habitable worlds observatory

Twelve stars have received X-ray passports. Now, for each of them, we know the exact radiation dose received by a planet in the habitable zone, the region where liquid water is possible.

A telescope stares at a star for many nights in a row. Somewhere in the stream of light hides a tiny dip in brightness — an Earth-sized planet briefly blocking part of the star. Such a dip lasts a few hours and repeats once a year or less. Catching it is like hearing a single quiet click in a noisy hall.

Two stars, AF Lep A and ε Indi A, have become the focus of close attention. Using the GHOST spectrograph on the Gemini telescope, astronomers split their light into colors and, from absorption lines, determined how much carbon, oxygen, sulfur, and thirteen other elements are in the stars' atmospheres.

The orchestra plays, but the musicians can't hear each other. The conductor keeps stopping the music and walking over to each player to tune the instrument. That's roughly how space telescopes with segmented mirrors work.

When an orchestra of thousands of musicians plays in harmony, the credit goes not only to each player's talent but also to the invisible work of the conductor.

Water comes in different varieties. Not just fresh or salty, but also "heavy"—when one of its hydrogen atoms is replaced by deuterium, its heavier cousin. Such water is called HDO, and it's a true cosmic passport: the amount of deuterium in water reveals where and when that water was born.

In 2024, the team led by David Charbonneau pointed the Magellan telescope with the WINERED spectrograph at LHS 1140. During transit, high-resolution spectroscopy caught the absorption line of metastable helium at 10833 Å.

The light of a distant star carries within it the silent hum of the atmospheres of planets orbiting it. For a long time, capturing it was like trying to make out a whisper over a roaring waterfall. But with the advent of the 39-meter Extremely Large Telescope (ELT) and the ANDES spectrograph with a resolution of 100,000, this task is no longer hopeless.

A spotlight blazes straight into your eyes, and a few steps away a tiny firefly flickers. That's roughly what it's like hunting for an Earth-like planet around a neighboring star: the planet is a hundred million to ten billion times fainter than its star, and in the sky they almost merge into a single point.

Imagine an artist whose canvas is an entire planet, and whose palette is molecules drinking starlight. His brush is billions of years of evolution, and his painting is a spectral portrait visible even from another star system.

The light of a distant star is no perfect beacon. Passing through the gravitational field of another star, it bends, splits, and magnifies, creating a fleeting Einstein ring in the sky. This is how gravitational microlensing manifests, predicted by Fritz Zwicky back in the 1930s.

The Sun is not just a source of heat; it's also the largest lens in the solar system. Its gravity bends light rays like glass, focusing them into a bright ring far beyond Pluto's orbit. If light from a distant planet enters this ring, astronomers could reconstruct its portrait — not a point, but a map with surface details.

When astronomers peer at distant worlds, they often don't see crisp lines of water vapor or methane, but a blurry silhouette, as if the planet has thrown on a thick veil. This veil, a haze of organic particles, behaves like a temperamental photographic plate: it darkens under harsh ultraviolet light, revealing hidden chemical patterns.

When a planet slips behind the edge of its star, the star backlights the planet's atmosphere, just as a setting sun illuminates clouds on the horizon. This brief moment, lasting only minutes, carries the imprint of the gases through which the starlight has passed.

Imagine a huge layered cake, where the layers of dough are space and the filling is a special region resembling an invisible wall. This wall is not made of bricks but of energy, and it could be as thick as the entire universe. If such a wall exists, it should stretch the dough layers differently: those lying along it spread apart faster, while those across it spread slower.

The search for extraterrestrial life is like a detective investigation: from tiny clues, you must distinguish traces of life from random imprints of non-living nature. On Saturn's moon Enceladus, the investigators are lucky — geysers burst from cracks in the icy crust, ejecting water from the subsurface ocean straight into space.

When the light of a distant planet is split into colors, it suddenly jumps at the boundary between red and invisible infrared, as if someone flipped a switch. This is how the vegetation red edge manifests itself: chlorophyll is transparent to near-infrared radiation, and the leaf, to avoid overheating, reflects it away.

Astronomers pointed JWST at a planet near the star Epsilon Indi — a giant gas ball resembling Jupiter, just 12 light-years away. In thermal images, the planet shone like a lantern. But nearby they noticed a faint dot — like a firefly. Calculations showed that two objects describe the picture better than one. However, it's most likely a lens flare — like a ghost of a lamp.

The smell of fresh bread unmistakably signals a nearby bakery. But to know if baking is happening right now, it's better to catch not the aroma itself but its intensification — the continuous stream of hot air from the oven. This everyday analogy helps grasp a revolution in the search for extraterrestrial life on exoplanets — planets beyond our solar system.

A handful of coins accelerates to one-fifth the speed of light. That's what Coracle interstellar probes will be like — tiny spacecraft weighing just a few grams, each with an ultrathin sail film. A powerful laser beam pushes them forward: light presses on the sail like wind fills a yacht's sails, except instead of air, it's a stream of photons.

Mars is an icy desert with an average temperature of minus 60. To warm it without biology, scientists propose three approaches with a single idea: create a thick heat-trapping blanket. First, deploy transparent film-blankets over bases. They let sunlight in but keep heat from escaping, allowing us to harvest water from the soil and grow plants.

Water isn't the only thing life needs. To assemble the first RNA-like chains from simple molecules, you need ultraviolet light, like the sunlight that helps plants, but harsher and with shorter wavelengths. Big stars like the Sun emit plenty of this light. Small, dim stars, however, have almost none: they shine mostly in red and infrared, like a glowing ember.

Simple equations that describe fox and rabbit cycles have been turned to bacteria on distant exoplanets, like K2-18 b. These worlds hold deep oceans under thick hydrogen skies. Like duckweed on a pond, light-eating microbes cover the sunlit water surface, stealing light from those below.

For exoplanets that always face their star with one side, the night side is doomed to eternal cold. But mountains can turn things around. Surface irregularities shake up the ocean of air, steering moisture flows across the day-night boundary. Once in the dark, water freezes into clouds, and clouds act like a blanket: they trap heat and keep the world from cooling down.

Scientists built a model of Earth with all living organisms removed — from bacteria to trees. Over billions of years, this 'empty house' didn't turn into an icy desert. Volcanoes, like a furnace, release carbon dioxide, and rock weathering, like a thermostat, absorbs it.

The night sky is dotted with stars, and many of them have planets. But how do you spot a tiny dark disk against the glare of a distant sun? The Kepler telescope spent nine years watching hundreds of thousands of stars, waiting for a planet to pass in front of its star and briefly dim it. That 'wink' is the only way to find worlds like ours.

To spot life on other planets, you don't necessarily need to search for oxygen in the air. Living beings paint the surfaces of their worlds: Earth's plants in green, bacteria in purple. The future HWO space telescope will capture these "paints of life" on exoplanets.

The lone planet KMT-2024-BLG-0816, one of many free-floating planets, was discovered when its gravity acted like a magnifying glass for a few hours. Passing in front of a distant star, the invisible body warped space like a glass marble, and boosted the background light.

Eavesdropping on a distant planet's atmosphere is hampered by the star's noise. In the TRAPPIST-1 system, astronomers used a planet-"bug": TRAPPIST-1 b — an airless neighbor that records only the interference.

The Comet Interceptor mission launches without a target. The spacecraft freezes at a point of space equilibrium, like a fighter jet on combat standby: engine warmed up, but takeoff only on alert.

A bus schedule drifts: if you don't check it, you'll miss your ride. Planets around other stars have the same problem – their crossings of the star's disk gradually shift. The ExoClock project pooled 30,000 observations from Earth and space to refine the schedule for 620 distant worlds. For 45% of the planets, transits were found to be off by hours.

Dark matter is the invisible scaffold of the Universe, revealing itself only through gravity. Vera Rubin, studying the rotation of galaxies, found that stars at the periphery move too fast, as if held by an unseen mass. This became compelling evidence for the existence of dark matter, yet its particles still elude direct detection.

The camera lens is no bigger than a quarter. You'd find it in a smartphone, but here it was mounted on the Hayabusa2 probe for asteroid landings.

Many planets around other stars — exoplanets — have elongated orbits. With each close approach, the star’s gravity squeezes and stretches them, like kneading dough. Friction heats up the interior to the point where rock melts, creating underground oceans of magma.

Every few hours, narrow beams of radio waves leave the Mojave Desert, near Madrid, and near Canberra, heading into the sky. This is NASA's Deep Space Network: three antenna complexes that keep in touch with spacecraft across the solar system.

In August 2024, the MIRI coronagraph on the James Webb Space Telescope stared at Alpha Centauri A, the nearest Sun-like star to our Sun. At 1.5 arcseconds from the star, a point source, S1, blinked into view. Flux: 3.5 mJy, contrast: 5.5×10⁻⁵. Four to six sigma. A lighthouse flashing in the fog.