In 1995, the Hubble telescope took the first picture of the atmosphere of a star other than the sun: Betelgeuse. This enormous star can be seen with the naked eye on clear evenings in the constellation of Orion, and its red color clearly distinguishes it from the other stars.
The famous Hubble image of Betelgeuse — also known as Alpha Orionis — is this week’s space photo of the week.
The red superstar is about 530 light-years from Earth and is roughly 14 times more massive than our Sun. Astronomers expect the star to explode as a supernova in the near future. How long will that take? “Given its mass and current age, Betelgeuse will transform into a supernova in roughly 1.5 million years,” said researcher Ralph Neuhäuser in conversation with Scientias.nl last year. Chances are small that we will ever see that.
Betelgeuse is regularly in the news. In 2019, the brightness of the red supergiant suddenly decreased. Was the star about to explode? This turned out not to be the case. The great eclipse was the result of a drop in temperature on the surface of the red supergiant. “We directly witnessed the formation of so-called stardust,” says researcher Miguel Montargès. The dust shroud Betelgeuse so handcrafted blocked some of the starlight, making Betelgeuse appear less bright.
Supernovae are the largest explosions that occur in space. They are caused by a change in the core of a star. That change may be the result of two different developments. In the case of Betelgeuse, the changes occur because the star has run out of fuel. Without that source of energy, the star can no longer compete with gravity and part of its own mass flows towards that core. It gets heavier and heavier until it collapses. This results in a gigantic explosion, or a supernova. Fortunately, the distance to the earth is large enough, so we will not be affected by the supernova explosion on our planet. Our distant descendants can expect a spectacular fireworks show!
Betelgeuse is getting redder
Did you know that Betelgeuse looked different in ancient times? Recent research reveals that barely 2,000 years ago, the star was yellow-orange rather than red in color. It is remarkable that a star can change color in barely 2,000 years. Neuhäuser: “Only at a mass of about fourteen solar masses would you expect a rapid color change in the past two millennia, so we can determine the mass more precisely.”
White spot is remarkably hot
The Hubble image shows a strikingly bright spot. This white spot is hundreds of times larger than the diameter of the sun and is at least 2,000 degrees Celsius hotter than the surface of the star.
It’s amazing that Hubble was able to photograph the star so clearly. The apparent size of Betelgeuse is 20,000 times smaller than the full moon. You can compare it to distinguishing the headlights of a car at a distance of about 10,000 kilometers.