Then Spitzer Imaged Baby Stars in the Orion Nebula…

The Orion Nebula's star-forming region (NASA)
The Orion Nebula's star-forming region (NASA).

Firstly, apologies that it’s been over a month since last posting to Astroengine.com. Call it slacking off, call it a sabbatical, either way, it’s not good. I’ve actually prepared several half-finished articles, but I just never got around to completing them. However, I have been on writing overdrive over at Discovery News, so if I go quiet over here, you know where to find me.

Speaking of Discovery News, I’ve just posted an incredible image of the heart of the Orion Nebula as seen by the Spitzer Space Telescope, so I can’t think of a better way to kick-start Astroengine with an image filled with awesomeness.

Although Spitzer has entered a new phase of operations since it depleted the liquid helium coolant used to maintain its instrumentation, that doesn’t mean its stopped producing some awe-inspiring imagery. In a new vista released on Thursday, a bustling star formation region in Orion is detailed, showing some 1,500 young stars the observatory watched for 40 days. This is an unprecedented study, allowing rapid variations in these baby stars to be tracked by Spitzer.

Young stars are generally highly variable in their brightness, a characteristic that is of huge interest to astrophysicists. If we can understand the mechanisms causing this variation, we can gain an insight to stellar evolution, possibly even understanding the history of our own Solar System.

As Spitzer observes in infrared wavelengths, it’s very sensitive to clouds of dust being heated by these young stars. Therefore, the proto-planetary disks surrounding these million year old stars glow brightly. Not only does this give an indication to the conditions surrounding the star, it also provides astronomers with an idea to how these disks of dust clump together, slowly evolving into exoplanets. And now Spitzer has data sets spanning weeks, dynamic changes in the emissions from the stars and their evolving planetary systems can be studied.

But science aside, the Spitzer imagery is a thing of beauty, reminding us how complex our cosmos really is. Don’t believe me? Take a look for yourself (click the pic to dive right in):

The star forming region in Orion as studied by Spitzer, rotated 90 degrees (NASA/JPL/Caltech)
The star forming region in Orion as studied by Spitzer, rotated 90 degrees (NASA/JPL/Caltech)
Advertisements

Warning, Over-Hyped Title Alert: But It’s A Frackin’ SUPERNOVA!

"SuperNova" by Shadow-Trance (DeviantArt)
"SuperNova" by Shadow-Trance (DeviantArt)

I’m not kidding, last week was a huge mess of a supernova doomsday circus. It was like whispering “there’s a bomb under your chair” to the person next to you in a crowded theater and then watching the resulting flood of people slam into the fire escape. It was internet chaos. And there was no stopping it.

I am of course talking about the first, great doomsday scare of 2010: T Pyxidis.

Luckily for me, the first headline I saw was in the UK’s Telegraph that read “Earth ‘to be wiped out’ by supernova explosion.” Uh oh, that title sounds rather definite. Immediately, the bullshit sensor in my brain was tripped so I stopped flicking through the embarrassing excuse for a UK newspaper and had a read.

According to the article, some star (that I can’t pronounce) was “set to self-destruct” (as a big hairy supernova), a little over 3,000 light years away. Global chaos will therefore ensue. The ozone layer will be stripped away… and the Earth will be “wiped out.” (I still can’t work out how the Earth will be “wiped out.”)

I’m only picking on the Telegraph.co.uk as my skepticism knives were already sharpened after a series of idiotic woo-fueled articles (here, here and here) the website has played host to in recent months, but they weren’t the only news outlet to go batshit crazy with the “WE’RE ALL GONNA DIE” angle.

But who was really to blame for this mess? After all, the media was just the messenger, they must have gotten their lead from somewhere. Ah yes, the scientists… what did those guys really say?

You can find out how I got to the bottom of the science behind the hype in my Discovery News article “Will Earth ‘Be Wiped Out’ by a Supernova?” but cutting to the chase, it turns out that the scientists may have been a little hasty in their attempt to make international headlines.

As my mate Phil Plait mentions in his excellent write up (about my write up) of the T Pyxidis debacle on Bad Astronomy, this isn’t just a simple case of media hype, a lot of the blame should lay with Edward Sion et al. from Villanova University in Philadelphia.

Sure, some of the numbers didn’t add up (mistakes happen), but issuing a press release with a huge wad of inaccurate doom wrapped inside is pretty irresponsible. Have a read for yourself:

An interesting, if a bit scary, speculative sidelight is that if a Type Ia supernova explosion occurs within [that distance] of Earth, then the gamma radiation emitted by the supernova would fry the Earth, dumping as much gamma radiation (~100,000 erg/square centimeter) into our planet [sic], which is equivalent to the gamma ray input of 1000 solar flares simultaneously. –Excerpt from the Villanova press release, “THE LONG OVERDUE RECURRENT NOVA T PYXIDIS: SOON TO BE A TYPE Ia SUPERNOVA?”

“…fry the Earth”? Come on, that’s not even an accurate scientific term about what would happen if we were hit by a surge of gamma-rays. What’s wrong with saying “…the Earth would be at the receiving end of a Death Ray”? If you’re going to do the job of the tabloid press, hyping up your own research before the tabloid press has even read the release, you may as well be accurate.

And speaking of accuracy, my colleague Ray Villard was at the AAS and confirmed that Sion’s numbers were out by a factor of 10. “A supernova would have to be 10 times closer [to Earth] to do the damage described,” Ray said.

Although I was tough on the Telegraph in my Discovery News article (let’s face it, with an inaccurate and inflammatory title like that, they had it coming), in this case I think the main issue lies with Sion and co.

Why over-hype your research to get attention, when the research was interesting enough without declaring doomsday? By me even writing about the subject again, I think I just answered my own question.

But on a plus point, at least everyone knows what T Pyxidis is now…

Whatever Happened to Hyper-Velocity Star HD 271791?

One scenario: Exploding star flings binary parter away at high velocity (Max Planck Institute for Astrophysics)
One scenario: Exploding star flings binary parter away at high velocity (Max Planck Institute for Astrophysics)

HC 271791 is a star with a problem, it’s moving so fast through our galaxy that it will eventually escape from the Milky Way all together. However, there is a growing question mark hanging over the reasons as to why HD 271791 is travelling faster than the galactic escape velocity.

So-called hyper-velocity stars were first predicted to exist back in 1988 when astrophysicist Jack Hills at Los Alamos National Laboratories pondered what would happen if a binary star system should stray too close to the supermassive black hole lurking in the galactic nucleus. Hills calculated that should one of the stars get swallowed by the black hole, the binary partner would be instantly released from the gravitational bind, flinging it away from the black hole.

This would be analogous to a hammer thrower spinning around, accelerating the ball of the hammer rapidly in a circle around his body. When the thrower releases the hammer at just the right moment, the weight is launched into the air, travelling tens of meters across the stadium. The faster the hammer thrower spins the ball, the greater the rotational velocity; when he releases the hammer, rotational velocity is converted to translational velocity, launching the ball away from him. Gold medals all ’round.

So, considering Hills’ model, when one of the stars are lost through black hole death, the other star is launched, hammer-style, at high velocity away from the galactic core. The fast rotational velocity is converted into a hyper-velocity star blasting through interstellar (and eventually intergalactic) space.

Hills actually took his theory and instructed the astronomical community to keep an eye open for speeding stellar objects, and sure enough they were out there. HD 271791 is one of these stars, travelling at a whopping 2.2 million kilometres per hour, a speed far in excess of the galactic escape velocity.

However, the 11 solar mass star didn’t originate from the Milky Way’s supermassive black hole (inside the radio source Sgr. A*), it was propelled from the outermost edge of the galactic disk. There is absolutely no evidence of a supermassive black hole out there, so what could have accelerated HD 271791 to such a high velocity? After all, stars aren’t exactly easy objects to throw around.

If HD 271791 used to be part of a binary pair, its partner would have had to suddenly disappear, releasing its gravitational grip rapidly. One idea is that HD 271791’s sibling exploded as a supernova. This should have provided the sudden loss in a gravitational field — the rapidly expanding supernova plasma will have dispersed the gravitational influence of the star.

However, according to Vasilii Gvaramadze at Moscow State University, the supernova theory may not be sound either; by his calculations a binary pair simply cannot produce such a large velocity. Gvaramadze thinks that a far more complex interaction between two binary pairs (four stars total) or one binary pair and another single star some 300 solar masses. Somehow, this “strong dynamical encounter” caused HD 271791 to be catapulted out of the system, propelling it at a galactic escape velocity.

Although this complex slingshot theory sounds pretty interesting, the supernova theory still sounds like the most plausible answer. But how could a sufficient rotational velocity be attained? As Gvaramadze points out, even an extreme rapidly orbiting binary pair cannot produce a star speeding at 530-920km/s.

This is in contrast to research carried out by scientists at the Max Planck Institute for Astrophysics and the University of Erlangen-Nuremberg. In a January 2009 press release, Maria Fernanda Nieva points out that this hyper-velocity star possesses the chemical fingerprint of having been in the locality of a supernova explosion. This leads Nieva to conclude that HD 271791 was ejected after its binary partner exploded. What’s more, a Wolf-Rayet may have been the culprit.

Up to now such a scenario has been dismissed for hyper-velocity stars, because the supernova precursor usually is a super-giant star and any companion has to be at large distance in order to orbit the star. Hence the orbital velocities are fairly modest. The most massive stars in the Galaxy, however, end their lives as quite compact so-called Wolf-Rayet stars rather than as super-giants. The compactness of the primary leaves room for a companion to move rapidly on a close orbit of about 1 day-period. When the Wolf-Rayet-star exploded its companion HD 271791 was released at very high speed. In addition, HD 271791 made use of the Milky Way rotation to finally achieve escape velocity. —Maria Fernanda Nieva

Even though Gvaramadze’s stellar pinball theory sounds pretty compelling, the fact that HD 271791 contains a hint of supernova remnant in its atmosphere, the supernova-triggered event sounds more likely. But there is the fact that just because this 11 solar mass star was near a supernova some time in its past, it certainly doesn’t indicate that a supernova was the cause of it’s high speed.

For now I suppose, the jury is still out…

Publication: On the origin of the hypervelocity runaway star HD271791, V.V.Gvaramadze, 2009. arXiv:0909.4928v1 [astro-ph.SR]

Original source: arXiv blog

Life is Grim on the Galactic Rim

The White Star approaches the Shadow's homeworld of Z'ha'dum on the Galactic Rim.
The White Star approaches the Shadow’s homeworld of Z’ha’dum on the Galactic Rim.

It would appear that scientists have confirmed that the outer edge of the Milky Way is a bad location for life to even think about existing.

This research reminded me of the “Galactic Rim” in the 90’s sci-fi TV series Babylon 5. The Rim is the mysterious region of space right at the edge of our galaxy where only the hardiest of explorers dared to venture. As explained in the season 2 episode of B5, “In the Shadow of Z’ha’dum,” Captain Sheridan (Bruce Boxleitner) discovers that his wife (when exploring The Rim) went missing on a planet called Z’ha’dum. It turns out that an angry ancient alien race — called the Shadows — lived on this mysterious world and their discovery led to them being used in all kinds of plots during the latter four seasons of this awesome sci-fi show.

However, the existence of any kind of life (let alone life as complex as the evil Shadows) in the badlands of the Milky Way is looking very unlikely.

Located some 62,000 light years from the core of our galaxy (over twice the distance of the Earth from the galactic centre), two very young star clusters in the constellation of Cassiopeia have been studied. Chikako Yasui, Naoto Kobayashi and colleagues at the University of Tokyo, Japan, found these clusters in a vast cloud of gas and dust called Digel Cloud 2. The stars inside these clusters are only half a million years old, and the majority of them should possess proto-planetary disks (which is characteristic of local star-forming regions). However, it would appear that these stars contain very little oxygen, silicon or iron (i.e. they have very low metallicity) and only 1 in 5 of the 111 baby stars analysed in both clusters have disks.

If proto-planetary disks are rare, this means there will be a rarity of planets. This is an obvious bummer for life to form. After all, Life As We Know It™ is quite attached to evolving on Earth-like planets.

So why are these young stars lacking proto-planetary disks, when local star forming regions don’t seem to have this affliction? The authors of the paper, soon to be published in the Astrophysical Journal, suggest that these stars did have disks, but some mechanism is rapidly eroding them.

The most likely scenario is that low metalicity proto-planetary disks are more susceptible to photoevaporation. Simply put, these disks evaporate when exposed to EUV and X-ray radiation from their parent stars far more rapidly than disks that are metal-rich.

Therefore, if an alien race was able to form, they’d be very rare or they’d be very different from what we’d expect “life” to be like (i.e. they thrive in low metalicity star systems). Sounds like the mysterious Shadow homeworld of Z’ha’dum would be a very rare sight on The Rim of our Milky Way after all.

Publication: The Lifetime of Protoplanetary Disks in a Low-Metallicity Environment, Chikako Yasui et al., 2009. arXiv:0908.4026v3 [astro-ph.SR]
via New Scientist

Brown Dwarfs: “Over-Achieving Jupiters” not “Failed Stars”

browndwarf3

Why is the term “failed star” synonymous with brown dwarfs? On the one hand, brown dwarfs lack the mass to sustain nuclear fusion in their cores. On the other hand, who said brown dwarfs were trying to be stars? Who ever said that becoming a star was the pinnacle of stellar living? Perhaps brown dwarfs are perfectly happy the way they are. In a world of equality and political correctness, brown dwarfs could be viewed as “over-achieving Jupiters”, or gas supergiants
Continue reading “Brown Dwarfs: “Over-Achieving Jupiters” not “Failed Stars””

Are Brown Dwarfs More Common Than We Thought?

A brown dwarf plus aurorae (NRAO)

In 2007, a very rare event was observed from Earth by several observers. An object passed in front of a star located near the centre of the Milky Way, magnifying its light. Gravitational lensing is not uncommon in itself (the phenomenon was predicted by Einstein in 1915), but if we consider what facilitated this rare “microlensing” event, things become rather interesting.
Continue reading “Are Brown Dwarfs More Common Than We Thought?”

WR 104: Not The Killer It Used To Be

WR 104. A killer? Not so much.
WR 104. A killer? Not so much.

It’s interesting how astronomical harbingers of doom have the ability to pop up more than once on the ‘net. However, the doom isn’t quite as terrifying when you’ve sat through a conference presentation by a scientist who has exhaustively given every reason as to why this particular killer won’t hurt you.

Enter WR 104.

To be honest, if it wasn’t a Wolf-Rayet star, I probably wouldn’t be writing about it (as we all know, or you should know, Wolf-Rayets are my favourite stellar objects), but this little fact combined with the fact that I know the Earth is no longer on the WR 104 hit-list, I feel compelled to correct an article that has just popped up on the web referencing out-of-date source material.

So, let’s wind this back the clock to January 2009 when I sat in on a very reassuring this-star-isn’t-actually-going-to-kill-us-after-all astro presentation…
Continue reading “WR 104: Not The Killer It Used To Be”

Star Formation: The Game

starformation

Dave Mosher, I’m pointing my finger at you for this late night effort! Usually I stay up late to write articles, but for the last 30 minutes I’ve been playing this game after Dave sent a message on Twitter saying he had been playing a “simple” and “addictive” star formation game. No kidding! I shouldn’t have even clicked the link. But like a caffeine-infused moth to a super-shiny flame, off I went for some simple star-creation fun.

It looks like the Star Formation game is part of Discover Magazine’s featured article about the mysteries of star birth (it’s a great read, check it out). The game is simple, yet captivating (despite a few minor bugs). You play the role of supernova progenitor, dropping some massive star fury on an unsuspecting nebulous cloud of hydrogen. According to the game developers, the situation is physically accurate, it is just up to you to create the perfect conditions for stars to form in the dense cloud. It would appear the lectures I attended on star formation paid off, as I speak I’m on top of the leaderboard with a whopping 21122 points (see the screengrab above, I saved it posterity, I doubt I’ll be at #1 for much longer).

I’m all for games with an educational element, and I can’t think of a better way to spend an evening (well, I can, but if you’re stuck in the office, this is a great alternative to work). I’m off to create some more stars, check out Discover so you can do the same (just you try to knock me from the #1 slot!).

What Will Happen When the Sun Turns into a White Dwarf?

Strong tidal interactions are thought to shred any asteroids or comets as they get too close to a white dwarf (NASA)

All the way back in January, I had the great fortune to attend the American Astronomical Society’s (AAS) conference in Long Beach, California. I had a lot of fun. However, between the free beer and desperately searching for wireless Internet signal, I also did some work. During my travels, I spent some time browsing the poster sessions, trying to get inspiration for an article or two. You’d think that when presented with hundreds of stunning posters that inspiration wouldn’t be that far away. However, I was repeatedly frustrated by information overload and defaulted to a clueless meander up and down the pathways walled with intense science debates.

But then I saw it, right at the end of one of the poster walls, a question that got my imagination bubbling: “Will The Sun become a Metal Rich White Dwarf After Post Main Sequence Evolution?” The Sun? After the Main Sequence? Metal rich? To be honest, these were questions I’d never really pondered. What would happen when the Sun turns into a white dwarf? Fortunately, I had Dr John Debes to help me out with the answers…
Continue reading “What Will Happen When the Sun Turns into a White Dwarf?”

Small but Mighty: KPD 0005+5106, the 200,000K White Dwarf

Sirius B1 - one of the more famous white dwarf stars (Frank Gregorio)

A white dwarf called KPD 0005+5106 has been identified as the hottest star observed, ever. KPD 0005+5106 lives in the globular cluster M4, 7,200 light years away, and astronomers have always been intrigued by this stellar lightweight as its emissions have previously hinted it was quite toasty. Now, astronomers using data from the defunct NASA Far-Ultraviolet Spectroscopic Explorer (FUSE), have studied the white dwarf in more detail. KPD 0005+5106 emits radiation in the far-ultraviolet, indicating that its surface has a temperature of 200,000K. This is an unprecedented discovery, far-ultraviolet emissions are usually reserved for superheated stellar coronae. It may be small, but it’s a record-breaker
Continue reading “Small but Mighty: KPD 0005+5106, the 200,000K White Dwarf”