Astronomers are hyped for the next generation of telescopes, and rightfully so. The James Webb Space Telescope, and others, will open the farthest reaches of the cosmos to us. But, the Hubble Space Telescope proves that even with its aging technology, it still has a few tricks up its sleeves.
It doesn’t look like much, but you are seeing a galaxy that existed just 400 million years after the Big Bang. The galaxy, named GN-z11, is incredibly faint. But, astronomers also describe it as “unusually bright considering its distance from Earth.”
This isn’t the first time astronomers have looked at GN-z11. Previous observations estimated its distance by analyzing the galaxy’s color in images snapped by Hubble and the Spitzer Space Telescope. But now astronomers used Hubble’s Wide Field Camera 3 to precisely measure the distance to GN-z11.
The Wide Field Camera 3 (white panel in the center) seen during Servicing Mission 4.
“Our spectroscopic observations reveal the galaxy to be even further away than we had originally thought, right at the distance limit of what Hubble can observe,” says Gabriel Brammer of the Space Telescope Science Institute.
In fact, before this discovery – astronomers believed these distances would only be reached by the James Webb Space Telescope.
How do astronomers figure this out?
Astronomers use redshift to figure out how far away GN-z11 is from Earth. What is redshift? It’s the Doppler effect. But with light instead of sound. As an object moves farther away from us (Earth), the light waves wavelength increases. This results in light shifting to redder wavelengths. The opposite, or blueshift, occurs when light wavelength decreases.
In astronomy, every distant object is moving further away thanks to the expansion of the Universe. Because these distant galaxies are moving away from us, light from them appears redder.
Ok, so how does GN-z11 stack up to previous distance record holders? The previous record holder was EGSY8p7 with a redshift of 8.68. GN-z11 has a redshift of 11.1, and places it at a time when galaxies were just beginning to form.
Here’s co-author Rychard Bouwens explaining the differences between EGSY8p7 and GN-z11.
“The previous record-holder was seen in the middle of the epoch when starlight from primordial galaxies was beginning to heat and lift a fog of cold, hydrogen gas. This transitional period is known as the reionization era. GN-z11 is observed 150 million years earlier, near the very beginning of this transition in the evolution of the Universe.”
What do we know about GN-z11?
Besides being the most distant galaxy ever seen, astronomers also know the galaxy is 25 times smaller than the Milky Way. Or, was. Remember, we’re looking into the past. The light we see from GN-z11 took 13.4 billion years to reach us.
Astronomers also say the infant galaxy has just one percent of the Milky Way’s mass in stars. But the stars are growing quickly. And, this quick star formation is why Hubble was even able to see it.
GN-z11 also shows us how little we know about the early Universe. “The discovery of GN-z11 was a great surprise to us, as our earlier work had suggested that such bright galaxies should not exist so early in the Universe,” says Marijn Franx from the University of Leiden.
Ivo Labbe echoes Franx’s remarks. “The discovery of GN-z11 showed us that our knowledge about the early Universe is still very restricted. How GN-z11 was created remains somewhat of a mystery for now. Probably we are seeing the first generations of stars forming around black holes?”
These are questions new telescopes like the James Webb Space Telescope will tackle in the coming years. Hubble’s newest discovery means the next generation of telescopes should have no problem finding even more distant galaxies. We could be talking about the very first galaxies in the next few years.