Some Stars Could Support as Many as 7 Habitable Planets

Most exoplanets orbit red dwarf stars because they're the most plentiful stars. This is an artist's illustration of what the TRAPPIST-1 system might look like from a vantage point near planet TRAPPIST-1f (at right). Credits: NASA/JPL-Caltech

In recent decades, over 4,000 extrasolar planets have been confirmed beyond our Solar System. With so many planets available for study, astronomers have learned a great deal about the types of planets that exist out there and what kind of conditions are prevalent. For instance, they have been able to get a better idea of just how common habitable planets are (at least by our standards).

As it turns out, a surprisingly high number of planets out there could support life. That is the conclusion reached by a team of astronomers and planetary scientists who conducted a study of the possible sizes of habitable zones (HZ) based on stellar classification. After considering many planets could stably orbit within them, they came to the conclusion that stars with no Jupiter-sized gas giants can have as many as seven habitable planets!

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Astronomers Have Found the Star/Exoplanet Combo That’s the Best Twin to the Sun/Earth

At times, it seems like there’s an indundation of announcements featuring discoveries of “Earth-like” planets. And while those announcements are exciting, and scientifically noteworthy, there’s always a little question picking away at them: exactly how Earth-like are they, really?

After all, Earth is defined by its relationship with the Sun.

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An Earth-Sized World Orbiting in its Star’s Habitable Zone Was Found in Older Kepler Data

To date, astronomers have confirmed the existence of 4,144 extrasolar planets in 3,074 systems, with a further 5,094 candidates awaiting confirmation. The majority of these planets were found by the Kepler Space Telescope, which spent nine years (between May of 2009 and February of 2018) monitoring distant stars for transit signals – where a planet passing in front of a star causes a dip in brightness.

And yet, even though it is now defunct, the data that Kepler accumulated over the years continues to lead to new discoveries. For instance, a transatlantic team of researchers recently found a signal in Kepler‘s archival data that eluded detection before. This signal indicates that there is a second planet orbiting Kepler-1649, an M-type red dwarf star located 302 light-years away.

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Five Snapshots of how the Earth Looked at Key Points in its History Could Help us Find Habitable Exoplanets

In the past few decades, astronomers have confirmed the existence of thousands of planets beyond our Solar System. Over time, the process has shifted from discovery to characterization in the hopes of finding which of these planets are capable of supporting life. For the time being, these methods are indirect in nature, which means that astronomers can only infer if a planet is inhabitable based on how closely it resembles Earth.

To aid in the hunt for “potentially habitable” exoplanets, a team of Cornell researchers recently created five models that represent key points in Earth’s evolution. These “snapshots” of what Earth looked like during various geological epochs could greatly enhance the search for extra-terrestrial life by providing a more complete picture of what a life-bearing planet could look like.

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Two Earth-Like Worlds Found Orbiting a Red Dwarf Only 12.5 Light-Years Away

In the past few decades, there has been an explosion in the number of planets discovered beyond our Solar System. With over 4,000 confirmed exoplanets to date, the process has gradually shifted from discovery towards characterization. This consists of using refined techniques to determine just how likely a planet is to be habitable.

At the same time, astronomers continue to make discoveries regularly, some of which are right in our cosmic backyard. For instance, an international team of researchers recently detected two new Earth-like planets orbiting Teegarden’s Star, an M-type (red dwarf) star located just 12.5 light-years from the Solar System in the direction of the Aries constellation.

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Complex Life Might Require a Very Narrow Habitable Zone

Kepler-452b

Since the Kepler Space Telescope was launched into space, the number of known planets beyond our Solar System (exoplanets) has grown exponentially. At present, 3,917 planets have been confirmed in 2,918 star systems, while 3,368 await confirmation. Of these, about 50 orbit within their star’s circumstellar habitable zone (aka. “Goldilocks Zone”) , the distance at which liquid water can exist on a planets’ surface.

However, recent research has raised the possibility that we consider to be a habitable zone is too optimistic. According to a new study that recently appeared online, titled “A Limited Habitable Zone for Complex Life“, habitable zones could be much narrower than originally thought. These finds could have a drastic impact on the number of planets scientists consider to be “potentially habitable”.

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New SPECULOOS Telescope Sees First Light. Soon it’ll be Seeing Habitable Planets Around Ultra-Cool Stars

This first light image from the Callisto telescope at the SPECULOOS Southern Observatory (SSO) shows the famous Horsehead Nebula . First light for a newly commissioned telescope is a tremendously exciting time, and usually well-known astronomical objects such as this are captured to celebrate a new telescope commencing operations. Image Credit: SPECULOOS Team/E. Jehin/ESO

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.

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Exoplanets Will Need Both Continents and Oceans to Form Complex Life

When it comes to the search for extra-terrestrial life, scientists have a tendency to be a bit geocentric – i.e. they look for planets that resemble our own. This is understandable, seeing as how Earth is the only planet that we know of that supports life. As result, those searching for extra-terrestrial life have been looking for planets that are terrestrial (rocky) in nature, orbit within their stars habitable zones, and have enough water on their surfaces.

In the course of discovering several thousand exoplanets, scientists have found that many may in fact be “water worlds” (planets where up to 50% of their mass is water). This naturally raises some questions, like how much water is too much, and could too much land be a problem as well? To address these, a pair of researchers from the Harvard Smithsonian Center for Astrophysics (CfA) conducted a study to determine how the ratio between water and land masses can contribute to life.

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It’s Over For Kepler. The Most Successful Planet Hunter Ever Built is Finally out of Fuel and Has Just Been Shut Down.

NASA's Kepler space telescope, shown in this artist's concept, revealed that there are more planets than stars in the Milky Way galaxy. Credit: NASA

It’s been quite a tumultuous time for space telescopes lately! Less than a month ago, the Hubble Space Telescope went into safe mode after experiencing a mechanical failure with one of its gyroscopes (which has since been remedied). Shortly thereafter, the Chandra X-ray telescope went into safe mode as well, and for similar reasons. After three days, it’s operations team managed to get it back in working order as well.

And now, after nine years of service, NASA has officially announced that the Kepler Space Telescope will be retiring. With no fuel remaining to conduct its science observations, NASA has decided to leave the telescope in its current safe orbit (well away from Earth). Far from being a sad occasion, Kepler’s retirement is an opportunity to reflect upon the immense accomplishments of this telescope and how it revolutionized the study of exoplanets.

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