The heat of the Pinwheel

By Phil Plait | July 25, 2011 7:00 am

Spiral galaxies are among the most beautiful objects in the sky, and one of the most beautiful of them is M101, also known as the Pinwheel Galaxy. It’s a reliable favorite among amateur astronomers because it’s big, bright, and located near the north pole of the sky, so it’s easy to find for a big part of the year.

I’ve seen it many times through a telescope, but not quite like the way NASA’s Wide-field Infrared Survey Explorer (WISE) saw it: glowing fiercely in colors our eyes cannot detect:

[Click to galactinate.]

This image shows the galaxy in the far-infrared. What you see here as blue is actually starlight; green is from long organic compounds called PAHs, and red is from glowing dust, warmed by nearby star formation. Look at the gigantic red clouds where stars are being born! Thousands of these have been catalogued in the Pinwheel.

It’s actually an immense galaxy, twice the diameter of the Milky Way and possessing as many as ten times the number of stars. Our galaxy is no lightweight, but the Pinwheel is a monster. I wrote about it when Hubble released a gorgeous and incredibly detailed image of it back in 2006. There’s also a spectacular Spitzer image of it as well, which is also in the infrared, though in a different part of the IR spectrum.

The WISE mission shut its eye earlier this year when it ran out of coolant to keep its detectors cold (warm objects emit lots of IR, so keeping things cold prevents the detectors themselves from glowing in the very light they’re designed to see), but it surveyed the entire sky, returning a whole lot of data. I imagine we’ll be seeing more pictures like this coming from the database, as well as lots of amazing discoveries as scientists pore over it. The mission itself may be done, but the information it gave us goes on.

Image credit: NASA/JPL-Caltech/UCLA


Related posts:

- The Triangulum galaxy writ large
- A galaxy choked with dust
- The punctuated spiral
- A taste of WISE galaxies

CATEGORIZED UNDER: Astronomy, Pretty pictures

Comments (14)

  1. Superluminously magnificent awesome image there. :-)

    Thankyou BA & the WISE guys (& girls – ‘guys’ being inclusive of them too!) ;-)

    For a second there you had me thinking of the “other Pinwheel” galaxy – M33 the Triangulum galaxy which shares that nickname with M101 too. ;-)

  2. QuietDesperation

    Aren’t all spirals basically pinwheels?

  3. Jamey

    So, the stellar density is higher, as well? Twice the size would be – 8x the number of stars?

  4. long organic compounds called PAHs

    http://ehp.niehs.nih.gov/realfiles/members/2000/108p709-717richter/richterfig1B.GIF
    Stable PAHs are compact
    http://www.daviddarling.info/images/PAH_structures.jpg
    Non-compact polyacenes are reactive.

    en.wikipedia.org/wiki/Dicoronylene
    One presumes the universe is mucked with dicoronylene.

  5. Chrisj

    Jamey: Cubes increase very rapidly; 10x the number of stars with the same density is only 2.15x the (linear) size. I suspect Phil is (understandably) rounding one number or the other for ease. It isn’t as though we can be absolutely precise about either anyway.

  6. Navneeth

    It’s a reliable favorite among amateur astronomers because it’s big, bright, and located near the north pole of the sky, so it’s easy to find for a big part of the year.

    From this we can (can’t we?) infer that there are no amateur astronomers south of the equator, perhaps even south of the tropics.
    :P

  7. Jon

    Somewhat arguably, he’s actually right.

    The four largest countries (by land area) are all entirely in the northern hemisphere, as are the largest ones by population (India is entirely north of the Equator, as is China).

    South, the largest country entirely below the equator (by land area) is Australia – Brazil is larger, but parts of Brazil are north of zero degrees.

    It would be an interesting question – The ratios of their sizes is roughly 8:7, and roughly 1/8th of Brazil is north of the Equator – Which country has more southern area? I don’t know.

    There are also Pacific Islander countries that cover huge areas – mostly of open water – but have very little land mass and not much population. Indonesia is a worthwhile exception, but it too borders on the Equator.

    Anyhow – Worthless factoids for the day (but hey, I went and looked them up, so they were at least interesting to me!)

  8. @2. QuietDesperation : “Aren’t all spirals basically pinwheels?”

    Not necessarily – there are, for instance, the barred spirals! ;-)

    Plus there’s those you see edge on, ones with little activity or massive starbursts or interactions warping their shape and so on.

    Of course, it depends whether we’re talking spirals generally or spiral galaxies specifically too! ;-)

  9. Brian

    Wow, I learned a word! Galactinate means “to click on a jpg” !!

  10. Messier Tidy Upper

    @6. Navneeth :

    “It’s a reliable favorite among amateur astronomers because it’s big, bright, and located near the north pole of the sky, so it’s easy to find for a big part of the year.”
    From this we can (can’t we?) infer that there are no amateur astronomers south of the equator, perhaps even south of the tropics.

    Er, NO you can’t infer that! :-o

    There are plenty of amateur (& professional too) astronomers based in the Southern hemisphere incl. those in Australia, New Zealand, South Africa, Chile and even a handful at or near the South Pole itself!

    See :

    http://en.wikipedia.org/wiki/South_Pole_Telescope

    for instance and say this wiki-page :

    http://en.wikipedia.org/wiki/Robert_Evans_(astronomer)

    for the amateur with the most supernovae discoveries ever or this one :

    http://en.wikipedia.org/wiki/Ruby_Payne-Scott

    for the first ever female radio astronomer. :-)

    Oh and we southern hemispherers have better skies getting to see the Magellanic Clouds, Omega Centauri and the Southern Cross too! :P

    *****

    PS. “..perhaps even south of the tropics.” Um, you do know what’s on the top of Mauna Kea (Hawaii) right? ;-)

  11. icemith

    Not wishing to go slightly off-topic, (I guess we are anyway), but I have that urge to say re the Northern verses the Southern Astronomers sub-topic, “What about us?”

    We, by dent of our good fortune to be located in the south, get to see all the new and exciting things not (mostly) available to the northerners. At least not without digging deep in the pocket for at least one ticket south. And you are most welcome, even to stay.

    So, we miss out on viewing M101 with virgin light, but have to be satisfied with reproductions. Mind you, I too consider it to be my best favorite galaxy, and the new interpretation only makes it better.

    So thanks Phil and the NASA/JPL-Caltech/UCLA guys for your work. Much appreciated.

    Ivan.

    PS, I know each of us can travel around the world to see everything, but you cannot move the Observatories to the other hemisphere, as we would be back where we started! What we need are more “Hubbles”, and canning the Webb is the wrong way to go about that. But still, that is not quite the same as having one’s own set-up in the backyard or more realistically, in an adjacent dark sky site for Amateurs, at a reasonable distance.

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