The New Horizons spacecraft measures all the background light in the universe in a follow-up mission designed to scan the visible light in the universe from the darkest region of the solar system
How dark is the dark? This is not a Dr. Seuss riddle, but a serious question that has occupied astronomers for years. Their big chance came with the New Horizons spacecraft, which is now beyond the planets, more than 5.4 billion miles from Earth. The great distance from the Sun allows it to be free from light pollution from the background dust in our solar system, which allows the spacecraft to measure the darkness of deep space.
The astronomers discovered a residual glow coming from thousands of background galaxies that fill the universe. The good news is that there is no other source of background light that can confuse astronomers. The 'New Horizons' completed a full mapping of the visible light. The spacecraft was launched in January 2006, flew by the dwarf planet Pluto in July 2015, and passed by a Kuiper belt object, Arroyoth, in January 2019.
The 'New Horizons' measurements shed new light on the darkness of the universe
How dark is deep space? Astronomers may have finally answered that question using the capabilities and distance of NASA's New Horizons spacecraft, making the most direct and accurate measurements ever of the total amount of light the universe produces.
More than 18 years after launch and nine years after the historic exploration of Pluto, New Horizons is more than 7.3 billion kilometers from Earth, in the region of the Solar System far enough from the Sun to be in the darkest sky possible to provide a perspective unique to measuring the general brightness of the distant universe.
The cosmic optical background: a new understanding
"If you hold your hand in deep space, how much light will illuminate it?" asked astronomer Mark Postman of the Space Telescope Science Institute in Baltimore, lead author of a new paper describing the research published Aug. 28 in The Astrophysical Journal.
"We now have a better understanding of how dark space really is. The results show that most of the visible light we receive from the universe is created in galaxies. Importantly, we also found that there is no evidence of significant levels of light originating from sources unknown to astronomers today."
Historical insights and modern challenges
The findings solve a puzzle that scientists have been trying to solve since the 1960s, when astronomers Arno Panzias and Robert Wilson discovered that space was filled with strong microwave radiation, which they hypothesized was leftover radiation from the creation of the universe itself. This result led to their winning the Nobel Prize. Since then, astronomers have also discovered evidence of background X-ray, gamma-ray, and infrared radiation also filling the sky.
The discovery of the visible light background—formally called the cosmic optical background (COB)—provided a way to sum up all the light produced in galaxies over the lifetime of the universe before NASA telescopes like the Hubble and James Webb could directly see the The weak background radiation of galaxies in visible light.
In the age of the Hubble and James Webb telescopes, astronomers are measuring the COB to detect light that might come from sources other than these known galaxies. But measuring the total amount of light in the universe is an extremely difficult task from Earth or anywhere else in the inner solar system.
"People have tried repeatedly to measure it directly, but our part of the solar system has too much sunlight and interplanetary dust that scatters the light around to create a fuzzy haze that hides the faint light from the distant universe," said Todd Lauer, a New Horizons co-investigator and an astronomer at the lab. NOIRLab of the National Science Foundation in Tucson, Arizona, and one of the authors of the new paper. "All attempts to measure COB intensity from the interior of the solar system suffer from large uncertainties."
The role of 'New Horizons' in cosmic observations
This is where New Horizons comes in, deep within the Kuiper Belt and heading out into interstellar space, billions of miles on its way beyond the planets. Last summer, New Horizons scanned the universe with its LORRI camera, which collected dozens of separate fields of view, from a distance 57 times greater than the distance between the Sun and Earth.
LORRI is shielded from the sun by the main body of the spacecraft—which prevented even the faintest sunlight from penetrating the sensitive camera—and the focused fields were directed away from the bright disk and core of the Milky Way and nearby bright stars.
brightening the light of the universe
The researchers who analyzed the New Horizons observations used additional data, collected in far-infrared light by the European Space Agency's Planck mission, of fields with a range of dust densities to calibrate the level of these infrared emissions to the level of visible light. This allowed them to accurately predict and correct for the amount of light coming from the dust-scattered Milky Way in the COB images—a technique that was not available to them during the 2021 COB observation attempt with New Horizons, where they overestimated the amount of dust-scattered light and overestimated Measure the amount of light from the universe itself.
But this time, after taking into account all known sources of light, such as background stars and light scattered by thin clouds of dust within the Milky Way galaxy, the researchers found that the remaining level of visible light matched exactly the intensity of light produced by all galaxies over the past 12.6 billion years.
Confirmation of theories and extension of tasks
"The simplest interpretation is that the COB comes entirely from the galaxies," Lauer said. "Looking outside the galaxies, we find there darkness and nothing more."
"This newly published work is an important contribution to fundamental cosmology, and something that could only be done with a distant spacecraft like New Horizons," said New Horizons principal investigator Alan Stern of the Southwest Research Institute in Boulder, Colorado. "And it shows that our current extended mission is making important scientific contributions well beyond the original purpose of the Planetary Mission to make the first close-up study of Pluto and Kuiper Belt objects."
Beyond Pluto: The Continuing 'New Horizons' Journey
New Horizons continues its second extended mission of documenting distant objects in the Kuiper Belt, characterizing the Sun's outer heliosphere and continuing astrophysical observations from its unique and distant vantage point.
More of the topic in Hayadan:
One response
I didn't understand, somewhere in space far away from the solar system and the rest of the celestial bodies can you read a newspaper? Is the light from the distant stars really shining?