Category Archives: star death

A Hypernova Sponsor

We go to a number of planetarium conferences every year, and like most folks who work in the planetarium business selling things to other colleagues, we get hit up for “donations” to help support the costs of conferences. Frequently we’re given a choice of ways to donate money, and they’re given cute names like “Nova” sponsors or “supernova” sponsors. Recently we’ve been seeing the term “Hypernova” for a sponsor who gives some huge amount of money (like around $5,000 or $10,000). I guess these are perceived as hierarchies, much as silver, gold, and platinum are used commonly to describe credit cards with higher and higher amounts.

It’s not quite the same kind of hierarchy as stellar explosions though. While a nova might be perceived as the “weakest” of the mighty outbursts that flow from stars, and a supernova is a strong one, with a hypernova being a really strong one, these terms really refer to distinctly different types of stellar explosions.

According to the National Radio Astronomy Observatory online dictionary of astronomy terms, a nova is a star that abruptly increases in brightness by a factor of a million. A nova is caused in a binary star system where hydrogen-rich material is transferred to the surface of a white dwarf until sufficient material and temperatures exist to kindle explosive nuclear fusion.

Skip down to supernova, and you get this: an extremely violent explosion of a star many times more massive than our Sun. During this explosion, the star may become as bright as all the other stars in a galaxy combined, and in which a great deal of matter is thrown off into space at high velocity and high energy. The remnant of these massive stars collapse into either a neutron star or a black hole.

There isn’t a definition for hypernova yet, because astronomers are still trying to figure out the precise conditions that would lead us to call a super-supernova explosion a “hypernova.”

Which brings me to a very cool announcement this week from a consortium of researchers in Europe, the U.S. and Japan, linking hypernovas to gamma-ray bursts. Here’s the scoop, as told by the National Observatory of Japan’s Subaru Telescope:

    An international research team, led by astronomers from the University of Tokyo, Hiroshima University, and the National Astronomical Observatory of Japan, used the Subaru telescope to obtain the spectrum of SN2003jd, a hypernova unaccompanied by a gamma-ray burst, and found the first evidence that it is a jet-like explosion viewed off-axis. Hypernovae are hyper-energetic Supernovae that are often associated with gamma-ray bursts. This result provides clear and firm evidence that all Hypernovae may be associated with gamma-ray bursts, but that gamma-ray bursts are observable only when jets produced by the hypernova explosion point towards Earth.

There’s more information at their web site, explaining the rationale behind the research.

All that being said, I find it amusing that a donor giving massive amounts of money is named after a stellar phenomenon that is so energetic, but yet is also can be so destructive and mysterious.

What Will Happen?

One of the things that has always fascinated me about public understanding of science is the question that somebody asks, and then immediately apologizes for asking a dumb question. Folks, there is NO such thing as a dumb question, but there are people who think they’ll LOOK dumb by asking something they think everybody but them knows the answer to.

One of those questions is “What’ll happen to the Sun?” Well, it’s a valid one. We’ve all heard that the Sun is about halfway through its life, that it’s about 4.5 billion years old. So, that suggests that in another five and a half billion years, something will happen. But what?

To tell you the truth, that’s a question we’ve been grappling with on this project I’m writing for. The current story is that the Sun will end its days as a white dwarf. Somewhere between now and that time, however, it might go through a giant phase and then a planetary nebula phase before it approaches white dwarfdom.

It’s a nice, orderly progression that satisfies our sense of science marching onward, but is it really going to happen? Maybe yes. Maybe no.

Not exactly what you want to know, is it? Well, science is like that. Based on the best available data, we try to give answers. When the data and models change, then the answers change. It doesn’t mean the original answer was wrong. It just means the data changed what we think is going to happen. If you give somebody directions down to the nearest shopping center or gas station and they come back and tell you that the stores are not there anymore, you weren’t wrong in your directions. You just didn’t know the truth of the matter.

So, what’s the truth of the matter when it comes to talking about the ultimate demise of our star? The current storyline could be written something like this: in about five billion or so years, the Sun will stop burning hydrogen in its core and start burning helium. The outer layers will expand with the added heat that is given off in the nuclear process, and the Sun may well become some sort of giant star. It may engulf Mercury. The orbits of Venus, Earth and possibly Mars could get shifted outward a bit. Then, after some amount of time, the outer atmosphere will blow off, and maybe (maybe!) there will be a planetary nebula surrounding the slowly shrinking (but still very hot) core of what’s left of the Sun. If there’s enough mass left over, the Sun will become a white dwarf.

That all sounds pretty iffy, but that’s the way it goes. Science aims to get us enough data to understand (and explain) these things. Right now the data point toward our Sun going through this set of steps in the far distant future. It’s a great story and I’d love to be around to see it happen!

However, keep in mind that some new data and observations could come in that will change this storyline—maybe subtly, maybe in a big way. That’s the way science works, too. And that is it’s greatest strength!