Probe peels back mysteries of the universe

Remote: Our solar system, the heliosphere, and the Voyagers — tiny specks in space. © NASA

Is remote exploration a form of escapism? NASA has sent a spacecraft 12 billion miles from Earth. One scientist says it is like exploring an elephant with a microscope. Why do we bother?

A matter of hours ago, almost exactly a year since it crossed into interstellar space, the probe has sent back a message.

Beyond Jupiter, beyond Neptune, beyond the furthest reaches of the Sun itself, a NASA spacecraft is wandering in interstellar darkness.

After completing a 41-year journey and the first-ever flybys of Uranus and Neptune, Voyager 2 left our solar system in November 2018. Scientists are astounded that the craft has made it so far.

“We didn’t know how large the bubble was, and we certainly didn’t know that the spacecraft could live long enough to reach the edge of the bubble and enter interstellar space,” said Professor Ed Stone.

Our Sun roars through space at 450,000 miles per hour, spiralling around the centre of the Milky Way. As it travels, the star’s fiery, volatile surface throws off bursts of solar wind, which form a bubble called the heliosphere.

Eventually, these winds crash headlong into the interstellar medium, the layer of debris and powerful radiation that hangs between our galaxy’s star systems.

We know about this strange barrier thanks to Voyager 2 and its older sibling, which left our solar system from a different angle in 2012.

At the edge of the heliosphere, Voyager 1 detected a boundary where temperatures dropped and the density of charged particles, known as plasma, rose sharply.

“It’s just really exciting that humankind is interstellar,” said physicist Jamie Rankin of Princeton University. “We have been interstellar travellers since Voyager 1 crossed but, now, Voyager 2 crossing is even more exciting because we can now compare two very different locations.”

Scientists have been hoping that these two pin-points could tell us more about the shape of the heliosphere. Some models predict that it is spherical, while others think it is more like a comet, leaving a long tail of solar matter in its wake.

The new data from Voyager 2 suggests that the bubble is indeed spherical, but not everyone is convinced that we’ve learned much at all.

“It’s kind of like looking at an elephant with a microscope,” says research scientist Bill Kurth. “You have no idea what’s going on between [the two points].”

Why do we bother to explore the vast expanse of our ignorance? Are there not enough problems at home on Earth? And would the money not be better spent on issues that have some kind of immediate relevance to us here and now?

Into the void

It is a total waste of time, say some. Interstellar space is like that blank look a friend gives you when they are not listening to something important you are trying to tell them. It is hugely tempting to devote your mind to something far, far away, which has absolutely no relevance. It is quite simply a respectable form of escapism. What better way to explain why you are not doing anything about the fire in your kitchen than to say you are busy exploring the origins of the Universe.

So unfair! Or so say the fans of space science. Forty-two years after they were launched, the spacecraft are still going strong and exploring the outer reaches of our cosmic neighbourhood. By analysing data sent back by the probes, scientists have worked out the shape of the vast magnetic bubble that surrounds the Sun. The two spacecraft are now more than 10 billion miles from Earth. What could be more valuable or exciting than that?

You Decide

  1. Why are we so fascinated by the stars?
  2. Is the vastness of space terrifying or exciting?


  1. Draw what you imagine the opposite edge of the Universe might look like.
  2. Write a poem, no more than 15 lines long, from the perspective of Voyager 2 after it has been travelling across the galaxy for billions of years.

Some People Say...

“For small creatures such as we, the vastness is bearable only through love.”

Carl Sagan (1934-1996), US astronomer and cosmologist

What do you think?

Q & A

What do we know?
Voyager 2 was launched by NASA in 1977. After taking the only ever close-up images of Uranus and Neptune, it exited our solar system in November 2018. After a year of waiting, the probe has sent back its first message about its passage through heliopause, which forms a porous barrier between the heliosphere and the interstellar medium.
What do we not know?
Exactly how long we will be able to stay in touch with Voyagers 1 and 2. Powered by steadily decaying plutonium, they are projected to drop below critical energy levels in the mid-2020s. However, they’ll continue travelling long after we lose contact with them. “The two Voyagers will outlast Earth,” said Bill Kurth. “They’re in their own orbits around the galaxy for five billion years or longer.”

Word Watch

Between star systems. “Stellar” refers to stars.
The only man-made object. Voyager 1 took a different route.
Solar wind
Charged particles that are released from the surface of the Sun. If they hit earth directly, these winds can cause disruption to electronics and power lines.
A huge bubble encompassing our solar system, which is full of solar weather.
Interstellar medium
A barrier of matter and radiation that floats between the stars in our galaxy.
From ancient stellar explosions.
The heliosphere protects us from interstellar radiation.
A gas so hot that its atoms have split up and are now highly charged.
Scientists use models or simulations to predict how things work.


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