Two-fer Twosday
A two-fer post seems applicable today….
Last week, a team of astronomers, that includes former NRC postdoc Guillaume Thomas, announced the discovery of the remains of another galaxy that merged with the young Milky Way long ago. Using data from the European Space Agency’s plucky Gaia satellite, the team found evidence of a new stream of stars orbiting the Galaxy, what was once a small galaxy of its own that was pulled and torn apart by the larger Milky Way about 8-10 billion years ago. The fact that we can still see this stream in the present day suggest the merger was relatively slow, otherwise the small galaxy’s stars would have been scattered all over the Milky Way’s halo. The team has named this formerly separate galaxy “Pontus,” a particularly cute name because in Greek mythology Pontus is the one of the children of Gaia, the goddess of the Earth. Pontus is the latest ancient merging event to have been spotted so far, joining only five others that were named previously (and rather haphazardly) Sagittarius, Cetus, Gaia-Sausage/Enceladus, LMS-1/Wukong, and Arjuna/Sequoia/I’itoi. In fact, the team sees the clear evidence of these previous five events too in their analysis, and see some evidence for yet another one. It’s mind-boggling to think that relics of the Milky Way’s early history are still discernable in the motions of the sky today, but here we are. Here’s a link to the paper and other link to the press release for those who’d like to read up more about this amazing discovery.
Meanwhile, last Tuesday everything seemed normal here on planet Earth but that day the Sun launched a huge flare that fortunately was directed away from us. Spotted by the NASA/ESA Solar Orbiter spacecraft, you can see in the attached image the flare extending away from the Sun to about the same (projected) distance as its diameter. This image is allegedly the largest eruption to have been captured in a single frame. Here’s some links to animations of the event taken by various satellite observatories at that time: STEREO A, SUVI, and SOHO. Rather impressive, especially since the flare seems to have scorched two “sungrazer” comets that happened to be in the wrong place at the wrong time! (See that last link for a picture of the comets.) Here also is a link to a nifty and short YouTube video showing the eruption as observed from STEREO A and SOHO side by side. I don’t think this flare presages anything wrong with the Sun – indeed the Solar Cycle that we’ve just started is predicted to be as tepid as the last one. We just happen to have more “eyes” on the Sun than ever before, and are able to see the fireworks when they go off better than ever!
Have a great ‘Twosday’ (22/02/2022), everyone!
