A red, metal-rich relic
23-03-2018 05:05 PM CET
europeanspaceagency posted a photo:
This idyllic scene, packed with glowing galaxies, has something truly remarkable at its core: an untouched relic of the ancient Universe. This relic can be seen in the large galaxy at the centre of the frame, a lenticular galaxy named NGC 1277. This galaxy is a member of the famous Perseus Cluster — one of the most massive objects in the known Universe, located some 220 million light-years from Earth. NGC 1277 has been dubbed a “relic of the early Universe” because all of its stars appear to have formed about 12 billion years ago. To put this in perspective, the Big Bang is thought to have happened 13.8 billion years ago. Teeming with billions of old, metal-rich stars, this galaxy is also home to many ancient globular clusters: spherical bundles of stars that orbit a galaxy like satellites. Uniquely, the globuar clusters of NGC 1277 are mostly red and metal-rich — very different to the blue, metal-poor clusters usually seen around similarly-sized galaxies. In astronomy, a metal is any element heavier than hydrogen and helium; these heavier elements are fused together in the hot cores of massive stars and scattered throughout the Universe when these stars explode as they die. In this way, a star’s metal content is related to its age: stars that form later contain greater amounts of metal-rich material, since previous generations of stars have enriched the cosmos from which they are born. Massive galaxies — and their globular clusters — are thought to form in two phases: first comes an early collapse accompanied by a giant burst of star formation, which forms red, metal-rich clusters, followed by a later accumulation of material, which brings in bluer, metal-poor material. The discovery of NGC 1277’s red clusters confirms that the galaxy is a genuine antique that bypassed this second phase, raising important questions for scientists on how galaxies form and evolve: a hotly debated topic in modern astronomy.
Credits: NASA, ESA, and M. Beasley (Instituto de Astrofísica de Canarias)
23-03-2018 10:24 AM CET
europeanspaceagency posted a photo:
The Dutch are now starting to see their famous spring flowers poke through the winter soil, but a few weeks ago it was a different story as a cold snap took grip.
This Copernicus Sentinel-2 image from 2 March 2018 shows Amsterdam and the IJmeer and Markemeer freshwater lakes covered by a thin layer of ice. As famous as the Netherlands is for flowers, it’s arguably equally renowned for ice skating. While the cold snap caused havoc throughout much of Europe, the Dutch were busy dusting off their skates and eager to hit the ice. The ice on these big lakes was much too thin to skate on, but some canals in Amsterdam were closed to boats to give the ice a chance to thicken and skaters took what is now a relatively rare opportunity to enjoy a national pastime.
A possible consequence of climate change, the Netherlands doesn’t see the ice that it used to. The Royal Netherlands Meteorological Institute rates winters using an index: those scoring above 100 are considered cold. Between 1901 and 1980, there were seven winters above 200 – very cold. The last time the index exceeded the magical 100 mark was in 1997. In fact, this was also the last time the weather was cold enough for an ‘Elfstedentocht’: a 200 km skating race between 11 towns in the north of the country. In 2014, for the first time since measurements began, the index fell to zero.
While people enjoyed the ice below, this Sentinel-2 image, which is also featured on the Earth from Space video programme, allows us to view the beauty of this short-lived layer of ice from above.
Credits: contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO