It is our ticket to finding other Earths and to knowing whether other worlds are home to life. The observatory’s powers will be as revolutionary as when seventeenth-century astronomers turned the first telescopes towards the planets and revealed them not as dots of light, but as globes with moons and rings. If all goes as planned, NASA’s super-telescope will launch in the 2040s and be the first to image potentially Earth-like planets in the habitable zones of Sun-like stars.

“Directly imaging temperate planets in reflected light will be completely game-changing for exoplanetary astrophysics,” says Penn State University exoplanet researcher Jason Wright. “We will be able to understand atmospheres, surface water, orbital architectures, rotation and a host of other properties that so far have been purely theoretical.”

Moreover, the Habitable Worlds Observatory (HWO) will be able to detect biosignatures. These are gases that are in disequilibrium, either because there is too much or too little to be explained by abiotic processes, or gases that shouldn’t be there at all if it were not for life. The supposed detection of dimethyl sulphide on the exoplanet K2 — 18b is the perfect example. Its signal is too weak for the James Webb Space Telescope to be sure, but the intention is that HWO will leave no room for doubt.

There are caveats. That phrase, “if all goes as planned,” is a hopeful one, but it leaves room for disappointment. If we look to the development of HWO’s predecessors, the Hubble and James Webb space telescopes, we find that both launched years after schedule, were plagued by technical difficulties, and went horrendously over budget. Indeed, the James Webb Space Telescope was on the verge of being cancelled at one point because of its cost overruns, only to be saved at the eleventh hour.

The Office of Management and Budget in the US tried to slash NASA’s funding for 2026, attempting to reduce money for the initial development of HWO from NASA’s requested $150 million to a meagre $3.3 million, only for the US Congress to reject the plans. For the 2027 budget, they are back at it again, with a proposed 46% cut to NASA’s overall science mission budget that would see just $5 million per annum for HWO through to at least 2031.

Hopefully, the US Congress will reject the administration’s budget cuts. However, were HWO not to go ahead as planned as a result of a lack of funding and development, what would we stand to lose? Supercluster spoke to several researchers in the exoplanets and astrophysics fields to find out.

First though, let’s learn a little more about the observatory, its science goals and how it will accomplish the magnificent things that it is intended to do.

As large as the HWO’s primary mirror will be, under normal circumstances it still won’t be able to see exoplanets that are tens of billions of times fainter than the glare of their star unless that glare is cut out. The secret to HWO’s success, therefore, is going to be its coronagraph.

An ordinary coronagraph would be a disk placed in front of the telescope aperture that masks the light of a bright object, such as the Sun (the name coronagraph comes from using disks to mask the body of the Sun so scientists could see the ghostly whispers of the corona). When dealing with the points of light that are stars with their planets in close attendance, this style of coronagraph is not feasible. Instead, a clever series of optical components and deformable mirrors will act to suppress the light of the star to leave only the light from the orbiting planets.

Not even HWO will be able to resolve these planets as globes the same way that a backyard telescope can resolve Jupiter. Nevertheless, even seeing these worlds as pinpricks of light reflected from their star can elicit details via spectroscopy, and how the planet’s light changes in brightness and color as it rotates can tell us roughly how much of its surface is covered in land, sea or vegetation.

It’s no easy task, though. For every photon of light from a planet, ten billion photons from its star have to be suppressed by the coronagraphic optics. It’s the key to making HWO work, and a prototype is flying on the recently launched Roman Space Telescope.

Prior to HWO being selected by the 2020 astrophysics Decadal Survey as a priority mission, NASA had solicited proposals for a next-generation telescope to replace Hubble and James Webb. Astronomers around the world teamed up to produce two concept missions, one called HabEx and the other referred to as LUVOIR (Large Ultraviolet Optical Infrared Surveyor). Martin Barstow, a professor of astronomy at the University of Leicester in the UK, was part of the LUVOIR team. He describes both HabEx and LUVOIR as “enablers” from which HWO came.

“In the LUVOIR study we looked at two design references, eight meters and 16 meters [aperture],” Barstow told Supercluster. “We still do not know exactly what the telescope configuration will be for HWO, as design studies are still underway. However, it will likely be at the lower end of the aperture range, as recommended by the decadal report.”

Aperture is only half the answer. The other half is the instruments that will be placed in the telescope’s focal plane, principally the aforementioned coronagraph as well as various imagers and spectrographs. These include a High Resolution Imager and Multi-Object Spectrograph, the development of both being led by the UK, while the Canadian Space Agency, the European Space Agency and the Japan Aerospace Exploration Agency are also participating in the mission. Its success will mean a lot to many astronomers around the world.

Since the 1990s, astronomers have discovered over 6,300 exoplanets. There’s a mix of warm Neptune-type worlds, hot Jupiter-like planets, and myriad super-earths and smaller rocky planets found orbiting close to red dwarf stars. Only a handful of rocky planets have been discovered orbiting in the habitable zone of stars that are similar in mass and temperature to our Sun. Unfortunately, because of our largely indirect means of detecting exoplanets, be it through transits, radial velocity Doppler shifts, astrometry, or microlensing, we can’t tell if any of those planets are like Earth, with an atmosphere and water on the surface.

That’s why HWO will be so important, because it will be able to tell.

“What really excites me about HWO is that it’s going to study true Earth analogs — rocky planets around Sun-like stars — for the first time, says Laura Kreidberg, who is a professor of astronomy and the Director of APEx, which is the department of Atmospheric Physics of Exoplanets at the Max Planck Institute for Astronomy in Germany.

Kreidberg draws a parallel with the work that the James Webb Space Telescope has been doing in trying to detect an atmosphere around various transiting rocky exoplanets.

“JWST is really powerful,” she says, “But it’s still limited to rocky planets around small M-dwarf stars, which may be quite different from our own Earth.”

JWST is searching for an atmosphere around the worlds of, for example, the TRAPPIST-1 system, one at a time as they transit their star. Through what’s referred to as transit spectroscopy, JWST watches for starlight filtering through an atmosphere and being absorbed by the atmospheric molecules. The results so far have been tentative and somewhat inconclusive.

HWO won’t have to worry about any of that. Its multi-object spectrograph will be able to take spectra of multiple planets simultaneously as it images them. Rather than waiting for years to get a null answer, HWO will be able to cover entire planetary systems to get firm answers in one fell swoop.

“The thing I get most excited about, other than searching for biosignature gases on Earth-like planets with HWO, is its potential to characterize entire solar systems’ worth of planets at one time,” says Eliza Kempton, a professor of astronomy at the University of Chicago who spends her time researching exoplanetary atmospheres. “The aspects of the HWO mission that make it good at characterizing Earth-like planets also make it good at detecting and characterizing a wide variety of other planets orbiting the same stars. Planets like super-Earths, mini-Neptunes, and gas giants should all be observable, alongside any Earth-like planets orbiting the HWO target stars.”

Those target stars will include 100 nearby star systems that have the greatest potential for harboring Earth-like planets, based on their Sun-like properties and predicted habitable zones at a similar distance as Earth is from the Sun. Included on the preliminary list is Alpha Centauri, Epsilon Eridani, and Tau Ceti, but this list will evolve as astronomers learn more about these systems and possibly even detect some candidate planets for HWO to follow up on.

HWO isn’t just an exoplanet mission. After all, it is being designed to succeed both Hubble and JWST, and therefore needs to be more of an all-rounder, although the ability to directly image Earth-like planets is the major requisite in its design. Still, with its giant eight-meter-plus mirror, stars, nebulae and galaxies far and wide will come under its scrutiny.

“It’s important to remember that the name of the observatory is a bit of political salesmanship,” says Jason Wright, emphasizing how it will be much more than just a planet-finding mission.

So besides finding other Earths, it will create deep fields of galaxies in the early Universe eight times faster than Hubble and four times faster than JWST, and be able to take 1.4 million ultraviolet spectra in a single image. It will study star formation in unprecedented detail and chart the evolution of galaxies, black holes and dark matter across cosmic time. In short, it will show us the Universe in a way we have never seen it before.

“Astrophysics as a whole will gain so much for an observatory of this size and power,” adds Wright. “Like JWST and Hubble before it, [HWO] promises to enable huge advances across astrophysics and planetary science and answer questions we didn’t even know we wanted to ask.”

That’s added pressure on HWO’s metaphorical shoulders, or perhaps on the actual shoulders of the people at NASA and other space agencies and those scientists working to make HWO happen. Yet given the uncertainty in the funding of science right now, not just in the United States but across the world, should we be worried that HWO might be severely delayed or worse, cancelled?

Everyone who we at Supercluster spoke to was confident that HWO would be made a reality.

“I believe that HWO will be funded — NASA has never failed to complete a flagship mission recommended by a Decadal Survey. Too much is at stake; without HWO, we will never know if there are other inhabited planets out there,” says Kreidberg.

Martin Barstow echoes her optimism. “I am sanguine about the funding risks to HWO,” he says. “It has been established with a congressional budget line, as Roman, JWST and Hubble before it. It’s extremely difficult for an administration to cancel such a project. I have watched attempts to do so over several decades. They have all failed when budgets eventually came before Congress, as they have to.”

However, Barstow knows that NASA cannot afford to make the same mistakes that were made during the development of the JWST. Budgeted at $4.5 billion in 2005, JWST eventually launched in 2021 with a projected lifetime cost of $9.7 billion, to the dismay of the US Congress, which cancelled the telescope in 2011 because of its cost overruns and mismanagement, only for it to be reinstated after an outcry from astronomers.

“The US Congress has made very clear to NASA that a repeat of JWST, in that sense, will not be tolerated,” says Barstow.

Barstow highlights how developing the science case for the telescope early and allowing that to drive the design should make for a smoother process without the delays and cost overruns that JWST faced. For example, JWST was originally going to have an eight-meter telescope, but partway through its development this was reduced to 6.5 meters regardless of its science goals. For HWO, the size of the telescope is going to be determined by the need to be able to directly image Earth-like planets in the habitable zone of Sun-like stars, leading to at minimum an eight-meter telescope.

“There are always risks with high-profile projects of this nature, and I am sure HWO will have its difficulties,” acknowledges Barstow. “However, an important difference between this and JWST, designed to mitigate these risks, is the extended development and definition phases we are now in.”

Suppose, though, that disaster strikes and HWO is cancelled for whatever reason. How much will astronomy and astrophysics lose? An awful lot, to the point that it will stunt the development of all manner of research fields.

“Most of the science envisaged for HWO cannot be carried out with any other facility,” says Barstow. “If HWO does not go ahead, a massive opportunity to answer some of the most exciting questions of our day will be missed.”

Kempton is more pointed in her appraisal of just what is at stake.

“HWO is *the* way that humanity will be able to search for the signatures of life on Earth-like planets orbiting Sun-like stars within the next several decades,” she says. “There isn’t really another feasible path forward toward achieving this goal in a comparable time frame. Any delays to the mission will just put off our ability to address this fundamentally important question for humanity.”

Kreidberg is of a similar opinion. “To find biosignatures we need HWO, no question about it!” she says.

There’s possibly also a greater issue at play. Over the past decade, we have witnessed how the commercialization of space has come to control low-Earth orbit, which is now increasingly seen as a billionaire’s playground. Furthermore, there has been the growing militarization of space, with the recent revelation that the United States has launched a space-based weapon of unknown capabilities, and Russia has been suspected of doing the same. Space missions such as JWST and HWO, which work to enhance all of us with the knowledge that they gather, remind us that there is still room for peaceful ambitions in our use of space.

“I think it’s great that a chunk of money that we spend putting things into space and developing new space technologies is used for entirely peaceful purposes that allows the entire world to learn more about its place in the cosmos,” says Jason Wright. “It would be a huge loss for us all if we didn’t continue that tradition.”

For millennia, humanity has wondered whether there is life elsewhere and whether Earth is unique. For thirty years and counting, astronomers have searched for Earth’s twin. With its ability to detect atmospheric biosignatures and infer certain surface details, HWO is going to be our best opportunity for answering the most profound of questions: are we alone?