Spring is upon us – the season when young lovers sit together under the clear night sky. It is not hard to imagine a young man expressing his feelings by declaring that he will love his companion "for as many days as there are stars in the sky".
That would be a romantic thing to say, but when we talk about visible stars, that's only about 5,000 stars. A smart young lady could do the math and realize that this is only about 14 years old. And so she could reconsider the relationship. But do not worry, young man – science can help save the situation.
This week the Gaia mission of the European Space Agency has released the richest and most detailed star chart yet. It covers about 1.7 billion stars, far more than the young couple would see with the naked eye.
The technology behind this map is the Gaia satellite, which contains two telescopes and other instruments, including nearly one billion pixels of cameras, it is the largest digital camera ever to enter space. In December 2013, the European Space Agency (ESA) sent an orbit in an orbit about 1.5 million kilometers away from Earth towards the Sun.
The satellite should conduct a five-year mission to collect collected data in waves. The first wave was released in September 2016 and the second – the new star chart – was released this week. By the end of 2020, there are continuing discussions about the progress of operations – and observations – and one can only imagine what one could learn more about the Universe.
Since its publication, the new star chart has inspired astronomers. The data catalog, which is publicly available, is incredibly impressive. It gives the magnitude and location of the two-dimensional sky for 1.7 billion stars, measures the distance and motion of 1.3 billion of them, and measures the color of about 1.4 billion. It also measures surface temperature, radius and luminosity, as well as the radial velocity of smaller numbers.
In addition to mapping the stars, the survey also measures the position and trajectory of more than 14,000 objects within the solar system (mostly asteroids). It determines exactly the locations of half a million distant quasars, which are bright galaxies that are made extremely bright by enormous black holes in the centers of the galaxies, devouring matter and heating the incoming matter until it glows. Determining the positions of these quasars is a tremendous achievement that allows astronomers to establish a fixed coordinate system in which they can determine the position of all objects.
It is difficult to overestimate the impact of this cornucopia on the astronomical community. It will undoubtedly help us to understand that which is beyond what we can see with our eyes alone.
For example, we can now determine the color and brightness of more than 4 million stars within 5,000 light years of Earth. By gathering these two quantities in a so-called Hertzsprung-Russell diagram, astronomers can see the properties of stars in all phases of their lives, from the first ignition through their Middle Ages to the time when they expand into giants with radii as big as Earth's orbit, to their declining years as white dwarfs. These data will allow astronomers to better understand the life cycle of stars.
The Gaia team has also studied the motion of stars in smaller nearby dwarf galaxies and globular clusters orbiting the Milky Way galaxy. Their observations can shed light on how the Milky Way formed and how dark matter surrounds it. Perhaps just as exciting, the exact data on the motion of stars in the Milky Way will likely lead to a better understanding of the distribution of dark matter within our galaxy. We were unable to observe dark matter in earthbound experiments. Maybe it's because not much is near the solar system.
Astronomy is perhaps the oldest scientific discipline and fascinates humans as long as they look up to the sky, but this star chart puts everything in the shade. Astronomers have certainly done their work for them, because the Gaia mission data will take years to analyze and understand.
There are some who claim that science is a dry endeavor, free of human passions – and it's true method is designed to determine the truth as objectively as possible. But scientists are also human beings, and the enthusiasm and passion that astronomers have for this new data is hard to beat. Well, except for our hypothetical young man, whose scientific knowledge was not quite equal to his sense of poetry. The new Gaia data release ensures that his expression of love really means forever.