One Night, Five Meteor Showers

On the night of Oct. 15-16, NASA’s All-sky camera network saw meteors from five different meteor showers! October is known to be a busy month in the world of meteor showers, but even five is an unusually high number.


 


 The last meteor seen in the early morning skies over Huntsville, Ala., on the night of the Oct. 15-16.

 

To see videos of these meteors, and others, go to fireballs.ndc.nasa.gov and select 20111016 on the left panel. In addition to those five shower meteors, eight sporadic or background  meteors were detected. The five showers were: Delta Aurigids, or DAU, October Ursa Majorids, or OCU, Chi Taurids, or CTA, Orionids , or ORI, and Eta Geminids, or EGE. See the list at the end of this post for more information on each shower.

 

The only shower mentioned above that would be worth observing for yourself is the Orionids. The Orionids peak this Friday evening — the night of Oct. 21-22 — and are best viewed anytime after midnight. They are one of the last showers of the year that may have favorable weather to lie outside all night. If you are in Northern Alabama, October evenings are still quite pleasant for stargazing. Luckily for you the moon won’t be too much of a problem. Only a small fraction of the moon is illuminated, unlike many major meteor showers this year whose rates were considerably hampered because the light from a full moon washed them out.

 

Delta Aurigids, or DAU: Active from Sept. 20 — Oct. 16, peaking on Oct. 3 with only two meteors per hour. Velocity of 143,000 miles/hour. The Delta Aurigids are not a well-known shower thus any observations refine the information we know about them.

 

October Ursa Majorids, or OCU: Active from Oct. 12-19, peaking on Oct. 15. Velocity of 119 miles/hour. This is a very minor shower rates of less than one per hour. Radiant — where the meteors appear to come from — is in Ursa Major.

 

Chi Taurids, or CTA:  Active from Oct. 10 — Nov. 10, peaking on Nov. 3. Velocity approximately 94,000 miles/hour. This is also a shower that has very little known about it. It was recently discovered in a survey to find minor meteor showers using a meteor radar (Brown et al, 2010).

 

Orionids, or ORI: Active from Oct. 2 — Nov. 7, peaking on Oct. 21 with rates up to 25 per hour. Velocity of 150,000 miles/hour. Radiant is in the constellation Orion.

 

Eta Geminids, or EGE:  Active from Oct. 14-27.  Peaking on Oct. 18 with rates of three per hour. These are fast-moving meteors that average at 157,000 miles/hour. Eta Geminids are often confused with Orionids since their velocity and peaks are similar.

 

Brown, P., Wong, D.K., Weryk, R.J., Wiegert, P.

A meteoroid stream survey using the Canadian Meteor Orbit Radar II: Identification of minor showers using a 3D wavelet transform

Icarus 207 (2010) 66–81.

 

 

Credits: NASA/MSFC/Meteoroid Environment Office/Rhiannon Blaauw, Bill Cooke

 

It's Raining Comet Halley!


We at the Meteoroid Environment Office are hoping that you have clear skies on May 5/6 when we have the opportunity to see pieces of Comet Halley whiz through Earth’s atmosphere!


Image of an Eta Aquarid meteor, taken the night of May 3, 2011. (NASA/MSFC)


Comet Halley (NASA)


Depending on your age, you may remember 25 years ago when people lined up for blocks to look through a telescope and get a glimpse of this popular comet. It will be another 51 years before the comet will pass close enough to earth for us to see it in its entirety, but the debris it has left orbit-after-orbit gives us a yearly show in the Eta Aquariid meteor shower.

Unfortunately the shower will not be seen in all its glory from the northern hemisphere. Our southern hemisphere friends will get a better show than us, seeing up to 60 meteors per hour if the skies are clear and dark. The radiant (the point in the sky that the meteors appear to come from) will not rise as high for those in northern latitudes, but we still may be able to see 20-30 per hour. Very few meteors will be seen if you live upwards of 40 degrees N latitude. Don’t let the low numbers stop you, though! With the radiant being fairly low in the sky these meteors may be ‘Earth grazers’ which hit the atmosphere at a shallow angle resulting in very long and lingering trails. Earth grazers aren’t numerous, but they are memorable. To see these meteors look straight up if you are in the southern hemisphere, and straight up but slightly to the east if you are in the northern hemisphere. Let your eyes adjust to the dark, and be patient.

Meteor showers are named after the constellation that their radiant is in, in our case the constellation Aquarius. Specifically the radiant is in the ‘water jar’ near one of the constellations brightest stars, Eta Aquariid.  The images below will help both southern and northern observers navigate the skies and locate the radiant (but don’t look directly at the radiant in order to see the meteors; look up!).

The Eta Aquariids are not only interesting because of their comet of origin. The Eta Aquariids have quite the history, being first recorded in old Chinese annals from the 8th century! It was’’t until 1868 that people suspected that Comet Halley and the Eta Aquariids were related, and not confirmed until 1900 by William F. Denning.

Another interest to scientists is the complexity/inconsistency of the activity rates. May 4-6 is always the main peak, but other maxima are frequently seen around this time. This unusual activity is likely caused by thick and thin filaments within the stream that Earth passes through. These filaments could be from planetary perturbations as well as a refreshing of the stream by comet Halley. One sure thing is that the Eta Aquariids are one of the oldest known showers, yet still one of the most interesting to study.

Since you are going to be out anyways, why not check out what else is in the sky! Saturn will be setting on the opposite side of the sky as the Eta Aquariid radiant and in the early morning you may be able to catch a party of planets; Venus, Mercury, Jupiter, and Mars (in that order) will rise in the east just before the sun does. Using a small telescope or binoculars may aid in seeing the planets. Happy viewing!


Eta Aquariid radiant in the water jar of Aquarius — orientation for northern observers
(Starry Night). Constellations as seen from Huntsville Alabama, 4 am local time
(UTC-5 hours) May 6.




Eta Aquariid radiant in the water jar of Aquarius — orientation for southern observers
(Starry Night). Constellations as seen from Brazil, 4 am local time (UTC-3 hours) May 6.


Quick facts on the Eta Aquarids:

  • Parent body: Comet 1P/Halley
  • Velocity:  66 km/s or 152,000 miles/hr
  • ZHR (meteors per hour): 60 max
  • Radiant constellation: Aquarius
  • First time recorded: 8th century by the Chinese, though the connection to Comet Halley wasn’t made until1900.


Courtesy of Rhiannon Blaauw, NASA’s Meteoroid Environment Office, Marshall Space Flight Center, Huntsville, Ala.

Live Web Chats Today: Geminid Meteor Shower


Baby, it’s cold outside — but you can still enjoy the best meteor shower of the year. The 2010 Geminid meteor shower promises to be lively, with realistic viewing rates of 50-80 meteors per hour and potential peaks reaching 120 meteors per hour. Anytime between Dec. 12-16 is a valid window for Geminid-watching, but the night of Dec. 13-14 is the anticipated peak.

You have two opportunities to learn more about the Geminids from meteor experts based at NASA’s Marshall Space Flight Center. On Monday, Dec. 13 from 3:00 to 4:00 p.m. EST, meteor experts Danielle Moser and Rhiannon Blaauw will answer your questions, then you can stay “up all night” to observe the Geminids with NASA astronomer Bill Cooke. Have the coffee ready, then join them online from 11:00 p.m. to 5:00 a.m. EST as the Geminids peak in the skies over Earth.

Joining the chats is easy. Simply go to https://www.nasa.gov/connect/chat/geminids2010.html a few minutes before each of the chat start times list above. The chat module will appear at the bottom of this page. After you log in, wait for the chat module to be activated, then ask your questions. Here’s to a spectacular viewing!

False-color composite view of 2008 Geminid meteor shower is courtesy of Bill Cooke, NASA’s Meteoroid Environment Office at the Marshall Space Flight Center.
 

When to look? In what direction?

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!

How low can they go?


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.