VARIABLE STAR RS PUPPIS AS SEEN BY HUBBLE
Image Credit & Copyright: NASA/ESA Hubble Space Telescope. CLICK image for larger view and look below for information and links.
6500 light years away in the southern constellation Puppis is this magnificent and seemingly mysterious object, shrouded in a cocoon of stellar material. This image comes to us from the “living legend” Hubble Space Telescope (HST) and it’s of a star (yes a star) known as RS Puppis. This is what’s known as an RS Type Cepheid Variable Star.
Don’t worry too much about the “RS” and “Cepheid” classifications as there is a vast list of various types of variable stars (link below). Just know that variable stars are stars that, over a regular given period of time brighten and dim. Cepheid’s in short, brighten greatly over a relatively long period. RS Puppis, has a brightness of 15,000 times brighter than the Sun.
RS Puppis here is roughly 20 times the mass of the Sun and 200 times larger. Its variability cycle or pulsation takes about 41.3 days or 6 weeks and its apparent magnitude ranges from a low of 7.6 to a naked eye visibility at 6.5.
So what is a variable star? To keep this post from running to a few thousand words I’m going to give you the “Cliff Notes” version. When a star begins to run low on hydrogen fuel in its core it’s millions of years as a stable, light bearing star begins to deteriorate. This instability causes the stars to swell and shrink over a given period of time. As they swell, they brighten. Conversely, when they shrink back down, they get dimmer. When they shrink back down they leave behind a massive shell of gas and dust which in turn becomes the shroud or cocoon that the star here is seen encased in.
Cepheid variables as many of you know are, because of their brightness and regularity known as “Standard Candles.” Standard Candles allow us to make high precision, distance measurements throughout the universe.
Finally, in this image exists a fairly common variable star phenomenon known as “Light Echo.” What is it? Well think first of what a standard sound wave echo is. You yell, or make an audible noise in a place with even the most rudimentary acoustics and in a moment’s time, hear your voice or that particular noise return to you after it has bounced off something. A light echo is pretty much the same thing just with light instead of sounds. Ya, that sounds pretty unrealistic but the distances here are large enough so that even at a speed that carries light 7 times around the Earth each second, we can still see it in motion. The material in this star’s environment enables this effect to be shown with stunning clarity. As the star expands and brightens, we see some of the light after it is reflected from progressively more distant shells of dust and gas surrounding the star, creating the illusion of gas moving outwards. Want to see this in amazing detail? Then watch the Hubblecast 71 video above!
NAME: HD 68860, SAO 198944, RS Puppis.
WHAT IS IT?: Cepheid Variable Star with a period of about 41.3 days.
HOW BIG IS IT?: Roughly 10 stellar masses & 200 X larger than the Sun.
HOW FAR AWAY IS IT?: 6500 light years or 2000 parsecs.
APPARENT MAGNITUDE?: 6.5 to 7.6.
WHERE IS IT? (General): Southern constellation Puppis.
WHERE IS IT? (Exact RA/DEC J2000): R.A. 08h 13m 04s / DEC -34° 34′ 42.7”.
NASA Hubble News Center release for this image with information: http://hubblesite.org/newscenter/archive/releases/2013/51/image/a/
European Space Agency (ESA) Hubble page for this image: http://www.spacetelescope.org/images/heic1323a/
ESA Hubble page for information on this object & image: http://www.spacetelescope.org/news/heic1323/
AAVSO Variable Star Type Designations: http://www.aavso.org/vsx/help/VariableStarTypeDesignationsInVSX.pdf
AAVSO RS Puppis page: http://www.aavso.org/vsots_rspup
SIMBAD data page for RS Puppis: http://simbad.u-strasbg.fr/simbad/sim-id?Ident=RS+Puppis