scorecardresearch Skip to main content

Voyager spacecraft detects ‘persistent hum’ past solar system

An illustration depicting one of NASA’s twin Voyager spacecraft. Both Voyagers have entered interstellar space, or the space outside our Sun’s heliosphere.NASA/JPL-Caltech

The Voyager 1 spacecraft has picked up a “persistent hum” in space beyond our solar system, a discovery that could play an instrumental role in the search for life on other planets, according to a Boston University professor involved with the project.

The discovery came from a group of researchers at Cornell University who published their findings in the journal Nature Astronomy on May 10. Merav Opher, a guest investigator with the Voyager project and a professor in BU’s astronomy department, said the hum can be translated to density, which in turn will allow researchers to gather new information about the “cocoon” the solar system resides in, known as the heliosphere.


Voyager 1 was launched in 1977, with the goal of exploring the outer edges of the solar system, according to NASA. In 2012, after making a series of discoveries on Jupiter and Saturn, the vessel exited the solar system and entered into interstellar space, the space between stars. Now, Voyager’s mission is to “explore the outermost edge of the Sun’s domain.”

Opher said she joined the project in 2001, when she went to work at NASA’s Jet Propulsion Laboratory.

Prior to the new discovery, researchers believed information about the interstellar medium where Voyager resides could only be collected when the sun becomes “turbulent” and “sends shocks into the interstellar medium,” Opher said. Now, however, researchers don’t have to wait for that turbulence to understand what is happening in the interstellar medium.

“It’s constant, you can see constant density, a constant hum that allows you ... to now say, I can characterize the medium beyond our cocoon continuously,” Opher said in a telephone interview.

Opher drew an analogy to explain the distinction, “In the past, we [would] map our backyard by two separate trees, we’ll say ‘okay this is what we can see every time the sun has an explosion, we can say there is a tree here and we got height, there’s another tree,’ but now we have this constant hum, you can map the grass, you can map everything because ... you don’t need big disturbances to see what’s going on there.”


The ability to constantly map the density of the medium will allow researchers to gather more information about it, which in turn will allow them to achieve a greater understanding of “how stars impact the medium beyond them,” Opher said.

“Now we can start putting much stronger constraints to in a bigger picture understand how stars affect the medium beyond them,” she said. “We’re trying to understand how these cocoons shield the sun from galactic cosmic rays coming into the cocoon, the heliosphere. Part of the thing Voyager discovered is the medium beyond the cocoon is turbulent, and ends up affecting the particles that come in so this measurement now of the hum can put strong constraints on models, it needs to match that density.”

Learning more about the medium beyond a star will aid researchers in their quest for life on other planets, as they can translate what they know about the medium surrounding the solar system to other planetary systems throughout space, Opher said.

“We know that our cocoon is a habitable one, we have life inside, and we know that that cocoon filters a whole lot of these particles that are part of the key story of the development of life, you need them, but you don’t need a lot of them,” she said. “We would like to understand when we are trying to discover other habitable worlds out there, what are the properties of the cocoons that we should look for. [We’re] trying to understand how the cocoon affects the medium beyond it, and which properties the cocoon has to have for life to happen.”


“It’s a really important key,” Opher continued.

Charlie McKenna can be reached at Follow him on Twitter @charliemckenna9.