Comets are known to be a mixture of dust and ice, and if fully compact, they would be heavier than water. However, measurements have shown some of them to have densities much lower than that of water ice, implying that comets must be highly porous. A new study of low-density Comet 67P/Churyumov-Gerasimenko using data from ESA’s Rosetta spacecraft rules out a cavernous interior.
The final primary mirror segment is installed on NASA’s James Webb Space Telescope. Once in space and fully deployed, the 18 hexagonal-shaped mirror segments will work together as one large 6.5-metre mirror. The crowning mirror installation marks an important milestone in the assembly of what will be the biggest and most powerful space telescope ever launched.
An international team led by a researcher from Hiroshima University has succeeded in revealing the detailed structure of a massive ionised gas outflow streaming from the starburst galaxy NGC 6240, 350 million light-years away in the constellation Ophiuchus. The team used the Suprime-Cam mounted on the 8.2-metre Subaru Telescope on Maunakea in Hawaii.
Astronomers have made the first direct measurement of the temperature of large dust grains in the outer parts of a planet-forming disc around a young star. Observations of an object nicknamed the Flying Saucer reveals that the grains are much colder than expected. This surprising result suggests that models of these discs may need to be revised.
It has been suggested that gamma rays coming from the dense region of space in the inner Milky Way galaxy could be caused when invisible dark matter particles collide, but two new studies suggest that the gamma ray bursts are due to other astrophysical phenomena such as fast-rotating stars called millisecond pulsars.
You might think that, in the rings of Saturn, more opaque areas contain a greater concentration of material than places where the rings seem more transparent. But this intuition does not always apply, according to a recent study of the rings using data from NASA’s Cassini mission. The research also suggests that the planet’s brightest B ring could be a few hundred million years old instead of a few billion.
By combining X-ray data from NASA’s Chandra X-ray Observatory over a 15-year period with radio data from the Australia Telescope Compact Array, astronomers have a better understanding of the active galaxy Pictor A, the supermassive black hole at its core and the enormous jet of particles it generates travelling at nearly the speed of light into intergalactic space.
A new image from NASA’s New Horizons spacecraft is the first look at Pluto’s atmosphere in infrared wavelengths, and the first image of the atmosphere made with data from the probe’s LEISA instrument. The blue ring around Pluto is caused by sunlight scattered from a haze of hydrocarbon particles in the form of a photochemical smog.
We can become very attached (even fondly) to the instruments that give us such a thrill observing the Universe. It can come very hard, then, for us to question their quality. Reviewer Steve Ringwood takes a look through a Ronchi eyepiece that permits the user to obtain a definitive and exacting exposure of a telescope’s optical quality.