Astronomy Picture of the Day

                         Astronomy Picture of the Day

    Discover the cosmos! [1] Each day a different image or photograph of our
 fascinating universe is featured, along with a brief explanation written by a
                           professional astronomer.

                                2018 August 29
                                      [2]
                        Nearby Cepheid Variable RS Pup
Image Credit: NASA [3] , ESA [4] , Hubble Heritage [5]  Team; Acknowledgement:
              Howard Bond [6] (STScI [7]  & Penn State U. [8] )

Explanation: In the center is one of the most important stars on the sky. This
is partly because, by coincidence, it is surrounded by a dazzling reflection
nebula [9] . Pulsating RS Puppis [10] , the brightest star in the image
center, is some ten times more massive than our Sun and on average 15,000
times more luminous. In fact, RS Pup is a Cepheid type [11] variable star [12]
, a class of stars whose brightness [13] is used to estimate distances to
nearby galaxies as one of the first steps in establishing the cosmic distance
[14]  scale. As RS Pup pulsates [15] over a period of about 40 days, its
regular changes in brightness are also seen along the nebula delayed in time,
effectively a light echo [16] . Using measurements of the time delay and
angular size of the nebula, the known speed of light [17]  allows astronomers
to geometrically determine the distance to RS Pup [18]  to be 6,500
light-years, with a remarkably small error of plus or minus 90 light-years
[19] . An impressive achievement for stellar astronomy, the echo-measured [20]
distance also more accurately establishes the true brightness of RS Pup [21] ,
and by extension other Cepheid stars, improving the knowledge of distances
[22]  to galaxies beyond [23] the Milky Way. The featured image [24] was taken
by the Hubble Space Telescope [25] .

                        Tomorrow's picture: open space

-------------------------------------------------------------------------------
< [26] | Archive [27] | Submissions [28] | Index [29] | Search [30] | Calendar
  [31] | RSS [32] | Education [33] | About APOD [34] | Discuss [35] | > [36]
-------------------------------------------------------------------------------

    Authors & editors: Robert Nemiroff [37] (MTU [38] ) & Jerry Bonnell [39]
                                  (UMCP [40] )
          NASA Official:  Phillip Newman Specific rights apply [41] .
              NASA Web Privacy Policy and Important Notices [42]
              A service of: ASD [43]  at NASA [44]  / GSFC [45]
                           & Michigan Tech. U. [46]
----------
Site notes:
  [1] archivepix.html
  [2] image/1808/RSPup_HubbleBond_3981.jpg
  [3] http://www.nasa.gov/
  [4] http://www.spacetelescope.org/
  [5] http://heritage.stsci.edu/
  [6] http://www.stsci.edu/~bond/
  [7] http://www.stsci.edu/
  [8] http://astro.psu.edu/
  [9] http://apod.nasa.gov/apod/reflection_nebulae....
  [10] http://en.wikipedia.org/wiki/RS_Pup
  [11] ap960110.html
  [12] http://www.aavso.org/types-variables
  [13] http://hyperphysics.phy-astr.gsu.edu/hbase/as... cepheid.html#c2
  [14] http://en.wikipedia.org/wiki/Cosmic_distance_...
  [15]  http://www.eso.org/public/news/eso0805/
  [16] http://en.wikipedia.org/wiki/Light_echo
  [17] http://www.physics.umd.edu/icpe/newsletters/n... marshmal.htm
  [18] http://www.aavso.org/vsots_rspup
  [19] https://starchild.gsfc.nasa.gov/docs/StarChil...
  [20] https://arxiv.org/abs/0802.1501
  [21]
http://www.eso.org/sci/publications/messenger...
messenger-no150-46-48.pdf
  [22] http://www.astro.ucla.edu/~wright/distance.ht...
  [23] http://www.atlasoftheuniverse.com/virgo.html
  [24] http://www.spacetelescope.org/images/heic1323...
  [25] http://hubblesite.org/the_telescope/
  [26] ap180828.html
  [27] archivepix.html
  [28] lib/apsubmit2015.html
  [29] lib/aptree.html
  [30] https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apo...
  [31] calendar/allyears.html
  [32] /apod.rss
  [33] lib/edlinks.html
  [34] lib/about_apod.html
  [35] http://asterisk.apod.com/discuss_apod.php?dat...
  [36] ap180830.html
  [37] http://www.phy.mtu.edu/faculty/Nemiroff.html
  [38] http://www.phy.mtu.edu/
  [39] https://antwrp.gsfc.nasa.gov/htmltest/jbonnel...
  [40] http://www.astro.umd.edu/
  [41] lib/about_apod.html#srapply
  [42] https://www.nasa.gov/about/highlights/HP_Priv...
  [43] https://astrophysics.gsfc.nasa.gov/
  [44] https://www.nasa.gov/
  [45] https://www.nasa.gov/centers/goddard/
  [46] http://www.mtu.edu/

--- Mystic BBS v1.12 A39 (Windows/32)
 * Origin: FIDONet - The Positronium Repository (1:393/68)