BD+60 1417b

BD+60 1417b is a confirmed exoplanet discovered in the year 2021 using the imaging method. BD+60 1417b is the only known exoplanet in the system BD+60 1417, around 45 parsecs from Earth. BD+60 1417 is a young K0 star, while BD+60 1417 b has a late-L spectral type. The planet might be the first discovery of a directly imaged exoplanet found by a citizen scientist. Discovery of exoplanets involving amateurs are usually transiting exoplanets and are rarely discovered with other methods. Another example of a non-transiting exoplanet discovery by an amateur is the microlensing exoplanet Kojima-1Lb.

Discovery
Previous direct imaging planet-searching surveys with Gemini, Keck and Palomar failed to detect an exoplanet around BD+60 1417. A co-moving source around the star was first spotted with the WiseView Tool by the Backyard Worlds citizen scientist Jörg Schümann. WiseView uses data from the Wide-Field Infrared Survey Explorer (WISE). Additional observations with optical spectroscopy of the star at the Lick Observatory and infrared spectroscopy at NASA IRTF confirmed the presence of a young star with a planetary-mass companion around BD+60 1417.

BD+60 1417b is the second directly imaged exoplanet the WISE-telescope was able to discover, after COCONUTS-2b.

Host Star
The host star BD+60 1417 is a young K0 star with a mass of 1 and a radius of 0.797 ±0.051. It has a brightness of 9.37 magnitude. The star shows typical signs of youth, such as x-ray detection with ROSAT and lithium absorption lines. Its age is estimated at 50-150 Million years. The star rotates with a period of 7.50 ± 0.86 days, which is seen due to evolving starspots in the TESS light curve.

BD+60 1417 is the only main sequence star with about one solar mass that is orbited by a planetary-mass object at a separation larger than 1000 astronomical units. All other systems with a separation >1000 au have a primary with <0.5 solar masses or are the stellar remnant WD0806.

Physical properties
The infrared spectrum of the planet shows a red L8γ-type object with water vapor, carbon monoxide, iron(I) hydride and potassium iodide in its atmosphere. In the near-infrared it is one of the reddest substellar objects discovered to date with $$J-Ks = 2.72$$ mag. The spectrum of the exoplanet closely resembles objects with a suspected low surface gravity. A low surface gravity is a sign of youth for substellar objects. The researchers also found similarities with an archived SINFONI spectrum of the exoplanet 2M1207b and spectra of the HR 8799 exoplanets.

Orbit
The planet has an orbital period of about 95,000 years. BD+60 1417b has a large separation of 1662 astronomical units from its host star. If this exoplanet has formed in this wide orbit, it is likely to have formed similar to isolated brown dwarfs. It could also have formed in a closer orbit around the star via core accretion or disk instability and was later dynamically disturbed into a higher orbit, for example by a planet-planet fly-by.

Status as an exoplanet
According to the NASA Exoplanet Archive BD+60 1417b is an exoplanet and it falls within their definition: An object with a minimum mass lower than 30 Jupiter masses and a not free-floating object with sufficient follow-up. The official working definition by the International Astronomical Union allows only exoplanets with a maximum mass of 13 Jupiter masses and according to current knowledge BD+60 1417b could be more massive than this limit.