Our newest planet-hunting telescope is up and running at the ESO’s Paranal Observatory in the Atacama Desert in Chile. SPECULOOS, which stands for Planets EClipsing ULtra-cOOl Stars, is actually four 1-meter telescopes working together. The first images from the ‘scopes are in, and though it hasn’t found any other Earths yet, the images are still impressive.
How many exoplanets are there? Not that long ago, we didn’t know if there were any. Then we detected a few around pulsars. Then the Kepler spacecraft was launched and it discovered a couple thousand more. Now NASA’s TESS (Transiting Exoplanet Survey Satellite) is operational, and a new study predicts its findings.
Gathering detailed information on exoplanets is extremely difficult. The light from their host star overwhelms the light from the exoplanet, making it difficult for telescopes to see them. But now a team using cutting-edge technology at the Keck Observatory has taken a big leap in exoplanet observation and has detected water in the atmosphere of a planet 179 light years away.
A powerful laser is just the thing to announce our presence as a technological species in this arm of the galaxy. Engineers would line up to work on that project. But is it a good idea to let any mysterious galactic neighbours know we’re here?
Continue reading “We Could Build a Powerful Laser and Let Any Civilizations Within 20,000 Light-Years Know We’re Here. Although… Should We?”
The most common type of star in the galaxy is the red dwarf star. None of these small, dim stars can be seen from Earth with the naked eye, but they can emit flares far more powerful than anything our Sun emits. Two astronomers using the Hubble space telescope saw a red dwarf star give off a powerful type of flare called a superflare. That’s bad news for any planets in these stars’ so-called habitable zones.
Red dwarfs make up about 75% of the stars in the Milky Way, so they probably host many exoplanets. In fact, scientists think most of the planets that are in habitable zones are orbiting red dwarfs. But the more astronomers observe these stars, the more they’re becoming aware of just how chaotic and energetic it can be in their neighbourhoods. That means we might have to re-think what habitable zone means.
“When I realized the sheer amount of light the superflare emitted, I sat looking at my computer screen for quite some time just thinking, ‘Whoa.'” – Parke Loyd, Arizona State University.
What exactly is a “normal” solar system? If we thought we had some idea in the past, we definitely don’t now. And a new study led by astronomers at Cambridge University has reinforced this fact. The new study found four gas giant planets, similar to our own Jupiter and Saturn, orbiting a very young star called CI Tau. And one of the planets has an extreme orbit that takes it more than a thousand times more distant from the star than the innermost planet.
A pair of astronomers combing through data from the Kepler spacecraft have discovered the first exomoon. The moon is in the Kepler 1625 system about 8,000 light years away, in the constellation Cygnus. It orbits the gas giant Kepler 1625b, and, unlike all the moons in our Solar System, this one is a “gas moon.”
It was only a matter of time before we found an exomoon. We’ve found thousands of exoplanets, thanks mostly to the Kepler spacecraft. And where there are planets, we can expect moons. But even though it seemed inevitable, the first confirmed exomoon is still exciting.
NASA is targeting technosignatures in its renewed effort to detect alien civilizations. Congress asked NASA to re-boot its search for other civilizations a few months ago. Their first step towards that goal is the NASA Technosignatures Workshop, held in Houston from September 26th to 28th, 2018.
Continue reading “Technosignatures are NASA’s New Target for Detecting Other Civilizations in Space. Wait. What’s a Technosignature?”
In the past few decades, thousands of extra-solar planets have been discovered within our galaxy. As of July 28th, 2018, a total of 3,374 extra-solar planets have been confirmed in 2,814 planetary systems. While the majority of these planets have been gas giants, an increasing number have been terrestrial (i.e. rocky) in nature and were found to be orbiting within their stars’ respective habitable zones (HZ).
However, as the case of the Solar System shows, HZs do not necessary mean a planet can support life. Even though Venus and Mars are at the inner and the outer edge of the Sun’s HZ (respectively), neither is capable of supporting life on its surface. And with more potentially-habitable planets being discovered all the time, a new study suggests that it might be time to refine our definition of habitable zones.
The study, titled “A more comprehensive habitable zone for finding life on other planets“, recently appeared online. The study was conducted by Dr. Ramses M. Ramirez, a research scientist with the Earth-Life Science Institute at the Tokyo Institute of Technology. For years, Dr. Ramirez has been involved in the study of potentially-habitable worlds and built climate models to assess the processes that make planets habitable.
As Dr. Ramirez indicated in his study, the most generic definition of a habitable zone is the circular region around a star where surface temperatures on an orbiting body would be sufficient to maintain water in a liquid state. However, this alone does not mean a planet is habitable, and additional considerations need to be taken into account to determine if life could truly exist there. As Dr. Ramirez told Universe Today via email:
“The most popular incarnation of the HZ is the classical HZ. This classical definition assumes that the most important greenhouse gases in potentially habitable planets are carbon dioxide and water vapor. It also assumes that habitability on such planets is sustained by the carbonate-silicate cycle, as is the case for the Earth. On our planet, the carbonate-silicate cycle is powered by plate tectonics.
“The carbonate-silicate cycle regulates the transfer of carbon dioxide between the atmosphere, surface, and interior of the Earth. It acts as a planetary thermostat over long timescales and ensures that there is not too much CO2 in the atmosphere (the planet gets too hot) or too little (the planet gets too cold). The classical HZ also (typically) assumes that habitable planets possess total water inventories (e.g. total water in the oceans and seas) similar in size to that on the Earth.”
This is what can be referred to as the “low-hanging fruit” approach, where scientists have looked for signs of habitability based on what we as humans are most familiar with. Given that the only example we have of habitability is planet Earth, exoplanet studies have been focused on finding planets that are “Earth-like” in composition (i.e. rocky), orbit, and size.
However, in recent years this definition has come to be challenged by newer studies. As exoplanet research has moved away from merely detecting and confirming the existence of bodies around other stars and moved into characterization, newer formulations of HZs have emerged that have attempted to capture the diversity of potentially-habitable worlds.
As Dr. Ramirez explained, these newer formulations have complimented traditional notions of HZs by considering that habitable planets may have different atmospheric compositions:
“For instance, they consider the influence of additional greenhouses gases, like CH4 and H2, both of which have been considered important for early conditions on both Earth and Mars. The addition of these gases makes the habitable zone wider than what would be predicted by the classical HZ definition. This is great, because planets thought to be outside the HZ, like TRAPPIST-1h, may now be within it. It has also been argued that planets with dense CO2-CH4 atmospheres near the outer edge of the HZ of hotter stars may be inhabited because it is hard to sustain such atmospheres without the presence of life.”
One such study was conducted by Dr. Ramirez and Lisa Kaltenegger, an associate professor with the Carl Sagan Institute at Cornell University. According to a paper they produced in 2017, which appeared in the Astrophysical Journal Letters, exoplanet-hunters could find planets that would one day become habitable based on the presence of volcanic activity – which would be discernible through the presence of hydrogen gas (H2) in their atmospheres.
This theory is a natural extension of the search for “Earth-like” conditions, which considers that Earth’s atmosphere was not always as it is today. Basically, planetary scientists theorize that billions of years ago, Earth’s early atmosphere had an abundant supply of hydrogen gas (H2) due to volcanic outgassing and interaction between hydrogen and nitrogen molecules in this atmosphere is what kept the Earth warm long enough for life to develop.
In Earth’s case, this hydrogen eventually escaped into space, which is believed to be the case for all terrestrial planets. However, on a planet where there is sufficient levels of volcanic activity, the presence of hydrogen gas in the atmosphere could be maintained, thus allowing for a greenhouse effect that would keep their surfaces warm. In this respect, the presence of hydrogen gas in a planet’s atmosphere could extend a star’s HZ.
According to Ramirez, there is also the factor of time, which is not typically taken into account when assessing HZs. In short, stars evolve over time and put out varying levels of radiation based on their age. This has the effect of altering where a star’s HZ reaches, which may not encompass a planet that is currently being studied. As Ramirez explained:
“[I]t has been shown that M-dwarfs (really cool stars) are so bright and hot when they first form that they can desiccate any young planets that are later determined to be in the classical HZ. This underscores the point that just because a planet is currently located in the habitable zone, it doesn’t mean that it is actually habitable (let alone inhabited). We should be able to watch out for these cases.
Finally, there is the issue of what kinds of star system astronomers have been observing in the hunt for exoplanets. Whereas many surveys have examined G-type yellow dwarf star (which is what our Sun is), much research has been focused on M-type (red dwarf) stars of late because of their longevity and the fact that they believed to be the most likely place to find rocky planets that orbit within their stars’ HZs.
“Whereas most previous studies have focused on single star systems, recent work suggests that habitable planets may be found in binary star systems or even red giant or white dwarf systems, potentially habitable planets may also take the form of desert worlds or even ocean worlds that are much wetter than the Earth,” says Ramirez. “Such formulations not only greatly expand the parameter space of potentially habitable planets to search for, but they allow us to filter out the worlds that are most (and least) likely to host life.”
In the end, this study shows that the classical HZ is not the only tool that can be used to asses the possibility of extra-terrestrial life. As such, Ramirez recommends that in the future, astronomers and exoplanet-hunters should supplement the classical HZ with the additional considerations raised by these newer formulations. In so doing, they just may be able to maximize their chances for finding life someday.
“I recommend that scientists pay real special attention to the early stages of planetary systems because that helps determine the likelihood that a planet that is currently located in the present day habitable zone is actually worth studying further for more evidence of life,” he said. “I also recommend that the various HZ definitions are used in conjunction so that we can best determine which planets are most likely to host life. That way we can rank these planets and determine which ones to spend most of our telescope time and energy on. Along the way we would also be testing how valid the HZ concept is, including determining how universal the carbonate-silicate cycle is on a cosmic scale.”
Further Reading: arXiv
Finally, a big update. Have there been news in the realm of exoplanets? More news that we can possibly cover. But we’ll try our best.
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