Just a few months before the COVID-19 epidemic began in early 2020, the world's attention was drawn to Betelgeuse, a distant supergiant star 700 light-years away. The gigantic furnace diminished dramatically, becoming ten times darker than usual. Some speculated that it signalled the start of a bomb, but tales of the star's death were grossly exaggerated. Only a few months later, it lightened up.
Several teams worked to figure out what caused the "Great Dimming," with one team analysing hundreds of photos of the star and concluding that stardust was most likely blocking our view from Earth. They discovered in June 2021 that Betelgeuse had likely belched out gas, which cooled and solidified, darkening the star. Another hypothesis was that the star was cooling slightly, and that this variability could have resulted in a drop in brightness. It certainly played a role in the creation of the dust cloud.
Is the mystery solved? Perhaps, but the Great Dimming has yielded one more surprising find.
A trio of astronomers describe their own stunning discovery in a new article published in the journal Nature on Monday: they were able to locate Betelgeuse lurking in the background of photographs acquired by the Japanese weather satellite Himawari-8. The chance discovery backs up some of the earlier studies on the Great Dimming's origins and hints to a new avenue to investigate our cosmic neighbourhood that has yet to be explored.
As the name implies, Himawari-8 is the eighth edition of Japan's Meteorological Agency's Himawari satellite. It orbits the earth at a distance of 22,236 miles above the equator in geostationary orbit. The International Space Station is more than 90 times farther away.
The satellite takes optical and infrared photographs of the entire Earth once every 10 minutes from that location, primarily to aid in weather forecasting in Asia and the Western Pacific. For example, it captured a large number of photographs of the Tongan volcano explosion on Jan. 15. However, a team of Japanese researchers started seeking for a pinprick of light that would be Betelgeuse, hidden in space behind our dazzling blue and green marble, in photographs dating back to 2017. They discovered it.
The researchers came to the same conclusion as their predecessors after studying that speck of light: Betelgeuse diminished due to both dust and natural variations in its luminosity. That's not particularly thrilling, but it's good evidence that we're all on the same track, and it's exactly what the scientific method entails.
The fact that a weather satellite was able to offer this data in the first place is fascinating.
For astronomers, this might be a huge thing. Building and deploying new space telescopes is neither cheap nor simple, and you'll need to reserve a rocket. However, there are currently satellites orbiting the Earth that may perform a similar function.
"Himawari is like a free space telescope!" astronomer Simon Campbell of Monash University in Australia said.
For example, weather satellites like Himawari-8 are constantly imaging the Earth and the space around it, generating mountains of data to sort through. This is significant because astronomers must frequently argue for time on telescopes, carving off blocks for their projects that allow them to choose where the telescope is focused.
When Betelgeuse inexplicably dimmed, for example, some of the world's most powerful telescopes were already booked to gaze elsewhere. One, the Very Large Telescope in Chile, allowed a team to use its telescope for observations, delaying the completion of other projects. However, these cases aren't always resolved.
So, as Campbell pointed out, there's a neat tale here about space observation. You may explore into repurposing Earth imaging satellites in orbit to study background stars. Another advantage is that they can view for up to 24 hours and may be able to see in wavelengths of light that are not obstructed by the Earth's atmosphere, such as infrared.
We might already be observing the next time a star threatens to go supernova on us.
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