Washington:

Astronomers have searched for years for rocky planets beyond our solar system with an atmosphere – a trait considered essential for any possibility of harboring life. Well, they finally seem to have located one. But this hellish planet – apparently with a surface of molten rock – offers no hope for habitability.

Researchers said on Wednesday the planet is a “super-Earth” – a rocky world significantly larger than our planet but smaller than Neptune – and it orbits perilously close to a star dimmer and slightly less massive than our sun, rapidly completing an orbit every 18 hours or so.

Infrared observations using two instruments aboard the James Webb Space Telescope indicated the presence of a substantial – if inhospitable – atmosphere, perhaps continuously replenished by gases released from a vast ocean of magma.

“The atmosphere is likely rich in carbon dioxide or carbon monoxide, but can also have other gases such as water vapor and sulfur dioxide. The current observations cannot pinpoint the exact atmospheric composition,” said planetary scientist Renyu Hu of NASA’s Jet Propulsion Laboratory and Caltech, lead author of the study published in the journal Nature.

The Webb data also did not make clear the thickness of the atmosphere. Hu said it could be as thick as Earth’s or even thicker than that of Venus, whose toxic atmosphere is the densest in our solar system.

The planet, called 55 Cancri e or Janssen, is about 8.8 times more massive than Earth, with a diameter about twice that of our planet. It orbits its star at one-25th the distance between our solar system’s innermost planet Mercury and the sun. As a result, its surface temperature is about 3,140 degrees Fahrenheit (1,725 degrees Celsius/2,000 degrees Kelvin).

“Indeed, this is one of the hottest-known rocky exoplanets,” said astrophysicist and study co-author Brice-Olivier Demory of the University of Bern’s Center for Space and Habitability in Switzerland, using the term for planets beyond our solar system. “There are likely better places for a vacation spot in our galaxy.”

The planet is probably tidally locked, meaning it perpetually has the same side facing its star, much like the moon does toward Earth. The planet is located in our Milky Way galaxy about 41 light-years from Earth, in the constellation Cancer. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). Four other planets, all gas giants, are known to orbit its host star.

That star is gravitationally bound to another star in a binary system. The other one is a red dwarf, the smallest kind of ordinary star. The distance between these companions is 1,000 times the distance between Earth and the sun, and light takes six days to get from one to the other.

After all their searching, the rocky exoplanet for which scientists finally found evidence of an atmosphere turned out to be one that probably should not even have one. Being so close to its star, any atmosphere should be stripped away by stellar irradiation and winds. But gases dissolved in the vast lava ocean thought to cover the planet may keep bubbling up to replenish the atmosphere, Hu said.

“The planet cannot be habitable,” Hu said, because it is too hot to have liquid water, considered a prerequisite for life.

All of the previous exoplanets found to have atmospheres were gaseous planets, not rocky ones. As Webb pushes the frontiers of exoplanet exploration, the discovery of a rocky one with an atmosphere represents progress.

On Earth, the atmosphere warms the planet, contains the oxygen people breathe, protects against solar radiation and creates the pressure needed for liquid water to remain on the planet’s surface.

“On Earth, atmosphere is key for life,” Demory said. “This result on 55 Cnc e entertains the hope that Webb could conduct similar investigations on planets that are much cooler than 55 Cnc e, which could support liquid water at their surface. But we are not there yet.”

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

Are we alone? This question is nearly as old as humanity itself. Today, this question in astronomy focuses on finding life beyond our planet. Are we, as a species, and as a planet, alone? Or is there life somewhere else?

Usually the question inspires visions of weird, green versions of humans. However, life is more than just us: animals, fish, plants and even bacteria are all the kinds of things we seek signs of in space.

One thing about life on Earth is that it leaves traces in the chemical makeup of the atmosphere. So traces like that, which are visible from a long way away, are something we look for when we’re hunting aliens.

Scientists in the United Kingdom and the United States have just reported some very interesting chemical traces in the atmosphere of a planet called K2-18b, which is about 124 light-years from Earth. In particular, they may have detected a substance which on Earth is only produced by living things.

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Meet exoplanet K2-18b

K2-18b is an interesting exoplanet – a planet that orbits another star. Discovered in 2015 by the Kepler Space Telescope’s K2 mission, it is a type of planet called a sub-Neptune. As you probably guessed, these are smaller than Neptune in our own Solar System.

The planet is about eight and a half times heavier than Earth, and orbits a type of star called a red dwarf, which is much cooler than our Sun. However, K2-18b orbits much closer to its star than Neptune does – in what we call the habitable zone. This is the area that is not too hot and not too cold, where liquid water can exist (instead of freezing to ice or boiling into steam).

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Earth is what is called a rocky planet (for obvious reasons), but sub-Neptunes are gas planets, with much larger atmospheres containing lots of hydrogen and helium. Their atmosphere can also contain other elements.

Which brings us to the excitement around K2-18b.

How to fingerprint an atmosphere

The planet was first discovered by the Kepler Space Telescope, which was monitoring distant stars and hoping for planets to pass in front of them. When a planet does pass between us and a star, the star becomes momentarily dimmer – which is what tells us a planet is there.

By measuring how big the dip in brightness is, how long it takes for the planet to pass in front of the star, and how often it happens, we can work out the size and orbit of the planet. This technique is great at finding planets, but it doesn’t tell us about their atmospheres – which is a key piece of information to understand if they hold life or are habitable.

NASA’s James Webb Space Telescope – the big space telescope launched at the end of 2021 – has now observed and measured the atmosphere of this exoplanet.

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The telescope did this by measuring the colour of light so finely, it can detect traces of specific atoms and molecules. This process, called spectroscopy, is like measuring the fingerprint of elements.

Each element and molecule has its own colour signature. If you can look at the colour signature, you can do a bit of detective work, and work out what elements or compounds are in the planet.

While the planet does not have its own light, astronomers waited for when K2-18b passed in front of its star, and measured the starlight as it went through the planet’s atmosphere, allowing the team to detect fingerprints of substances in the atmosphere.

Alien marine farts?

The new study found a lot of carbon dioxide and methane. This is interesting as this is like what is found on Earth, Mars, and Venus in our Solar System – rather than Neptune.

However, it also found a small amount of dimethyl sulfide. Dimethyl sulfide is an interesting molecule, made up of carbon, hydrogen, and sulfur.

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On Earth, it’s generally a bit smelly. But it’s also closely linked to life.

The only process we know that creates dimethyl sulfide on our planet is life. In particular, marine life and plankton emit it in the form of flatulence.

So yes, scientists are excited by the potential idea of alien marine farts. If it is real. And linked to life.

The search continues

While on Earth, dimethyl sulfide is linked to life, on other planets it may somehow be related to geological or chemical processes.

After all, K2-18b is something like Neptune – a planet we do not really know a lot about. Just last month, researchers discovered that clouds on Neptune are strongly linked to the Sun’s 11-year cycle of activity. We have a lot to learn about planets and their atmospheres.

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Also, the measurement of dimethyl sulfide is very subtle – not nearly as strong as the carbon dioxide and methane. This means more detailed measurements, to improve the strength of the signal, are required.

Other telescopes may need to join the effort. Instruments on the Very Large Telescope in Chile are able to measure the atmospheres of planets around other stars – as is a new instrument called Veloce on the Anglo Australian Telescope at Siding Spring Observatory in Australia.

And new space telescopes, like Europe’s PLATO which is under construction, will also help us get a better look at alien atmospheres.

So while the signs of dimethyl sulfide on K2-18b may not be linked to life, they are still an exciting prospect. There is plenty more to explore.

The interaction between a supermassive black hole in a galaxy named 2MASX J02301709+2836050 and a star orbiting it is seen in this image captured by the Pan-STARRS telescope, in Hawaii, U.S., in an undated handout image provided by NASA.
| Photo Credit: Reuters

Black holes, celestial objects known for their gluttony, usually eat stars unlucky enough to stray too close to them in one big gulp, annihilating them with their enormous gravitational pull. But some, it turns out, tend to snack rather than gorge.

Researchers said they have observed a supermassive black hole at the center of a relatively nearby galaxy as it takes bites out of a star similar in size and composition to our sun, consuming material equal to about three times Earth’s mass each time the star makes a close pass on its elongated oval-shaped obit.

Black holes are extraordinarily dense objects with gravity so strong that not even light can escape.

The star is located about 520 million light years from our solar system. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km). It was observed being plundered by a supermassive black hole at the heart of a spiral-shaped galaxy.

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As such black holes go, this one is relatively small, estimated to have a mass a few hundred thousand times larger than the sun. The supermassive black hole at the center of our galaxy, called Sagittarius A*, possesses about 4 million times the mass of our sun. Some other galaxies harbor supermassive black holes hundreds of millions times the mass of the sun.

Most galaxies have such black holes at their center, and the environment around them can be among the most violent places in the universe.

Most of the data used by the scientists in the new study came from NASA’s orbiting Neil Gehrels Swift Observatory.

The star was observed orbiting the black hole every 20 to 30 days. At one end of its orbit, it ventures near enough to the black hole to have some material from its stellar atmosphere sucked away, or accreted, each time it passes – but not so close as to have the whole star shredded. Such an event is called a “repeating partial tidal disruption.”

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The stellar material that falls into the black hole heats up to around 3.6 million degrees Fahrenheit (2 million degrees Celsius), unleashing an immense amount of X-rays. Those were detected by the space observatory.

“What’s most likely to happen is the star’s orbit will gradually decay and it will get closer and closer to the supermassive black hole until it gets close enough to be completely disrupted,” said astrophysicist Rob Eyles-Ferris of the University of Leicester in England, one of the authors of the study published this week in the journal Nature Astronomy.

“That process is likely to take years at least – more likely decades or centuries,” Eyles-Ferris added.

This marked the first time that scientists had observed a sun-like star being repeatedly snacked upon by a supermassive black hole.

“There are lots of unanswered questions about tidal disruption events and exactly how the orbit of the star affects them,” Eyles-Ferris said. “It’s a very fast-moving field at the moment. This one has shown us that new discoveries could come at any time.”