Amazing New Views of Betelgeuse Courtesy of ALMA

This orange blob is the nearby star Betelgeuse, as imaged recently by the Atacama Large Millimeter/submillimeter Array (ALMA). ALMA/ESO/NRAO

Just. Wow.

An angry monster lurks in the shoulder of the Hunter. We’re talking about the red giant star Betelgeuse, also known as Alpha Orionis in the constellation Orion. Recently, the Atacama Large Millimeter Array (ALMA) gave us an amazing view of Betelgeuse, one of the very few stars that is large enough to be resolved as anything more than a point of light.

Located 650 light years distant, Betelgeuse is destined to live fast, and die young. The star is only eight million years old – young as stars go. Consider, for instance, our own Sun, which has been shining as a Main Sequence star for more than 500 times longer at 4.6 billion years – and already, the star is destined to go supernova at anytime in the next few thousand years or so, again, in a cosmic blink of an eye.

Still lumpy… Betelgeuse imaged by Hubble in 1996. Hubble/ESA/STScI

An estimated 12 times as massive as Sol, Betelgeuse is perhaps a staggering 6 AU or half a billion miles in diameter; plop it down in the center of our solar system, and the star might extend out past the orbit of Jupiter.

As with many astronomical images, the wow factor comes from knowing just what you’re seeing. The orange blob in the image is the hot roiling chromosphere of Betelgeuse, as viewed via ALMA at sub-millimeter wavelengths. Though massive, the star only appears 50 milliarcseconds across as seen from the Earth. To give you some idea just how small a milliarcsecond is, there’s a thousand of them in an arc second, and 60 arc seconds in an arc minute. The average Full Moon is 30 arc minutes across, or 1.8 million milliarcseconds in apparent diameter. Betelgeuse has one of the largest apparent diameters of any star in our night sky, exceeded only by R Doradus at 57 milliarcseconds.

The apparent diameter of Betelgeuse was first measured by Albert Michelson using the Mount Wilson 100-inch in 1920, who obtained an initial value of 240 million miles in diameter, about half the present accepted value, not a bad first attempt.

You can see hints of an asymmetrical bubble roiling across the surface of Betelgeuse in the ALMA image. Betelgeuse rotates once every 8.4 years. What’s going on under that uneasy surface? Infrared surveys show that the star is enveloped in an enormous bow-shock, a powder-keg of a star that will one day provide the Earth with an amazing light show.

The bowshock created by Betelgeuse as it plows through the local interstellar medium. JAXA/Akari

Thankfully, Betelgeuse is well out of the supernova “kill zone” of 25 to 100 light years (depending on the study). Along with Spica at 250 light years distant in the constellation Virgo, both are prime nearby supernovae candidates that will on day give astronomers a chance to study the anatomy of a supernova explosion up close. Riding high to the south in the northern hemisphere nighttime sky in the wintertime, +0.5 magnitude Betelgeuse would most likely flare up to negative magnitudes and would easily be visible in the daytime if it popped off in the Spring or Fall. This time of year in June would be the worst, as Alpha Orionis only lies 15 degrees from the Sun!

An early springtime supernova in the future? Stellarium

Of course, this cosmic spectacle could kick off tomorrow… or thousands of years from now. Maybe, the light of Betelgeuse gone supernova is already on its way now, traversing the 650 light years of open space. Ironically, the last naked eye supernova in our galaxy – Kepler’s Star in the constellation Ophiuchus in 1604 – kicked off just before Galileo first turned his crude telescope towards the heavens in 1610.

You could say we’re due.

Lights in the Sky: Meteors, Reentry, or E.T.?

It happens a few times every year.

Last week, we poured our morning coffee, powered up our laptop and phone, and prepared to engage the day.

It wasn’t long before the messages started pouring in. ‘Bright fireball over the U.S. West Coast!’ ‘Major event lights up the California skies!’ and variations thereof. Memories of Chelyabinsk came immediately to mind. A bit of digging around ye ole web revealed video and a few authentic stills from the event.

Now, I always like to look these over myself before reading just what other experts might think. Chelyabinsk immediately grabbed our attention when we saw the first videos recording the shock wave of sound generated by the blast. ‘That sucker was close,’ we realized.

Thursday’s (Wednesday evening Pacific Time) event was less spectacular, but still interesting: the nighttime reentry of the Long March CZ-7 rocket body NORAD ID 2016-042E as it broke up over the U.S. West Coast.

How do we know this, and what do we look for? Is that flash a meteor, bolide, reentry or something stranger still?

Most good meteor footage comes from video recorders that are already up and running when the event occurs, to include security and dashboard cameras, and mobile phones already recording another event, such as a concert or game. How fast can YOU have your smartphone camera out and running? We only recently learned that a quick double tap of the home button will bring the camera on our Android to bear, no unlock needed.

If the event occurs on a Friday or Saturday night with lots of folks out on the town on a clear evening, we might see multiple captures come streaming-in of the event. Just such a fireball was witnessed over the United Kingdom on Friday evening, September 21st, 2012.

Likewise, the fakes are never far behind. We’ve seen ’em all, though you’re welcome to try and stump us. Such ‘meteor-wrongs’ that are commonly circulated as authentic are the reentry of Mir, the 1992 Peekskill meteor, Chelyabinsk, the reentry of Hayabusa, and screen grabs from the flick Armageddon… has anyone ever been fooled by this one?

Meteors generally have a very swift motion, and occur with a greater frequency as the observer rotates forward into the path of Earth’s motion around the Sun past local midnight. Remember, it’s the front of the windshield that picks up the bugs rolling down the highway.

Evening meteors, however, can have a dramatic slow, stately motion across the sky, as they struggle to catch up with the Earth. If they reach a brilliance of magnitude -14 — about one whole magnitude brighter than a Full Moon — said meteor is known as a bolide.

Sometimes, such a fireball can begin shedding fiery debris, in a dramatic display known as a meteor train or meteor precession. Such an event was witnessed over the northeastern United States on July 20th, 1860.

1860 meteor train. Painting by Frederic Church.
The 1860 meteor train. Painting by Frederic Church.

Bright meteors may exhibit colors, hinting at chemical competition. Green for nickel (Not kryptonite!) is typically seen. MeteoriteMen’s Geoffrey Notkin once told us a good rule of thumb: if you hear an accompanying sonic boom a few minutes after seeing a meteor, it’s close. Folks often think what they saw went down behind a hill or tree, when it was actually likely more than 50 miles distant — if it hit the ground at all.

Is that a meteor or a reentry? Reentries move slower still, and will shed lots of debris. Here’s what we’re looking at to judge suspect sighting as a reentry:

Heavens-Above: A great clearing house for satellite passes by location. One great tool is that Heavens-Above will generate a pass map for your location juxtaposed over a sky chart.

Aerospace Corp current reentries: Follows upcoming reentries of larger debris with refined orbits.

Space-Track: The U.S. Joint Space Operations Command’s tracking center for artificial objects in orbit around Earth. Access is available to backyard satellite spotters with free registration. The most accurate source for swiftly evolving orbital elements.

SeeSat-L: This message board always lights up with chatter whenever a possible reentry lights up the skies worldwide.

Stranger Skies

Bizarre sights await the keen eyed. A tumbling rocket booster can often flare in a manner similar to Iridium satellites. Satellites way out in geostationary orbit can flare briefly into naked eye visibility during ‘GEOSat flare season’ near the weeks surrounding either equinox.

Some gamma ray bursts, such as GRB 080319B flare up briefly above magnitude +6 into naked eye visibility from far across the Universe. As of yet, there’s never been a reliable observer sighting of such an event, though it should be possible… probably someone far back in humanity’s history witnessed just such a brief flash in the sky, pausing silently to wonder just what it was…

Kaboom! Image credit: NASA/Pi of the Sky.
Kaboom! Image credit: NASA/Pi of the Sky.

Going further back still, a nearby supernova or gamma-ray burst would leave a ghostly blue afterglow from Cerenkov radiation as it pummeled our atmosphere… though it would be a deadly planet-sterilizing indigo glow, not something you’d want to see. Thankfully, we live in the ‘Era of Mediocrity,’ safely outside of the 25-50 light year ‘kill zone’ for any potential supernova.

And what if those lights in the sky really were the vanguard of an alien invasion force? Well, if they really did land rayguns ablaze on the White House lawn, you’ll read it first here on Universe Today!