Blogs about stars

Artist's illustration of the exoplanet Tahay / GJ 367 b (Image NASA)

An article published in “The Astrophysical Journal Letters” reports a study on the exoplanet GJ 367 b, or Gliese 367 b, formally known by the name Tahay, which concludes that its core is composed almost entirely of iron for a density that is almost twice the Earth’s. The researchers also announced the discovery of two more planets in the system of the star GJ 367, formally known as Añañuca, which may be super-Earths.

Just over 30 light-years from Earth, Añañuca is a red dwarf with a mass and size just under half of the Sun’s. Observations began in 2019 with NASA’s TESS space telescope and in 2021 the data collected led to the exploration of the possibility that a planet orbited very close to this star, subsequently confirmed with other instruments. Tahay’s roughly 7.7-hour year is the shortest in the cosmic neighborhood, one reason for interest and worthy of its own name.

The HIP 81208 system seen by SPHERE

An article published in the journal “Astronomy & Astrophysics” reports the discovery of an object that could be a gas giant planet or a brown dwarf in the HIP 81208 system. A team of researchers analyzed data from the archive of the observations conducted with the SPHERE instrument mounted on the VLT in Chile discovering an object that was cataloged as HIP 81208 Cb orbiting the smaller of the two stars in this binary system. A brown dwarf was discovered around the more massive star together with the smaller and more distant star in an analysis also published some time ago in an article in “Astronomy & Astrophysics”. The new discovery makes HIP 81208 a so-called hierarchical quadruple system, the first of its kind discovered using a direct imaging system.

A diagram illustrating the combined power of the James Webb and Hubble space telescopes in studying Cepheids present in the galaxy NGC 5584 with the NIRCam (Near-Infrared Camera) and WFC3 (Wide Field Camera 3) instruments, respectively

An article accepted for publication in “The Astrophysical Journal” reports the results of calculating the universe’s expansion rate based on the observation of Cepheids with the James Webb Space Telescope. In particular, a team of researchers led by Adam Riess used the NIRCam instrument to observe over 330 cepheids in the galaxies NGC 4258 and NGC 5584. The results are more precise than those obtained in the past with the Hubble Space Telescope but confirm the accuracy of the previous calculation of the universe’s expansion rate. This leaves open the question of the difference in results obtained with different methods.

Artist's concept of the TOI-4600 system (Image courtesy Tedi Vick)

An article published in the “Astrophysical Journal Letters” reports the discovery of two exoplanets orbiting the star TOI-4600 of which the outermost is the one with the longest year discovered so far. A team of researchers used observations conducted with NASA’s TESS space telescope to find traces of these two gas exoplanets. Other ground-based observatories were used to confirm the existence of these two exoplanets and obtain more information about them. TOI-4600 b has a year of nearly 83 Earth days, a bit shorter than Mercury’s, while TOI-4600 c has a year of nearly 483 days, the longest of all known exoplanets. This is a useful discovery to understand what other planetary systems are like because exoplanets close to their stars are much easier to discover while we still know very little about the ones far from their stars.

The Aditya-L1 space probe at blastoff (Image courtesy ISRO)

A few hours ago, the Indian space probe Aditya-L1 blasted off from the Satish Dhawan space center atop a PSLV-XL rocket. After about ten minutes, it regularly separated from the rocket’s last stage. In about 109 days, Aditya-L1 will reach the Lagrange point called L1, about 1.5 million kilometers from the Earth, where it will begin its mission of observing the solar atmosphere and various processes taking place on the Sun’s surface. It will join other space probes and solar observatories helping to unlock the last secrets of the Sun.