In the centre of this otherwise inconspicuous starfield lies an extraordinary star: A potential long-lost sibling of our own Sun!

Our Sun is believed to have formed in a cluster 4.6 billion years ago, and its siblings have likely dispersed throughout the galaxy.
HD 186302 is a G3 type main sequence star of visual magnitude 8.76 located approximately 185 light-years away from Earth in the southern constellation Pavo. In November 2018 it was identified as a potential solar sibling to the Sun due to its similar spectrum, size, and chemical composition, leading scientists to suspect a common origin in the same stellar nursery around 4.6 billion years ago.

The discovery of HD 186302 as a solar sibling was made by the AMBRE project, a collaboration between the European Southern Observatory (ESO) and the Observatoire de la Cote d’Azur (OCA). The project focuses on characterizing star atmospheres based on their spectra to identify solar siblings. The researchers used high-resolution spectrographs from ESO, such as FEROS, UVES, HARPS, and Flames/GIRAFFE, along with Gaia mission data, to analyse chemical compositions and ages of hundreds of thousands of stars.

HD 186302 was found to be not just a solar sibling but a solar twin, sharing similarities with the Sun in terms of chemical composition, age, size, and mass. The discovery is significant for understanding the Sun's history, and the researchers plan to further investigate the star for the presence of planets using spectrographs like HARPS and ESPRESSO. This search could provide insights into the formation of planets in a common environment and possibly unveil an Earth-like planet in the habitable zone, referred to as "Earth 2.0." The potential existence of such a planet could contribute to our understanding of planetary formation and the possibility of life beyond Earth.

The search for the Sun's long-lost siblings continue, and a 2019 paper has suggested that HD 186302's galactic orbit differs significantly from that of the Sun, making a common origin less likely. However, it is not the only candidate, another star, HD 162826 in the constellation Hercules, is also a suspected solar sibling!

Image details:
Date: November 2022
Exposure: LRGB: 185:55:50:70 mins, total 6 hours @ -25C
Telescope: Homebuilt 12.5" f/4 Serrurier Truss Newtonian
Camera: QSI 683wsg with Lodestar guider
Filters: Astrodon LRGB E-Series Gen 2
Taken from my observatory in Auckland, New Zealand