Nasa / Space

Exploring our solar system

Edge-on view of our Milky Way

From its orbit around Earth, the Goddard Space Flight Center's Cosmic Background Explorer (COBE) captured this edge-on view of our Milky Way galaxy in infrared light in 1990.

Credit: NASA Goddard Space Flight Center

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15 comments
FhMsu
FhMsu

"When I was your age, Pluto was a planet." :)

donweber
donweber

When I was in middle school, my science teacher taught how we could remember the order of the planets. The words had the same first letter of the planets and sung to the tune of Suwannee River. My Very Educated Mother Just Served Us Nine Pizza Pies. (it must have worked since I remember it 30 years later). Now I guess we just get served nine whatevers.

dennis
dennis

in the 60's. When Pluto was discovered they simply added a period to the sentence: Mother Visits Every Morning and (asteroids) Just Stays Until Noon...Period

Tink!
Tink!

Very true too. It was a planet when I was growing up. It was a planet for one of my kids. It was debated for another of my kids. It is now no longer a planet for all the kids.

Michael Jay
Michael Jay

Cool video taken 11/20/08 of a meteor or falling space debris; http://spaceweather.com/archive.php?view=1&day=21&month=11&year=2008

donweber
donweber

Would somebody explain what classifies a planet, and why Pluto isn't one any more?

Michael Jay
Michael Jay

not really, Google is your friend. look here; http://en.wikipedia.org/wiki/Dwarf_planet

donweber
donweber

Thanks for the link Michael. As I understand it, Pluto is not a planet anymore because it doesn't clear out its neighborhood. Perhaps if Eris had been discovered before Pluto, it could have been out ninth planet for a while. I also found www.astronomycast.com, a weekly podcast.

david.silkstone
david.silkstone

Fantastic, when was the spacecraft the took this picture launched ?

Michael Jay
Michael Jay

The Cosmic Background Explorer. (COBE) The satellite stopped working in 1993. more info here; http://lambda.gsfc.nasa.gov/product/cobe/ The picture is not actually an edge on photo of the Milky Way but rather a representation made from the data collected by COBE.

Funker
Funker

the text states that the photo was taken from COBE, in an earth orbit using infrared. the photo is possible because we are on the edge of the galaxy. Alternatively, a satellite could have been launched 150 000 years ago and sent the photo back.

SObaldrick
SObaldrick

Question: Pluto is not classed as a planet in our solar system. So what defines a body as a moon? Les.

jck
jck

According to the IAU: [i]RESOLUTION B5 Definition of a Planet in the Solar System Contemporary observations are changing our understanding of planetary systems, and it is important that our nomenclature for objects reflect our current understanding. This applies, in particular, to the designation "planets". The word "planet" originally described "wanderers" that were known only as moving lights in the sky. Recent discoveries lead us to create a new definition, which we can make using currently available scientific information. The IAU therefore resolves that planets and other bodies, except satellites, in our Solar System be defined into three distinct categories in the following way: (1) A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit. (2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite. (3) All other objects,except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".[/i] http://www.iau.org/static/resolutions/Resolution_GA26-5-6.pdf

Michael Jay
Michael Jay

there are many answers. From Wikipedia; "There is no established lower limit on what should be considered a moon. Every body with an identified orbit, some as small as a kilometer across, has been identified as a moon, though objects a tenth that size within Saturn's rings, which have not been directly observed, have been called moonlets. Small asteroid moons, such as Dactyl, have also been called moonlets. The upper limit is also vague. When the masses of two orbiting bodies are similar enough that one cannot be said to orbit the other, they are described as a double body rather than primary and satellite. Asteroids such as 90 Antiope are considered double asteroids, but they have not forced a clear definition as to what constitutes a moon. Some authors consider the Pluto-Charon system to be a double (dwarf) planet. The most common dividing line on what is considered a moon rests upon whether the barycentre is below the surface of the larger body, though this is somewhat arbitrary, as it relies on distance as well as relative mass." http://en.wikipedia.org/wiki/Natural_satellite And more references to keep you reading through the day; http://www.google.com/search?hl=en&client=firefox-a&rls=org.mozilla:en-US:official&hs=k7&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=definition+of+moon&spell=1