Washington | To mark the 26th anniversary of the launch of NASA’s Hubble Space Telescope, astronomers have unveiled an image captured by it of an enormous bubble being blown into space by a super-hot, massive star located 7,100 light-years from Earth.
The Hubble was launched into the Earth orbit by the STS-31 space shuttle crew on April 24, 1990. As Hubble makes its 26th revolution around our home star, the Sun, we celebrate the event with a spectacular image of a dynamic and exciting interaction of a young star with its environment, said John Grunsfeld, Hubble astronaut and associate administrator of NASA’s Science Mission Directorate.
The Bubble Nebula (NGC 7635) is seven light-years across – about one-and-a-half times the distance from our Sun to its nearest stellar neighbour, Alpha Centauri, and resides 7,100 light-years from Earth in the constellation Cassiopeia. The seething star forming this nebula is 45 times more massive than our Sun.
Gas on the star gets so hot that it escapes away into space as a stellar wind moving at over four million miles per hour. This outflow sweeps up the cold, interstellar gas in front of it, forming the outer edge of the bubble much like a snowplow piles up snow in front of it as it moves forward.
As the surface of the bubble’s shell expands outward, it slams into dense regions of cold gas on one side of the bubble. This asymmetry makes the star appear dramatically off-centre from the bubble. Dense pillars of cool hydrogen gas laced with dust appear at the upper left of the picture, and more fingers can be seen nearly face-on, behind the translucent bubble.
The gases heated to varying temperatures emit different colours. Oxygen is hot enough to emit blue light in the bubble near the star, while the cooler pillars are yellow from the combined light of hydrogen and nitrogen. The pillars are illuminated by the strong ultraviolet radiation from the brilliant star inside the bubble.
The Bubble Nebula was discovered in 1787 by British astronomer William Herschel. It is being formed by an extremely bright, massive and short-lived star that has lost most of its outer hydrogen and is now fusing helium into heavier elements.
The star is about four million years old, and in 10 million to 20 million years, it will likely detonate as a supernova. Hubble’s Wide Field Camera-3 imaged the nebula in visible light with unprecedented clarity in February 2016.
The Bubble Nebula is one of only a handful of astronomical objects that have been observed with several different instruments onboard Hubble. Hubble also imaged it with the Wide Field Planetary Camera (WFPC) in September 1992, and with Wide Field Planetary Camera-2 (WFPC2) in April 1999.
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