HD 162826 (HR 6669, HIP 87382) is a

star A star is an astronomical object comprising a luminous spheroid of plasma (physics), plasma held together by its gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked ...

in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The origins of the e ...

Hercules Hercules (, ) is the Roman equivalent of the Greek divine hero Heracles, son of Jupiter and the mortal Alcmena. In classical mythology, Hercules is famous for his strength and for his numerous far-ranging adventures. The Romans adapted the Gr ...

. It is about away from Earth. With an

apparent magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's li ...

of 6.55, the star can be found with binoculars or a low-power telescope by reference to nearby

Vega Vega is the brightest star in the northern constellation of Lyra. It has the Bayer designation α Lyrae, which is Latinised to Alpha Lyrae and abbreviated Alpha Lyr or α Lyr. This star is relatively close at only from the Sun, an ...

in the constellation

Lyra Lyra (; Latin for lyre, from Greek ''λύρα'') is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was ...

. The star is considered to be a stellar sibling of the Sun and is the first such sibling to be discovered. Solar siblings are those stars that formed from the same gas cloud and in the same star cluster; the term was introduced in 2009. No planets have been detected orbiting HD 162826, but due to its metallicity, it is likely to harbor terrestrial planets; the star's spectra had been under observation previously. In November 2018, a second potential solar twin was announced, HD 186302, an 8th magnitude star in the Pavo constellation. King, Bob P. (2018-11-24). Did Astronomers Just Find The Sun’s Sister? Astro Bob, Duluth News Tribune, 24 November 2018. Originally retrieved from http://astrobob.areavoices.com/2018/11/24/did-astronomers-just-find-the-suns-sister. Archived on 2018-11-25 at https://web.archive.org/web/20181125115534/http://astrobob.areavoices.com/2018/11/24/did-astronomers-just-find-the-suns-sister/.

Origin

In May 2014, astronomers at the

University of Texas at Austin The University of Texas at Austin (UT Austin, UT, or Texas) is a public research university in Austin, Texas. It was founded in 1883 and is the oldest institution in the University of Texas System. With 40,916 undergraduate students, 11,075 ...

announced that HD 162826 is "almost certainly" one of what may be thousands of siblings of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, emerging from the same

stellar nursery Star formation is the process by which dense regions within molecular clouds in The "medium" is present further soon.-->interstellar space

some 4.5 billion years ago. This conclusion was reached by determining it has the same chemical composition as the Sun, including rare elements such as

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

and

yttrium Yttrium is a chemical element with the symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and has often been classified as a "rare-earth element". Yttrium is almost always found in com ...

, and by determining its orbit and projecting backward its revolutions about the

galactic center The Galactic Center or Galactic Centre is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact rad ...

. The cluster in which HD 162826 and the Sun formed is believed to have been an

open cluster An open cluster is a type of star cluster made of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way galaxy, and ...

, permitting the stars to scatter widely over time. The stars in this cluster were not too closely packed during their formation to disrupt planetary disk development, but were not so far apart as to prevent the seeding of Earth with radioactive elements produced by a nearby

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

. The discovery of a first solar sibling by searching for specific rare elements may make it easier to identify other siblings in the future. However, HD 162826 is probably the nearest solar sibling, because others would have been identified first if they had been closer to the Sun. It had not been expected that even one sibling would be found at this relatively short distance; the study that identified this star worked on a dataset of only 100,000 stars, to prepare to receive data about billions of stars expected from the Gaia Space Telescope in five to ten years.

Possible planets and habitability

HD 162826 has no known planets. The current state of knowledge excludes

hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods (). The close proximity to their stars and high surface-atmosphere temp ...

s and suggests that a more distant "Jupiter" is unlikely, but

terrestrial planet A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Sun: Mercury, Ve ...

s are possible. Lead researcher Ivan Ramirez explained the significance of finding solar siblings:

"We want to know where we were born. If we can figure out in what part of the galaxy the Sun formed, we can constrain conditions on the early Solar System. That could help us understand why we are here."

He suggested a "small, but not zero" chance that planets with

life Life is a quality that distinguishes matter that has biological processes, such as signaling and self-sustaining processes, from that which does not, and is defined by the capacity for growth, reaction to stimuli, metabolism, energ ...

might orbit solar sibling stars, because during the frequent collisions during planetary formation material might have travelled from one system to another. He said the siblings might be "key candidates" in the search for

extraterrestrial life Extraterrestrial life, colloquially referred to as alien life, is life that may occur outside Earth and which did not originate on Earth. No extraterrestrial life has yet been conclusively detected, although efforts are underway. Such life might ...

. A scenario for transfer of life by this means might require life or a precursor molecule to be shielded from radiation for millions of years, dormant within an outgoing chunk of planetary debris a meter or more in diameter that is produced by a meteorite impact, until this new meteorite impacts on a different planet. Such an unlikely event might have transferred life from another planet to Earth or ''vice versa''.

References

{{DEFAULTSORT:HD 162826 Hercules (constellation) 162826 087382 6669 BD+40 3225 F-type main-sequence stars

Origin

Possible planets and habitability

See also

References