An astronomer's work never ends. Europe's Gaia mission has mapped billions of stars, planets and asteroids in our galaxy but the job is far from done.
Asteroid Day: ESA's Gaia telescope has detected almost 10 times as many asteroids in our galaxy as previously thought Image: blickwinkel/McPHOTO/M. Gann/picture alliance
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Think of our galaxy — the Milky Way — and you will likely see stars and planets. You may also see satellites and asteroids. But while all that is most often only in our minds' eye, astronomers use space-based missions, like the European Space Agency's Gaia telescope, to see billions of celestial bodies.
ESA describes Gaia as an "ambitious mission to chart a three-dimensional map of our Galaxy, the Milky Way" and in the process reveal the composition, formation and evolution of the Galaxy.
Gaia has already revealed that there are almost 10 times more asteroids than we thought in the solar system. We now know more about the physical properties — shape, size, color and motion — of over 60,000 asteroids.
These details can give us an insight into what our solar system is made of and how it could have originated and evolved over time.
Gaia: A 'fingerprint' of the Milky Way
The Gaia mission released its third and largest set of data on June 13, 2022, and revealed 'starquakes and stellar DNA' in the Milky Way Image: ESA
The Gaia mission has identified at least 2 billion objects in our galaxy. And with the third and largest set of data, released on June 13, 2022, scientists can start to describe what they are actually seeing because we are now able to see the color of light that different stars emit. It is like a person with color blindness seeing colors for the first time.
But what information does the color of these stars give us?
First, the color of a star indicates what metals or gasses make it what it is. A star emits different colors depending on its elements.
Gaia uses a process called spectroscopy, which studies the association between these materials and the colors they create. It is giving us what scientists call a "fingerprint" of the galaxy.
Second, based on these colors, we can point to stars that may have originated in the same regions. That means we can look back in time and understand how various stellar populations emerged over time and how stars may form in the future.
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Gaia observes the widest range of the Milky Way
Many space-based telescopes observe a fixed range. But Gaia has one of the widest ranges of coverage we have ever achieved.
Gaia resides at about 1,5 million kilometers from the Earth in what's called the "anti-Sun direction" — it orbits the sun together with the Earth, while looking away from the sun. It rotates at a 45 degree angle and spins around its own vertical axis every six hours.
That gives Gaia one of the widest fields of vision we have ever had in the Milky Way.
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Gaia sees the fastest stars in the galaxy
Gaia can observe the galaxy in six dimensions of space and velocity.
This has allowed astronomers to track the speed of around 33 million stars and detect whether they are moving towards or away from our solar system.
And that helps researchers observe star formations. Gaia Mission Manager, Uwe Lammers, told DW this information could throw new light on the formation and history of the sun and the solar system itself.
Gaia also sees stellar quakes
How do you find out if there was a quake in the stars? Well, Gaia can observe tsunami-like turbulences on the sun's surface to identify so-called star quakes.
These quakes are observed through the "blinking" of stars and ripples that are released when quakes happen and that are then converted into sound.
Learning about these stellar tremors has helped astronomers better understand what is happening inside the stars. It gives us an idea of a stars age and size.
Seeing binary systems of stars and black holes
Gaia observes binary star systems in our galaxy. Binary systems can include pairs of stars or stars and black holes and stars and planets that orbit each other.
Seeing those things can allow researchers to calculate the mass of a star or a black hole. Black holes teach us a lot about the laws of nature.
In the next data release from Gaia, scientists hope to see details on over 20,000 giant exoplanets. This will be achieved by measuring their gravitational effect on the movement of their host stars. Studying that will provide us with better clarity on the formation of plants in our own solar system.
Edited by: Zulfikar Abbany
Earth-like planets and other celestial discoveries
Astronomers have found a new Earth-like planet in our neighboring solar system, Proxima Centauri. We take a look at this and other discoveries from Earth- and space-based telescopes.
Image: L. Calçada/ESO
Another planet Earth?
The European Southern Observatory (ESO) has discovered a third Earth-like planet orbiting the star Proxima Centauri, the closest star to our sun at four light years away. A planet is considered Earth-like if scientists suspect it provides conditions that could make life theoretically conceivable, such as a certain temperature range, gravity, an atmosphere and the possibility of water.
Image: L. Calçada/ESO
Discovery via the Very Large Telescope
Astronomers discovered the planet through the Very Large Telescope (VLT) in Chile's Atacama Desert. Proxima d is the lightest of the three planets discovered around our closest star. ESO researchers also discovered the somewhat larger Proxima b, but with a different telescope supported by the planet-search instrument HARPS.
Image: ESO/G. Lombardi
Spaceship Kepler: On the hunt for planets
Many Earth-like planets haven't been discovered by telescopes situated on Earth but by ones in space. Spaceship Kepler has been searching for Earth-like planets since 2009. Besides meeting the physical conditions, they must also consist of rock or metal compounds and have a solid surface, in contrast to gas giants like Jupiter and Saturn.
Image: NASA Ames/JPL-Caltech/T Pyle
A longer distance away
Exoplanet Kepler-186f is located 500 light years away from us, orbiting red dwarf Kepler-186. That small sun has only about 4% of the energy of our sun. Kepler-186f orbits Kepler-186 at a perfectly calibrated distance: Water would neither freeze nor evaporate on the planet, which is a precondition for life. But the question of whether there is water on Kepler-186f at all remains unanswered.
There are no detailed pictures of exoplanets, just artistic representations like this one of Kepler-186f. But not even a drawing exists of another recently discovered exoplanet, Kepler-438b, which orbits a sun-like star about 470 light years away from Earth and is just slightly larger than our planet. NASA published the discovery on January 6, 2014.
Image: picture-alliance/dpa
Ocean-covered giants?
This artist's drawing of Kepler-62e shows a planet covered by ocean. Scientists agree that Earth-like exoplanets most likely have large oceans. Kepler-62e can be found in the constellation of Lyra, located 1,200 light years away from us. And its mother star, Kepler-62, has yet another Earth-like planet ...
Image: NASA Ames/JPL-Caltech
The Kepler-62 brothers
... Kepler-62f, whose diameter is 1.4 times that of Earth. The Earth-like planet is located a bit further out in its solar system than its larger brother Kepler-62e, which is 1.61 times as big as Earth. Both may be suited for life. Researchers believe that the existence of rocks and water is plausible.
Image: NASA Ames/JPL-Caltech
Orbiting two suns
Even though Kepler-16b is located on the edge of an inhabitable zone, it probably doesn't host any life. This is a pity, because the planet orbits two suns — every morning and evening, its inhabitants would be able to observe two sunrises and sunsets! Too bad Kepler-16b is most likely a gas planet, composed of rock and ice — not good for beings needing to breathe fresh air.
Image: imago/UPI Photo
The Hubble Space Telescope offers many perspectives
The Pillars of Creation are located in the Eagle Nebula about 7,000 light years away. The joint ESA and NASA Hubble Space Telescope took new pictures of the formation through an infrared light spectrum. The pillars are home to numerous bright and young stars, including entire solar systems.
Image: NASA, ESA/Hubble and the Hubble Heritage Team
Lights on!
The same picture through visible light: more fog, but also more color. Dust and gas in the pillars are pierced by radiation originating from young stars. These new Hubble Telescope pictures enable researchers to monitor changes in the formation over a longer period of time.
Image: NASA, ESA/Hubble and the Hubble Heritage Team
A star is born
NGC 4102 is a LINER galaxy: a low-ionization nuclear emission-line region. This means it emits ionized radiation, like roughly one-third of all galaxies. At its center, there is a sun-burst region, where young stars seem to be born. It has a diameter of about 1,000 light years. Scientists don't understand the exact processes in the center yet.
Image: ESA/Hubble, NASA and S. Smartt (Queen's University Belfast)
A messier cluster
This cluster of stars, located in the northern part of the Hercules formation, is called Messier 92. On dark nights with clear skies, we can see it from Earth with bare eyes. The cloud includes roughly 330,000 stars, most of which consist of hydrogen and helium. Heavier elements like metals are rare.
Image: ESA/Hubble & NASA/Gilles Chapdelaine
The best view of Andromeda
The original version of this photo of the Andromeda Galaxy is 1.5 billion pixels in size — the most detailed picture ever taken of that galaxy. It includes 100 million stars and thousands of star clusters. To watch it in its entire beauty, one would need 600 HD-TV screens. The ends of the picture are 40,000 light years apart.
Image: NASA, ESA, J. Dalcanton (University of Washington, USA), B. F. Williams (University of Washington, USA), L. C. Johnson (University of Washington, USA), the PHAT team, and R. Gendler
