Scientists look over the Euclid space telescope in Cannes, France, on Feb. 21.VALERY HACHE
After ten years of working on the Euclid space telescope Will Percival has gotten used to thinking long term. But when he met with European colleagues to talk about the project earlier this month, things suddenly felt much more immediate.
“We know we’ll be getting data in a few months time and we know we have to be ready to start analyzing,” said Dr. Percival, an astrophysicist at the University of Waterloo in Ontario and a senior member of Euclid’s science team.
It’s a far cry from last year when the war in Ukraine brought an end to plans for Euclid to be launched atop a Russian Soyuz rocket, leaving the European Space Agency looking for other options.
Now, if the current schedule holds, Euclid is set to begin its journey on Saturday aboard a SpaceX Falcon 9 at Cape Canaveral in Florida, which will send it on its way to ‘L2′ – a position about 1.5 million kilometres from Earth, where NASA’s James Webb Space Telescope is also located.
But unlike Webb, which is busy making the most distant stars and galaxies in the universe visible to us, Euclid is built to explore something that will never be visible to anyone, at least not directly.
“Our number one goal is focused around dark energy,” said Dr. Percival. “We want to understand what it is. We want to know why the expansion of the universe is accelerating.”
It’s been nearly a century since Edwin Hubble first clocked the speeds of distant galaxies and showed that space – but not the stuff in it – is getting larger at a measurable rate. The process was initiated by the Big Bang, the explosive event that gave rise to the universe.
In 1998 astronomers announced a second startling discovery. By measuring the motion of still more distant galaxies, they found that the expansion of the universe has been speeding up. The term “dark energy” was coined to put a label on the effect, but understanding exactly what dark energy is has proved far more challenging.
“It’s arguably one of the biggest mysteries we have in physics” said Dr. Percival.
Theorists have speculated about the nature of dark energy and what it means for the fate of the universe. It could be that it is simply an innate kind of energy that is embedded in the vacuum of space. Hence, as the universe grows, the total amount of dark energy grows with it, exerting an outward pressure that continues to strengthen until the end of time.
Map of dark matter sheds new light on forces shaping the universe
In such a scenario all of the hundreds of billions of galaxies that we can see in the universe today will eventually be pushed away so rapidly that they outpace the ability of light to cross the growing gap and vanish from our sight. Each galaxy will then become an isolated island, with its stars gradually burning out like embers in the midst of an eternally deepening darkness.
As dismal as that may seem, this is the scenario that best fits what astronomers have observed thus far. But there is also a chance that a more precise reading of the phenomenon would show that dark energy is changing over time, and may even shut off at some point in the future.
To accurately measure how much space has stretched over cosmic time one needs a measuring stick. Enter Euclid — a mission aptly named after the famous geometer of antiquity.
“If you want to observe the cosmos as a whole, then you need to take a big survey,” said Giuseppe Racca, the European Space Agency’s project manager for Euclid during a media briefing last week.
The mission is designed with the big picture in mind. Over the course of its six year mission Euclid is expected to take in about 36 per cent of the surrounding sky as seen from our solar system to a depth of some 10 billion light years.
Euclid’s quest
A European mission with partners in Canada and elsewhere is
set to measure the expansion of the universe across cosmic
time in hopes of better understanding dark energy –
a phenomenon that has caused the expansion to accelerate.
EUCLID SPACE TELESCOPE
Euclid: Will launch
to orbit around
sun-earth Lagrange
point L2
Lagrange point L2:
Equilibrium point
of sun-earth system
is located 1.5 million
kilometres from
earth in opposite
direction of sun
Sunshield:
Blocks light
from sun,
earth and
moon
MOON
384,000 km
from earth
L2
SUN
L2 is locked
in perfect unison
with earth’s
orbit around sun
Radiators
Thrusters
EARTH
150 million km
from sun
Euclid’s orbit has
diameter of about
1 million km
around L2
Star trackers
graphic news, Sources: Euclid Consortium;
European Space Agency; Space.com
Euclid’s quest
A European mission with partners in Canada and elsewhere
is set to measure the expansion of the universe across
cosmic time in hopes of better understanding dark energy –
a phenomenon that has caused the expansion to accelerate.
Lagrange point L2:
Equilibrium point
of sun-earth system
is located 1.5 million
kilometres from
earth in opposite
direction of sun
EUCLID SPACE TELESCOPE
Euclid: Will launch
to orbit around
sun-earth Lagrange
point L2
Sunshield:
Blocks light
from sun,
earth and
moon
MOON
384,000 km
from earth
L2
SUN
L2 is locked
in perfect unison
with earth’s
orbit around sun
Radiators
Thrusters
EARTH
150 million km
from sun
Euclid’s orbit has
diameter of about
1 million km
around L2
Star trackers
graphic news, Sources: Euclid Consortium;
European Space Agency; Space.com
Euclid’s quest
A European mission with partners in Canada and elsewhere is set to measure the expansion
of the universe across cosmic time in hopes of better understanding dark energy – a phenomenon
that has caused the expansion to accelerate.
EUCLID SPACE
TELESCOPE
Euclid: Will launch to orbit around
sun-earth Lagrange point L2
1.2 m Korsch telescope:
Operates in visible and
near-infrared wavelengths
Sunshield:
Blocks light
from sun,
earth and
moon
Lagrange point L2:
Equilibrium point
of sun-earth system
is located 1.5 million
kilometres from
earth in opposite
direction of sun
MOON
384,000 km
from earth
L2
SUN
L2 is locked
in perfect unison
with earth’s
orbit around sun
EARTH
150 million km from sun
Euclid’s orbit has
diameter of about
1 million km around L2
Thrusters
Radiators
Star trackers
graphic news, Sources: Euclid Consortium; European Space Agency; Space.com
The depth is crucial, because Euclid is not only looking across space but back in time. And as it measures the expansion of the universe at different epochs it will cover the time period when dark energy became dominant.
To achieve this, Euclid is equipped with two instruments. One is a camera that will record the shapes of distant galaxies. This is important because galaxies appear slightly warped when their incoming light is distorted by clumps of dark matter located along the line of sight. (The nature of dark matter is another big cosmic mystery, but in this case it serves as a tool to show mass is distributed in the universe.)
Euclid’s second instrument is an infrared spectrometer and photometer that can be used to measure the motions of receding galaxies.
When combined, data from both instruments will provide a three dimensional map that shows how the contents of the universe are spreading out and how that has changed over cosmic time.
To get a better sense of whether dark energy is constant or changing, astronomers will also need to refer to data taken over many years by ground based observatories, including the Canada-France-Hawaii Telescope on Mauna Kea. It’s these data that have allowed Canada entry into the mission, with several participating researchers at Waterloo, the University of British Columbia and other centres.
Now, with Euclid finally ready to fly, the next chapter in the dark energy hunt is ready to begin, and the last ten years feel more like a blink in cosmic time.
“That’s why I stuck with it,” said Dr. Percival. “It’s taking that step forward into the unknown.”