Rare 'cosmic telescope' amplifies light from dawn of time
This is the newly discovered Einstein Cross, J2211-3050. The observed effect is due to the alteration caused by a galaxy that acts like a magnifying glass amplifying and distorting, in four separate images in the form of a cross, the light of another galaxy located 20 billion light-years away. (Photo: Hubble Space Telescope with GRANTECAN overlay)
Astronomers plumbing the depths of space for light dating back to just after the Big Bang have received another unlikely assist from a galaxy some 20 billion light-years away.
That galaxy, unremarkable on its own, created what’s known as a gravitational lens — effectively a cosmic telescope — to amplify the light from another galaxy. It’s a remarkable phenomenon that not only allows us to glimpse light dating back to the very dawn of time, but also yet again validates one of Einstein’s general relativity predictions.
The more recent example above is the work of a team of Italian scientists led by Daniela Bettoni of the Padova Observatory and Riccardo Scarpa of the IAC, who observed the lens spectroscopically with the Gran Telescopio CANARIAS (GTC) in La Palma, Spain.
Scarpa described the success to Phys.org:
“The result could not have been better. The atmosphere was very clean and with minimum turbulence (seeing), which allowed us to clearly separate the emission of three of the four images. The spectrum immediately gave us the answer we were looking for, the same emission line due to ionized hydrogen appeared in all three spectra at the same wavelength. There could be no doubt that it was actually the same source of light.”
A perfect alignment of time, space and mass
The quasar shown in this image, also captured by the Hubble Space Telescope, lies at a distance more than 12.8 billion light-years from Earth. It’s only possible to see thanks to a gravitational lens effect produced by the dim galaxy to the left. (Photo: NASA, ESA, Xiaohui Fan, University of Arizona)
Their work followed a similar discovery by another team in January, which found the quasar in the photo above.
“If it weren’t for this makeshift cosmic telescope, the quasar’s light would appear about 50 times dimmer,” study leader Xiaohui Fan of the University of Arizona said in a statement. “This discovery demonstrates that strongly gravitationally lensed quasars do exist despite the fact that we’ve been looking for over 20 years and not found any others this far back in time.”
In Einstein’s Theory of General Relativity, he explained how the gravitational mass of an object, expanding far into space, can cause light rays passing close to that object to be bent and refocused somewhere else. The larger the mass, the greater capacity for it to bend light.
In the case of this particular cosmic lens, there are a couple of fortuitous circumstances at play that allowed us — billions of light-years away — to get a peek at an ancient cosmic event. For one, we’re lucky the galaxy in the foreground providing the lensing effect wasn’t more of a scene-stealer.
“If this galaxy were much brighter, we wouldn’t have been able to differentiate it from the quasar,” said Fan.
Quasars, objects of high energy that generally contain super-massive black holes at their center, are bright. This one, however, is exceptional. According to measurements made by both ground telescopes and the Hubble Space Telescope, the gravitationally lensed quasar known officially as J0439+1634 shines with the combined light of about 600 trillion suns. Further, the team estimates that the mass of the black hole powering this reaction is at least 700 million times that of our own sun.
You can see a visualization of the quasar, which now holds the record as the brightest object yet discovered in the early universe, below.
“This is one of the first sources to shine as the Universe emerged from the cosmic dark ages,” Jinyi Yang of the University of Arizona, another member of the discovery team, said in a statement. “Prior to this, no stars, quasars, or galaxies had been formed, until objects like this appeared like candles in the dark.”
The researchers say they’ll be taking advantage of the lensing effect, in particular with upcoming space-based telescopes like the James Webb, to study this ancient quasar in greater detail over the coming years. They’re particularly interested in learning more about the supermassive black hole at its center, which is estimated to be ejecting enough super-heated gas to produce as many as 10,000 stars per year. By comparison, they explain, our own Milky Way galaxy is capable of creating only one star per year.
“We don’t expect to find many quasars brighter than this one in the whole observable Universe,” added Fan.
Editor’s note: This story has been updated since it was originally published in January 2019.
Rare ‘cosmic telescope’ amplifies light from dawn of time
A gravitational lens theorized by Einstein has allowed us to spot light dating back 12.8 billion years.