#AstroMiniBR: Why are there different seasons throughout the year?

Every week, TecMundo and #AstroMiniBR brings together five relevant and entertaining astronomical curiosities produced by the world’s collaborators. profile on twitter to spread the knowledge of this science, which is the oldest!

#1: Why does Earth change seasons throughout the year?

It is not unusual to believe that the Earth is closer to the Sun during the summer and therefore everything is warmer at this time of year. And similarly, when the Earth is farther from the Sun, winter occurs with its coldest temperatures. While this idea makes sense intuitively, it is wrong.

In fact, the Earth’s orbit around the Sun, that is, its orbit is not a complete circle, and this asymmetry makes the Earth closer and farther from the Sun at different times of the year. But this difference is not enough to make a significant change in our climate, nor is it the main reason why we have seasons.

Seasons occur because the axis of Earth’s rotation, that is, the imaginary axis on which the Earth rotates and forms day and night, is tilted relative to the orbital plane. The Earth’s axis always points in the same direction, so different parts of the Earth receive the Sun’s direct rays differently throughout the year. For example, in the summer, the sun’s rays hit that area more directly than at other times of the year, while the incidence of sunlight is less in the winter.

#2: We are made of stardust

Ever wondered where it came from? Where did all this structure that makes up our organs, muscles, and bones come from? Of course, you might think, “I came from my mother,” and that may be true, but on a more fundamental level, everything about us that we can see and touch is made up of particles, atoms, and molecules.

And where did these little ingredients come from?

This answer goes back billions of years and has cosmic origins. Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur compounds are the basic building blocks of all life on Earth. Despite a strong poetic connotation, the phrase “we are made of stardust” has broad scientific truth: all of the heaviest chemical elements found in our organism (as well as in everything that exists), such as atoms. More than 4.5 billion years ago, carbon, nitrogen, and oxygen were created in previous generations of stars.

In our case, about 40% of all our atoms were forged in stars, while most of the hydrogen was formed in the early universe, just after the Big Bang. But since these 40% atoms are definitely the heaviest chemical elements, the sum of our mass formed in stars reaches 93%!

#3: When did the first stars and galaxies appear in the universe?

The answer to this question lies at the moment when the Universe was still in its infancy. The first stars likely formed before the first galaxies were formed, when the Cosmos was about 100 million years old.

Known as population III stars, these primordial objects were made almost entirely of hydrogen and helium, as the elements that make up most of planet Earth have yet to form. When they exploded as supernovae, they ejected the heavy elements produced within them into the interstellar medium. This initiated the cosmic chemical enrichment that led to the formation of other stars, including the stars we see in the Milky Way today. The first generation of galaxies probably appeared a little later, between 200 and 400 million years after the Big Bang, when the first stars and surrounding cosmic gas and dust material merged due to the gravitational effect.

#4: The beauty of star nurseries

About 170,000 light-years from us, the beautiful Tarantula Nebula features a magnificent array of stellar nurseries. Located in the Large Magellanic Cloud, one of our closest galactic neighbors, the Tarantula Nebula features massive clouds of dust and gas that give rise to new stars over millions of years.

The shapes of these clouds are constantly shaped by these star-forming dynamics as new, bright, and extremely hot stars are created.

In the images above you can see an animation showing the combination of observations of the beautiful nebula in optical, infrared and radio wavelengths.

#5: Veil Nebula

The above image shows the Veil Nebula about 2,400 light-years from the Solar System. It is a large cloud of heated, ionized gas and dust that is the remnant of a supernova that occurred about 10,000 to 20,000 years ago. The source of this catastrophic event was a star about 20 times more massive than the Sun, and at the time of the explosion, its light would appear brighter in the sky than Venus, and would even be visible during the day here on Earth.