Monthly Archives: September 2008

talk like a pirate day

Sailin’ the Starry Sea!

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‘Tis Talk Like a (Starry) Pirate Day

The Official Pirate Star Pattern!
The Official Pirate Star Pattern!

Yarrrr, ye lasses and lads of the starry deeps! Today is Talk Like a Pirate Day, which means ye can affect all FUN piratey attitudes (but NOT the pillagin’ and other law-breakin’ activities–those are frowned upon in TLAPD circles). “All in good fun” is the piratey watchword.

How to celebrate TLAPD if yer an astronomer?  Well, stargazin’ like a pirate is always in good form.  First, wait til it gets dark (if ye want to see stars).  If ye want to see just one star, then go outside and pretend yer on a desert isle with yer piratey treasure.  Count yer doubloons and cackle with glee.  And, let the sunshine warm ye, but do not be a chumbucket and actually LOOK at the Sun — it’ll mess with yer eyes somethin’ fierce!  Just enjoy it, and as Captain Jack warns ye, wear sunblock!

Nighttime starlubbers should wander out after the Sun’s been down fer a while (darkness is a good clue) –and look up!  Check out the stars. Look for a piratey planet!  See if ye can spot the Milky Way. (If ye need a star chart, look at this piratey navigator’s favorite: the Skyview Cafe.

That’s all there is to sailin’ the starry seas!  Oh, and ye must talk like a piratey astronomer!  Every once in a while say something like “Shiver me timbers, look at Jupiter there!”  or “Yarrrrr…. will ya look at that Milky Way!”  or “Take this telescope to the Lagoon Nebula!”

Wear somethin’ warm (even pirates get the shivers in cool night air), and if ye like, bring a grog or other beverage (our personal favorite is piratey hot chocolate).  After yer done, go back inside and watch a good piratey movie.  Pirates of the Caribbean comes to mind, or maybe even Aye, Robot, or Men in Blackbeards. Or maybe Yarrrrrrr Wars… or one of my personal favorites, The Pirate Wears Prada…

astronomy

Ye Olde Well-tuned Black Hole

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“Hearing” an X-ray Hum from a Black Hole

If you had x-ray-sensitive ears (or eyes), the universe would sound (and look) very different from the one we “normally” hear with our frequency-limited ears or see with our wavelength-limited eyes. We’re tuned to hear vibrations that can move through our atmosphere, and since our atmosphere doesn’t get many signals from things like black holes, we didn’t evolve to hear them. Our eyes are essentially sensitive to the wavelengths of light put out by the Sun, as filtered through our atmosphere.

Artists impression of material falling into a supermassive black hole. As it does, x-rays are emitted in a precisely timed oscillation.
Artist's impression of material falling into a supermassive black hole. As it does, x-rays are emitted in a precisely timed oscillation pattern. The yellow curves are an approximation of the x-ray signal. Aurore Simonnet, Sonoma State University (Adapted by M. Gierlinski)

But, we do have instruments orbiting out beyond our atmosphere that “hear” (and actually “see” is a more precise description) x-ray signals from supermassive black holes in the centers of galaxies. The XMM-Newton satellite has been studying these cosmic monsters and has found a periodic x-ray signal from the heart of the galaxy RE J1034+396. It is emitting what is called a quasi-periodic x-ray oscillation that has a period of one hour. That is a very well-tuned black hole!

How can this happen?  We know that a black hole sucks matter in. As matter spirals in, it forms into an accretion disk. The matter gets heated up through a variety of processes and emits x-rays. As the matter wobbles in the disk around the black hole, the x-ray emission gets modulated at a certain frequency. That frequency is what XMM-Newton detected as a periodic signal. Astronomers can use the frequency of the signal to estimate the size of the black hole.

Scientists have suspected that the underlying physical processes behind black hole accretion mechanisms are the same for all such black holes. This is true no matter what size the black hole is. This implies that periodic signals (like the one XMM-Newton has detected) should also be emitted by super-massive black holes lodged at the hearts of galaxies. These active regions are called active galactic nuclei. These periodic signals are widely observed in lower-mass black holes seen in our galaxy. But, until now, no supermassive black hole was known to display such a periodic signal. This discovery is confirms that the fundamental physical processes behind black hole accretion mechanisms are the same. So, this x-ray “hum” is a new diagnostic tool that astronomers can use to learn more about active galactic nuclei.