Massive star may explode any day

News in Science ^ | Tuesday, 4 February  2003 | Danny Kingsley - ABC Science Online

[vannrox]

	Artist's impression of Rho Cassiopeiae (Pic: Instituto de Astrofisica de Canarias)

A massive and very unstable star in our galaxy is likely to explode any day, ejecting mass equal to 10,000 Earths, astronomers have predicted.

The giant star, known as Rho Cassiopeiae, was first observed shedding an equivalent mass of material three years ago by the Isaac Newton Group of Telescopes - more than astronomers have ever witnessed in a single stellar eruption.

Recently, they have noted the star exhibiting some of the same behaviour that lead to that explosion. A study of the build-up is published in the February issue of The Astrophysical Journal.

"Rho Cassiopeiae could end up in a supernova explosion at any time as it has almost consumed the nuclear fuel at its core," said Dr Garik Israelian of the Instituto de Astrofisica de Canarias in Spain.

"It is perhaps the best candidate for a supernova in our galaxy, and the monitoring of this and other unstable evolved stars may help us to shed some light on the very complicated evolutionary episodes that precede supernova explosions," he said.

Rho Cassiopeiae is one of the most massive stars known, about 40 times heavier and 700 times bigger than our Sun, and shining some 50,000 times more brightly.

Such massive stars are called hypergiants, and Rho Cassiopeiae is the brightest of the only seven yellow hypergiants known in our galaxy. Hypergiants are very bright and very hot, with temperatures of between 3,500°C to 7,000°C.

Between 1993 and 2002, five telescopes in Europe and the United States have been trained on the star, and the astronomers were rewarded in 2000 when they were able to record the first eruption.

At the time, the star brightened considerably, then dimmed. "This dimming is corresponding to the star shedding a shell, by producing a shock wave which is about four times as fast as the speed of sound," Dr Alex Lobel of the Harvard-Smithsonian Centre for Astrophysics, in Boston, told reporters.

The team analysed the event's spectra, or separated light, to determine temperature changes and learn how much material was shot into space. The star cooled down from 7,000°C to 4,000°C within a few months during the event. Over 200 days, the star ejected about three per cent of its mass - equal to 10,000 Earths.

Since then, the star has been restless. Its outer atmosphere seems to be collapsing, an event that looks similar to one that preceded the last outburst. The researchers think another eruption, possibly a stronger one, is imminent.

Despite being 10,000 light-years away from Earth, in the constellation Cassiopiea, Rho Cassiopeiae has a brightness of 4.5 on a scale that runs from 6 being the dimmest that can be seen by the unaided eye and 0 for the brightest objects.

This massive distance means that the events being observed occurred about 10,000 years ago. A light year is the distance light travels in a year, so each light year an object is away represents a delay of a year between an event occurring and us being able to observe it.

In 1946, the star was first seen dimming by six-fold as it ejected material; dimming indicates a steep drop in surface temperature. This variation in temperature appears to happen about every 50 years. Astronomers estimate that over the next 10,000 years, the star will experience 200 more eruptions, losing 0.1 times the mass of the Sun each time.

Unfortunately for Australians, Rho Cassiopeiae is only visible to the naked eye in the Northern Hemisphere.

Danny Kingsley - ABC Science Online

More Info?

Chandra's stunning debut, News in Science 27 Aug 1999

Threat to Earth from supernova blast falls, News in Science 4 Dec 2002

© ABC 2003 | privacy

[vannrox]

Hum. I wonder if we can see it in the Northern Hemisphere, or will we have to get or sue some telescope to see it. Anyone know?

[Khurkris]

...uhhh...yep....any day now....yep...gonna explode...uh, yeah...pretty soon now...uhh...moving along.....

[<1/1,000,000th%]

A Palestinian star?

[RansomOttawa]

Recently, they have noted the star exhibiting some of the same behaviour that lead [sic] to that explosion.

Pardon the off-topic pedantry, but is this increasingly annoying spelling error finding its way into journalistic writing now?

"Lead" (the noun) is a poisonous heavy metal. The past tense of "lead" (the verb) is "led."

That being said, you asked:

Hum. I wonder if we can see it in the Northern Hemisphere, or will we have to get or sue some telescope to see it. Anyone know?

The article says the star is visible only in the northern hemisphere (In the winter or summer, though, that's the question.)

As for seeing the explosion itself, I think the key is this:

Astronomers estimate that over the next 10,000 years, the star will experience 200 more eruptions, losing 0.1 times the mass of the Sun each time.

Obviously "any day now" means something different to astronomers than to the rest of us. 8-)

[dd5339]

Super Nova ping!

Semper Fi

[SoCal Pubbie]

Marlon Brando?

[ofMagog]

Last time I wanted to sue a telescope 1800 lawyers were willing to take the case.

[HuntsvilleTxVeteran]

ABC junk science

[humblegunner]

I thought this was another Rosie thread....

[Chancellor Palpatine]

ping

[Dog Gone]

Arguably, the star could explode any day now, and we won't be able to notice it for 10,000 years.

[Willie Green]

I hope it doesn't have any inhabited planets orbittine it.
Think of all the species that would become extinct.
Congress The United Nations needs to prevent this!

[dighton]

Buy gold!

[Semper Paratus]

Arguably, the star could explode any day now, and we won't be able to notice it for 10,000 years.

More likely that the star already exploded but we won't see it for 10,000+ years.

[dead]

This is just silly. I've never seen stellar evolution discussed in a "days" time frame.

If they could narrow down the explosion date to a few tens of thousands of years, I'd be impressed.

[Chancellor Palpatine]

"The future looks robust for gold and silver certificates. While we've been saying that the world will end for the last 50 years, this time, we REALLY mean it. Buy now!"

[Kay Soze]

I can think of a few I'd like to see explode:

Martin(all my kids are drug addicts but I know whats morally right)Sheen,Susan Bug eyed Sarandon, Sean I am Penn, George (My aunt got me in)Clooney, Whoredonna.

[KarlInOhio]

Cassiopeia

Look west and a little south of Caph. The Greek letter rho looks like a p.

Cassiopeia is the big W (or M) in the northern sky.

[rogers21774]

Arguably, the star could explode any day now, and we won't be able to notice it for 10,000 years.

More likely that the star already exploded but we won't see it for 10,000+ years.

Most likely of all is it exploded some 10,000 years ago (give or take a few days) and we're about to see it in action.

[RansomOttawa]

Arguably, the star could explode any day now, and we won't be able to notice it for 10,000 years.

Good point, one I'd not thought of (oops!). Still, the shifting of time frames between what astronomers can observe today vs. what is happening in real time 10,000 ly away is confusing, and poor writing.