New Earth-like exoplanets discovered around red dwarf Teegarden star

New Earths discovered around a very small star
Credit: Instituto de Astrofísica de Canarias

An international team led by the University of Göttingen (Germany) with participation by researchers from the Instituto de Astrofísica de Canarias (IAC) have discovered, using the CARMENES high-resolution spectrograph at the Calar Alto Observatory (Almería) two new planets like the Earth around one of the closest stars within our galactic neighbourhood.

The Teegarden star is only 12.5 away. It is a in the direction of the constellation of Aries. Its surface temperature is 2,700 degrees C, and its mass is only one-tenth that of the sun. Even though it is so near, its faintness impeded its discovery until 2003.

"We have been observing this star for three years to look for periodic variations in its velocity, explains Mathias Zechmeister, a researcher at the University of Göttingen, the first author of the paper. The observations showed that two planets are orbiting it, both of them similar to the planets in the inner part of the Solar System. They are just a little bigger than the Earth and are situated in the "inhabitable zone" where water can exist as a liquid. "It is possible that the two planets are part of a larger system," says Stefan Dreizler, another University of Göttingen researcher and a co-author of the paper.

Photometric campaigns on this star have been carried out with instruments such as Muscat2 on the Carlos Sánchez Telescope at the Teide Observatory (Tenerife), and with the network of telescopes of the Las Cumbres Observatory, among others. These studies demonstrate that the signals of the two planets cannot be due to the activity of the star, even though we could not detect the transits of the two new planets," says Victor Sánchez Béjar, an IAC researcher and another author of the article which is being published in the journal Astronomy and Astrophysics.

New Earths discovered around a very small star
Credit: Instituto de Astrofísica de Canarias

For the transit method to be viable, the planets must pass across the face of the stellar disc and block some of the light from the star during a short time, which means that it must lie on a line joining the sun and the Earth. This lucky alignment occurs for only a small fraction of planetary systems.

Planet hunters

The type of star to which the Teegarden star belongs consists of the smallest for which researchers can measure the masses of their planets with current technology. "This discovery is a great success for the CARMENES project, which was designed to look for planets around low mass ," says Ignasi Ribas, a researcher at the Institut d"Estudis Espacials (IEEC) of Catalonia and a co-author of the article.

Since 2016, German and Spanish scientists have been searching for planets around nearby stars using CARMENES, which is on the 3.5m telescope of the Calar Alto Observatory (Almería) These new planets are the 10th and 11th discovered by the project.have been carried out with instruments such as Muscat2 on the Carlos Sánchez Telescope at the Teide Observatory (Tenerife), and with the network of telescopes of the Las Cumbres Observatory, among others. These studies have allowed us to show that the signals of the two planets cannot be due to the activity of the star, even though we could not detect the transits of the two new planets" comments Victor Sánchez Béjar, an IAC researcher and another author of the article which is being published in the journal Astronomy and Astrophysics.

For the to be viable, the planets must pass across the face of the stellar disc and block some of the light from the star during a short time, which means that it must lie on a line joining the sun and the Earth. This lucky alignment occurs for only a small fraction of planetary systems.

Planet hunters

The type of star to which the Teegarden star belongs consists of the smallest for which researchers can measure the masses of their planets with current technology. "This discovery is a great success for the CARMENES project, which was designed to look for planets around low mass stars," says Ignasi Ribas, a researcher at the Institut d"Estudis Espacials (IEEC) of Catalonia and a co-author of the article.

Since 2016, German and Spanish scientists have been searching for planets around nearby stars using CARMENES, which is on the 3.5m telescope of the Calar Alto Observatory (Almería). These new are the 10th and 11th discovered by the project.


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More information: M. Zechmeister et al. The CARMENES search for exoplanets around M dwarfs. Two temperate Earth-mass planet candidates around Teegarden's Star, Astronomy & Astrophysics (2019). DOI: 10.1051/0004-6361/201935460
Citation: New Earth-like exoplanets discovered around red dwarf Teegarden star (2019, June 18) retrieved 18 July 2019 from https://phys.org/news/2019-06-earth-like-exoplanets-red-dwarf-teegarden.html
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Jun 18, 2019
Amazing discovery of two close, Earth-sized, habitable zone planets. I have to wonder if the polar regions of Teegarden star b and the equatorial regions of Teegarden star c might offer the most hospitable areas on each of those worlds.

Jun 18, 2019
Amazing discovery of two close, Earth-sized, habitable zone planets. I have to wonder if the polar regions of Teegarden star b and the equatorial regions of Teegarden star c might offer the most hospitable areas on each of those worlds.


Not sure about that. Perhaps, depending on temperature, and assuming they are tidally locked, then somewhere near the terminator might be preferable. The problem with these red dwarves is the flaring. Although the star seems to be relatively quiet at the moment, it may not have been in the past.
Then there is the question of tidal locking. If the planets are essentially only rotating once per orbit, can this maintain a magnetic field? Without one, you are toast. Even with one, around a red dwarf, you may still be toast. And if you have got one, then it will funnel the impinging solar wind onto the poles. Underground may be best!

Jun 18, 2019
Whether they are tidally locked is always a good question with these red dwarf stars. The age of the system is also a factor in tidal locking and how much atmosphere remains. Assuming they are both tidally locked but with some atmosphere, then being near the terminator on Teegarden's Star b may buy some relief from the heat depending on how much atmosphere is left. Teegarden's Star c is nearly outside the habitable zone, so a point close to being directly under the star might be better. Interestingly, in many of these situations, there are places that may be habitable for at least single cell life if there is some atmosphere. Otherwise, I agree that underground may be best.

Jun 18, 2019
Interestingly, in many of these situations, there are places that may be habitable for at least single cell life if there is some atmosphere. Otherwise, I agree that underground may be best.


If they retain volatiles (atmosphere), temperate planets should retain water. A just-so dry planet like Earth is unlikely, so underwater (+ underground) may be the best bet.

They would likely not be high productive land plant planets, but theoretically "surface habitable" - inasmuch a global ocean is a surface - so "Earth like". Just from eye balling the conventional zone placement diagram, it looks like they are outside the newly proposed, tight "Earth analog" zone filter for oxygen breathers, so no complex body plan animal analogs either. Multicellular yes, likely, arguably most "multicellular" lineages (say, Myxobacteria) are prokaryotes (make multicellular fruiting bodies during replication) and one clade of cyanobacteria even differentiates germ and nitrification soma cell lines.

Jun 19, 2019
If they retain volatiles (atmosphere), temperate planets should retain water.


Agreed.

I find it incredibly interesting that somewhere on both of these nearby worlds there is a good chance there are areas suitable for life. However, I would not give too much credence to anyone drawing hard conclusions or setting strict limits on habitability just yet. We barely understand Earth, and with so MANY variables affecting surface conditions, we can't really say just how habitable Teegarden's Star b or c actually are. My hypothesis is every "habitable zone" planet is going to be far more unique than we are imagining right now. I suspect we will eventually find large numbers of nearly-identical planets in terms of size, mass and solar isolation, all with very different surface conditions.

Like Q said in Star Trek: "It's wondrous, with treasures to satiate desires both subtle and gross. But it's not for the timid."

Jun 19, 2019
Depending on the orbital distance, even a tidally locked planet can produce a magnetic field via the Coriolis effect (in this case the closer the better). That said, I've never been convinced a magnetic field is a pre-requisite for atmospheric retention. The interplay between the mass of the planet, the initial stock of volatile, the temperature of the atmosphere and the strength of the solar wind dictates whether or not volatiles will be retained. Venus for instance has no magnetic field and has lost its volatiles, while Mars has no magnetic field and has only lost some of its volatiles (its lesser temperature and weaker solar wind better balancing its smaller mass). Here's to hoping these planets started with a ton of volatiles!

Jun 20, 2019
Venus is my favorite example of why a magnetic field is clearly not necessary to have a thick atmosphere. Nearly double our sunlight, 10% less gravity, and the super hot CO2 atmosphere is still 93 times thicker with no magnetic field. This is also one piece of evidence that Earth's atmosphere of Earth is on the thin side for a planet as large and robust as ours. Clearly Earth could hold onto the atmosphere Venus possesses and even a larger atmosphere. Another piece of evidence is Saturn. The atmosphere on Saturn is immense, but the gravity only 6.5% stronger.


Jun 21, 2019
When can we start emigrating?

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