrees Celsius and is much cooler than the Sun.

TOI-1899 is about 60% the size and mass of the Sun and is around 7.4 billion years old.

The newfound planet orbits the star once every 29 days at a distance of only 0.16 AU.

Designated TOI-1899b, the alien world is two-thirds the mass of Jupiter but 10% larger in radius.

The single-transit, indicated by the dip, of the planet TOI-1899 b passing in front of its host star as detected by NASA’s TESS mission. The single 5-hour event can only reveal the size of planet and a detailed characterization of the transiting object required data from the Habitable-zone Planet Finder Spectrograph, a Penn State led near-infrared spectrograph recently installed on the 10m Hobby-Eberly Telescope at McDonald Observatory in Texas. Credit: Caleb Cañas, Penn State

TOI-1899b was detected by TESS using the transit method, which searches for stars showing periodic dips in their brightness as a telltale sign of an orbiting object crossing in front of the star and blocking a portion of its light.

The signal was then confirmed as a planet using precision observations from the HPF spectrograph.

References: Caleb I. Cañas et al, A Warm Jupiter Transiting an M Dwarf: A TESS Single-transit Event Confirmed with the Habitable-zone Planet Finder, The Astronomical Journal (2020). DOI: 10.3847/1538-3881/abac67