WASHINGTON – Fire and ice captured the attention of the worldwide astronomical community in the past 24 hours.
The fire came from the explosion of one of the closest supernovas to Earth since February 1987 and was observed by astronomers in a galaxy in the constellation of Ursa Major — the Big Dipper — on Tuesday night. We are in no danger from this event as it is 11.4 million light years away. The supernova in 1987 was 160,000 light years away in a dwarf galaxy and was only visible in the Southern Hemisphere.
When an event like this occurs a worldwide notification goes out by the International Astronomical Union (IAU) Central Bureau for Astronomical Telegrams (CBAT) so the observation can be confirmed and others made by observatories. It’s a safe bet every telescope in the Northern Hemisphere and our space-based telescopes, including the Hubble Space Telescope (HST) will be zeroing in on PSN
— the archaic temporary name given to the supernova.
Located in a galaxy called M82, also known as the “Cigar Galaxy” because of its distinctive shape, it’s a favorite of amateur astronomers because it’s fairly bright in their telescopes.
A college professor and some of his students decided to take a look at M82 and get a few images before clouds rolled in on Tuesday night. When they looked at the images they knew something was up. After eliminating other causes they notified the CBAT and confirmation was obtained. The supernova won’t be named for its discoverers like comets are but will get an official designation by the IAU soon.
This was a “Type Ia” supernova which means that a white dwarf starexploded; “Type II” supernovas involve stars far more massive than the Sun that explode. A white dwarf star is the remnant core of a star like our Sun that has run out of hydrogen and helium fuel and no longer undergoes nuclear fusion — the process of burning hydrogen into helium (and eventually other elements) and creating energy. Nuclear fusion is how stars shine and the elements are created but all stars’ fuel supplies are limited — eventually they run out of gas — literally.
Our sun will eventually run out of fuel and become a white dwarf, about the size of the Earth with about half of the mass of the Sun. It will be white hot and eventually cool down to blackness. A teaspoon of white dwarf matter is so compressed that it weighs a ton. But the white dwarf that was our Sun will not go supernova because it is not massive enough.
To go supernova a white dwarf must be in a binary star system, that is another star must be close enough to the white dwarf so that matter from the other star falls upon it. When enough matter has fallen on to the white dwarf a critical limit is reached from which there is no return – the white dwarf will become a supernova as happened in M82.
Type Ia supernovas are well behaved in how they evolve in their brightness after they explode, so much so that astronomers use them as a “standard candle for measuring distances in the Universe.
With this new Type Ia supernova in our galactic backyard we will get a lot of valuable data with our most sophisticated telescopes and their detectors, ground and space based. HST may have actually captured the star that blew up in previous images. If we can identify the star that exploded we will learn a lot about pre- supernova conditions and the binary system involved.
Type Ia supernovas are also used to study of the expansion of the Universe and dark energy- – the force behind the acceleration of the Universe’s expansion. It was the study of Type !a supernovas that led to the discovery that our Universe was accelerating due to dark energy.
In two weeks the supernova should be bright enough to see with regular binoculars — quite an event! I will try to capture an image the supernova in my own telescope and post the picture.
I’ll follow this story closely and provide updates.
Ice, or more accurately water vapor, was the other big astronomical story on Jan. 22 as it was announced that the largest body in the asteroid belt, Ceres, was detected to have water vapor erupting from its surface. Reclassified in 2006 from being an asteroid to a dwarf planet (similar to what happened to Pluto) Ceres is roughly 600-miles across. Ceres has been known for hundreds of years, discovered in 1801 and is visible to the unaided eye when closest to the Earth — if you know where to look.
Wednesday’s announcement is significant as it’s the first confirmed detection of water vapor from Ceres or any other body in the asteroid belt. Astronomers calculate that if all of the water ice in Ceres were to melt it would have more fresh water than Earth.
The bonus to this story is that NASA’s Dawn spacecraft is headed to Ceres and will arrive in the spring of 2015 to explore this dwarf planet up close and personal. We’ll learn much more about the water vapor plumes, atmosphere and surface of this intriguing world.