Level 1 — Absolute Beginner

Scientists study a young star. The star is called PDS 70. It is about 370 light-years from Earth. The star is only 5.4 million years old. That is very young for a star.

PDS 70 has two big planets. The planets are named PDS 70b and PDS 70c. These are exoplanets. An exoplanet is a planet that goes around a different star, not our Sun.

Scientists also find exocomets near the star. An exocomet is a comet in a different star system. Comets are big balls of ice and rock. The comets travel close to the star.

The comets may carry water. The water goes to the middle of the star system. This is where rocky planets can form. Long ago, comets may have brought water to Earth in the same way.

star

A giant, hot ball of gas in space that gives off light, like our Sun.

exoplanet

A planet that orbits a star other than our Sun.

exocomet

A comet that orbits a star other than our Sun.

comet

A ball of ice, dust, and rock that travels through space.

orbit

The path an object takes as it moves around a star or planet.

light-year

The distance that light travels in one year, used to measure space distances.

telescope

A tool that helps people see faraway objects in space.

protoplanetary disk

A flat, spinning cloud of gas and dust around a very young star, where planets can form.

Level 2 — Elementary

A team of astronomers has found new clues about how water might reach young, forming planets. The star at the center of the study, PDS 70, sits about 370 light-years from Earth. It is only 5.4 million years old, which makes it extremely young compared to our own 4.6-billion-year-old Sun.

PDS 70 is already famous because it has two confirmed giant planets, PDS 70b and PDS 70c. These are exoplanets, planets that circle a star other than the Sun. They were among the very first exoplanets ever photographed directly, with PDS 70b first captured in 2018 using a powerful telescope in Chile.

Now researchers have found evidence of exocomets, icy objects that travel around PDS 70 the same way comets travel around our Sun. They noticed that a gas called sodium appeared and changed in front of the star, and they think this could be a sign of comets passing close by.

Scientists also modeled how the two giant planets' gravity could push distant icy objects toward the star, sending them speeding inward. Since earlier observations with the James Webb Space Telescope already found water near the star, the new study suggests that comets may be delivering that water, much like scientists believe comets once delivered water to the early Earth.

astronomer

A scientist who studies stars, planets, and other objects in space.

exoplanet

A planet that orbits a star other than our Sun.

exocomet

An icy object that orbits a star other than our Sun, similar to a comet in our solar system.

gas giant

A large planet made mostly of gas, such as Jupiter or Saturn.

gravity

A force that pulls objects toward each other, such as a planet pulling on a comet.

sodium gas

A chemical element that can appear as a gas and be detected by telescopes near a star.

protoplanetary disk

A spinning disk of gas and dust surrounding a young star, out of which planets can form.

James Webb Space Telescope

A powerful space telescope used to study distant stars and planets in detail.

Level 3 — Intermediate

Researchers at Lund University in Sweden have uncovered new evidence that exocomets, icy bodies orbiting stars beyond our own, may be transporting water toward the inner region of a young planetary system still under construction. The star in question, PDS 70, lies roughly 370 light-years away and is classified as a T-Tauri star, a designation for very young, still-forming stars. At only 5.4 million years old, it is a cosmic infant, yet it already hosts two confirmed giant planets.

Those planets, PDS 70b and PDS 70c, hold a special place in astronomy history. They were among the first exoplanets ever imaged directly, rather than inferred indirectly through their effects on starlight. PDS 70b was first captured in 2018 by the European Southern Observatory's Very Large Telescope in Chile, offering astronomers a rare direct look at a planet still embedded in the material from which it formed.

The new findings center on variations in sodium gas detected in front of the star, a signature the researchers argue is consistent with comets sweeping through the system's inner reaches. By modeling the orbital dynamics at play, the team showed that the gravitational influence of the two giant planets could perturb distant, icy objects, flinging them on paths that carry them close to the star, mirroring the behavior of comets within our own solar system.

This discovery gains significance alongside earlier observations from the James Webb Space Telescope, which had already detected water within the inner disk surrounding PDS 70. Taken together, the two findings suggest a plausible delivery mechanism: comets ferrying water from the system's colder outer reaches into the region where rocky planets are likely to form, a process that closely echoes a leading theory for how water first arrived on early Earth. The work was published in the journal Nature Communications.

T-Tauri star

A category of young, still-forming star that has not yet reached a stable, mature phase.

exocomet

An icy body orbiting a star other than the Sun, analogous to a comet in our solar system.

protoplanetary disk

The rotating disk of gas and dust around a young star from which planets gradually form.

perturb

To disturb the motion or orbit of an object through an outside force, such as gravity.

orbital dynamics

The study of how objects move and interact under gravitational forces in space.

sodium gas

A gaseous form of the element sodium, which can be detected spectroscopically near a star.

European Southern Observatory

An international organization that operates major astronomical telescopes, including facilities in Chile.

Nature Communications

A peer-reviewed scientific journal that publishes research across many fields of science.

Level 4 — Advanced

In a study that reads like a snapshot of our own solar system's infancy, astronomers led by researchers at Lund University in Sweden have identified compelling evidence that exocomets, icy relics orbiting a star other than the Sun, are ferrying water toward the planet-forming heart of a system still very much under construction. The star, PDS 70, is a T-Tauri object, the designation astronomers reserve for young stars that have not yet settled into stable adulthood. At a mere 5.4 million years old and situated some 370 light-years from Earth, it offers a rare, real-time vantage on processes that shaped our own planetary neighborhood billions of years ago.

PDS 70 has long occupied a privileged position in exoplanet science. Its two confirmed giant companions, PDS 70b and PDS 70c, were among the first worlds beyond our solar system to be observed directly, rather than detected through the subtler indirect signatures, such as a star's dimming or wobble, that most exoplanet discoveries rely upon. PDS 70b's 2018 direct image, captured by the European Southern Observatory's Very Large Telescope in Chile, remains a landmark achievement, showing a planet still enshrouded in the very disk of gas and dust from which it emerged.

The latest research builds on that legacy by turning to a subtler signal: fluctuations in sodium gas observed in front of the star. The team argues these variations bear the fingerprints of exocomets transiting the system's inner reaches, and their orbital modeling demonstrates a plausible mechanism for how such comets arise in the first place. The gravitational influence of PDS 70's two giant planets, the researchers show, is sufficient to perturb icy bodies from the system's outer reaches, dispatching them on star-grazing trajectories analogous to the comets that periodically streak through our own solar system.

What elevates this finding beyond an astrophysical curiosity is its convergence with an earlier discovery. The James Webb Space Telescope had previously detected water within PDS 70's inner disk, the very zone where rocky, Earth-like planets are expected to coalesce. Together, the two results sketch a coherent narrative: comets, laden with ice, may be the couriers transporting water inward, a scenario that closely parallels one of the leading hypotheses for how the early Earth acquired the water that now fills its oceans. Published in Nature Communications, the findings offer a tantalizing, observationally grounded glimpse of a mechanism long confined to theory and simulation, now apparently caught in the act around a star only a few million years old.

T-Tauri star

A pre-main-sequence star in an early, still-contracting stage of stellar evolution, not yet stably fusing hydrogen.

exocomet

An icy planetesimal orbiting a star other than the Sun, inferred through its interaction with starlight or circumstellar gas.

protoplanetary disk

The circumstellar disk of gas and dust surrounding a young star, serving as the raw material and setting for planet formation.