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Planet hunters

publicado a la‎(s)‎ 9 jul 2020, 5:51 por Plataforma Sites Dgac   [ actualizado el 17 sept 2020, 7:53 ]
On June 25, 2020, the Science journal published an article reporting the discovery of two “super-Earth” exoplanets orbiting the star Gliese 887, a faint red dwarf with about half the mass from the Sun and located 11 light-years from Earth.
Professor James Jenkins, astronomer and academic from the Faculty of Physical Sciences and Mathematics of the University of Chile.

Matías Díaz, student of the Ph.D. in Sciences, mention Astronomy, of the University of Chile.

An artist's concept of an exoplanet of the "Super-Earth" kind.
The discovery was made by a team of astronomers who are part of the Red Dots project, led by Guillem Anglada and Sandra Jeffers, who observed Gliese 887 every night for three months using the European Southern Observatory (ESO), in Chile. The High Accuracy Radial Velocity Planet Finder, known as the HARPS spectrograph, was the one that detected two signals corresponding to planets around the star. 

To learn more about this finding, we spoke with two scientists and planet hunters who collaborate in the Red Dots project at the local level and who contributed to the discovery of the “super-Earths” around Gliese 887. They are Professor James Jenkins, astronomer and academic from the Faculty of Physical Sciences and Mathematics of the University of Chile, and Matías Díaz, student of the Ph.D. in Sciences, mention Astronomy, of the University of Chile. 

CEFAA: Why did the team decide to observe the star Gliese 887 in particular? Why did they say, “let's focus on this one”, specifically? 

Matías Díaz: Well, the explanation has to do, first, with the design of the observation campaign. In general, one chooses certain stars according to the properties and depending on what one wants to look for. 

So, the choice of these stars falls within the program that was made during 2017 and 2018 with HARPS, which is called Red Dots. A sample of the type “M” stars was chosen, the closest to the Sun, which are slightly redder stars and with a mass lower than the Sun’s. 

What does that mean? That the study of these stars allows us to investigate or try to find planets in the habitable zone with relatively shorter periods, compared to other stars such as the Sun, which are a little hotter and the habitable zones are at a slightly greater distance. 

James Jenkins: In the Red Dots project we are trying to map all the closest stars around the Sun. We want to understand what the planetary systems are like around the Sun. 

The closer these stars are, the easier it is for us to follow up. The nearest stars are the most important stars. The closer we find these planets, the easier it is for us to characterize them going forward in the near future. We want to better characterize these planets, see if they have atmospheres, if there are more planets in the system and what kinds of chemicals we can detect in their atmospheres.

CEFAA: And now, after this finding, what comes next in the study of the star and the planets?

Matías Díaz: I believe that what comes next is trying to have more data to confirm a third signal. As it is not confirmed yet, some more observations are necessary to say “Ok, we are sure there is a third planet.”

What it’s interesting about this third possible planet is that it would fall into the habitable zone, because the two that are “super-earths” are a bit out of the area, on the edge of the habitable zone. 

Likewise, it is a bit debatable to talk about “habitability”s when one does not know the properties of the planet. You only know that it is located in a place that allows liquid water to exist. You don’t know anything else; like if the planet actually has water, etc. 

And the other thing is that once that planet is confirmed, we should try to study its atmosphere. It is interesting to study a planet that is in the habitable zone, to try to see if it looks like the Earth, which is what we are looking for. Planets that resemble Earth and that can support life on other stars. But so far we don’t know. But that’s where the study of this star leads us. 

James Jenkins: We try to develop new codes, new algorithms for understanding the signals that we measure from stars and see if they are from what’s called the Doppler effect or if it is an artifact of the star, the star’s magnetic activity. 

The star’s magnetic activity, when it’s coupled with the rotation of the star, can give us signals that look very much like the signals we see from planets, so we’ve developed codes to try to really, really detect very, very small planets and understand if the signals that we see are from planets or from the star. 

So, in this case we helped confirm that those signals were really planets and not stellar activity, as we call it. 

CEFAA: And these two planets are bigger than Earth, “super-Earths.”

James Jenkins: Yes. We believe they will be. We actually don’t know their physical size at the moment, but what we do know is the mass. And there is a relationship between the mass and the radius, so we expect they will be bigger, maybe two or three times the size of the Earth. 

That is one of the next key points. We want to continue to observe this star, and measure the velocity of the star with really high precision to try to confirm this signal we see (a possible third planet), which looks like it could be real. It is in a very interesting area. 

CEFAA: Do you hope to confirm the existence of this third planet this year, or next year, for example?

James Jenkins: I think we need a lot more data so we’ll probably be looking try to confirm that in the next couple of years. And especially now, the observatories are closed at the moment because of the pandemic. We have already lost telescope time.

In the next two to three years we will get enough data to be able to confirm that this third possible planet in the habitable zone really exists or if we are just seeing excess noise in the data.

Matías Díaz: We have limited time. We apply for telescope time once a semester and on average they give us about 10 nights per semester. So there we try to do the most with the time we are given. But, in general terms, it is a very demanding endeavor that requires a lot of observation time. That’s why it takes a long time, sometimes even years, to confirm these planets. 

CEFAA: At a speculative level, 11 light-years (away) is quite a lot. So we will probably never reach to such a great distance, as to try, in the far future, to colonize a planet that is habitable, for example. 

Matías Díaz: Sure; on current scales, and given the technology we have at the moment, it would take us hundreds of thousands of years to reach the nearest star. Proxima Centauri is the closest star, which is also a red, “M” type. That’s the closest, which is four light-years away. This one (Gliese 887) is almost three times Proxima’s distance. So it would take hundreds of thousands of years with today’s technology. 

Now, if progress is made in that area in the coming decades... I think we are not talking about human scale at this time. There would have to be a very significant advance in technology to allow us to do interstellar travel.

Unless there is a very important advance in a relatively short period, I think that is out of the question.