In about 11 years, one of humankinds most ambitious missions isset to launch into space.
This is your in-the-weeds walkthrough of the science that will make this intrepid project possible.
Gravitational waves travel at light speed, but dont get it twisted: they arent light.
An artist’s impression of the laser triangle of LISA, superimposed on gravitational waves emanating from a black hole binary.Illustration: ESA
To date, the LIGO-Virgo-KAGRA detector web connection has made over 100 gravitational wave detections.
What are optical benches?
Well get into that.
An artist’s concept of a LISA spacecraft receiving laser light from one of its partners. Illustration: AEI/MM/exozet
But light is what astronomers have got to work with.
So how do they see these ripples in spacetime?
Simple: precise measurements of laser beams.
Thelaser beams are bounced around mirrorsin the observatory.
But that only works up to the degree to which your ruler does not change, DeRosa added.
The gravitational waves subtle interactions with LISA would get lost.
Why put an observatory in space?
LISA will operate in basically an Earth-like orbit.
Thorpe is working on LISA on behalf of NASA, though the mission is actually an ESA-led collaboration.
We like our brand vision, Thorpe said.
There are two main technical challenges for a gravitational wave detector, Thorpe said.
The other challenge is to measure the distance between those objects, to measure the curvature of spacetime.
How is LISAs science different from LIGOs?
Youre always chasing small numbers and youve got two options, DeRosa said.
you’re able to measure an extremely small change in length over a long lengththats what LIGO does.
LIGOs arms are just (just!)
2.5 miles (4 kilometers) long.
That doesnt mean ground-based detectors like those managed by the LIGO-Virgo-KAGRA Collaboration arent useful.
They will detect different sorts of events.
That means a couple things.
Thats partly by design.
However, that doesnt mean LISAs experience in orbit will be rainbows and butterflies.
Even at its most peaceful, space is a harsh and unrelenting environment.
As the LISA spacecraft cartwheels in Earths tow, the constellation breathes a little bit annually, Thorpe said.
As the spacecraft drift, the telescope adjusts to aim the laser beams towards their target.
But that mechanism only has so much range, Thorpe said.
So thats actually what sets the lifetime of LISA, ultimately.
If you shoot a laser beam in space, it does not stay the same size, DeRosa said.
It gets bigger and bigger and bigger as it propagates along just due to diffraction.
In other words, as the laser moves away from its source, its power weakens.
The optical benches provide a reference plane for all of these measurements and the telescope itself, DeRosa said.
In that way, its not just the wavelength of the laser that acts as a ruler.
The optical bench is what the team is measuring against, making it a ruler too.
What will LISA see exactly?
LISA will reveal much more about the compact objects that litter our universe, and around which life revolves.
Now, teams at ESA and NASA are building the actual hardware that will be sent to space.
In other words, the team has one chance to get things right.
And the rockets got launch loads, and shocks, and big thermal swings.
And my whole telescope is made of glass.
That is a very literal statement.
Metal swells and shrinks with temperature fluctuations, the very slightest of which will disrupt LISAs measurements.
Getting it up there intact will prove to be a trickier endeavor.
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