Asteroids Smack Jupiter More Often Than Astronomers Thought

Jupiter Impact
Jupiter Impact
Pow: The July 1994 impact of Comet Shoemaker-Levy 9 on Jupiter, captured by the Hubble Space Telescope. Credit: R. Evans/J. Trauger/H. Hammel/HST Comet Science Team/NASA.

Are you keeping a eye on Jupiter? The King of the Planets, Jove presents a swirling upper atmosphere full of action, a worthy object of telescopic study as it heads towards another fine opposition on May 9th, 2018.

Now, an interesting international study out of the School of Engineering in Bilbao, Spain, the Astronomical Society of France, the Meath Astronomical Group in Dublin Ireland, the Astronomical Society of Australia, and the Esteve Duran Observatory in Spain gives us a fascinating and encouraging possibly, and another reason to keep a sharp eye on old Jove: Jupiter may just get smacked with asteroids on a more regular basis than previously thought.

The study is especially interesting, as it primarily focused in on flashes chronicled by amateur imagers and observers in recent years. In particular, researchers focused on impact events witnessed on March 17th 2016 and May 26th, 2017, along with the comparison of exogenous (of cosmic origin) dust measured in the upper atmosphere. This allowed researchers to come up with an interesting estimate: Jupiter most likely gets hit by an asteroid 5-20 meters in diameter (for comparison, the Chelyabinsk bolide was an estimated 20 meters across) 10 to 65 times every year, though researchers extrapolate that a dedicated search might only nab an impact flash or scar once every 0.4 to 2.4 years or so.

Compare this impact rate with the Earth, which gets hit by a Chelyabinsk-sized 20-meter impactor about once every half century or so. Incidentally, we know this impact rate on Earth better than ever before, largely due to U.S. Department of Defense classified assets in space continually watching for nuclear tests and missile launches, which also pick up an occasional meteor “photobomb.”

Small asteroid impacts over the span of the Earth over a 20 year period. NASA/Planetary Science.

One reason we may never have witnessed a meteor impact on Jupiter is, astronomers (both professional and amateur) never thought to look for them. The big wake-up call was the impact of Comet Shoemaker-Levy 9 in July 1994, an event witnessed by the newly refurbished Hubble Space Telescope as the resulting impact scars were easily visible in backyard telescopes for weeks afterward. Back in the day, speculation was rampant in the days leading up to the impact: would the collision be visible at all? Or would gigantic Jupiter simply gobble up the tiny comet fragments with nary a belch?

Australian amateur astronomer Anthony Wesley also caught an interesting impact (scar?) in 2009, and every few years or so, we get word of an elusive flash reported on the Jovian cloudtops, sometimes corroborated by a secondary independent observation or a resulting impact scar, and sometimes not.

An impact scar (top center on the disk) on Jupiter, captured on July 19th, 2009. Image credit: Anthony Wesley.

Of course, there are factors which will lower said ideal versus the actual observed impact rate. There’s always a month or so a year, for example, when Jupiter is near solar conjunction on the far side of the Sun, and out of range for observation. Also, we only see half of the Jovian disk from our Earthly perspective at any given time, and we’re about to lose our only set of eyes in orbit around Jupiter – NASA’s Juno spacecraft – later this summer, unless there’s a last minute mission extension.

On the plus side, however, Jupiter is a fast rotator, spinning on its axis once every 9.9 hours. This also means that near opposition, you can also track Jupiter through one full rotation in a single evening.

Finding Jupiter: looking eastward tonight at around 11PM local. Credit Stellarium.

Then there’s the planet’s location in the sky: Currently, Jupiter’s crossing the southern constellation of Libra, and opposition for Jove moves about one astronomical constellation eastward along the ecliptic a year. Jupiter will bottom out along the ecliptic in late 2019, and won’t pop back up north of the celestial equator until May 2022. And while it’s not impossible for northern observers to keep tabs on Jupiter when it’s down south, we certainly get more gaps in coverage around this time.

Hale-Bopp’s close inbound passage near Jupiter in 1996. Credit: NASA/JPL-Horizons.

Should we hail Jove as a protective ‘cosmic goal-tender,’ or fear it as the bringer of death and destruction? There are theories that Jupiter may be both: for example, Jupiter altered the inbound path of Comet Hale-Bopp in 1997, shortening its orbital period from 4,200 to 2,533 years. The 2000 book Rare Earth even included the hypothesis of Jupiter as a cosmic debris sweeper as one of the factors for why life evolved on Earth… if this is true, it’s an imperfect one, as Earth does indeed still get hit as well.

All reasons to keep an eye on Jupiter in the 2018 opposition season.

-See something strange? The ALPO Jupiter observers section wants to know!

Debunking Comet ISON Conspiracy Theories (No, ISON is Not Nibiru)

Comets always seem to bring ‘em out of the wood work.

There’s a scene from the 1998 movie Deep Impact where the president, played by Morgan Freeman, reveals a terrible truth… the U.S. government has known for over a year that a doomsday comet is headed straight towards Earth, with Hollywood CGI destruction sure to follow.

While dramatic, the scenario is also extremely implausible. On any given evening, amateur astronomers are sweeping the skies using telescopes mounted in backyard observatories that are the envy of many major universities. This effort to discover comets is collaborative and worldwide. If the “Big One” were headed our way, even the likes of Morgan Freeman couldn’t keep it secret.

Trouble is, many unfounded claims are already making their way around the internet about this years’ much anticipated “Comet of the Century,” C/2012 S1 ISON.

Many of these conspiracy theories seem to be a recycling of last years’ Nibiru nonsense. The train of thought runs something like this: Does NASA know something that they’re not telling us? Why are they so interested in this comet? We’ve even had folks ask us why certain patches of Google Earth are “blacked out!”

What ARE they hiding, man?

It’s funny how pseudoscience seems to bubble to the top on YouTube, but I won’t give these conspiracy videos the exposure of the Universe Today platform. With hundreds of thousands of hits, they certainly don’t seem to need it. A simple YouTube search of “ISON” will scare up many wacky ideas about the comet.

In any event, we’ve already fielded several questions from friends and the public on the “dangers” posed by this comet, so we can only imagine that these will grow in intensity as the comet approaches the inner solar system, especially if it performs up to expectations.

What are some of the conspiracy theories out there about Comet ISON?

One currently circulating claim states that Comet ISON has “companions” that have been imaged trailing it. While comets do indeed fragment on occasion, the culprits that can be seen in the .gif animation circulating the internet are easily identified by photography experts as hot pixels in the camera.

Another even more extravagant claim is that Comet ISON will somehow appear “as bright as the Sun.” Even if Comet ISON reaches an expected magnitude equal to that of the full Moon at -13, it will do so when it is less than a degree  from the Sun. Our Sun shines at magnitude -26.74, or over 158,000 times brighter, so it would be very difficult for this comet to compete with the Sun’s brightness in the daytime!

Others seem to worry that this comet — or particles from ISON — could impact Earth. Comet ISON will be making its inner solar system passage safely 0.426 A.U., or a little over 63 million kilometers from Earth even on its closest approach on December 26th. Scientists have defined this comet’s orbit very precisely, and it won’t hit Earth. So, no Comet ISON is not Nibiru — that ‘tenth planet’ destined to destroy Earth that conspiracy lovers can’t seem to let go of.

The debris — which might create a very nice meteor shower — is made up of extremely tiny grains of dust, no more than a few microns wide. Since they will be hitting Earth’s atmosphere at speeds up to 200,000 km/hr (125,000 miles per hour), the particles will burn up.

Here’s a video NASA released about the potential meteor shower from ISON:

Other claims focus on how this comet may cause earthquakes or wreak other untold havoc on Earth. This type of comet hysteria is nothing new. Name a bright comet in history, and you can find a historical event for a convenient tie-in. When haven’t there been earthquakes, pandemics, and wars in history? Plus, according to the US Geological Survey, on any given day there will be an average of 2,750 earthquakes around the world of which 275 are large enough to be felt by humans. But only about 100 earthquakes a year are large enough to cause any damage.

And so, its too easy to tie the “causes” of earthquakes and other events to comets in the sky. Comets have been seen before and during the Norman invasion of England in 1066, an outbreak of the Black Plague in London in 1665, and much more. Gary Kronk maintains a wacky and wonderful list of historical (and sometimes comical) comet “signs and omens” on his Cometography site.

Comet Lovejoy as seen from the International Space Station.
Another brilliant sungrazer, Comet Lovejoy as seen from the International Space Station on December, 2011. (Credit: NASA).

Halley’s Comet produced one of the first great comet hypes of the 20th century with its 1910 passage. Ironically, another comet made a brilliant passage just a few months prior, which became known as the Great Comet of 1910. In fact, many viewers in the general public actually saw this comet and confused it with Halley’s! The recent discovery of cyanogen in the comet’s spectra sparked a panic in the public as hucksters made a small fortune hawking “comet pills” and gas masks to panicked buyers. Never mind that folks ingest more toxic carcinogens from their daily environment than are ever seeded by the tenuous tails of comets.

Another curious bit of hype sprung up in 2011 around Comet Elenin, which promptly broke up and dissipated without even putting on a show. And the supposed earthquakes that conspiracy theorists predicted? Well, the evidence speaks loudly: nothing happened. And the same will be true of Comet ISON. It won’t cause any earthquakes or other disasters. As Don Yeomans from NASA said about Comet Elenin, “It will have an immeasurably miniscule influence on our planet. By comparison, my subcompact automobile exerts a greater influence on the ocean’s tides than comet Elenin ever will.”

So, what’s the harm in all the comet hysteria? Well, one only has to look at the mass suicide of the Heaven’s Gate cult in 1997 to realize that it can be no laughing matter. The suicide was sparked by the idea popularized on the late night Coast to Coast with Art Bell radio show that a spacecraft had been spotted following Comet Hale-Bopp.

Dozens of comets are discovered every year. A great majority are tiny iceballs in unfavorable orbits that never rise above magnitude +10 and are thus of little interest to backyard observers. A couple of times a year, a comet might reach magnitude +6 to +10 and become a fine binocular object.

When a discovery is made — be it by amateur or professional — the first task is to gain enough observations of the object to ascertain its orbit. Once again, we see the international collaborative methods employed by modern science. Already, the cosmic cat’s out of the bag as observatories worldwide make follow up measurements. There are no secrets about Comet ISON that hundreds of astronomers could keep quiet.

You get the idea... a 1687 leaflet depicting the havoc that a comet is sure to bring. (Wikimedia Commons image in the Public Domain).
You get the idea… a 1687 leaflet depicting the havoc that a comet is sure to bring. (Wikimedia Commons image in the Public Domain).

But here are some facts about Comet C/2012 S1 ISON. It was discovered last September by Russian amateurs Vitali Nevski and Artyom Novichonok while making observations for the International Scientific Optical Network (ISON), hence the comet’s name. At the time, it was farther than Jupiter and impossibly faint, but once ISON’s orbit was determined, astronomers realized the comet would pass only 1.1 million miles from center of the Sun (680,000 miles above its surface) on November 28, 2013.

Comet ISON belongs to a special category of comets called sungrazers. As the comet performs a hairpin turn around the Sun on that date, its ices will vaporize furiously in the intense solar heat. Assuming it defies death by evaporation, ISON is expected to become a brilliant object perhaps 10 times brighter than Venus, or maybe even brighter. But that would only occur for a brief time around at perihelion (closest approach to the Sun).

In the end, Comet ISON may put on a good show, but don’t believe the hype.

Comets are notoriously unpredictable when it comes to brightness estimations. To quote comet-hunter David Levy, “Comets are like cats… they have tails, and they do exactly what they want.” But they cannot, however, violate the laws of orbital mechanics!

The orbit and orientation of Comet ISON the day after Christmas 2013 on closest approach to the Earth. (Credit: NASA/JPL's Small-Body Database Browser).
The orbit and orientation of Comet ISON the day after Christmas 2013 on it closest approach to the Earth. (Credit: NASA/JPL’s Small-Body Database Browser).