A ghostly glow surrounds the solar system and no one can explain it

A new analysis of Hubble data has concluded: there is too much light in space around the solar system.

Not much extra light, of course. Just a subtle, ghostly glow, a slight excess that cannot be counted in a count of all light-emitting objects.

All the stars and galaxies surrounding the solar system – and the zodiacal light, aka the dust on the plane of the solar system – none of which can account for what astronomers now call “phantom light”.

After analyzing 200,000 Hubble images and taking thousands of measurements in a project called SKYSURFan international collaboration is sure that the excess of light is real.

And, moreover, they cannot quite account for it. There are possibilities, but none have been confirmed. Not yet anyway.

The strongest possibility? A component of solar system dust that we have yet to directly detect: tiny particles of dust and ice from a population of comets traveling inward from dark parts of the solar system, reflecting sunlight and generating a diffuse and global glow.

This source would be a little closer to us than the additional light detected by the New Horizons space probewho found an excess of optical light in space beyond Pluto, outside the solar system.

“If our analysis is correct, there is another component of dust between us and the distance where New Horizons made measurements. This means that it is some kind of additional light coming from inside our solar system”, says astronomer Tim Carleton from Arizona State University.

“Because our measurement of residual light is superior to New Horizons, we believe this is a local phenomenon that is not very far from the solar system. It may be a new element of the content of the solar system which has been hypothesized but not quantitatively measured so far.”

There are a lot of really bright things floating around the Universe: planets, stars, galaxies, and even gas and dust. And usually the shiny things are the ones we want to look at. So detecting ambient light in interstitial places – interplanetary, interstellar and intergalactic space – is a tricky thing to do.

However, when we look, we sometimes find that things are not as we expected them to be.

For example, something that we cannot explain to the galactic center produces high energy light. Traveling I found an excess of luminosity associated with hydrogen at the edge of the solar system. There is New Horizons detection. Things just look weirdly bright there.

The goal of SKYSURF was to completely characterize the luminosity of the sky.

“More than 95% of the photons in the images from the Hubble Archive come from distances less than 3 billion kilometers from Earth. Since the very early days of Hubble, most Hubble users have dismissed these photons from the sky, as they are interested in faint discrete objects. in Hubble images, like stars and galaxies”, says astronomer and Hubble veteran Rogier Windhorst from Arizona State University.

“But these photons from the sky contain important information that can be extracted thanks to Hubble’s unique ability to measure low levels of light with high precision over its three decades of life.”

Across three separate papers, the researchers scoured the Hubble Archive for signs of faint galaxies we might have missed and quantified the light that should be emitted by objects known to glow.

The Hidden Galaxy Search team determined that there weren’t enough missed galaxies to account for the extra light.

The resulting excess was, according to the scientists, equivalent to a constant glow emitted by 10 fireflies throughout the sky.

It may not seem like much, but it’s enough to know that we are missing something. And that’s important. Increasingly, scientists are finding ways to see the light between stars. If there is a local excess, we need to know about it, as it could skew our understanding of more distant ghostly glows.

And, of course, there’s the impact it could have on our understanding of the solar system and how it’s put together.

“When we look at the night sky, we can learn a lot about Earth’s atmosphere. Hubble is in space,” says astronomer Rosalia O’Brien of Arizona State University.

“When we look at this night sky, we can learn a lot about what is happening in our galaxy, our solar system and on a large scale like the entire universe.”

The three published SKYSURF articles were published in The Astronomical Journal and Letters from the Astrophysical Journaland can be found here, hereand here. A fourth article, submitted to The Astronomical Journal and which has not yet been published, can be found on the arXiv preprint server.