What is an exoplanet?

Two-exoplanets-against-red-dwarf-elements-of-this-image-furnished-by-NASA-scaled.jpg

Two exoplanets against red dwarf, elements of this image furnished by NASA (Image Credit: shutterstock)

An exoplanet, or extrasolar planet, is a planet outside our solar system that usually orbits another star in our galaxy.

What is an exoplanet?

The Sun is the center of our solar system, and all planets revolve around it. Exoplanets are planets that revolve around other stars. Exoplanets are exceedingly hard to observe directly using telescopes. They are veiled by the brilliant glare of the stars they orbit.

To find and analyze these faraway planets, astronomers must turn to other detection and investigation methods. Exoplanets explore extrasolar planets by observing how their movements affect the stars around which they orbit.

How do we find exoplanets?

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Extrasolar planets or exoplanets and red dwarf or red supergiant. 3D illustration
(Image Credit: shutterstock)

There are five approaches scientists frequently utilize to find exoplanets.

The transit and radial velocity methods are the two most often used approaches.

When a planet passes directly between an observer and the star, it orbits, it blocks part of that brightness. For a bit of a moment, the brightness of that star drops. Astronomers have discovered an extrasolar exoplanet orbiting a distant star thanks to this minute shift in the star’s light curve. The transit technique is what it’s called.

1. Radial Velocity

  • Watching for Wobble
  • 899 planets discovered
  • Orbiting planets cause stars to wobble in space, changing the color of the light astronomers observe.

2. Transit

  • Searching for Shadows
  • 3746 planets discovered
  • When a planet passes directly between its star and an observer, it dims the star’s light by a measureable amount.

3. Direct Imaging

  • Taking Pictures
  • 54 planets discovered
  • Astronomers can take pictures of exoplanets by removing the overwhelming glare of the stars they orbit.

4. Gravitational Microlensing

  • Light in a Gravity Lens
  • 120 planets discovered
  • Light from a distant star is bent and focused by gravity as a planet passes between the star and Earth.

5. Astrometry

  • Minuscule Movements
  • 1 planet discovered
  • The orbit of a planet can cause a star to wobble around in space in relation to nearby stars in the sky.

As a result of the star-wobbling caused by planets in space, astronomers may now discern a different light hue while studying a star. Stars are impacted by the gravitational push of their circling planets, and when examined via a telescope, this changes the star’s light spectrum. If the star travels in the observer’s direction, it will seem to be moved toward blue. If it travels away from the observer, it will change toward the red. The radial velocity approach is a technique for observing this.

NASA’s exoplanet space telescopes

Hundreds of thousands of exoplanets have been discovered and verified beyond our solar system. The earliest indication of exoplanets dates to 1917 when Van Maanen found the first polluted white dwarf, but the first definite observation of an exoplanet would not arrive until the 1990s. After the Kepler Space Telescope was launched, the search for extrasolar exoplanets exploded.

The “Godilocks zone,” the region around a star where rocky planets might have liquid water on their surfaces, is where the Kepler mission was specifically designed to survey our area of the Milky Way galaxy to discover hundreds of Earth-size and more minor planets in or near the habitable zone and determine the fraction of stars that might have such planets around them. After the second of Kepler’s four gyroscope-like wheels failed in 2013, Kepler completed its core mission that November and started its extended mission, K2. Although Kepler was decommissioned in 2018, the collected data is still being utilized for hunting for extrasolar exoplanets (more than 2,700 confirmed so far).

Despite the telescope’s original purpose of not looking for extraterrestrial life, infrared equipment on NASA’s Spitzer Space Telescope (2013-2020) has made it an influential exoplanet explorer. It was employed in the noteworthy discovery of the TRAPPIST-1 system. Exoplanets orbiting around bright dwarf stars, the most common form of a star in our Galaxy, were discovered by Kepler, which was replaced in 2018 by the Transiting Exoplanet Survey Satellite (TESS). Future space projects such as NASA’s James Webb Space Telescope and the Nancy Grace Roman Space Telescope offer enormous potential for what we may learn from exoplanets. Through spectroscopy, scanning light fingerprints for information, astronomers aim to understand more about planet atmospheres and the circumstances of the planets themselves.

What is an exoplanet candidate?

There hasn’t been any conclusive evidence to support the planet of an exoplanet candidate discovered by a telescope.

How the first exoplanet was discovered

According to observations made at the Jodrell Bank Observatory in Cheshire, the dense relic of an exploding star, the pulsar, seemed to be orbited by a planet.

Pulsars are so termed because the beams of light they release sweep over Earth at regular intervals because of their fast spin.

If we look at them from Earth, we find that they flicker like a lighthouse beam. This means that their spin rate can be estimated by measuring how fast they pulse.

However, it turned out that the software used to analyze the pulsar data included a systematic mistake, which was quickly discovered by the Jodrell Bank team.

The ‘pull’ on the pulsar’s spin attributed to an unknown planet’s mass was eliminated after the error was fixed.

Yet immediately after Jodrell Bank’s Andrew Lyne had officially retracted his team’s findings at the January 1992 meeting of the American Astronomical Society, held in Atlanta, he was followed on stage by Aleksander Wolszczan, principal author of a paper that detailed his own detection of at least two planets around another pulsar.

This was to be the first verified finding of an exoplanet.

Wolszczan was especially interested in ‘millisecond pulsars’, which spin hundreds of times a second.

He had found it impossible to construct a sufficiently precise mathematical model to describe how one specific millisecond pulsar, named PSR B1257+12, was behaving.

A new set of data didn’t help his models anticipate the arrival timings of the pulse, he says.

Wolszczan started to notice a recurring malfunction in the pace at which the pulses reached Earth after a focused monitoring period of about a month.

Many pulsars have companion dwarf stars contributing material and energy. Still, Wolszczan recognized that the observed abnormalities in these pulses were best explained by the presence of “two planetary mass objects” encircling the star.

Because he had previously spotted another binary pulsar that did not exhibit the same abnormalities, Wolszczan was confident that his discovery was not the product of “anything in the data analysis software,” unlike the Jodrell Bank team.

Several months later, Wolszczan’s observations were independently corroborated by colleague astronomer Dale Frail and himself.

Then in 1995, an exoplanet was identified for the first time, orbiting a Sun-like star – 51 Pegasi – by Michel Mayor and Didier Queloz. Similarly, discovering a large gas giant known as a “hot Jupiter” orbiting close to its parent star was a total shock.

Insights into our own Solar System that Exoplanets provide

what is an exoplanet, what is a exoplanet, what is the closest exoplanet to earth, what does exoplanet mean, what is outside our solar system, what are super earths, what is kepler 186f, what does proxima b look like, what is the definition of an exoplanet
Our Solar System (Image Credit: Shutterstock)

By locating diverse sorts of exoplanets, astronomers may learn much more about our own Solar System.

We know that ‘hot Jupiters’, for example, can’t have originated that close to their stars; therefore, they must have formed further away and migrated in.

This means planets may migrate from their initial formation locations. There’s the notion that there was a lot of movement in the early days of our own Solar System: Jupiter and Saturn coming in, Neptune and Uranus potentially being pushed out and perhaps switching places.

During the Late Heavy Bombardment, a period (approximately half a million years after the creation of the Solar System) during which massive volumes of material were shot into the inner planets, it has even been hypothesized that this gas giant dance was the reason.

There are also various sorts of exoplanets, such as gigantic ‘super Earths’, that don’t exist in our Solar System. In fact, the more we understand about other star systems, the odder our own Solar System looks.

How many exoplanets are there?

Over 4,300 exoplanets have been discovered and verified too far, but the number continues growing.

The enormity of this ever-growing list means astronomers can now replace some of the elements in the Drake Equation, which famously seeks to determine the number of active, communicative alien civilizations in the Universe.

Suppose an Earth-like planet in an Earth-like orbit is the most probable site to locate sophisticated alien life. In that case, we may be sure that those conditions really exist in quite significant numbers across the Galaxy.

What are the nearest, most significant, oddest exoplanets ever discovered?

  • Proxima b is the nearest exoplanet.
what is an exoplanet, what is a exoplanet, what is the closest exoplanet to earth, what does exoplanet mean, what is outside our solar system, what are super earths, what is kepler 186f, what does proxima b look like, what is the definition of an exoplanet
Proxima b (Image Credit: ESO)

Astronomers discovered in 2016 that a planet somewhat more significant than Earth orbits the red dwarf star Proxima Centauri, only 4.25 lightyears away, every 11 days, raising the possibility that the world might be rocky and home to liquid water.

  • SWEEPS-11 is the furthest exoplanet known.
what is an exoplanet, what is a exoplanet, what is the closest exoplanet to earth, what does exoplanet mean, what is outside our solar system, what are super earths, what is kepler 186f, what does proxima b look like, what is the definition of an exoplanet
SWEEPS-11 (Image Credit: NASA)

Detected by the Hubble Space Telescope and SWEEPS-4 in 2006, this vast gas planet has a radius 1.13 times that of Jupiter and is 27,710 lightyears distant.

  • Smallest exoplanet: Kepler 37 b
what is an exoplanet, what is a exoplanet, what is the closest exoplanet to earth, what does exoplanet mean, what is outside our solar system, what are super earths, what is kepler 186f, what does proxima b look like, what is the definition of an exoplanet
Kepler 37 b (Image Credit: NASA Ames/JPL-Caltech/T. Pyle)

Kepler 37 b is the smallest known exoplanet that orbits a Sun-like star. It circles a main-sequence star in Lyra, while the predicted mass of PSR B1257+12 b (Draugr) might top it.

  • Most massive exoplanet: HAT-P-6b
what is an exoplanet, what is a exoplanet, what is the closest exoplanet to earth, what does exoplanet mean, what is outside our solar system, what are super earths, what is kepler 186f, what does proxima b look like, what is the definition of an exoplanet
HAT-P-6b (Image Credit: Livia Pietrow )

HAT-P-67 b is a gas giant exoplanet whose mass is 0.34 Jupiters, but its diameter is nearly 2 times that of Jupiter. Even though its orbit around its star takes almost five Earth days, it is very close to the star: just 0.06 AU apart (where 1 AU is the average distance between Earth and the Sun).

More Info: Exoplanets

How do astronomers name exoplanets?

Compared to familiar names like Venus and Mars, exoplanet names might seem obtuse and convoluted. However, there is a rationale that is vital to how scientists categorize hundreds of planets. Astronomers distinguish between the alphanumeric “designations” and alphabetical “proper names.” All-stars and exoplanets have names, but only a small number of them are given to us in this manner.

The telescope or survey that discovered an exoplanet is generally the first element of the name. According to its location, the star was assigned a number from 1 to 31. The lowercase letter stands for the planet in the sequence in which the planet was discovered. The first planet detected is usually designated b, with succeeding planets named c, d, e, f, etc. Even if it is not always the system, the star around which the exoplanet revolves is often called the system’s undeclared “A.” (Stars have capital letters; planets get lowercase designations.) If some exoplanets surrounding the same star are identified at once, the planet nearest to its star is dubbed b with more distant planets named c, d, e and so on.

An example of an exoplanet name is Kepler-16b, where “Kepler” is the telescope’s name that saw the system, 16 is the order in which the star was catalogued, and “b” is the nearest planet to the star. Earth would be named Sun d if it were an exoplanet (Sun is the name of our star, and Earth is the third planet, starting with b, Mercury).

Also Read: What Is an astronaut costume (Spacesuit)?

Reference

https://exoplanets.nasa.gov/what-is-an-exoplanet/in-depth/

https://www.skyatnightmagazine.com/space-science/exoplanets/

https://en.wikipedia.org/wiki/Exoplanet

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4,663 Replies to “What is an exoplanet?”

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