Whenever the subject is results from the ESA (European Space Agency) Gaia satellite, it is difficult not to be enchanted. In the midst of its enormous database, a group of astronomers has just established a path to determine with great precision the complete fate of the Sun, from birth to death.
Yes, stars are born and they die, and the same is true of the Sun, the star that lives at the heart of our planetary system. We know that it is 4.57 billion years old (information that we can obtain from the analysis of meteorites, largely originating from the same nebula that gave rise to the rest of the Solar System). But how is it possible to project its past and its future? Does it change over time?
This story is already fairly mapped out, and the secret to unraveling it is to look for stars that are all similar to the Sun, but of different ages. It’s the closest astronomers can get to a photo album with the full story of our star king.
Where does Gaia fit into this? Providing tons of “pictures”, on an unprecedented scale. Mining the satellite data (which already contain the basic properties of hundreds of millions of stars in our galaxy, the Milky Way), the group led by Orlah Creevey, from the Observatory of Côte d’Azur, in France, made a cut to select only those with mass and chemical composition similar to that of the Sun, but the most varied ages. In this sieve, they ended up with 5,863 stars.
That’s it: Gaia has produced a list of almost 6,000 stars that are “solar analogs”, stars that, at least in some basic parameters, are as similar to the Sun as possible (not all of them “solar twins”, virtually indistinguishable from our star, but there are certainly several of them in the group).
And then past and future draw themselves. Starting with a lower surface temperature than today, the Sun has gradually increased in temperature over billions of years. At some point around 8 billion years old, this trend will reverse: it will start to cool, while it swells and continues to increase in brightness, until, by 11 billion years, it becomes a red giant, more than 100 times the size. current diameter (in this process, it will engulf Mercury, Venus and Earth). Eventually, when its ability to generate internal energy is exhausted, the Sun will eject its outer layers and only a cooling, ultra-dense core will remain, a corpse astronomers call a white dwarf.
Gaia’s main contribution, beyond this history, is in the details that the identification of thousands of analogous stars can reveal. Do they all have planetary systems? Are they similar to ours? And is your rotation the same? With the list of targets in hand, astronomers will be able to look at each one of them with special attention and discover what there is in common and diverse among all solar-type stars.
This column is published on Mondays, in Folha Corrida.
Follow the Sidereal Messenger on Facebook, twitterInstagram and YouTube
