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EI2GYB > ASTRO 24.10.25 20:55l 79 Lines 10935 Bytes #999 (0) @ WW
BID : 46888_EI2GYB
Subj: This New Super Earth May Have Liquid Water And It's In Our
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Sent: 251024/1843Z 46888@EI2GYB.DGL.IRL.EURO LinBPQ6.0.25
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This New Super Earth May Have Liquid Water And It's In Our Neighbourhood
Is humanity alone in the Milky Way? In the Universe? Are there other sentient species out there that use their minds and technology to investigate and understand Nature as we do? Do other beings wrestle with the same things we do? Do they struggle with their species' dark impulses? Do they suffer through narcissistic, psychopathic rulers who spread carnage across the pages of their histories?
And do they create works of art, literature, and music that pierce their souls? Have the angels of their better nature triumphed?
Who knows. But if there are other beings out their, they're likely residing on a rocky planet similar to Earth. Even if other life is just beginning its prokaryotic adventure, it's likely gained its foothold on a planet similar to ours, where liquid surface water persists.
That's what makes this age of exoplanet discovery so intriguing. Every Earth-similar world we discover represents another opportunity for life to appear, and hopefully, to flourish like Earth life has.
The latest exoplanet discovery in this vein is a super-Earth named GJ 251 c and it was detected by an exquisite and rigorous investigation into light. The discovery is presented in new research published in The Astronomical Journal. It's titled "Discovery of a Nearby Habitable Zone Super-Earth Candidate Amenable to Direct Imaging." Researchers from Penn State University played leading roles in the work, as did powerful technological instruments designed and built by Penn State.
GJ 251 c orbits an M-dwarf star about 18 light years away. The planet is a super-Earth about four times more massive than Earth, and very likely rocky. It's also in its star's habitable zone (HZ), where liquid water can persist on its surface.
"We look for these types of planets because they are our best chance at finding life elsewhere," said Suvrath Mahadevan, the Verne M. Willaman Professor of Astronomy at Penn State and co-author on the paper. "The exoplanet is in the habitable or the 'Goldilocks Zone,' the right distance from its star that liquid water could exist on its surface, if it has the right atmosphere," Mahadevan said in a press release.
"We have found so many exoplanets at this point that discovering a new one is not such a big deal," said co-author Paul Robertson, UC Irvine associate professor of physics & astronomy. "What makes this especially valuable is that its host star is close by, at just about 18 light-years away. Cosmically speaking, it's practically next door," Robertson said in a separate press release.
This discovery has its roots in 2019, when radial velocity studies detected a pair of planets orbiting the dim, low-mass star. A subsequent study cancelled both of those planets, claiming stellar activity caused the detection. Then the existence of one of those planets, the innermost one named GJ 251 b, was confirmed. The confirmation of that planet helped lead to the discovery of GJ 251 c.
The researchers used 20 years of radial velocity data to detect the planet. Radial velocity uses the Doppler shift to detect the extremely faint changes in light coming from a star, caused by planets orbiting the star and tugging on it gravitationally. Stars rotate, and light coming from the approaching side of the star is blue-shifted, while light from the receding half are red-shifted. The gravitational tug of planets produces a nearly imperceptible yet regular change in this light, which powerful spectrographs can detect.
The Penn State-led Habitable Zone Planet Finder (HPF) played a leading role in this detection. The researchers established strong baselines for the wobble caused by the first confirmed exoplanet. Then they took that strong baseline and combined it with new data from the HPF. The existing planet orbits the star every 14 days, but the new data revealed a stronger signal showing a second planet on a 54-day orbit. The researchers then used another Penn State instrument, the NEID spectrometer at Kitt Peak National Observatory, for confirmation.
*The Habitable Zone Planet Finder (HPF) provides the highest precision measurements to date of infrared signals from nearby stars. It's shown here during installation in its clean-room enclosure in the Hobby Eberly Telescope at McDonald Observatory. Image Credit: GuĞmundur Stef nssonn / Penn State. CC BY-NC-ND 4.0*
"We are at the cutting edge of technology and analysis methods with this system," said Corey Beard, corresponding author on the paper who conducted the research while earning a doctorate in astrophysics from the University of California, Irvine. "We need the next generation of telescopes to directly image this candidate, but what we also need is community investment."
Direct imaging is a next step in exoplanet science. Researchers have managed to directly image a handful of exoplanets, but those images are quite limited. They typically show dots or blobs, usually with the star blocked out by a coronagraph. Currently, we only have the technology to image exoplanets in certain conditions. They're either young planets still emitting heat, extremely massive gas giants, or planets on very wide orbits. But these images are still scientifically valuable, and the best direct image is probably of the HR 8799 system.
*The JWST captured the direct images of the iconic HR 8799 system and its four planets. As telescope technology continues to improve, direct imaging of exoplanets will get better. Image Credit: By Image: NASA, ESA, CSA, STScI, Laurent Pueyo (STScI), William Balmer (JHU), Marshall Perrin (STScI) - HR 8799 (NIRCam Image), Public Domain, https://commons.wikimedia.org/w/index.php?curid=162292518*
The biggest obstacle to finding distant exoplanets is the weakness of the signals. It's all about light, and stars are far brighter than the planets that orbit them. A coronagraph can help, but there's an additional obstacle. Stars aren't static. Their light varies over time due to flaring and other stellar activity. That light can confuse the signal, and what might seem like an exoplanet can actually be stellar light pollution.
"This is a hard game in terms of trying to beat down stellar activity as well as measuring its subtle signals, teasing out slight signals from what is essentially this frothing, magnetospheric cauldron of a star surface," Mahadevan said.
Researchers utilize complex models, data analysis, and technology to weed out stellar interference. Mahadevan points out that it takes many people across multiple disciplines and institutions to obtain good results. It's nothing like the old days, when a lone astronomer sat on a stool in front of his telescope with a sketchbook.
"This discovery is a great example of the power of multi-disciplinary research at Penn State," said Eric Ford, distinguished professor astronomy and astrophysics and director of research for Penn State's Institute of Computational & Data Sciences (ICDS). "Mitigating stellar activity noise required not just cutting-edge instrumentation and telescope access, but also customizing the data science methods for the specific needs of this star and combination of instruments. The combination of exquisite data and state-of-the art statistical methods enabled our interdisciplinary team to transform data into an exciting discovery that paves the way for future observatories to search for evidence of life beyond our solar system."
Direct imaging of exoplanets will get a huge boost when the Nancy Grace Roman Space Telescope launches in 2026, although political leadership in the US has threatened to cancel the nearly-completed telescope. It has the potential to directly image exoplanets with as much 1000 times more detail than any current telescope, and will be especially useful at imaging Jupiter-sized worlds. Unfortunately, it's not expected to image Earth-like planets in habitable zones.
*An illustration of the Nancy Grace Roman Space Telescope. The Roman will have a field of view 100 times larger than the Hubble's. One of its science goals is to use its coronagraph and directly image exoplanets around our nearest neighbouring stars. Image Credit: NASA GSFC*
But NASA's Habitable Worlds Observatory (HWO) should be able to. It's primary mission is to image Earth-size rocky planets in habitable zones. Currently, the HWO is only a proposed mission. But if it or something like it gets built, it will be a proverbial game-changer.
Upcoming ground-based telescopes in the 30 meter range are coming online in the near future, and they should be able to directly image exoplanets, especially close ones like GJ 251 c. One way or another, we're poised to get a growing number of direct images of exoplanets. Who knows what we'll find?
It's possible we'll never discover life on another planet. Maybe there is none. Or maybe one of the exoplanet's we've already discovered is inhabited by simple life. Maybe one of the habitable zone exoplanets we've discovered a great distance awat has intelligent life.
Maybe we've already examined distant stars whose planets host fledgling technological civilizations like ours, but we're currently unaware. Maybe one day we'll contact them and begin some type of stuttering conversation with them, with decades in between each message. At least we'd know we're not alone.
If we keep improving our telescopes, and if we keep hanging on and forestalling our own demise, one day our descendants may have an answer. Maybe we'll even find it on GJ 251 c.
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