Earth-Size Planet Found by Astronomers: Hopeful Target for the Search for Extraterrestrial Life

 By MAX PLANCK INSTITUTE FOR ASTRONOMY 

February 05, 2023

Rare Earth-mass rocky planets are ideal for the search for life, according to astronomers.

It would be worthwhile to look for life on a recently discovered exoplanet. A planet that orbits its star, the red dwarf Wolf 1069, in the habitable zone is described in studies by a team led by astronomer Diana Kossakowski of the Max Planck Institute for Astronomy. This region of space encompasses the ranges where a planet's surface can support liquid water. The planet Wolf 1069 b also has a mass similar to Earth. This planet is most likely rocky and may or may not have an atmosphere. As a result, the planet is one of the few worthwhile places to look for biosignatures and evidence of life-supporting environments.

Earth-like planets are a focus of great interest for astronomers who are looking for planets outside of our solar system. Only roughly a dozen of the more than 5,000 exoplanets they have found so far have an Earth-like mass and are found in the habitable zone, which is the region in a planetary system where water can remain liquid on a planet's surface. The number of such exoplanets where life might have originated has increased by one contender with Wolf 1069 b.

A planet where day and night never end

It remains very difficult to find planets with such low masses. This effort has been taken up by Diana Kossakowski and her group at the Heidelberg-based Max Planck Institute for Astronomy. A tool was created specifically for the Carmenes project's search for potentially livable worlds. This equipment is being used by the Carmenes team at the Calar Alto Observatory in Spain. Diana Kossakowski says, "We found a distinct, low-amplitude signal of what looks to be a planet of about Earth mass when we examined the data of the star Wolf 1069. It travels one-fifth of the distance between the Earth and the Sun every 15.6 days to complete one orbit around the star. The journal Astronomy & Astrophysics has now published the study's findings.

The surface of the dwarf star is reportedly rather cool, giving it an orange-reddish appearance. According to Kossakowski, "as a result, the so-called habitable zone is moved inwards." Thus, the planet Wolf 1069 b only receives around 65% of the incident radiant power that Earth receives from the Sun while being relatively close to the primary star. Because of these unique circumstances, planets like Wolf 1069 that orbit red dwarf stars may be suitable for supporting life. Furthermore, they can all possess a unique quality in common. They are most likely tidally locked to the host star's orbit. Thus, the star is always pointed toward the same side of the planet. As a result, there is always day, whereas it is always darkness on the opposite side. We always look at the same side of the moon for the same reason.

Exoplanet climate simulations

Wolf 1069 b's average temperature, even on the side facing the star, would only be minus 23 degrees Celsius if it were thought to be a barren and stony planet. But given what is known, it's very likely that Wolf 1069 b has developed an atmosphere. Based on this supposition, computer simulations using climate models indicate that its temperature may have gone up by 13 degrees. Because water is essential to life as we know it, under these conditions, water would remain liquid and life-friendly conditions may prevail.

From a climatic perspective, an atmosphere is not the only prerequisite for the genesis of life. Additionally, it would shield Wolf 1069 b from electromagnetic radiation and particles with great energy, which would obliterate any potential biomolecules. Either the central star or interstellar space are the source of the radiation and particles. A planet's atmosphere may be stripped off if the star's radiation is too strong, as it was for Mars. However, Wolf 1069 only radiates in a very weak way because it is a red dwarf. As a result, it's possible that the newly discovered planet's atmosphere was preserved. It's even conceivable that the planet possesses a magnetic field to shield it from charged particles in the star wind. Numerous rocky planets have liquid cores that, like Earth, use the dynamo process to produce magnetic fields.

The challenging hunt for Earth-mass extrasolar planets

Since the first of its kind was found 30 years ago, the quest for exoplanets has made enormous strides. However, the signs that astronomers want to find in order to find planets with masses and diameters similar to Earth's are rather weak and challenging to extract from the data. The Carmenes team is searching the star spectra for minute periodic frequency shifts. These shifts are predicted to occur when a companion's gravitational influence causes the host star to tremble. As a result, the Doppler effect causes a change in the frequency of the light as measured on Earth. These variations can be measured in the example of Wolf 1069 and its recently found planet. One explanation is because the star and planet have relatively tiny mass differences, which causes the star to wobble more visibly than in other situations around the common centre of mass. The periodic signal can also be used to estimate the planet's mass.

There are only a few potential contenders for upcoming exoplanet characterisation

Wolf 1069 b is the sixth nearest Earth-mass planet in the habitable zone of its host star, located at a distance of 31 light-years. It is one of a select few objects that can be used in biosignature searches, along with Proxima Centauri b and Trappist-1 e. However, at this time, astronomical research is unable to make such observations. Kossakowski notes that "we'll probably have to wait another ten years for this." The Extremely Large Telescope (ELT), which is now being built in Chile, might be able to examine the atmospheres of those planets and perhaps even find molecular proof of life.