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APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 5:09 am
by APOD Robot
Sky Lights in the New Year
Explanation: Triggered by the impact of a coronal mass ejection on New Year's eve, a moderate geomagnetic storm brought a
celebration of sky lights to planet Earth's high latitudes yesterday.
In this New Year's nightscape, the shimmering reddish curtains of
aurora australis along a southern horizon are captured over Morgiana, SW Victoria, Australia. Of course, more permanent jewels of the southern skies are on the scene. The southern Milky Way, Alpha and Beta Centauri, and bright stars of the
Southern Cross are on the left. In silhouette, branches of the large foreground tree stretch across the Milky Way's satellite galaxies, the Large and Small Magellanic clouds. The bright star framed near the tips of tree branches at right is Achernar. Alpha star of the constellation Eridanus, Achernar is sometimes known as the southern
end of the river.
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Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 5:23 am
by Beyond
Ann is going to love the "end of the river" in this APOD!!
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 7:37 am
by Ann
Beyond wrote:Ann is going to love the "end of the river" in this APOD!!
I do!
But I also love the difference in color between our own galaxy and the Magellanic Clouds. The two
Clouds of Magellan are really dominated by young blue stars in a way that make them so different from our own galaxy.
In his book
The Galaxies of the Local Group, Sidney van den Bergh discussed the star formation of the Magellanic Clouds. His discussion of the Large Cloud is the most interesting. Sidney van den Bergh wrote:
The idea that a violent burst of star formation in the LMC followed a rather lengthy period of quiescence was first introduced by Butcher(1977).
...
Butcher concluded that a dramatic increase in the rate of star formation had taken place in the LMC 3-5 Gyr ago.
...
Bertelli et al. (1992) estimated that the mean rate of star formation in the Large Cloud was as much as ten times higher after the burst had started than it had been previously.
...
From their observation of a field located (..) from the center of the LMC Elson et al. (1997) found that only ~5% of the stars in this field belong to the old disk population that predated the great burst of star formation that started ~3 Gyr ago.
Teh Large Magellanic Cloud. Photo: Alan Dyer.
The expression "Gyr" means "billion years. The gist of what Sidney van den Bergh wrote here is that most of the stars in the Large Magellanic Cloud seem to have formed in the last 3 billion years. Fascinatingly, van den Bergh speculated that the Large Magellanic Cloud might have been a mild example of a
low surface brightness galaxy before it suddenly ran into starburst mode about three billion years ago. And while the greatest burst of star formation in the LMC took place about 3 billion years ago, the LMC keeps forming new stars at a very high rate.
This is so different from our own galaxy, which probably formed most of its stars about 10 to 12 billion years ago or so, and its rate of star formation has likely been decreasing ever since then. Because our own galaxy contains so many old stars, it has a large yellow bulge, an old yellow thick disk and huge amounts of dust from eons of star formation. The Magellanic Clouds contain no bulges and little dust.
Other large galaxies typically have
satellite galaxies that are mostly devoid of star formation. What makes the Magellanic Clouds so different? Although I can't find the source now, I know there has been speculation that the Magellanic Clouds might have only rather recently been captured by the Milky Way. It is fascinating to speculate that the great burst of star formation in the Large Magellanic Cloud (and to a lesser extent in the Small Magellanic Cloud) might have something to do with them being captured by our own big bully of a galaxy and having their gas stirred up and jostled by the powerful gravity of the Milky Way.
Ann
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 12:51 pm
by Animal of Stone
Well done Gill Fry. The most beautiful New Years fireworks i have ever seen.
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 1:22 pm
by Boomer12k
The Sky is celebrating....
Time goes on....
:---[===] *
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 2:07 pm
by ThePiper
Ann wrote:
But I also love the difference in color between our own galaxy and the Magellanic Clouds. The two Clouds of Magellan are really dominated by young blue stars in a way that make them so different from our own galaxy...
But I preferre to stay here on earth where I need a whole summer to tan. @LMC it would be done in some seconds. Right?
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 4:35 pm
by Chris Peterson
Ann wrote:The expression "Gyr" means "billion years.
It does (although "billion" is ambiguous). However, if you're doing your own writing, "Ga" is the preferred unit for 10
9 years.
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 8:33 pm
by neufer
Chris Peterson wrote:
"Ga" is the preferred unit for 109 years.
https://en.wikipedia.org/wiki/Algebraic_geometry_and_analytic_geometry wrote:
GAGA:
Géometrie Algébrique et Géométrie Analytique by Serre proves general results that relate classes of algebraic varieties, regular morphisms & sheaves with classes of analytic spaces, holomorphic mappings & sheaves. It reduces all of these to the comparison of categories of sheaves.
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 8:42 pm
by Beyond
Are you rejoicing while bringing in those sheaves, neufer? You could use those sheaves to celebrate the 10,000th member of the good ship Asterisk* coming on board.
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 9:01 pm
by neufer
Beyond wrote:
Are you rejoicing while bringing in those sheaves, neufer?
You could use those sheaves to celebrate the 10,000th member of the good ship Asterisk* coming on board.
Would that be 'jebersole'
(joined: Sat Jan 02, 2016 8:13 am)
Another 'sole' saved... Hallelujah
"
He that goeth forth and weepeth, bearing precious seed, shall
doubtless come again with rejoicing, bringing his sheaves with him."
https://en.wikipedia.org/wiki/Sheaf_%28mathematics%29 wrote:
<<A sheaf is a tool for systematically tracking locally defined data attached to the open sets of a topological space. The data can be restricted to smaller open sets, and the data assigned to an open set is equivalent to all collections of compatible data assigned to collections of smaller open sets covering the original one. For example, such data can consist of the rings of continuous or smooth real-valued functions defined on each open set. Sheaves are by design quite general and abstract objects, and their correct definition is rather technical. They exist in several varieties such as sheaves of sets or sheaves of rings, depending on the type of data assigned to open sets.>>
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sat Jan 02, 2016 10:49 pm
by BillBixby
Chris Peterson wrote:Ann wrote:The expression "Gyr" means "billion years.
It does (although "billion" is ambiguous). However, if you're doing your own writing, "Ga" is the preferred unit for 10
9 years.
Thank you Chris, for reminding us that from 'ten to the ninth,' onward, this world does not agree on what the words billions, trillions, etc mean. It was discussed in the link below.
http://asterisk.apod.com/viewtopic.php? ... 12#p193812
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Sun Jan 03, 2016 12:40 pm
by DavidLeodis
The photo is superb.
In information in Gill's resume in the Network SW Consulting website that can be brought up through her Facebook section it states of Gill (Gillian) "Gillian Fry B.Ag.Sc(hons), Dip Bus Mgt" and she is "The Principal Consultant of Network SW Consulting". So not only is Gill an excellent photographer (not just astrophotography) she is also a very active business person.
Re: APOD: Sky Lights in the New Year (2016 Jan 02)
Posted: Mon Jan 04, 2016 5:29 pm
by Ron-Astro Pharmacist
DavidLeodis wrote:The photo is superb.
In information in Gill's resume in the Network SW Consulting website that can be brought up through her Facebook section it states of Gill (Gillian) "Gillian Fry B.Ag.Sc(hons), Dip Bus Mgt" and she is "The Principal Consultant of Network SW Consulting". So not only is Gill an excellent photographer (not just astrophotography) she is also a very active business person.
neufer wrote:Chris Peterson wrote:
"Ga" is the preferred unit for 109 years.
https://en.wikipedia.org/wiki/Algebraic_geometry_and_analytic_geometry wrote:
GAGA:
Géometrie Algébrique et Géométrie Analytique by Serre proves general results that relate classes of algebraic varieties, regular morphisms & sheaves with classes of analytic spaces, holomorphic mappings & sheaves. It reduces all of these to the comparison of categories of sheaves.
These look like lots of fun. So do sheaves and other
shapes that inhabit the mind.
