Exoplanets
52 questions tagged Exoplanets — spanning every one of the seven Ws.
What is an exomoon?
An exomoon is a moon that orbits a planet outside our Solar System. It is the extraterrestrial equivalent of Earth’s Moon.
What is a circumbinary planet?
A circumbinary planet is a planet that orbits two stars instead of one. It circles around both stars as they orbit each other.
What is a hot Jupiter?
A hot Jupiter is a gas giant exoplanet that orbits very close to its star and has extremely high temperatures. Many complete an orbit in just a few days.
When was the first dedicated exoplanet-hunting space telescope launched?
Kepler launched on 7 March 2009. It was designed to find planets around other stars by watching for tiny dips in starlight.
When was the first image of an exoplanet around a normal star taken?
The first widely accepted direct image of an exoplanet around a Sun-like star was captured in 2004, after earlier detections had been made by indirect methods.
When did the first exoplanet around a Sun-like star get discovered?
In 1995, astronomers announced 51 Pegasi b, the first exoplanet found orbiting a Sun-like star.
When was the first exoplanet orbiting a Sun-like star discovered?
The first confirmed exoplanet around a Sun-like star was announced in 1995. It orbited 51 Pegasi and was discovered by Michel Mayor and Didier Queloz.
When was the first exoplanet around a pulsar discovered?
The first known exoplanet discovery was announced in 1992. It was found around the pulsar PSR B1257+12.
When was the first direct image of an exoplanet around a normal star taken?
One of the earliest widely recognized direct images of an exoplanet was announced in 2004. It was 2M1207 b, orbiting a brown dwarf.
Where was the first exoplanet around a Sun-like star discovered?
It was discovered around the star 51 Pegasi in the constellation Pegasus. The planet, 51 Pegasi b, was announced in 1995.
Which telescope first captured exoplanet light directly?
The Hubble Space Telescope helped make some of the first direct detections of light from exoplanets and their atmospheres, but the first widely recognized direct imaging detections came from ground-based telescopes in the early 2000s. The field has since advanced rapidly with Webb and other observatories.
Which exoplanet is one of the hottest known?
KELT-9b is one of the hottest known exoplanets, with temperatures around 4,000°C on its dayside. It is so hot that metal atoms can exist in its atmosphere as gas.
Which exoplanet is among the largest known inflated gas giants?
WASP-17b is one of the puffiest known exoplanets, with a radius larger than Jupiter’s despite having much less mass. It is an extreme hot Jupiter orbiting very close to its star.
Which known exoplanet system has one of the most tightly packed resonances?
The TRAPPIST-1 system is famous for its chain of near-resonant planets packed into a tiny space. Seven Earth-sized planets orbit an ultracool dwarf star.
Which cosmic object was the first discovered of its kind beyond the Solar System?
51 Pegasi b was the first exoplanet found orbiting a Sun-like star, announced in 1995. It changed astronomy by proving planets are common beyond the Solar System.
Whose telescope mission first found thousands of exoplanets?
NASA’s Kepler mission, led by William Borucki, revolutionized exoplanet hunting starting in 2009. It confirmed that planets are common around other stars.
How do scientists find planets around other stars?
They look for tiny dips in starlight when a planet passes in front of its star, or for subtle wobbles in the star’s motion. These methods have discovered thousands of exoplanets.
How do astronomers find planets around other stars?
They use methods such as transits and radial velocity to detect a planet’s effect on its star. The transit method has found thousands of exoplanets.
How do astronomers measure the atmosphere of an exoplanet?
They study the starlight that passes through, or is blocked by, the planet’s atmosphere. Different gases absorb different wavelengths and leave measurable signatures.
Why do some exoplanets orbit much closer to their stars than Mercury does to the Sun?
Planet formation and later migration can move worlds inward, creating “hot Jupiters” and tightly packed systems.
Why are many exoplanets discovered by the transit method rather than by direct imaging?
A planet crossing its star slightly dims the starlight, making it much easier to detect than the faint planet itself.
Why are many exoplanets found by the transit method rather than direct imaging?
Transits cause tiny, measurable dips in a star’s brightness, while direct images are much harder because planets are faint and lost in stellar glare.
Why are some exoplanets found by transit surveys rather than direct images?
A planet is vastly dimmer than its star and usually too close to it to see separately. Transit surveys detect the tiny dip in starlight when a planet passes in front of its star.
Why do many hot Jupiters orbit much closer to their stars than Mercury does to the Sun?
Many hot Jupiters likely formed farther out and then migrated inward through interactions with the disk or other planets. Once close in, they are heated to extreme temperatures.
When was the first exoplanet directly imaged?
The first widely accepted direct image of an exoplanet was announced in 2004, for 2M1207 b.
When was the first exoplanet discovered around a Sun-like star?
The first confirmed exoplanets around a Sun-like star were announced in 1995.
When was the first planet discovered orbiting a pulsar?
The first pulsar planets were discovered in 1992.
When was the first confirmed exoplanet around a Sun-like star discovered?
In 1995, astronomers announced 51 Pegasi b, the first confirmed exoplanet orbiting a Sun-like star.
When was the first direct image of an exoplanet taken?
In 2004, astronomers obtained the first widely accepted direct image of an exoplanet, 2M1207 b.
Where is the Hycean candidate exoplanet K2-18 b located?
K2-18 b orbits the star K2-18, about 124 light-years away in the constellation Leo. It is one of the best-known potentially habitable exoplanet candidates.
Where is Proxima Centauri b located?
Proxima Centauri b orbits the nearest known star to the Sun, Proxima Centauri. It lies about 4.24 light-years away in the constellation Centaurus.
Which telescope first found thousands of exoplanets?
NASA’s Kepler Space Telescope found more than 2,600 confirmed exoplanets and thousands of candidates. It transformed the search for planets beyond our Solar System.
Which space telescope first found thousands of exoplanets?
NASA’s Kepler Space Telescope was the first mission to identify thousands of exoplanet candidates. It transformed exoplanet science after its launch in 2009.
Which exoplanet was the first discovered around a Sun-like star?
51 Pegasi b was the first exoplanet found orbiting a Sun-like star, announced in 1995. It was discovered by Michel Mayor and Didier Queloz.
Which known object has the largest ring system?
The super-Earth exoplanet candidate J1407b is associated with the largest known ring system, far bigger than Saturn’s. Its rings may span tens of millions of kilometers.
How do astronomers detect exoplanets by the transit method?
They watch for tiny dips in a star’s brightness when a planet passes in front of it. Repeating dips reveal the planet’s size and orbital period.
How do scientists find planets around pulsars?
They track tiny irregularities in the timing of a pulsar’s pulses. If the pulsar wobbles because of orbiting planets, the arrival times shift in a detectable pattern.
How do scientists search for life by studying exoplanet atmospheres?
They analyze starlight that passes through or reflects off a planet’s atmosphere and look for absorption features from gases such as water vapor, methane, or carbon dioxide. These spectral clues can hint at habitability or unusual chemistry.
When did the first exoplanet around a star like the Sun get directly imaged?
The first widely accepted direct image of an exoplanet was published in 2004, for 2M1207 b; a planet around a Sun-like star was directly imaged in 2008 around the star 1RXS J160929.1−210524.
When was the first exoplanet discovered orbiting a normal star?
In 1995, astronomers announced 51 Pegasi b, the first exoplanet found orbiting a Sun-like star.
When was the first pulsar planet discovered?
The first confirmed planets beyond the Solar System were announced in 1992 around the pulsar PSR B1257+12.
When was the first confirmed detection of an exoplanet atmosphere made?
The first confirmed detection of an exoplanet atmosphere was made in 2001.
Which is the nearest known exoplanet to Earth?
Proxima Centauri b is the nearest known exoplanet to Earth, orbiting the closest star to the Sun. It lies about 4.24 light-years away.
Which exoplanet was one of the first Earth-sized planets found in a habitable zone?
Kepler-186f was one of the first Earth-sized exoplanets found in its star’s habitable zone. It was announced in 2014 by NASA’s Kepler mission.
Which known exoplanet is one of the largest by radius?
WASP-17b is one of the puffiest known exoplanets, with a radius roughly twice that of Jupiter. Despite its huge size, it has very low density.
Which exoplanet orbits its star fastest?
Some ultra-short-period exoplanets, such as TOI-178 b, complete an orbit in just a few hours. These are among the fastest-orbiting known planets.
How do astronomers detect planets around other stars?
They often look for tiny dips in starlight when a planet crosses in front of its star, or for slight wobbles in the star’s motion. These methods have found thousands of exoplanets.
How do scientists estimate the temperature of a planet from far away?
They measure the light and heat a planet emits or reflects, then use physics to estimate its surface or cloud temperature.
How do astronomers discover planets around other stars?
They look for tiny dips in starlight or small wobbles in a star's motion caused by an orbiting planet.
How do astronomers weigh an exoplanet without going there?
They measure how the planet affects its star or nearby planets, then use gravity to estimate mass.
How do astronomers detect exoplanets around other stars?
They look for tiny dips in brightness when a planet transits its star or for small wobbles in the star’s motion caused by the planet’s gravity. These methods have discovered thousands of exoplanets.
How do astronomers tell whether an exoplanet could have liquid water?
They estimate the planet’s temperature based on its star and orbit, then compare it to the habitable zone. They also look for atmosphere clues that could raise or lower surface temperatures.