#AstroMiniBR: we have already discovered more than 5,000 planets outside the Solar System!

Every Saturday, the TecMundo and the #AstroMiniBR bring together five relevant and fun astronomical curiosities produced by the collaborators of the non-Twitter profile to spread the knowledge of this science that is the oldest of all!

#1: Five thousand planets outside the Solar System!

We live in a golden age in astronomy. Great discoveries and advances in our understanding of the Cosmos no longer take as many decades or centuries to achieve as they used to in times of yore. This week, last Monday (21), NASA announced the arrival of another new cosmic milestone: 5,000,000 exoplanets were detected in the Milky Way! Perhaps the number is not as impressive as the even larger numbers we commonly see when talking about astronomy, but in reality it marks the culmination of 30 years of research and a journey in search of planets beyond our Solar System.

In the list of extrasolar planets you will find the most diverse variety of categories: there are those worlds that are small and rocky like Earth; those that are gas giants, even many times larger than Jupiter and Saturn; those that are extremely hot and inhospitable due to their orbits being very close to their stars; there are “super-Earths”; the “mini-Neptunes” and many, many others. That’s considering the planets themselves! If we add the planets in binary systems, those orbiting two stars at the same time, this list gets more and more exotic. In any case, this milestone represents how much we have advanced in the understanding of planetary sciences, in which we increasingly know how planets form and evolve in the history of the Universe.

#2: The incredible record of a solar eclipse!

A total solar eclipse is nowhere near the most common astronomical event out there. Quite the contrary: it is a very unusual phenomenon when compared to the possibility of being observed by a certain person in a certain place on the planet! Many people have never seen one and will never have the chance to see one. However, this is an event that can and should be placed on the calendar of anyone who is excited enough about astronomy! As it is possible to know where and when a total solar eclipse will be visible in advance, many enthusiasts schedule themselves to observe it in a certain place on the planet many months and even years in advance! That’s exactly what astrophotographer Jon Carmichael did in the August 21, 2017 eclipse, the first over US soil in 99 years. He programmed himself not only to observe it, but bought a ticket on a commercial flight that passed just at the exact moment of the solar eclipse. The result is the one above!

#3: Autumn has arrived in the southern hemisphere!

Last Sunday (20), the southern hemisphere said goodbye to summer and welcomed autumn! The day marked one of the two equinoxes of the year, which is defined by the exact passage of the Sun across the celestial equator. During the autumnal equinox, the southern hemisphere begins to receive gradually less light from the Sun, while the opposite occurs in the northern hemisphere: there it begins to receive more and more solar radiation. This is because the Earth’s axis of rotation is slightly tilted, which causes the four seasons!

#4: The difference between star clusters

Star clusters are groups of nearby stars linked by gravitational interaction. They comprise from a few thousand to several million stars. In general, they are characterized in two distinct groups: globular or closed clusters, which are very concentrated groups of older stars; and open clusters, more widely spaced and dispersed groups of stars whose populations are normally quite young. A few years ago, globular clusters were one of the biggest mysteries in astronomy because the estimates of the ages of the stars that constituted them resulted in values ​​greater than the estimated age of the Universe. This problem was solved with the more sophisticated distance measurements of the latest generations of telescopes, which assigned a few hundred million years less than the cosmic age to the oldest stars in these clusters.

#5: Where does the sun rise and set?

We all carry the remote memory of geography and science classes during our school days of having learned that the sun always rises in the east and always sets in the west. However, what we may not have learned (or not remember) is that this occurs exactly only on the autumn and spring equinox days, that is, only two days in the year! But for practical purposes, the Sun never strays that far from these two points throughout the year: in fact, on the other days of the year, it always rises and sets slightly north and south of these two cardinal points.

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