An international team of astronomers reports the discovery of a new exoplanet orbiting a sunlike star as part of the Next Generation Transit Survey (NGTS). The newfound alien world, designated NGTS-39 b, is a Jupiter-sized planet with an equilibrium temperature of about 519 K. The discovery was detailed in a paper published July 2 on the preprint server arXiv.
NGTS confirms TESS findings
NGTS-39 (also known as TIC-453147896) is a relatively bright star of spectral type F9 located some 910 light-years from Earth. The star was observed multiple times between 2019 and 2024 with NASA’s Transiting Exoplanet Survey Satellite (TESS), which detected a transit signal in its light curve.
Now, a group of astronomers led by Ioannis Apergis of the University of Warwick, UK, have used NGTS’ 12 robotic Newtonian telescopes to perform follow-up photometric observations of NGTS-39. This, together with radial velocity measurements from CORALIE and HARPS spectrographs, allowed the team to confirm the planetary nature of the TESS-detected signal.
“NGTS-39 b was first identified from a TESS single transit event, and subsequently confirmed with NGTS photometry and radial velocity measurements from CORALIE and HARPS,” the researchers wrote in the paper.
The properties of the system
According to the study, NGTS-39 b has a radius of approximately 1.09 Jupiter radii and a mass of 1.47 Jupiter masses, yielding a density of 1.411 g/cm3. The planet orbits its host every 58.2 days at a distance of some 0.31 AU, on an eccentric orbit. The equilibrium temperature of NGTS-39 b is estimated to be 519 K.
Based on the derived parameters, the astronomers classified NGTS-39 b as a long-period warm Jupiter. They assume that the planet has a composition dominated by hydrogen and helium, although its density is higher than that of Jupiter and may indicate an enhanced heavy-element content.
As for the parent star, NGTS-39 is about 16% larger and more massive than the sun. The star has an effective temperature of 6,053 K, and its age is estimated to be 2.2 billion years.
Atmospheric study prospects and a potential outer companion
Summing up the results, the authors conclude that the discovery of NGTS-39 b is an important addition to the still small but growing population of transiting gas giant planets on wide orbits.
They note that the planet lies near the transition between molecular nitrogen and ammonia on the stellar effective temperature-planetary equilibrium temperature diagram, which makes it an excellent target for follow-up spectroscopic observations aimed at probing atmospheric chemistry in this temperature regime (500-850 K).
The researchers also note that there may be another exoplanet in the NGTS-39 system, farther out than the newly detected one. This is suggested by the radial velocity data; however, further observations are required to confirm this.
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Publication details
Ioannis Apergis et al, NGTS-39 b: A 58 d transiting warm Jupiter in an eccentric orbit, arXiv (2026). DOI: 10.48550/arxiv.2607.02061
Journal information:
arXiv
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Warm Jupiter exoplanet transiting a sun-like star discovered (2026, July 10)
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