Astronomy: There might still be many earths out there that are overlooked

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Image taken by the Hubble telescope from the center of our Milky Way

Photo by NASA / ESA / Hubble Heritage Team

The search for planets on which life seems possible has preoccupied astronomers for far longer than the recent report on suspicious UFO sightings by the US secret services suggests. A few decades ago, some scientists were looked at a little obliquely when they reported that they were working on so-called Seti programs (Search for Extraterrestrial Intelligence). But that has changed, even if the main aim is to find life in space at all - it doesn't have to be particularly smart right away.

So far, astronomers have discovered thousands of exoplanets orbiting some strange star like our earth around the sun. That is still negligibly small, because in our Milky Way alone there are up to 40 billion earth-sized planets. But for life to be possible there, they have to be in the so-called habitable zone, in which liquid water could occur. You must not be too close or too far from your energy-giving star.

In order to track down such exoplanets of Earth-like size, researchers use the transit method, for example, with which most of the exoplanets found so far have been discovered.

Thereby planets are detected indirectly.

If they pass in front of the star, seen from the earth, its light flickers a little.

Spectroscopic analyzes of this radiation then provide information about the type of planet.

But a team led by Kathryn Lester from the Nasa Ames Research Center has now come to the conclusion: A good half of the earth-sized planets could be overlooked with this method.

As a result, there could be many more undiscovered worlds out there, the researchers wrote in a study that will soon be published in the Astronomical Journal.

The reason for the assumption lies in binary star systems, they make up about half of all stars.

And according to the researchers, planets the size of the earth in such systems of two suns are easily overlooked, as the light from the second star changes the data and the planets pass undetected.

"Small planets are easily lost in the light of their two parent stars," Lester is quoted in a press release.

For the study, the astronomer took another closer look at the stars examined by the research satellite TESS (Transiting Exoplanet Survey Satellite).

It initially showed that TESS found both large and small exoplanets orbiting individual stars, but only large planets in binary star systems.

Stellar companions and high resolution images

Then the researchers looked again at the stars observed by TESS - this time with the Kitt Peak National Telescope in Arizona and the high resolution of the Gemini Observatory's twin telescopes.

One of the eight-meter devices is in Chile, the other in Hawaii.

The result: 73 of the stars that TESS took to be a normal sun were actually double stars.

However, they appeared as a single point of light and could only be recognized as a dual system on closer analysis and extremely high-resolution images.

"We discovered stellar companions at very short intervals," says Lester.

It was previously suspected that double stars could be problematic in the hunt for exoplanets. But the study shows that it is important for astronomers to know whether they are dealing with a single star or a binary star. In addition, astronomers should use different techniques when considering before they come to the conclusion that a particular binary star system has no Earth-like planets, the researchers conclude.

After all, the TESS satellite, which has been flying through space since 2018, has recently succeeded for the first time in discovering an interesting exoplanet in a binary star.

A 17-year-old NASA intern succeeded in doing this last year.

The planet TOI 1338 b is about 1,300 light years away, but seven times the size of Earth.

In the course of its mission, TESS has tracked down more than 3500 candidates for exoplanets.

Of these, 130 observations have been confirmed so far.

joe