Extrasolar Planets Archives

July 30, 2023July 30, 2023 by Matt Williams

The PLATO Mission Could be the Most Successful Planet Hunter Ever

Artist's impression of the ESA's PLATO mission. Credit: ESA/ATG medialab

In 2026, the European Space Agency (ESA) will launch its next-generation exoplanet-hunting mission, the PLAnetary Transits and Oscillations of stars (PLATO). This mission will scan over 245,000 main-sequence F, G, and K-type (yellow-white, yellow, and orange) stars using the Transit Method to look for possible Earth-like planets orbiting Solar analogs. In keeping with the “low-hanging fruit” approach (aka. follow the water), these planets are considered strong candidates for habitability since they are most likely to have all the conditions that gave rise to life here on Earth.

Knowing how many planets PLATO will likely detect and how many will conform to Earth-like characteristics is essential to determining how and where it should dedicate its observation time. According to a new study that will be published shortly in the journal Astronomy & Astrophysics, the PLATO mission is likely to find tens of thousands of planets. Depending on several parameters, they further indicate that it could detect a minimum of 500 Earth-sized planets, about a dozen of which will have favorable orbits around G-type (Sun-like) stars.

May 18, 2023May 18, 2023 by Nancy Atkinson

Astronomers Find an Earth-Sized World That May Be Carpeted in Volcanoes

LP 791-18 d, shown here in an artist's concept, is an Earth-size world about 90 light-years away. The gravitational tug from a more massive planet in the system, shown as a blue disk in the background, may result in internal heating and volcanic eruptions – as much as Jupiter’s moon Io, the most geologically active body in the solar system. Credits: NASA’s Goddard Space Flight Center/Chris Smith (KRBwyle)

Astronomers think they’ve found an extrasolar planet covered in volcanoes like Jupiter’s moon Io, but this world is about the same size as Earth. Designated LP 791-18 d, the planet is probably tidally locked around a small, red dwarf star about 90 light-years away in the constellation Crater. There are two other more massive planets in the system, and their tidal interactions could cause enough tidal flexing that it unleashes planet-wide volcanoes on LP 791-18 d.

Planet d is located within the habitable zone of the star, and with all the other conditions, astronomers think it might be temperate enough on the permanent night side of this world to allow water to exist.

May 3, 2023May 3, 2023 by Matt Williams

JWST Tries to Untangle the Signals of Water. Is it Coming From the Planet or the Star?

This artist concept represents the rocky exoplanet GJ 486 b. Credits: NASA, ESA, CSA, Joseph Olmsted (STScI)

The number of known extrasolar planets has exploded in the past few decades, with 5,338 confirmed planets in 4,001 systems (and another 9,443 awaiting confirmation). When it comes to “Earth-like” planets (aka. rocky), the most likely place to find them is in orbit around M-type red dwarf stars. These account for between 75 and 80% of all stars in the known Universe, are several times smaller than the Sun and are quite cool and dim by comparison. They are also prone to flare activity and have very tight Habitable Zones (HZs), meaning that planets must orbit very closely to get enough heat and radiation.

In addition, red dwarfs are highly-active when they are young, exposing planets in their HZs to lots of ultraviolet and X-ray radiation. As such, whether planets orbiting these stars can maintain or reestablish their atmospheres over time is an open question. Using the James Webb Space Telescope (JWST), researchers from the Space Telescope Science Institute (STScI) observed an exoplanet known as GJ 486 b. As they stated in a recent study, the team detected traces of water vapor, though it is unclear if the signal was coming from the planet or its parent star.

April 26, 2023April 26, 2023 by Matt Williams

The Next Generation of Telescopes Will Tell Us About the Weather on Other Worlds

This artist’s rendering shows the Extremely Large Telescope in operation on Cerro Armazones in northern Chile. The telescope is shown using lasers to create artificial stars high in the atmosphere. Image: ESO/E-ELT

The field of astronomy is about to be revolutionized, thanks to the introduction of Extremely Large Telescopes that rely on primary mirrors measuring 30 meters (or more) in diameter, adaptive optics (AO), coronographs, and advanced spectrometers. This will include the eponymously-named Extremely Large Telescope (ELT), the Giant Magellan Telescope (GMT), and the Thirty Meter Telescope (TMT). These telescopes will enable astronomers to study exoplanets using the Direct Imaging (DI) method, which will yield valuable data on the composition of their atmospheres.

According to a new study by a team of researchers from Ohio State University (OSU), these telescopes will also allow astronomers to study “ultracool objects,” like very low-mass stars (VLMs), brown dwarfs, and exoplanets. In addition to being able to visualize magnetic starspots and determine the chemical compositions of these objects, ELTs will be able to reveal details about atmospheric dynamics and cloud systems. These types of studies could reveal a wealth of information about some of the least-studied objects in our Universe and significantly aid in the search for life beyond our Solar System.

March 28, 2023March 28, 2023 by Matt Williams

Moons Orbiting Rogue Planets Could be Habitable

An artist's conception of a potentially-habitable exomoon. It seems reasonable that exoplanets have exomoons, and now we're going to look for them. Credit: NASA

When looking for signs of life beyond the Solar System, astrobiologists are confined to looking for life as we understand it. For the most part, that means looking for rocky planets that orbit within their star’s circumsolar habitable zone (HZ), the distance at which liquid water can exist on its surface. In the coming years, next-generation telescopes and instruments will allow astronomers to characterize exoplanet atmospheres like never before. When that happens, they will look for the chemical signatures we associate with life, like nitrogen, oxygen, carbon dioxide, methane, and ammonia.

However, astrobiologists have theorized that life could exist in the outer Solar System beneath the surfaces of icy moons like Europa, Callisto, Titan, and other “Ocean Worlds.” Because of this, there is no shortage of astrobiologists who think that the search for extraterrestrial life should include exomoons, including those that orbit free-floating planets (FFPs). In a recent study, researchers led by the Max Planck Institute for Extraterrestrial Physics (MPE) determined the necessary properties that allow moons orbiting FFPs to retain enough liquid water to support life.

March 21, 2023March 21, 2023 by Matt Williams

A New Mission Will Search for Habitable Planets at Alpha Centauri

Artist's impression of a hypothetical planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Credit: ESO

Alpha Centauri is our closest stellar neighbor, a binary star system located just 4.376 light-years away. Despite its proximity, repeated astronomical surveys have failed to find hard evidence of extrasolar planets in this system. Part of the problem is that the system consists of two stars orbiting each other, which makes detecting exoplanets through the two most popular methods very challenging. In 2019, Breakthrough Initiatives announced they were backing a new project to find exoplanets next door – the Telescope for Orbit Locus Interferometric Monitoring of our Astronomical Neighbourhood (TOLIMAN, after the star’s ancient name in Arabic).

This low-cost mission concept was designed by a team from the University of Sydney, Australia, and aims to look for potentially-habitable exoplanets in the Alpha Centauri system using the Astrometry Method. This consists of monitoring a star’s apparent position in the sky for signs of wobble, indicating that gravitational forces (like planets) are acting on it. Recently, the University of Sydney signed a contract with EnduroSat, a leading microsatellites and space services provider, to provide the delivery system and custom-built minisatellite that will support the mission when it launches.

March 20, 2023March 20, 2023 by Matt Williams

Sci-Fi Christmas is Ruined! Planet Vulcan Doesn’t Exist

Fans of Star Trek were over the Moon when, in 2018, astronomers with the Dharma Planet Survey (DPS) announced the possible detection of 40 Eridani b, an extrasolar planet in the star system 40 Eridani. Located just 16.3 light-years away, this triple-star system happens to be where the planet Vulcan was located in the popular franchise. Based on radial velocity measurements of the system’s primary star (40 Eridani A), the discovery team estimated that “Vulcan” was a rocky planet several times the mass of Earth (a Super-Earth) with an orbital period of 42 days or so.

The existence of this exoplanet has remained a controversial subject ever since. A study released in 2021 concluded that the signal was a false positive, but the debate remained open. Now, according to a new study by an international team of researchers, the detection of 40 Eridani b was a false positive that astronomers mistook for an exoplanet. The study was part of an archival review of exoplanets to identify promising candidates for follow-up studies. So while “Vulcan” is currently off the table, these results could lead to other exciting discoveries in the coming years.

February 28, 2023March 1, 2023 by Matt Williams

Do Red Dwarfs Provide Enough Sunlight for Plants to Grow?

This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser

To date, 5,250 extrasolar planets have been confirmed in 3,921 systems, with another 9,208 candidates awaiting confirmation. Of these, 195 planets have been identified as “terrestrial” (or “Earth-like“), meaning that they are similar in size, mass, and composition to Earth. Interestingly, many of these planets have been found orbiting within the circumsolar habitable zones (aka. “Goldilocks zone”) of M-type red dwarf stars. Examples include the closest exoplanet to the Solar System (Proxima b) and the seven-planet system of TRAPPIST-1.

These discoveries have further fueled the debate of whether or not these planets could be “potentially-habitable,” with arguments emphasizing everything from tidal locking, flare activity, the presence of water, too much water (i.e., “water worlds“), and more. In a new study from the University of Padua, a team of astrobiologists simulated how photosynthetic organisms (cyanobacteria) would fare on a planet orbiting a red dwarf. Their results experimentally demonstrated that oxygen photosynthesis could occur under red suns, which is good news for those looking for life beyond Earth!

February 25, 2023February 25, 2023 by Matt Williams

Astronomers Suspected There Should Be a Planet Here, and Then They Took a Picture of it

Direct images of AF Lep b, acquired by the SPHERE instrument on the VLT. Credit: ESO/Paranal Observatory

To date, astronomers have confirmed 5,272 exoplanets in 3,943 systems using a variety of detection methods. Of these, 1,834 are Neptune-like, 1,636 are gas giants (Jupiter-sized or larger), 1,602 are rocky planets several times the size and mass of Earth (Super-Earths), and 195 have been Earth-like. With so many exoplanets available for study (and next-generation instruments optimized for the task), the process is shifting from discovery to characterization. And discoveries, which are happening regularly, are providing teasers of what astronomers will likely see in the near future.

For example, two international teams of astronomers independently discovered a gas giant several times the mass of Jupiter orbiting a Sun-like star about 87.5 light-years from Earth. In a series of new papers that appeared in Astronomy & Astrophysics, the teams report the detection of a Super-Jupiter orbiting AF Leporis (AF Lep b) using a combination of astrometry and direct imaging. The images they acquired using the Spectro-Polarimetric High-contrast Exoplanet REsearch instrument (SPHERE) have since become the ESO’s Picture of the Week.

February 25, 2023February 25, 2023 by Matt Williams

59 New Planets Discovered in Our Neighborhood

An artist’s concept of a high-resolution image of an Earth-size planet in the cool range of the habitable zone of a nearby M dwarf. © José A. Caballero (CAB, CSIC-INTA), Javier Bollaín (Render Area)

The hunt for habitable extrasolar planets continues! Thanks to dedicated missions like Kepler, TESS, and Hubble, the number of confirmed extrasolar planets has exploded in the past fifteen years (with 5,272 confirmed and counting!). At the same time, next-generation telescopes, spectrometers, and advanced imaging techniques are allowing astronomers to study exoplanet atmospheres more closely. In short, the field is shifting from the process of discovery to characterization, allowing astronomers to more tightly constraint habitability.

Finding potentially-habitable “Earth-like” planets around these fainter stars is the purpose of the Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Echelle Spectrographs (CARMENES), located at the Calar Alto Observatory in Spain. In a study that appeared in Astronomy & Astrophysics today, the CARMENES Consortium published data (Data Release 1) data from about 20,000 observations taken between 2016 and 2020. Among the measurements obtained from 362 nearby cool stars, the DR1 contained data on 59 new planets.