There are planets outside our solar system known as exoplanets that orbit stars beyond our own sun.
Proxima Centauri b is the nearest exoplanet to Earth and potential potentially habitable exoplanet, four light years away and orbiting Proxima Centauri star system.
Proxima Centauri
Astronomers have discovered a planet known as Proxima Centauri b that is Earth-sized and orbiting the nearest star to our Sun. It lies within its habitable zone and could contain liquid water on its surface – prompting speculation that humans could one day visit it; however, scientists are yet to be able to establish whether or not it is suitable for life.
On 24 August, Proxima Centauri b was finally discovered thanks to years of hard work. Astronomers used the radial velocity method – where telescopes examine stars for changes in light frequency as they orbit planets – as a method to spot new planets orbiting it. Proxima Centauri’s red dwarf nature makes this technique particularly challenging as its light tends to flare up dramatically and hide any planet-induced signals.
Proxima Centauri b, also known as PC-1, was discovered in 2016. It is the nearest exoplanet to Earth with an approximate mass 3.2 times greater than Earth, likely featuring rocky surfaces and liquid water; and orbiting Proxima Centauri every 11.2-days.
As it lies closest to our Sun, Europa may provide the ideal environment for an extraterrestrial life form to exist and thrive. While its closeness may make it warmer than Earth, its icy surface could protect it from harsh radiation found more commonly on rocky planets like Venus and Mars.
The team that discovered this planet employed ESO’s 3.6-metre Very Large Telescope (VLT), specifically its HARPS instrument, to observe a star’s spectrum for signs of five-day periodic signals indicating planet presence, followed by follow-up observations with even higher precision via the VLT’s ESPRESSO instrument.
The team analyzed additional data from Proxima Centauri star system, such as its asteroid belt, in order to understand how its stars and planets formed. It’s believed that its mass is roughly equivalent to that of our Sun, having formed from debris left from two smaller red dwarf stars merging together over time.
Wolf 1069
Astronomers have identified more than 5,000 exoplanets to date, though only a select few fit into the habitable zone of their host stars. Wolf 1069 b, recently discovered by Diana Kossakowski of the Max Planck Institute for Astronomy is one such candidate planet; researchers believe its orbit around its host red dwarf star could sustain life-supportive temperatures that support life forms on this distant world.
The newly identified exoplanet may resemble Earth, with similar temperatures and likely having an atmosphere. According to its discovery team, an atmosphere may help shield its planet from high-energy electromagnetic radiation from its host star as part of stellar wind; additionally, an atmosphere would protect it against extreme ultraviolet radiation which can strip away surface layers of planets rendering them inhabitable.
The team’s study, published in Astronomy & Astrophysics journal, also notes that Wolf 1069 b is likely tidally locked; that is, one side always faces its host star at all times. However, this doesn’t have to be an insurmountable hurdle: in fact, as long as there remains sufficient contact between its surface and that of Wolf 1069 b’s host star for sustainable habitability to exist, tidal locking may provide sustainable habitability solutions.
Wolf 1069 b is located 31 light years away and is the sixth closest Earth-mass exoplanet within its host star’s conservative habitable zone. Wolf 1069 b belongs to an exclusive club of exoplanets such as Proxima Centauri b and TRAPPIST-1 e that could serve as potential targets for biosignature searches; however, such analyses currently go beyond current capabilities in astronomy research.
Wolf 1069 b is located near an inactive red dwarf star compared to our Sun, which provides some respite from stellar activity in its youth and preserves its atmosphere. Unfortunately, early results don’t indicate this trend will apply across all red dwarfs with dangerous stellar winds.
WASP-76
Astronomers could use many words to describe WASP-76b, an exoplanet so close to its yellow star that its temperature can cause metal to vaporize, but until recently they never used “glorious.” But thanks to recent observations made by European Space Agency’s Characterizing Exoplanets Satellite (CHEOPS) this changed.
As is typical for giant planets, WASP-76b features an atmosphere rich in elements that can form rocks while also being extremely hot; surface temperatures reach temperatures hot enough to melt lead. But its atmosphere is unique among planets our size as it hosts an atmospheric phenomenon called glory which appears as bright halo around dark planets caused by light from stars reflecting off clouds on their dark side and creating an atmospheric glow or spot around its dark side.
Astronomers behind this discovery, published in Astronomy & Astrophysics, were monitoring WASP-76b as it crossed in front of its star using CHEOPS over three years. Through these observations, scientists noted an excess of light coming from WASP-76b’s eastern “terminator”, the boundary between its day and night sides; this contrasted with lack of illumination coming from its western “terminator”.
Demangeon and his team were able to identify the source of excess light through data analysis. They determined that a particular kind of reflection in night-side clouds was responsible, which could indicate perfectly spherical droplets continually renewing themselves on this exoplanet planet’s atmosphere and creating this backscattered light phenomenon. If confirmed, this would imply that its environment can support such droplets.
This event marks the first instance of light scattering observed on an extrasolar planet; however, scientists hope to use NASA/ESA James Webb Space Telescope, due to launch in 2024, to further study this phenomenon.
Kepler 51b
Kepler successfully discovered 2,662 extrasolar planets over its 15-year mission, some of which may support life. Of these planets, 37 may be Earth-size or smaller and in their stars’ habitable zones – it may even be possible that more exist nearby but using transit method would take much more time to confirm them.
These planets were identified through studying tiny variations in starlight as they passed in front of it as each planet made an orbit around its respective star, dimming slightly with every passing planet as measured with telescopes like Hawaii’s W.M. Keck Observatory which has monitored this star for twenty years.
Kepler-51 is a Sun-like star that hosts three super-puff planets orbiting it, raising much speculation due to their low densities – in fact they boast some of the lowest densities among known exoplanets.
Astronomers are currently studying why planets have such low densities. One theory proposes that their formation occurred outside a star’s snowline – where icy planets form – before migrating closer towards it and losing atmospheres as they moved closer towards it.
Astronomers continue to study this theory. Another possible scenario involves exoplanets having very thick atmospheres. Unfortunately, this requires lots of water which does not easily form at high temperatures – something which cannot be easily found on exoplanets. Astronomers continue to work with this hypothesis.
The third theory holds that our planets have distinct structures compared to exoplanets; in particular, they lack puffy spheres like Jupiter. This creates interesting questions regarding evolution since mass-determining objects typically gravitate toward circular shapes like this.
These theories might provide some explanation for the seemingly incorrectly low densities of planets in Kepler-51 system, but there could be another more fundamental cause behind their lower densities: Astronomers have not been able to account for them properly yet and our understanding of planetary architecture might still be incomplete.