Ultraviolet light reveals dark secrets
The Hubble Space Telescope — with its ability to see in ultraviolet wavelengths — provides astronomers a unique tool to examine the Universe. As anyone who as seen glowing metal can attest, materials predominantly give off a range of colors as they heat. Using this knowledge, astronomers are able to determine the temperatures of distant objects by looking at the color given off by the target. This is also why stars are different colors — red stars are the coolest stars commonly seen, followed by middle-of-the-road stars like our Sun, while blue and white stars are the hottest.
But, just like our own Sun, temperatures in the atmospheres surrounding stars are significantly hotter than they are on the surface. The peak frequency given off by this greatly-heated material is found in ultraviolet wavelengths of the electromagnetic spectrum — perfect for observations by Hubble.
“Hubble’s ultraviolet-light sensitivity allowed researchers to probe the layers above the star’s surface, which are so hot — more than 20,000 degrees Fahrenheit — they cannot be detected at visible wavelengths. These layers are heated partly by the star’s turbulent convection cells bubbling up to the surface,” the Hubble team reports.
Betelgeuse is doomed to end its life as a supernova explosion. If this occurs, the eruption will easily be visible from Earth. The red giant star is roughly 725 light years from Earth — far enough away to prevent any dangerous effects from befalling our homeworld. However, the supernova would likely create a “daytime star” that could last for months on end, and light from the star could cast shadows at night.
However, Betelgeuse is currently lost in the glare of the Sun, as seen from Earth (or Hubble, which hugs close to our planet).
Betelgeuse is out of view from mid-May to early August due its close angular proximity to the Sun (as seen from Earth). This summer, thanks to the STEREO mission, Betelgeuse cannot hide in the Sun’s glare.
“While unobservable from Earth, Betelgeuse and surrounding stars have been imaged from the Solar Terrestrial Relations Observatory spacecraft (STEREO-A) located about 69 degrees behind the Earth in the Earth’s orbit,” researchers write in an article published in The Astronomer’s Telegram.
Observations from the STEREO space observatory reveal Betelgeuse had a second, less dramatic, dimming from the middle of May to mid-July. When the star expands once more in late August and early September, Dupree will study the star using the STEREO observatory, watching for signs of another outburst.
Supernova eruptions of supermassive stars like Betelgeuse form the heavy atoms on which planets and life are constructed — including the carbon in our bodies.
It takes light 725 years to traverse the distance between Betelgeuse and Earth. This means that if Betelgeuse exploded around the year 1295, as the Middle Ages ended, we would be seeing light from that event right about… now.
This article was originally published on The Cosmic Companion by James Maynard, founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat. You can read this original piece here.
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