DETROIT – One of humanity’s greatest questions remains unanswered: Is life anywhere else in the universe?
Research on this topic accelerated with the first confirmation of an exoplanet (meaning outside of our solar system) back in the 1990s and, since then, 4,000 of these planets have been discovered around stars.
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Many of these planets are deemed to be gas giants, like Jupiter and Saturn. Some are rocky planets like Earth, but with these planets, the important thing to know is location, location, location: too close to its star and it’s too hot for life as we know it; too far and it’s too cold.
So scientists are especially looking for planets in what’s called the “habitable zone” around their stars--not too close, and not too far--like Earth!
And then there’s the case of water: Life as we know it must have water.
That’s why it was huge news this past week when researchers at the University College London Centre for Space Exochemistry Data announced that they have definitively detected water vapor in the atmosphere of a super-Earth exoplanet (they call it a super-Earth because it is eight times the mass of our planet). Its name is K2-18b, and this is the first planet discovered orbiting a star outside our solar system known to have both water and temperatures that could support life as we know it.
One member of the research team, Dr. Angelos Tsiaras, says that “Finding water on a potentially habitable world other than Earth is incredibly exciting. K2-18b is not ‘Earth 2.0,’ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?”
The team used archive data from 2016 and 2017 captured by the NASA/ESA Hubble Space Telescope and developed open-source algorithms to analyze the starlight filtered through K2-18b’s atmosphere. How do they do this? By looking at the star’s light as it is altered after moving through K2-18b’s atmosphere whenever the planet passes in front of it. The results revealed the molecular signature of water vapor, also indicating the presence of hydrogen and helium in the planet’s atmosphere. The researchers believe that other molecules, including nitrogen and methane, may be present but they remain undetectable with current observations. Further studies are required to estimate cloud coverage and the percentage of atmospheric water present.
The planet orbits the cool dwarf star K2-18, which is 110 light years from Earth in the constellation of Leo. Given the high level of activity of its red dwarf star, K2-18b may be more hostile than Earth and is likely to be exposed to more radiation.
K2-18b, discovered in 2015, is one of hundreds of super-Earths — planets with masses between those of Earth and Neptune — found by NASA’s Kepler spacecraft. NASA’s TESS mission is expected to detect hundreds more super-Earths in the coming years.
Another of the researchers, Dr. Ingo Waldmann, said: “With so many new super-Earths expected to be found over the next couple of decades, it is likely that this is the first discovery of many potentially habitable planets. This is not only because super-Earths like K2-18b are the most common planets in our Milky Way, but also because red dwarfs — stars smaller than our sun — are the most common stars.”
The next generation of space telescopes, including the NASA/ESA/CSA James Webb Space Telescope and ESA’s ARIEL mission, will be able to characterize atmospheres in more detail as they will carry more advanced instruments. ARIEL is expected to launch in 2028 and will observe 1,000 planets in detail to get a truly representative picture of what they are like.
An interstellar comet!
A newly discovered comet has excited the astronomical community this week because it appears to have originated from outside the solar system.
The object designated C/2019 Q4 (Borisov) - was discovered Aug. 30 by Gennady Borisov at the MARGO observatory in Nauchnij, Crimea. The official confirmation that comet C/2019 Q4 is an interstellar comet has not yet been made, but if it is interstellar, it would be only the second such object detected. The first, 'Oumuamua, was observed and confirmed in October 2017.
The new comet, C/2019 Q4, is still inbound toward the sun, but it will remain farther than the orbit of Mars and will approach no closer to Earth than about 190 million miles. For perspective, the moon is about 239,000 miles from Earth.
After the initial detection of the comet, Scout System, which is located at NASA's Jet Propulsion Laboratory in Pasadena, California, automatically flagged the object as possibly being interstellar. Davide Farnocchia, of NASA's Center for Near-Earth Object Studies at JPL worked with astronomers and the European Space Agency's Near-Earth Object Coordination Center in Frascati, Italy, to obtain additional observations. He then worked with the NASA-sponsored Minor Planet Center in Cambridge, Massachusetts, to estimate the comet's precise trajectory and determine whether it originated within our solar system or came from elsewhere in the galaxy.
The comet is currently 260 million miles from the sun and will reach its closest point, or perihelion, on Dec. 8 at a distance of about 190 million miles.
"The comet's current velocity is high, about 93,000 mph, which is well above the typical velocities of objects orbiting the sun at that distance," said Farnocchia. "The high velocity indicates not only that the object likely originated from outside our solar system, but also that it will leave and head back to interstellar space."
Currently on an inbound trajectory, comet C/2019 Q4 is heading toward the inner solar system and will enter it on Oct. 26 from above at roughly a 40-degree angle relative to the ecliptic plane. That's the plane in which the Earth and planets orbit the sun.
C/2019 Q4 was established as being cometary due to its fuzzy appearance, which indicates that the object has a central icy body that is producing a surrounding cloud of dust and particles as it approaches the sun and heats up. Its location in the sky (as seen from Earth) places it near the Sun - an area of sky not usually scanned by the large ground-based asteroid surveys or NASA's asteroid-hunting NEOWISE spacecraft.
C/2019 Q4 can be seen with professional telescopes for months to come. "The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020," said Farnocchia. "After that, it will only be observable with larger professional telescopes through October 2020."
Observations completed by Karen Meech and her team at the University of Hawaii indicate the comet nucleus is somewhere between 1.2 and 10 miles in diameter. Astronomers will continue collect observations to further characterize the comet's physical properties (size, rotation, etc.) and also continue to better identify its trajectory.