Tag Archives: Perseids

The Greatest Meteor Show of All Time

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By Bill Cooke

At NASA, we get very excited about many astronomical events — to name just a few, the return of Halley’s Comet back in 1985/86; the impact of the fragments of Comet Shoemaker-Levy 9 with Jupiter in 1992; the Leonid meteor storms of 1998, 1999, 2001 and 2002; and, of course, the upcoming total solar eclipse on Aug. 21 of this year.

Some of these events get blown a bit out of proportion. A classic example is that every time Mars comes to opposition (closest approach to Earth), the internet reverberates with the very false statement that Mars will appear as large as the Moon at that time. Nothing could be farther from the truth, as Mars, at its very closest to Earth, appears only 1/70th the apparent diameter of the Moon.

This year we have a new one — reports are circulating that this year’s Perseids will be the “brightest shower in recorded human history,” lighting up the night sky and even having some meteors visible during the day. We wish this were true… but no such thing is going to happen.

In this 30 second exposure, a meteor streaks across the sky during the annual Perseid meteor shower Thursday, Aug. 13, 2015, in Spruce Knob, West Virginia. Photo Credit: (NASA/Bill Ingalls)

For one thing, the Perseids never reach storm levels (thousands of meteors per hour). At best, they outburst from a normal rate between 80-100 meteors per hour to a few hundred per hour. The best Perseid performance of which we are aware occurred back in 1993, when the peak Perseid rate topped 300 meteors per hour. Last year also saw an outburst of just over 200 meteors per hour.

This year, we are expecting enhanced rates of about 150 per hour or so, but the increased number will be cancelled out by the bright Moon, the light of which will wash out the fainter Perseids. A meteor every couple of minutes is good, and certainly worth going outside to look, but it is hardly the “brightest shower in human history.” The Leonid meteor storms of the late 1990’s and early 2000’s were much more spectacular, and had rates 10 times greater than the best Perseid display.

So, if not this year’s Perseid shower, what was the greatest meteor show of all time? I think many meteor researchers would give that award to the 1833 Leonids, which had rates of tens of thousands, perhaps even 100,000, meteors per hour. During a good Perseid shower under ideal conditions, you can see about one meteor per minute. Now imagine yourself being back in 1833, on the night of Nov. 12. Looking outside, you would see something like 20 to 30 meteors PER SECOND. No wonder we read accounts like this one from South Carolina (Chambers, A Handbook of Descriptive and Practical Astronomy, Volume 1, 1889):

“Upwards of 100 lay prostrate on the ground…with their hands raised, imploring God to save the world and them. The scene was truly awful; for never did rain fall much thicker than the meteors fell towards the Earth; east, west, north and south, it was the same.”

Now, THAT’s a meteor shower. The 1833 storm had a profound effect on those that witnessed it; it also gave birth to modern meteor science. Those of us who study meteors dream of such a display happening sometime within our lifetimes.

But it won’t be caused by this year’s Perseids.

Cooke leads NASA’s Meteoroid Environment Office at the agency’s Marshall Space Flight Center.

 

Perseids Are Already Appearing in the Huntsville Sky

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This composite image shows the meteors detected by the NASA All Sky Fireball Network station here in Huntsville, Alabama this morning.   The majority of the meteors are Perseids, but a handful belong to the Northern Delta Aquariid, Southern Delta Aquariid, Alpha Capricornid, and Southern Iota Aquariid meteor showers that are also active.

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This Perseid meteor was observed by the NASA Wide-field Meteor Camera Network in the skies over Huntsville, Alabama on the morning of August 12.

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Perseid Fireball Over New Mexico

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This Perseid fireball was observed by the NASA All Sky Fireball Network in the skies over New Mexico on the morning of August 12.

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Join Us For the May Camelopardalids!

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Step outside and take a look at the skies on the evening of May 23 into the early morning of May 24. Scientists are anticipating a new meteor shower, the May Camelopardalids. No one has seen it before, but the shower could put on a show that would rival the prolific Perseid meteor shower in August. The Camelopardalids shower would be dust resulting from a periodic comet, 209P/LINEAR.

“Some forecasters have predicted a meteor storm of more than 200 meteors per hour,” said Bill Cooke, lead for NASA’s Meteoroid Environment Office. “We have no idea what the comet was doing in the 1800s. The parent comet doesn’t appear to be very active now, so there could be a great show, or there could be little activity.”

The best time to look is during the hours between 06:00 and 08:00 Universal Time on May 24, or between 2-4 a.m. EDT. That’s when forecast models say Earth is most likely to encounter the comet’s debris. North Americans are favored because their peak occurs during nighttime hours while the radiant is high in the sky.

On the night of May 23-24, NASA meteor expert Bill Cooke will host a live web chat from 11 p.m. to 3 a.m. EDT. Go to this page to learn more about the May Camelopardalids, to get information about the live chat and to view the live Ustream view that will be available during the chat.

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NASA All Sky Fireball Network Cameras Catch Perseids

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The annual Perseid meteor shower peaked on Aug. 12 and 13, 2013, filling the sky with streaks of light caused by the meteoroids burning up in Earth’s atmosphere. Big meteor showers like the Perseids, are caused when Earth travels through a region of space filled with debris shed by a comet. The Perseids have been observed for at least 2,000 years and are the small fragments from comet Swift-Tuttle. These bits of ice and dust wander in space for centuries, finally burning up in the Earth’s atmosphere to create one of the best meteor showers of the year.

Compilation of Perseid meteors taken by the NASA All Sky Fireball Network cameras. Video credit: NASA/MSFC/MEO

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This Perseid fireball meteor was observed in the skies over Chickamauga, Ga., on Aug. 11, 2013, at 2:14:49 a.m. EDT. It was also recorded by four other cameras in the NASA All Sky Fireball Network. Image Credit: NASA/MSFC/MEO

Perseids Already Lighting Up The Night

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Here is a video of a bright Perseid seen by our all-sky camera located at PARI (NC) in the early morning hours of July 30. Several Perseids have already been detected and they are not set to peak for over a week! The nights of August 11-12 and 12-13 will be the best time to observe, but check out fireballs.ndc.nasa.gov regularly to see how many have already been detected by our all-sky cameras!

 

Geminids: How Low Do They Go?

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The Marshall Meteoroid Environment office put together the plot below showing the distribution of end heights of Geminids seen with our fireball camera network. 85% of Geminids burn up 40 to 55 miles above Earth’s surface and 15% get below 40 miles altitude.
 
Geminids penetrate deeper into the atmosphere than the Perseids because they are moving slower (78,000 mph for the Geminids compared to 130,000 mph for the Perseids) and are made up of denser material, owing to the fact that the Geminid parent body is rocky asteroid 3200 Phaethon and the Perseid parent is a comet yielding more fragile material.
 

This video shows meteors captured by a wide-field camera at the NASA Marshall Space Flight Center on the night of December 12. There are 141 events; at least 77 of these are Geminids, based on their angular speed and direction of travel. Near the end of the movie, a couple of satellites are visible crossing the field of view.

For those of us sky watching for meteors , this means we have a good chance of viewing a Geminid meteor. Tonight, December 13, into the early morning of December 14 is the peak. Happy meteor watching!

When to look? In what direction?

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Lots of questions coming in, so I thought I would deal with them here.

I live in xxx… Can I see Perseids?

Check out the map below. Unless you live in the red shaded area, you will be able to see the shower. EVERYONE in the United States and Europe with clear weather will be able to see it, provided they are away from city lights and have clear, dark skies. Most other parts of the world will be able to see the shower as well.

When do I look?

You should start to see Perseids around 10 PM local time. The rate will increase throughout the night until just before dawn (3 to 4 am), when you may be able to see as many as 80-100 per hour. Be sure to allow about 45 minutes to allow your eyes to dark adapt.

Where do I look?

Lie on your back on a sleeping bag, blanket, or lawn chair and look straight up and take in as much sky as possible. Do not look at the constellation Perseus, where is the shower radiant is located, as you will see fewer meteors. This is because the length of the meteor gets longer the farther it appears from the radiant; to see nice bright meteors, you need to look some distance away from Perseus, which for U.S. observers is off to the northeast. Looking straight up, towards the Zenith, is a good choice and enables you to take in a lot of sky.

Do not use binoculars or a telescope, as they have narrow fields of view and will greatly reduce your chances of seeing meteors.

Hope this helps and wish everyone lots of meteors!

Will the Perseid shower be visible from {insert your location}?

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I am asked this question over and over again, and it’s a good one. Everyone knows that you have to be in the right place to observe solar eclipses and other astronomical goings-on, so why should meteor showers be any different?

You do have to be in the right part of the planet to view meteor outbursts or storms, because the trails of comet debris are so narrow (hundreds of thousands of miles) that it only takes a few hours for the Earth to pass through the stream. A few hours is not enough time for the Earth to do a complete rotation (which takes 24 hours), so only those people located in areas where it is night and where the radiant is visible will be able to see the outburst or storm. These dramatic events require the viewers to be in the right ranges of both latitude AND longitude.

This is not true for normal meteor showers, like this year’s Perseids. The main stream of particles extends for millions of miles along Earth’s orbit, requiring days for it to cross. All we need is one day to take the longitude out of the visibility calculations, because then the entire planet will experience night while the shower is still going on. That’s the good news.

The kicker is that we not only have to have darkness, but also the radiant — in this case, located in the constellation of Perseus — has to be visible, i.e. above the horizon. The elevation of the radiant depends in part on latitude of the observer, and one can derive — or look up, in this age of Google — a relatively simple equation that gives the maximum elevation of the radiant:

maximum elevation = 90 – |dec -lat|

where dec is the declination of the radiant and lat is latitude of the observer (all in degrees). The vertical lines before dec and after lat mean to take the absolute value of dec — lat.  In order to see meteors from the shower, the maximum elevation must be 0 or greater (preferably more than 15 degrees). In the case of the Perseids, dec = 58 deg, so it is easy to calculate the maximum elevation for various latitudes:

 

We see that everyone in the northern hemisphere has a shot at seeing Perseids (weather permitting), but folks south of -32 degrees latitude get the shaft.

 

On the world map above, the red shaded area is the region where the Perseids will not be visible. If you live south of Brazil, at the very southern tip of Africa, or southern Austrailia, you need to take a road trip to the North if you wish to see Perseids. If you want see decent numbers, it will be a long ride, as you need to trek to somewhere above  -17 degrees latitude.

So will I see Perseids? You can find out on your own — look up your latitude (remember, Google is your friend), use the equation above, stick in 58 degrees for the dec, and calculate the maximum elevation. If it is above 15 degrees, you are good.

Remember to get away from city lights. A dark sky is important.

Enjoy the show!

How low can they go?

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Real-life meteor showers are not like what you see in movies — there are no flaming rocks barreling out of the sky blasting holes in buildings, or sending cars hurling many yards through the air. Most meteor showers are caused by debris left behind by comets, icy particles mixed with dust and organics that stand no chance of surviving their kamikaze death dives through Earth’s atmosphere. The meteors that actually do make it through, becoming meteorites when they strike ground, are very, very few in number and originate from asteroids (and much more rarely, Mars and the Moon). There are only a handful of recorded falls each year.

So how low can a Perseid get? The NASA all-sky cameras can provide the answer, at least for the bigger Perseids (inch or so across); the smaller particles burn up higher. Our two station camera network can determine the trajectory of a meteor through triangulation, and tell us the start height of the meteor (the location where it is first seen) and its end height (the location where it disappears or “burns up”). Both cameras observed 80 Perseids last year and 24 so far this year, which gives us enough data to tackle the problem.

We start out by taking the end heights of the Perseids and throwing them into 1 mile wide altitude bins. This results in the following graph:

 

Looking at the plot, it is apparent that most large Perseids burn up at about 56 miles (90 km) altitude. Some ablate as high as 65 miles (104 km), whereas others may get as low as 47 miles (76 km) altitude. We see none getting down to 45 miles or lower, which gives this old ground dweller a warm fuzzy feeling — I can enjoy the shower, secure in the knowledge that the meteors are going poof way up there.

It turns out that our friends the Perseids don’t get very low at all, ending their interplanetary journeys at least 46 miles above our heads.