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Spongebob thousands of years later3/13/2023 With this data, we could literally rewind our journey to determine that our Solar System was closer to Sco-Cen 5-7 million years ago. In 1997, the European Space Agency released one of the first comprehensive catalogs of star positions and motion through the Galaxy relative to Earth using the Hipparcos Satellite. (By comparison, our Sun is already 4.6 billion years old.) Within Sco-Cen lies the famous red giant star Antares located in the constellation Scorpius seen in Summer night skies. The largest stars in the association are class O and B stars – many times more massive than our Sun and very short lived on the order of a few million years before exploding as supernova. Associations are groupings of stars that formed together in star-birthing nebular clouds of dust and gas. NASAĤ00 light years away from Earth is a group of stars called the Scorpius-Centaurus OB Association (Sco-Cen). If we know two stars are similar enough that they should share the same brightness, but one appears dimmer than another, we can infer it is being seen through more dust and gas in the medium which absorbs some of the light from the star – a process called “dust extinction.” By observing local stars, we see sharp rises in dust extinction in a region surrounding our Solar System and have mapped out the boundaries of an enormous low(er)-density bubble or cavity in the ISM referred to as the “Local Bubble.” That cavity was carved out by the powerful shockwaves of ancient supernova – and we are inside of it.ĭepiction of Local Bubble where our Sun is location and adjacent bubble structures c. Despite being so diffuse, we can measure variations in the ISM by comparing light from similar stars. Where Earth’s atmosphere has thousands of trillions of particles per cubic centimetre, the ISM can be as low density as a few dozen particles per cubic meter. But there is incredibly diffuse gas and dust drifting between stars called the Interstellar Medium (ISM). We typically think of the space between stars as a void – an empty vacuum. Supernova shape the galactic landscape that the Earth and Solar System travel through. In fact, we seem to be travelling through the fallout cloud of supernovae right now. And along Earth’s epic 4.5 billion-year journey, it appears that we’ve had close encounters with supernova several times. But while supernova happen in the Galaxy twice a century, those in close proximity to Earth, within 400 light years, do happen once every few million years. Given the immense size of the Galaxy at around 150,000 light years in diameter, the odds of one of those stars exploding in our backyard is low. Stars explode in the Milky Way about once every fifty years. If you could time travel to a distant past, you’d look up and see an unfamiliar sky – different stars, different constellations, and sometimes the glow of a brilliant supernova. NASA/ESA/HubbleĪs the Sun travels through the Galaxy, so too do the hundreds of billions of other stars that comprise the Milky Way all swirling and spiraling in varying directions. The Crab Nebula is the remains of a Supernova which occurred about a thousand years ago and was visible on Earth recorded by ancient astronomers – C.
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