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(978 posts)
Fri Oct 6, 2023, 09:35 AM Oct 2023

On This Day: First planet discovered around a sun-like star - Oct. 6, 1995

(edited from article)
Nobel Winners Changed Our Understanding with Exoplanet Discovery

First planet discovered around a sun-like star - 51 Pegasi-b
Discovered - October 6, 1995

The Swiss team of Michel Mayor and Didier Queloz made a stunning announcement in October 1995: the first detection of a planet orbiting a star like our Sun. Though not quite the first “exoplanet” – a planet beyond our solar system – it captured the world’s attention and opened the floodgates of discovery. Today more than 4,000 exoplanets are confirmed to be in orbit around other stars. 51 Peg orbits its star every four days and has a temperature of 1,000-1,800 degrees F (538-982 degrees C). It's 51 light-years from Earth.

These large planets make such tight orbits that they cause a pronounced “wobble” in their stars, their gravity tugging them first this way, then that. That made them easier to find in the early days of planet hunting, using a detection method known as radial velocity.

This strange assortment would also include the first-ever exoplanet detections, “pulsar planets” that orbit the rapidly spinning remnant of an exploded star known as a pulsar. A significant portion of the exoplanets discovered so far also include rocky planets in Earth’s size range, some at the right distance from their stars to allow the possibility of liquid water pooling on their surfaces.

Fast Facts

The discovery of 51 Pegasi b helped launch a whole new field in astronomical research.

It was the first exoplanet to have its reflected visible light spectrum observed.

51 Peg b was the first exoplanet confirmed around a Sun-like star; a previous discovery in 1992 found planets orbiting a pulsar star, but at the time many were skeptical planets could exist around these volatile stars



(edited from Wikipedia)
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917, but was not recognized as such. The first confirmation of the detection occurred in 1992. A different planet, initially detected in 1988, was confirmed in 2003. As of 1 October 2023, there are 5,506 confirmed exoplanets in 4,065 planetary systems, with 878 systems having more than one planet. The James Webb Space Telescope (JWST) is expected to discover more exoplanets, and also much more about exoplanets, including composition, environmental conditions and potential for life.

There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone. In several cases, multiple planets have been observed around a star. About 1 in 5 Sun-like stars have an "Earth-sized" planet in the habitable zone. Assuming there are 200 billion stars in the Milky Way, it can be hypothesized that there are 11 billion potentially habitable Earth-sized planets in the Milky Way, rising to 40 billion if planets orbiting the numerous red dwarfs are included.

The least massive exoplanet known is Draugr, which is about twice the mass of the Moon. The most massive exoplanet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter. However, according to some definitions of a planet (based on the nuclear fusion of deuterium), it is too massive to be a planet and might be a brown dwarf instead. Known orbital times for exoplanets vary from less than an hour (for those closest to their star) to thousands of years. Some exoplanets are so far away from the star that it is difficult to tell whether they are gravitationally bound to it.

Almost all of the planets detected so far are within the Milky Way. However, there is evidence that extragalactic planets, exoplanets farther away in galaxies beyond the local Milky Way galaxy, may exist. The nearest exoplanets are located 4.2 light-years (1.3 parsecs) from Earth and orbit Proxima Centauri, the closest star to the Sun.

The discovery of exoplanets has intensified interest in the search for extraterrestrial life. There is special interest in planets that orbit in a star's habitable zone (or sometimes called "goldilocks zone" ) , where it is possible for liquid water, a prerequisite for life as we know it, to exist on the surface. However, the study of planetary habitability also considers a wide range of other factors in determining the suitability of a planet for hosting life.

Rogue planets are those that do not orbit any star. Such objects are considered a separate category of planets, especially if they are gas giants, often counted as sub-brown dwarfs. The rogue planets in the Milky Way possibly number in the billions or more.

In February 2018, researchers using the Chandra X-ray Observatory, combined with a planet detection technique called microlensing, found evidence of planets in a distant galaxy, stating, "Some of these exoplanets are as (relatively) small as the moon, while others are as massive as Jupiter. Unlike Earth, most of the exoplanets are not tightly bound to stars, so they're actually wandering through space or loosely orbiting between stars. We can estimate that the number of planets in this [faraway] galaxy is more than a trillion."


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On This Day: First planet discovered around a sun-like star - Oct. 6, 1995 (Original Post) jgo Oct 2023 OP
According to My Son The Astronomer PoindexterOglethorpe Oct 2023 #1


(26,041 posts)
1. According to My Son The Astronomer
Fri Oct 6, 2023, 11:07 AM
Oct 2023

who is doing exoplanet research, we have not yet found a truly earth-like planet. Clearly the conditions that led to life on this planet are extremely unusual. It's highly likely that a relatively large moon is crucial.

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