HD 162826 (HR 6669, HIP 87382) is a

star A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...

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 first constellati ...

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 Irradiance, brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity, its distance, and any extinction (astronomy), ...

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, and ...

in the constellation

Lyra , from ; pronounced: ) 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 often represented on star ...

. 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/. but this star’s status as a solar twin is disputed.

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 university, public research university in Austin, Texas, United States. Founded in 1883, it is the flagship institution of the University of Texas System. With 53,082 stud ...

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 centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...

, emerging from the same

stellar nursery Star formation is the process by which dense regions within molecular clouds in interstellar space—sometimes referred to as "stellar nurseries" or "star-forming regions"— collapse and form stars. As a branch of astronomy, star formation inclu ...

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; it has 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; it has Symbol (chemistry), 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 a ...

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

Galactic Center The Galactic Center is the barycenter of the Milky Way and a corresponding point on the rotational axis of the galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a ...

. However, other papers dispute this finding and give an extremely low probability of HD 162826 being a solar sibling. 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 tens 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 (: supernovae or supernovas) is a powerful and luminous explosion of a star. A supernova occurs during the last stellar evolution, evolutionary stages of a massive star, or when a white dwarf is triggered into runaway nuclear fusion ...

. 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 (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...

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

terrestrial planet A terrestrial planet, tellurian 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 ...

s are possible. The star is of spectral type F8V, meaning it is somewhat larger and hotter than the Sun. Any habitable Earthlike planets would have to orbit farther out, at roughly the distance of

Mars Mars is the fourth planet from the Sun. It is also known as the "Red Planet", because of its orange-red appearance. Mars is a desert-like rocky planet with a tenuous carbon dioxide () atmosphere. At the average surface level the atmosph ...

from the Sun. 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, also known as biota, refers to matter that has biological processes, such as Cell signaling, signaling and self-sustaining processes. It is defined descriptively by the capacity for homeostasis, Structure#Biological, organisation, met ...

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, or alien life (colloquially, aliens), is life that originates from another world rather than on Earth. No extraterrestrial life has yet been scientifically conclusively detected. Such life might range from simple forms ...

. 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