Category Astronomy/Space

Star Clusters are only the Tip of the Iceberg

Alpha Persei star cluster
A panoramic view of the nearby Alpha Persei star cluster and its corona. The member stars in the corona are invisible. These are only revealed thanks to the combination of precise measurements with the ESA Gaia satellite and innovative machine learning tools (© Stefan Meingast, made with Gaia Sky)

Finding lost star siblings. Star clusters have been part of the Imaginarium of human civilization for millennia. The brightest star clusters to Earth, like the Pleiades, are readily visible to the naked eye. A team has now revealed the existence of massive stellar halos, termed coronae, surrounding local star clusters.

“Clusters form big families of stars that can stay together for large parts of their lifetime...

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The Mountains of Pluto are Snowcapped, but not for the same reasons as on Earth

At left, the “Cthulhu” region near Pluto’s equator, at right the Alps on Earth. Two identical landscapes created by highly different processes.
© NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
© Thomas Pesquet/ESA

In 2015, the New Horizons space probe discovered spectacular snowcapped mountains on Pluto, which are strikingly similar to mountains on Earth. Such a landscape had never before been observed elsewhere in the Solar System. However, as atmospheric temperatures on our planet decrease at altitude, on Pluto they heat up at altitude as a result of solar radiation.

So where does this ice come from? An international team led by CNRS scientists* conducted this exploration...

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Astronomers Solve Dark Matter Puzzle of Strange Galaxy

Image and amplification (in colour) of the ultra-diffuse galaxy Dragonfly 44 taken with the Hubble space telescope. Many of the dots on the galaxy are the globular clusters studied in this article to explore the distribution of dark matter. The galaxy is so diffuse that other galaxies can be seen behind it. Credit: Teymoor Saifollahi and NASA/HST.
Image and amplification (in colour) of the ultra-diffuse galaxy Dragonfly 44 taken with the Hubble space telescope. Credit: Teymoor Saifollahi and NASA/HST.

Astronomers have found that the total number of globular clusters around Dragonfly 44 and, therefore, the dark matter content, is much less than earlier findings had suggested, which shows that this galaxy is neither unique nor anomalous.

At present, the formation of galaxies is difficult to understand without the presence of a ubiquitous, but mysterious component, termed dark matter. Astronomers have measure how much dark matter there is around galaxies, and have found that it varies between 10 and 300 times the quantity of visible matter...

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A new look at Sunspots

Scientists created light curves using the high-resolution images of the Sun to understand what a sunspot would look like on a distant star. They studied different layers of the Sun from the visible surface to the outer atmosphere using 14 different wavelengths, including the six shown here (top left to right: photosphere, magnetic flux of the photosphere, ultraviolet 304 angstroms; bottom left to right: ultraviolet 171 angstroms, ultraviolet 131 angstroms, x-ray).
Credits: NASA/SDO/JAXA/NAOJ/Hinode

NASA’s extensive fleet of spacecraft allows scientists to study the Sun extremely close-up — one of the agency’s spacecraft is even on its way to fly through the Sun’s outer atmosphere. But sometimes taking a step back can provide new insight.

In a new study, scientists looked at sunspots ...

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