Water is mapped exactly where a planet is forming

A large amount of water has been found in the protoplanetary disk of a star in the exact place where a planet is emerging. The discovery can show not only how its presence influences planetary formation, but also help to understand its emergence here on Earth.

In the study recently published in the journal Nature Astronomy, researchers investigated a young Sun-like star known as HL Tauri, which is located about 450 light-years away from Earth. The observations were the first to map the distribution of water in a protoplanetary disk of a star that could host life.

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Water in the protoplanetary disk

The origin of water on Earth is a great mystery, there are researchers who point out that it came from asteroids that collided with the planet, while others suggest that it has been present here since its formation. Others still believe it to be a mixture of both mechanisms.

As it is not possible to go back in time to discover how this process occurred, the solution is to observe water in other planetary systems, still in formation. This is where HL Tauri is located, less than a million years old and with a large, cold, stable protoplanetary disk and planets beginning to form.

The star's inclination allows a good observation of its proplane disk from Earth (Credit: ALMA/ESO/NAOJ/NRAO)
The star's inclination allows a good observation of its proplane disk from Earth (Credit: ALMA/ESO/NAOJ/NRAO)

Water has previously been detected in the star system. Due to its inclination, it is possible to have a clear view of the stars and the protoplanetary disk with the gaps characteristic of the formation of planets. So researchers led by astronomer Stefano Facchini decided to take a closer look.

To achieve this, the Atacama Large Millimeter/submillimeter Array (ALMA) was used to observe the star in two different wavelength bands, which allowed water vapor to be seen.

  • A significant amount of water was discovered about 17 astronomical units away from the star, where rocky planets usually form;
  • The amount of water in this region is equivalent to 3.7 times that found in all of Earth's oceans;
  • Coincidentally, in this region, there is a gap that is giving rise to a planet in the star system.
Mapping water in another star system could help discover its origin on planet Earth (Image: Pexels)

Researchers believe this is a strong indication that if a planet is forming there, there is a high chance that water is being incorporated in the process. A recent study revealed that there was a lot of water in the early Solar System before the Earth formed. Thus, this mapping may indicate that our planet may have formed with a large proportion of water, even if asteroids later brought more of it.

Our results show how the presence of water can influence the development of a planetary system, as happened around 4.5 billion years ago in our own Solar System.

Stefano Facchini, in a statement

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