| Southern Delta Aquariids (SDA) | |
|---|---|
| Parent body | 96P/Machholz[1] |
| Radiant | |
| Constellation | Aquarius |
| Right ascension | 23h 20m |
| Declination | −16° |
| Properties | |
| Occurs during | July 12 – August 23 |
| Date of peak | July 30 |
| Zenithal hourly rate | 16[1] |
The Southern Delta Aquariids[2] are a meteor shower visible from mid July to mid August each year with peak activity on 28 or 29 July. The comet of origin is not known with certainty. A suspected candidate is Comet 96P Machholz. Earlier, it was thought to have originated from the Marsden and Kracht Sungrazing comets.[1]
The Delta Aquariids get their name because their radiant appears to lie in the constellation Aquarius, near one of the constellation's brightest stars, Delta Aquarii. The name derives from the Latin possessive form "Aquarii", whereby the declension "-i" is replaced by "-ids" (hence Aquariids with two i's). There are two branches of the Delta Aquariid meteor shower, Southern and Northern. The Southern Delta Aquariids are considered a strong shower, with an average meteor observation rate of 15–20 per hour, and a peak zenithal hourly rate of 18. The average radiant is at RA=339°, DEC=−17°. The Northern Delta Aquariids are a weaker shower, peaking later in mid August, with an average peak rate of 10 meteors per hour and an average radiant of RA=340°, DEC=−2°.
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Watch the Delta Aquarids, and Meet NASA's 'Aquanauts'
Transcription
As we speak -- or at least, as I speak -- Earth is crossing the path of an unusual comet, and you may be able to see pieces of it for yourself in the next couple days. Plus, you’ll learn about what’s probably the only NASA mission that you can appropriately celebrate with a mojito, today on SciShow Space News. [Intro] If you’ve seen a shooting star -- or more accurately, a meteoroid -- in the last few weeks, chances are it was part of the Delta Aquarids, a meteor shower that will last until the end of August. Though dimmer than the more famous Perseids, which start next month, these meteoroids are special. The Delta Aquarids are known for leaving persistent trains -- trails of glowing gas that can last several seconds, even minutes after the meteoroid has faded. When meteoroids of any sort hit the dense atmosphere of the Earth, friction with air molecules heats up and vaporizes the space rock, leaving behind a glowing streak of gases. That’s what makes the so-called “shooting star.” But when a meteoroid hits the atmosphere at supersonic speeds, it can actually ionize the air around it, tearing the electrons from their parent atoms. As the electrons slowly re-attach to their atoms, they emit light, sometimes for several minutes. And this might be why the Delta Aquarids leave their trademark persistent trains. But we still don’t know very much about them. Meteor showers are the result of Earth passing through the rocky debris left behind by a nearby comet. And the Delta Aquarids correspond with Earth crossing the path of an odd comet known as 96P/Machholz. It was discovered in 1986, but only during its pass by us in 2007 did astronomers find that it has far less carbon than any other comet or asteroid we know. Scientists at the Lowell Observatory discovered that it contained 72 times less cyanogen, which is a common carbon-containing molecule, than the average space rock. And we don’t know why! Unlike many other comets, which are believed to originate in the suburbs of our solar system -- the Oort Cloud -- astronomers think that 96P might come from even farther outside our system, where carbon may be less abundant. So on Monday and Tuesday, when the Delta Aquarids peak, you may see the light from burning gas and rock that came to you from very, very far away. The meteor shower will reach its max around July 28th, with 15 to 20 meteors per hour in the constellation Aquarius. The best viewing will be in the southern hemisphere and northern tropics, but if you live farther north, you might still be able to seem them zooming around the southern horizon. And as a bonus, they’ll peak during the new moon, so the sky will be extra dark for your meteoroid-viewing pleasure. Speaking of the tropics, check out the latest from of one of NASA’s least publicized missions, the NASA Extreme Environment Mission Operation, or NEEMO. If you’re looking for Bill Murray in that picture, you can stop now. This is part of how astronauts train for the extreme environment of space. 19 meters below the surface of the Atlantic Ocean, 10 kilometers off the coast of Key West, Florida, astronauts from around the world have taken up residence in the remote Aquarius Reef Base, the world’s only undersea research station. On Monday, a crew of four “aquanauts,” as they’re called, from the US, France, and Japan started NEEMO’s 18th training mission, which will last nine days. It began with 15 hours of decompression time, which they’ll have to repeat before they resurface. And now they’re living in a 37-square-meter habitat that mimics the cramped quarters aboard a real spacecraft. Inside the base, and during 10 trips outside of it, the crew will test will test technology and training techniques for use in the International Space Station, including the first-ever manned drilling operation in low gravity, using a meter-long underwater drill at the end of a 4-meter-long boom. And all the while, the aquanauts themselves will be subjects of the study into behavioral health and habitability in a confined environment. So, we wish you well, brave aquanauts! Thanks for doing yet another thing that I myself would never want to do, but I’m glad is being done. And thank you, person on the other side of the computer, as always for watching SciShow Space News! If you want to keep exploring the universe with us, check out Subbable.com/SciShow to learn how you can help support us. And don’t forget to go to youtube.com/scishowspace and subscribe!
History
Observations of the (then unidentified) Delta Aquariids (δ Aquariids) were recorded by G. L. Tupman in 1870, who plotted 65 meteors observed between July 27 and August 6. He plotted the radiant's apparent beginning and ending points (RA=340°, DEC=−14°; RA=333°, DEC=−16°). This was corrected later. Ronald A. McIntosh re-plotted the path, based on a greater number of observations made from 1926 to 1933. He determined it to begin at RA=334.9°, DEC=−19.2° and end RA=352.4°, DEC=−11.8°. Cuno Hoffmeister and a team of German observers were the first to record the characteristics of a Northern Aquariid radiant within the stream around 1938. Canadian D. W. R. McKinley observed both branches in 1949, but did not associate the two radiants.[3] That was accomplished by astronomer Mary Almond, in 1952, who determined both the accurate velocity and orbit of the δ Aquariids. She used a "more selective beamed aerial" (echo radio) to identify probable member meteors and plotted an accurate orbital plane. Her paper reported it as a broad "system of orbits" that are probably "connected and produced by one extended stream."[4] This was confirmed in the 1952–1954 Harvard Meteor Project, via photographic observation of orbits. The Project also produced the first evidence that the stream's evolution was influenced by Jupiter.[3]
Viewing
The Delta Aquariids are best viewed in the pre-dawn hours, away from the glow of city lights. Southern Hemisphere viewers usually get a better show because the radiant is higher in the sky during the peak season. Since the radiant is above the southern horizon for Northern Hemisphere viewers, meteors will primarily fan out in all compass points, east, north and west. Few meteors will be seen heading southward, unless they are fairly short and near the radiant.[citation needed]
See also
References
- ^ a b c Jenniskens, Peter (2006). "The sunskirting streams: Arietids and δ-Aquariids". Meteor Showers and Their Parent Comets. Cambridge University Press. pp. 423–37. ISBN 978-0-521-85349-1.
- ^ "Meteor Shower Calendar | IMO | Page 2009". Retrieved 2022-09-27.
- ^ a b "Meteor Showers Online".
- ^ Öpik, Ernst (September 1950). "Interstellar Meteors and Related Problems". Irish Astronomical Journal. 1 (3): 80–96. Bibcode:1950IrAJ....1...80O.
External links
- Worldwide viewing times for the 2011 Delta Aquariids meteor shower
- Delta Aquariids at Meteor Showers Online
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This page was last edited on 19 November 2023, at 10:16