Tag Archives: exoplanet

Indian-British Scientist’s Exoplanet Discoveries Stir Hope On Alien Life

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The vast cosmos has always been a source of intrigue, with the quest for life beyond Earth spanning decades. The recent revelation of potential biosignatures on the exoplanet K2-18b has sent ripples through the astronomical community. This has prompted a retrospective look at the past decade of discoveries that have revolutionized our understanding of planetary habitability.

The journey began with NASA’s Kepler mission, which opened the floodgates to the discovery of thousands of exoplanets, planets beyond our solar system. Among these, a select few have been found within the coveted habitable zone, a region around a star where conditions could potentially support liquid water, a key ingredient for life as we know it.

One of the earliest and most celebrated discoveries was Kepler-186f, a rocky planet approximately 500 light-years away from Earth. Similar in size to our home planet and orbiting within its star’s habitable zone, the discovery of Kepler-186f in 2014 marked a significant milestone in the search for Earth-like planets.

New Discoveries

In 2017, the discovery of a system of seven Earth-sized planets orbiting a dim red dwarf named TRAPPIST-1 further piqued the interest of the scientific community. Three of these planets, named e, f, and g, were found within the habitable zone. Their size and proximity to each other made them ideal candidates for atmospheric analysis. However, subsequent studies raised concerns about the extreme stellar flares of their host star, which could potentially strip away their atmospheres, casting a shadow over their habitability.

Closer to home, the discovery of Proxima b in 2016, a mere 4.2 light-years away, sparked global interest. Slightly larger than Earth and orbiting within a potentially temperate zone, Proxima b seemed a promising candidate for life. However, its parent star, Proxima Centauri, is known for its volatility, raising doubts about the planet’s long-term habitability.

In recent years, LHS 1140 b, a dense, rocky planet 40 light-years away, has emerged as a strong contender in the search for extraterrestrial life. With a stable orbit and early indications of an atmosphere, it is a prime target for upcoming investigations by the James Webb Space Telescope (JWST).

The Spotlight on K2-18b

Adding to the growing list of potential life-supporting planets is TOI 700 d, confirmed in 2020 by NASA’s TESS observatory. Receiving nearly the same amount of light as Earth and orbiting a quiet red dwarf, it raises hopes for a relatively undisturbed environment. However, atmospheric data remains elusive, leaving its habitability status uncertain.

The current spotlight, however, is on K2-18b, a sub-Neptune-sized planet first identified in 2015. Located 124 light-years away, the planet has shown signs of water vapor, methane, and carbon dioxide. In 2023, astronomer Nikku Madhusudhan and his team reported faint traces of dimethyl sulfide (DMS), a molecule produced on Earth only by life. New observations in 2025 using a different JWST instrument strengthened the case for DMS and a related compound, dimethyl disulfide (DMDS).

Despite these promising findings, experts urge caution. Dr. Ryan MacDonald of the University of Michigan stated, “These new JWST observations do not offer convincing evidence that DMS or DMDS are present.” Others, like NASA’s Nicholas Wogan, have acknowledged the improved data but stress the need for independent verification.

The consensus among scientists is that while these planets show potential, confirming life—or even just conditions for it—remains an immense challenge. The “five-sigma” statistical confidence required to claim a discovery in physics is still a long way off for most of these detections.

As we continue to explore the cosmos, we are reminded of the words of Dr. Thomas Beatty of the University of Wisconsin-Madison, who encapsulated the current state of affairs, saying, “Right now, we’re seeing a lot of ‘maybes.’” He added, “But even a maybe is remarkable, considering how far we’ve come.”

The search for extraterrestrial life has transformed our place in the cosmos—from passive observers to active explorers of worlds that, not so long ago, existed only in science fiction. As technology advances and instruments like JWST continue to refine their vision, the quest continues, reminding us of the vastness of the universe and the potential it holds.

NASA’s Webb Detects Carbon Dioxide in Exoplanet Atmosphere

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NASA’s James Webb Space Telescope has captured the first clear evidence for carbon dioxide in the atmosphere of a planet outside the solar system. This observation of a gas giant planet orbiting a Sun-like star 700 light-years away provides important insights into the composition and formation of the planet. The finding, accepted for publication in Nature, offers evidence that in the future Webb may be able to detect and measure carbon dioxide in the thinner atmospheres of smaller rocky planets.

WASP-39 b is a hot gas giant with a mass roughly one-quarter that of Jupiter (about the same as Saturn) and a diameter 1.3 times greater than Jupiter. Its extreme puffiness is related in part to its high temperature (about 1,600 degrees Fahrenheit or 900 degrees Celsius). Unlike the cooler, more compact gas giants in our solar system, WASP-39 b orbits very close to its star – only about one-eighth the distance between the Sun and Mercury – completing one circuit in just over four Earth-days. The planet’s discovery, reported in 2011, was made based on ground-based detections of the subtle, periodic dimming of light from its host star as the planet transits, or passes in front of the star.

Previous observations from other telescopes, including NASA’s Hubble and Spitzer space telescopes, revealed the presence of water vapor, sodium, and potassium in the planet’s atmosphere. Webb’s unmatched infrared sensitivity has now confirmed the presence of carbon dioxide on this planet as well.

NASA Prepares Webb Telescope /NASA

Filtered Starlight

Transiting planets like WASP-39 b, whose orbits we observe edge-on rather than from above, can provide researchers with ideal opportunities to probe planetary atmospheres.

During a transit, some of the starlight is eclipsed by the planet completely (causing the overall dimming) and some is transmitted through the planet’s atmosphere.

Because different gases absorb different combinations of colors, researchers can analyze small differences in brightness of the transmitted light across a spectrum of wavelengths to determine exactly what an atmosphere is made of. With its combination of inflated atmosphere and frequent transits, WASP-39 b is an ideal target for transmission spectroscopy.

First Clear Detection of Carbon Dioxide

The research team used Webb’s Near-Infrared Spectrograph (NIRSpec) for its observations of WASP-39b. In the resulting spectrum of the exoplanet’s atmosphere, a small hill between 4.1 and 4.6 microns presents the first clear, detailed evidence for carbon dioxide ever detected in a planet outside the solar system.

“As soon as the data appeared on my screen, the whopping carbon dioxide feature grabbed me,” said Zafar Rustamkulov, a graduate student at Johns Hopkins University and member of the JWST Transiting Exoplanet Community Early Release Science team, which undertook this investigation. “It was a special moment, crossing an important threshold in exoplanet sciences.”

No observatory has ever measured such subtle differences in brightness of so many individual colors across the 3 to 5.5-micron range in an exoplanet transmission spectrum before. Access to this part of the spectrum is crucial for measuring abundances of gases like water and methane, as well as carbon dioxide, which are thought to exist in many different types of exoplanets.

“Detecting such a clear signal of carbon dioxide on WASP-39 b bodes well for the detection of atmospheres on smaller, terrestrial-sized planets,” said Natalie Batalha of the University of California at Santa Cruz, who leads the team.

Understanding the composition of a planet’s atmosphere is important because it tells us something about the origin of the planet and how it evolved. “Carbon dioxide molecules are sensitive tracers of the story of planet formation,” said Mike Line of Arizona State University, another member of this research team. “By measuring this carbon dioxide feature, we can determine how much solid versus how much gaseous material was used to form this gas giant planet. In the coming decade, JWST will make this measurement for a variety of planets, providing insight into the details of how planets form and the uniqueness of our own solar system.”

Planet Nine or Exoplanet? Scientists find startling resemblance in star 336 light years away

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As astronomers are looking for a hypothetical “Planet Nine” in our solar system, an exoplanet 336 light years from Earth is looking more like the Planet Nine of its star system.

Planet Nine, potentially 10 times the size of Earth and orbiting far beyond Neptune in a highly eccentric orbit around the sun, was proposed in 2012 to explain perturbations in the orbits of dwarf planets beyond Neptune’s orbit, so-called detached Kuiper Belt objects. However, it has yet to be found, if ever it exists.

A similarly weird extrasolar planet was discovered far from the star HD 106906 in 2013 was much heavier than the predicted mass of Planet Nine at probably 11 times the mass of Jupiter, or 3,500 times the mass of Earth. And it was located in an unexpected location, far above the dust plane of the planetary system and tilted at an angle of about 21 degrees.

It is not known whether the planet, HD 106906 b, is in an orbit perpetually bound to the binary star — which is 15 million years old compared to the 4.5 billion-year age of our sun or on its way out of the planetary system, never to return.

In a paper published on Dec. 10, 2020, in the Astronomical Journal, astronomers answer that question. By precisely tracking the planet’s position over 14 years, they determined that it is likely bound to the star in a 15,000-year, highly eccentric orbit, making it a distant cousin of Planet Nine.

If it is in a highly eccentric orbit around the binary, “This raises the question of how did these planets get out there to such large separations,” said Meiji Nguyen, a recent UC Berkeley graduate and first author of the paper. “Were they scattered from the inner solar system? Or, did they form out there?”

According to senior author Paul Kalas, University of California, Berkeley, the resemblance to the orbit of the proposed Planet Nine shows that such distant planets can really exist and that they may form within the first tens of millions of years of a star’s life. “Something happens very early that starts kicking planets and comets outward, and then you have passing stars that stabilize their orbits,” he said.

What makes HD 106906 unique is that it is the only exoplanet that we know that is directly imaged, surrounded by a debris disk, misaligned, and widely separated, Nguyen said. “This is what makes it the sole candidate we have found thus far whose orbit is analogous to the hypothetical Planet Nine.”

Japan scientist finds 1 out of 15 exoplanets habitable

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Japanese astronomer team led by Teruyuki Hirano of Tokyo Institute of Technology has validated 15 exoplanets orbiting red dwarf systems and found one of them highly akin to Earth and habitable. It could be of particular interest as researchers describe it as a ‘super-Earth’, which could harbour liquid water, and potential alien life.

One of them, K2-155 located around 200 light years away from Earth, has three transiting super-Earths, which are slightly bigger than ours and interestingly the outermost planet, K2-155d, with a radius 1.6 times that of Earth, could be within the host star’s habitable zone, they said.

The findings, published in The Astronomical Journal, are based on data from NASA Kepler spacecraft’s second mission, K2, and other data from the ground-based telescopes, including the Subaru Telescope in Hawaii and the Nordic Optical Telescope (NOT) in Spain.

The Japanese researchers found that K2-155d could potentially have liquid water on its surface based on 3D climate simulations. Hirano said: “In our simulations, the atmosphere and the composition of the planet were assumed to be Earth-like, and there’s no guarantee that this is the case.”

A key outcome from the current studies was that planets orbiting red dwarfs may have remarkably similar characteristics to planets orbiting solar-type stars.

“It’s important to note that the number of planets around red dwarfs is much smaller than the number around solar-type stars,” says Hirano. “Red dwarf systems, especially coolest red dwarfs, are just beginning to be investigated, so they are very exciting targets for future exoplanet research.”

While the radius gap of planets around solar-type stars has been reported previously, this is the first time that researchers have shown a similar gap in planets around red dwarfs. “This is a unique finding, and many theoretical astronomers are now investigating what causes this gap,” says Hirano.

He adds that the most likely explanation for the lack of large planets in the proximity of host stars is photoevaporation, which can strip away the envelope of the planetary atmosphere.

The researchers also investigated the relationship between planet radius and metallicity of the host star. “Large planets are only discovered around metal-rich stars,” Hirano says, “and what we found was consistent with our predictions. The few planets with a radius about three times that of Earth were found orbiting the most metal-rich red dwarfs.”

The studies were conducted as part of the KESPRINT collaboration, a group formed by the merger of KEST (Kepler Exoplanet Science Team) and ESPRINT (Equipo de Seguimiento de Planetas Rocosos Intepretando sus Transitos) in 2016.

With the planned launch of NASA’s Transiting Exoplanet Survey Satellite (TESS) in April 2018, Hirano is hopeful that even more planets will be discovered. “TESS is expected to find many candidate planets around bright stars closer to Earth,” he says. “This will greatly facilitate follow-up observations, including investigation of planetary atmospheres and determining the precise orbit of the planets,” he said.

Figure 1. Results of 3D global climate simulations for K2-155d

Surface temperatures were plotted as a function of insolation flux (the amount of incoming stellar radiation) estimated at 1.67±0.38. When the insolation exceeds 1.5, a so-called runaway greenhouse effect occurs, signaling a cut-off point for life-friendly temperatures. If the insolation is under 1.5, the surface temperature is more likely to be moderate.

Figure 2. Distribution of planet sizes

Histogram of planet radius for the validated and well-characterized transiting planets around red dwarfs: The number counts for mid-to-late red dwarfs (those with a surface temperature of under 3,500 K) are shown above those for early red dwarfs (those with a surface temperature of around 3,500–4,000 K). The results show a “radius gap”, or a dip in the number of stars with a radius between 1.5–2.0 times that of Earth.