Photo taken in Bogor, Indonesia

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Photo taken in Bogor, Indonesia

Photo by: Eko Agung Wahyudi / EyeEm

Eko Agung Wahyudi / EyeEm

What’s the Farthest Thing We Can See?

Beyond the most distant star you can see with the naked eye, beyond the most extreme faint galaxy that we discern with our telescopes, lays something extraordinary: the leftover light from the big bang itself.

March 31, 2022

And it’s everywhere.

The farthest object you can spot with your naked eye is actually a healthy distance away from us. If you find yourself enjoying a gorgeous dark sky, you can gaze at a fuzzy patch of light in the constellation Andromeda. Astronomers once thought that this fuzzy patch was just another nebula, but a hundred years ago Edwin Hubble discovered that it’s really an entire galaxy sitting two and a half million light-years away from us.

That’s an extreme distance for sure, but the combined light of the trillion-or-so stars within the galaxy allows you to see it, all the way from Earth.

The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons. The CMB can be used to probe the cosmos via something known as the Sunyaev-Zel’dovich (SZ) effect, which was first observed over 30 years ago. We detect the CMB here on Earth when its constituent microwave photons travel to us through space. On their journey to us, they can pass through galaxy clusters that contain high-energy electrons. These electrons give the photons a tiny boost of energy. Detecting these boosted photons through our telescopes is challenging but important — they can help astronomers to understand some of the fundamental properties of the Universe, such as the location and distribution of dense galaxy clusters. The NASA/ESA Hubble Space Telescope observed one of most massive known galaxy clusters, RX J1347.5–1145, seen in this Picture of the Week, as part of the Cluster Lensing And Supernova survey with Hubble (CLASH). This observation of the cluster, 5 billion light-years from Earth, helped the  Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to study the cosmic microwave background using the thermal Sunyaev-Zel’dovich effect. The observations made with ALMA are visible as the blue-purple hues. Links   ESO Picture of the Week  RX J1347.5–1145 seen by Hubble only

Astronomical cooperation

The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons.

Photo by: ESA/Hubble & NASA, T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA

ESA/Hubble & NASA, T. Kitayama (Toho University, Japan)/ESA/Hubble & NASA

The events surrounding the Big Bang were so cataclysmic that they left an indelible imprint on the fabric of the cosmos. We can detect these scars today by observing the oldest light in the Universe. As it was created nearly 14 billion years ago, this light — which exists now as weak microwave radiation and is thus named the cosmic microwave background (CMB) — has now expanded to permeate the entire cosmos, filling it with detectable photons.

Telescopes let you peer further into the universe, and the current record holder for the most distant known galaxy is called GN-z11. It’s a small potato, as far as galaxies go, just 1/25th the size of our own Milky Way and only 1% of the mass. But it’s firing off stars about twenty times faster than the Milky Way, allowing it to shine fiercely. It formed when our universe was only 400 million years old, making it amongst the first generation of galaxies to appear in the universe, and it’s right around 32 billion light-years away from us.

28 Billion Light-Years Away: The Most Distant Star Ever Discovered

On Wednesday, NASA announced the Hubble telescope broke a new record– detecting the most distant star ever seen.

But wait, there’s more!

Different wavelengths of light allow us to see different creatures inhabiting the cosmos. For example, infrared light can punch through dense clouds of dust, letting us see as stars form inside them.

And when you switch on your microwave telescopes, you can see the farthest – and oldest – object in the universe.

It’s called the cosmic microwave background, and it completely soaks the entire cosmos. It was formed when our universe was a mere 380,000 years old. Back then, the universe was only 1/1000th its current size, and it was much, much hotter around 10,000 degrees.

A jet from a very distant black hole being illuminated by the leftover glow from the Big Bang, known as the cosmic microwave background (CMB), has been found. Astronomers using NASA’s Chandra X-ray Observatory discovered this faraway jet serendipitously when looking at another source in Chandra’s field of view.  Jets in the early Universe such as this one, known as B3 0727+409, give astronomers a way to probe the growth of black holes at a very early epoch in the cosmos. The light from B3 0727+409 was emitted about 2.7 billion years after the Big Bang when the Universe was only about one fifth of its current age.  This main panel graphic shows Chandra’s X-ray data that have been combined with an optical image from the Digitized Sky Survey. (Note that the two sources near the center of the image do not represent a double source, but rather a coincidental alignment of the distant jet and a foreground galaxy.)   The inset shows more detail of the X-ray emission from the jet detected by Chandra. The length of the jet in 0727+409 is at least 300,000 light years. Many long jets emitted by supermassive black holes have been detected in the nearby Universe, but exactly how these jets give off X-rays has remained a matter of debate. In B3 0727+409, it appears that the CMB is being boosted to X-ray wavelengths.  Scientists think that as the electrons in the jet fly from the black hole at close to the speed of light, they move through the sea of CMB radiation and collide with microwave photons. This boosts the energy of the photons up into the X-ray band to be detected by Chandra. If this is the case, it implies that the electrons in the B3 0727+409 jet must keep moving at nearly the speed of light for hundreds of thousands of light years.   The significance of this discovery is heightened because astronomers essentially stumbled across this jet while observing a galaxy cluster in the field. Historically, such distant jets have been discovered in radio waves first, and then followed up with X-ray observations to look for high-energy emission. If bright X-ray jets can exist with very faint or undetected radio counterparts, it means that there could be many more of them out there because astronomers haven’t been systematically looking for them.  A paper describing these results was published in the 2016 January 1st issue of The Astrophysical Journal Letters and is available online. The authors are Aurora Simionescu (Institute of Space and Astronautical Science, Kanagawa, Japan), Łukasz Stawarz (Jagiellonian University, Kraków, Poland), Yuto Ichinohe (Institute of Space and Astronautical Science, Kanagawa, Japan), Teddy Cheung (Naval Research Laboratory, Washington, DC), Marek Jamrozy (Jagiellonian University, Kraków, Poland), Aneta Siemiginowska (Harvard-Smithsonian Center for Astrophysics, Cambridge, MA), Kouichi Hagino (Institute of Space and Astronautical Science, Kanagawa, Japan), Poshak Gandhi (University of Southampton, Southampton, UK) and Norbert Werner (Stanford University, Stanford, CA).  NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

A jet from a very distant black hole being illuminated by the leftover glow from the Big Bang, known as the cosmic microwave background (CMB), has been found.

Photo by: Chandra X-ray Observatory Center

Chandra X-ray Observatory Center

A jet from a very distant black hole being illuminated by the leftover glow from the Big Bang, known as the cosmic microwave background (CMB), has been found.

At that time, the universe cooled enough for the first atoms to form, as electrons could finally find homes around atomic nuclei without getting bumped off. When that happened, the high-energy light that had been bouncing around the cosmos finally got to zoom off, free and clear.

Initially, that light was literally white-hot. But as our universe aged, expanded, and cooled, that light shifted down into longer and longer wavelengths.

Today, all that light is firmly in the microwave band of the electromagnetic spectrum and has a temperature of only a handful of degrees above absolute zero.

Because the cosmic microwave background is so old, it is by far the most distant thing we can see. It completely covers our sky, and the light that is only now reaching our telescopes left its home over 42 billion light-years away.

Dive Deeper into the Universe

Journey Through the Cosmos in an All-New Season of How the Universe Works

The new season premieres on Science Channel and streams on discovery+.

Paul M. Sutter

Paul M. Sutter is an astrophysicist at Stony Brook University and the Flatiron Institute, host of Ask a Spaceman and Space Radio, and author of How to Die in Space.

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