10 Amazing Eyes We Have on the Sky
There is much more to the Universe than what it appears at first sight. It shines in all kinds of different lights ranging from radio waves to gamma rays. This very minute we are being bombarded by elusive neutrinos and inundated by gravitational waves. Until fairly recently, humanity was unaware of most of what the Universe is trying to show us.
(Originally, I wrote this for Listverse. Then I realized that I am not eligible for submission because I live in the wrong country. Too bad.)
In astronomy, bigger is better. Larger telescopes collect more light and can see fainter stars and galaxies. One should also opt for large telescopes to see more details in images. The latter is especially true for observations of radio waves.
Meet FAST, a radio telescope located in a green, hilly basin in southeast China. With a diameter of 500 meters, it is the largest single-dish radio telescope in the world. The behemoth has been in operation for only a few years and has already discovered tens of neutron stars. Scientists will also use the telescope to observe different molecules within and outside the Milky Way Galaxy. Who knows, maybe one day FAST even discovers a signal from an alien civilization.
Instead of building one huge telescope, one can make many smaller ones and connect them together. With this ingenious technique, scientists can even connect radio telescopes from all over the world, effectively assembling a telescope as big as Earth!
ALMA is an array of 66 telescopes standing at an altitude of about 5000 meters in the Atacama desert in Chile. It may not be as big as a planet, but it is one of the finest radio observatories on Earth. The telescope is especially well suited to search for molecules in space. Among other discoveries, scientists used ALMA to find baby stars surrounded by gas and dust that will turn into planets in millions of years to come.
8. Very Large Telescope
Four giant cupolas proudly stand on the top of Cerro Paranal in the North of Chile. Every night since 1998 the cupolas open and allow four eight-meter telescopes to gaze at the stars. Each telescope can detect stars roughly four billion times fainter than what can be seen with the naked eye. The four telescopes are part of the Very Large Telescope (VLT) facility.
Don’t let the unimaginative name fool you! The Very Large Telescope is the most productive astronomical facility on the ground, surpassed only by the famous Hubble Space Telescope. Observations with VLT led to many breakthroughs in astronomy. For example, scientists used the VLT to make the first image of an exoplanet. The VLT also contributed to discovering the accelerated expansion of the Universe and the massive black hole residing in the center of the Milky Way Galaxy.
7. Hubble Space Telescope
Who hasn’t heard of the Hubble space telescope? The famous telescope was launched into space in 1990. It has been orbiting Earth 540 km above the surface ever since, observing the Universe in the ultraviolet, optical, and infrared light. Surprisingly, the first images were a huge disappointment. The mirror was misshapen due to a manufacturing error, but fortunately, astronauts could reach the telescope with a space shuttle and put spectacles on the telescope.
After the rocky start, the telescope became an ambassador for astronomy and science at large. Iconic images such as the Pillars of Creation or the Hubble Ultra Deep Field caught the attention of the masses. The telescope has played a leading role in the discovery of the accelerating expansion of the Universe. It showed us that the Universe is swarming with hundreds of billions of galaxies and helped establish that most of them have a massive black hole in their center. Even though the telescope is still indispensable, astronomers are eagerly waiting for the launch of its successor, the James Webb Space Telescope.
The International Space Station is not only a home for astronauts and cosmonauts, but it also carries several scientific instruments. One of them is NICER, an X-ray telescope dedicated to the study of neutron stars. This washing machine impersonator can accurately determine the time of the received light, which proves to be critical for precise observations of neutron stars.
NICER has already observed several neutron stars. Scientists found that they can use the data to accurately measure the neutron star’s radius and mass, which will lead to a better understanding of the interiors of these strange objects. Furthermore, they found that neutron stars have wacky, complicated magnetic fields.
Apart from neutron stars, NICER has also proved useful to observe black holes. More precisely, to look at the regions very close to black holes. These results help scientists to understand how material funnels in to the black hole and how energy is released in this process.
5. Neil Gehrels Swift Observatory
Several times per week, a burst of gamma-rays reaches Earth. Traveling across the Universe, the burst echoes an explosive death of a massive star or a violent merger of two compact stellar cores. But we can’t see these bursts from Earth because the atmosphere absorbs gamma rays. Since 2004 the Neil Gehrels Swift Observatory—or simply Swift—serves as our eyes and ears in space, looking out for these explosions. A long-lived light at other wavelengths typically follows the bursts. To observe that light as well, Swift carries three telescopes on board: a gamma-ray detector, an X-ray telescope, and an ultraviolet telescope.
When Swift detects a gamma-ray burst, it swiftly turns the other two telescopes in the burst’s direction. It immediately transmits a message about the detection to the phones of astronomers all over the world. The astronomers leave whatever they’re doing at the moment and run to their computers to start analyzing the data and to observe the optical light following the burst with the telescopes on Earth. Swift has detected more than a thousand bursts and changed our understanding of the phenomena.
4. MAGIC Telescopes
Sometimes science feels like magic. Certain processes in the Universe emit light with very high energies. That light cannot penetrate the atmosphere and we cannot observe it from the ground—at least not directly. When high-energy light comes in contact with air molecules, it creates a shower of particles traveling through the air incredibly fast and emitting light on their own. The light they emit is the visible light, and that light we can observe with the telescopes on Earth.
On the mountain peak of La Palma, an island in the Canary Islands archipelago, stand two MAGIC telescopes. Their task is to search for the faint, evasive light that comes from the bombardment of the upper layers of the atmosphere. It is an arduous work with little success. But when they do detect something, it has major scientific implications. A famous example is the detection of the high-energy light that accompanied a gamma-ray burst explosion in 2019. That was a surprise that revolutionized our view of these cosmic explosions.
3. IceCube Neutrino Observatory
Standing on the permanent layer of white snow on the South Pole, amidst the laboratories and telescopes of the Amundsen-Scott South Pole station, you would never guess that below you is one of the Earth’s largest scientific instruments. The IceCube Neutrino Observatory is buried deep in the ice of Antarctica. It covers one square kilometer of surface and reaches 2500 meters below the surface; the bulk of the detector encompasses over one cubic kilometer in volume. Ironically, this humongous detector is searching for one of nature’s most elusive and tiniest of particles: neutrinos.
Neutrinos are byproducts of many processes in nature: nuclear reactions in stellar cores, radioactive decays, nuclear reactors, supernova explosions, and collisions of high energy particles with the atmosphere. These particles have no charge, and their small mass is tiny even compared to the mass of an electron. They practically don’t interact with other matter. That is why we need such giant detectors to find them.
IceCube is searching for high-energy neutrinos. In 2017 it detected a neutrino originating in the center of a nearby galaxy. Scientists hope that more neutrinos will be detected, perhaps coming from mergers of neutron stars or gamma-ray bursts. A neutrino here, a neutrino there—in time, we might catch enough of them to understand their astrophysical sources and get answers to the more fundamental questions regarding basic physics.
2. LIGO and Virgo Gravitational Wave Observatories
Violent events like collisions of black holes create ripples in the fabric of spacetime, called gravitational waves. Gravitational waves squeeze and stretch everything in their path as they travel through spacetime. When gravitational waves pass Earth, the whole planet shrinks and extends with the frequency of the waves. The stadiums and mountains, countries and continents, and you and me—we all get distorted. But we don’t notice that because these effects are minuscule. A distance between two points, separated for several kilometers, changes for a thousandth of a proton’s width, or less. How on Earth are we supposed to measure that?
Believe it or not, scientists built gravitational detectors that can do just that. Three detectors that have been observing so far are two LIGO detectors in the US and the Virgo detector in Italy. In 2015, for the first time, LIGO detected gravitational waves from the merger of two black holes. By now, scientists have found tens of gravitational waves. Among the more spectacular discoveries are the finding of the most massive stellar-mass black holes so far and the first merging of neutron stars.
1. Human eyes
One can find many faults with our visual organ. Eyes can collect only a small amount of light compared to giant telescopes. We can see but the brightest stars in the night sky, about 4000 from any point on Earth, which is nothing compared to the hundred billion stars forming our Milky Way galaxy. And we can’t see radio waves or gamma rays, let alone neutrinos or gravitational waves. Without the telescopes, we would be oblivious to the gigantic storms on Jupiter and we would never know what a galaxy is.
But try as you may, you will never experience the night sky with a telescope in the same way as with naked eyes. As you stare into the darkness, far from the brightness of the city lights, and your eyes slowly adapt to the pitch-dark night, the magnificent outline of the Milky Way stretches across the sky. The breathtaking immensity is humbling, but it also connects you with the Universe. No computer-processed image, no matter how colorful and pretty, can replace that feeling. That sight is what triggered curiosity and led to everything we have built hence. And that is why our eyes are our most precious and amazing observatory.