Skip to main content

Hubble and Spitzer spot two far-off watery worlds

While we have discovered over 5,000 exoplanets to date, most of the information we have about these planets is fairly basic. Researchers typically know about a planet’s mass or radius and its distance from its host star, but little more than that, making it hard to predict what these worlds are actually like. However, new tools and techniques are allowing researchers to learn more about details like a planet’s density, allowing a better understanding of what these places are like.

Recently, researchers using data from the Hubble Space Telescope and Spitzer Space Telescope have identified two planets that seem to be water worlds, with oceans that are 500 times deeper than the oceans on Earth.

In this illustration super-Earth Kepler-138 d is in the foreground. To the left, the planet Kepler-138 c, and in the background the planet Kepler 138 b, seen in silhouette transiting its central star.
In this illustration super-Earth Kepler-138 d is in the foreground. To the left, the planet Kepler-138 c, and in the background the planet Kepler 138 b, seen in silhouette transiting its central star. Kepler 138 is a red dwarf star located 218 light-years away. The low density of Kepler-138 c and Kepler-138 d — which are nearly identical in size — means that they must be composed largely of water. ILLUSTRATION: NASA, ESA, Leah Hustak (STScI)

The planets Kepler-138 c and Kepler-138 d were first identified by the Kepler Space Telescope in 2014, but it wasn’t until recently that data from Hubble and Spitzer was used to reveal their density. Research shows that up to half of the planets’ volume could be made up of water, raising questions about planets of this size and type.

Recommended Videos

“We previously thought that planets that were a bit larger than Earth were big balls of metal and rock, like scaled-up versions of Earth, and that’s why we called them super-Earths,” said one of the researchers, Björn Benneke of the University of Montreal, in a statement. “However, we have now shown that these two planets, Kepler-138 c and d, are quite different in nature and that a big fraction of their entire volume is likely composed of water. It is the best evidence yet for water worlds, a type of planet that was theorized by astronomers to exist for a long time.”

To picture what these watery worlds are like, experts say we should not be thinking about any of the planets in our solar system but rather some of the moons. “Imagine larger versions of Europa or Enceladus, the water-rich moons orbiting Jupiter and Saturn, but brought much closer to their star,” said lead author Caroline Piaulet of the Trottier Institute for Research on Exoplanets. “Instead of an icy surface, they would harbor large water-vapor envelopes.”

However, these planets wouldn’t be really similar to any place in our solar system as the planets in question have extremely hot atmospheres. Instead, they would likely have a thick atmosphere of steam with liquid water at high pressure beneath.

As unusual as that sounds, we may find more similar worlds in the future. “As our instruments and techniques become sensitive enough to find and study planets that are farther from their stars, we might start finding a lot more of these water worlds,” Benneke said.

Georgina Torbet
Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…
Feast your eyes on 10 years of Hubble images of Jupiter, Saturn, Uranus, Neptune
This is a montage of NASA/ESA Hubble Space Telescope views of our solar system's four giant outer planets: Jupiter, Saturn, Uranus, and Neptune, each shown in enhanced color. The images were taken over nearly 10 years, from 2014 to 2024.

While the Hubble Space Telescope might be most famous for its images of beautiful and far-off objects like nebulae or distant galaxies, it also takes images of objects closer to home, including the planets right here in our own solar system. For the past 10 years, Hubble has been studying the outer planets in a project called OPAL (Outer Planet Atmospheres Legacy), capturing regular images of each of the four outer planets so scientists can study their changes over time.

The planets Jupiter, Saturn, Uranus, and Neptune are different in many ways from Earth, as they are gas giants and ice giants rather than rocky planets. But they do have some similar phenomena, such as weather that regularly changes, including epic events like storms that are so large they can be seen from space. Jupiter's Great Red Spot, for example, the big orange-red eye shape that is visible on most images of the planet, is an enormous storm larger than the width of the entire Earth and which has been raging for centuries.

Read more
Webb and Hubble snap the same object for two views of one galaxy
Featured in this NASA/ESA/CSA James Webb Space Telescope Picture of the Month is the spiral galaxy NGC 2090, located in the constellation Columba. This combination of data from Webb’s MIRI and NIRCam instruments shows the galaxy’s two winding spiral arms and the swirling gas and dust of its disc in magnificent and unique detail.

With all the excitement over the last few years for the shiny and new James Webb Space Telescope, it's easy to forget about the grand old master of the space telescopes, Hubble. But although Webb is a successor to Hubble in some ways, with newer technology and the ability to see the universe in even greater detail, it isn't a replacement. A pair of new images shows why: with the same galaxy captured by both Webb and Hubble, you can see the different details picked out by each telescope and why having both of them together is such a great boon for scientists.

The galaxy NGC 2090 was imaged by Webb, shown above, using its MIRI and NIRCam instruments. These instruments operate in the mid-infrared and near-infrared portions of the electromagnetic spectrum respectively, which is why the arms of this galaxy appear to be glowing red. These arms are made of swirling gas and dust, and within them are compounds called polycyclic aromatic hydrocarbons that glow brightly in the infrared. The blue color in the center of the galaxy shows a region of young stars burning hot and bright.

Read more
Creepy cosmic eyes stare out from space in Webb and Hubble image
The gruesome palette of these galaxies is owed to a mix of mid-infrared light from the NASA/ESA/CSA James Webb Space Telescope, and visible and ultraviolet light from the NASA/ESA Hubble Space Telescope. The pair grazed one another millions of years ago. The smaller spiral on the left, catalogued as IC 2163, passed behind NGC 2207, the larger spiral galaxy at right. Both have increased star formation rates. Combined, they are estimated to form the equivalent of two dozen new stars that are the size of the Sun annually. Our Milky Way galaxy forms the equivalent of two or three new Sun-like stars per year. Both galaxies have hosted seven known supernovae, each of which may have cleared space in their arms, rearranging gas and dust that later cooled, and allowed many new stars to form. (Find these areas by looking for the bluest regions).

These sinister eyes gazing out from the depths of space star in a new Halloween-themed image, using data from both the Hubble Space Telescope and the James Webb Space Telescope. It shows a pair of galaxies, IC 2163 on the left and NGC 2207 on the right, which are creeping closer together and interacting to form a creepy-looking face.

The two galaxies aren't colliding directly into one another, as one is passing in front of the other, but they have passed close enough to light scrape by each other and leave indications. If you look closely at the galaxy on the left, you can see how its spiral arms have been pulled out into an elongated shape, likely because of its close pass to the gravity of the other nearby galaxy. The lines of bright red around the "eyes" are created by shock fronts, with material from each galaxy slamming together.

Read more