Astronomy Picture of the Day [1]Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2022 May 21 [2]See Explanation. Clicking on the picture will download the highest resolution version available. Planetary Nebula Abell 7 Image Credit & [3]Copyright: [4]Donald Waid, Ron Dilulio Explanation: Very faint planetary nebula Abell 7 is some 1,800 light-years distant, just south of Orion in planet Earth's skies in the constellation [5]Lepus, The Hare. Surrounded by Milky Way stars and near the line-of-sight to distant background galaxies, its [6]generally simple spherical shape, about 8 light-years in diameter, is outlined in [7]this deep telescopic image. Within its confines are beautiful, more complex details enhanced by the use of [8]narrowband filters. Emission from hydrogen is shown in reddish hues with oxygen emission mapped to green and blue colors, giving Abell 7 a natural appearance that would otherwise be much too faint to be appreciated [9]by eye. A [10]planetary nebula represents a very brief final phase in stellar evolution that our own Sun will experience 5 billion [11]years hence, as the nebula's central, once sun-like star shrugs off its outer layers. Abell 7 itself is estimated to be 20,000 years old. Its central star is seen here as a [12]fading white dwarf some 10 billion years old. Tomorrow's picture: Tsunami on the Sun __________________________________________________________________ [13]< | [14]Archive | [15]Submissions | [16]Index | [17]Search | [18]Calendar | [19]RSS | [20]Education | [21]About APOD | [22]Discuss | [23]> __________________________________________________________________ Authors & editors: [24]Robert Nemiroff ([25]MTU) & [26]Jerry Bonnell ([27]UMCP) NASA Official: Phillip Newman [28]Specific rights apply. [29]NASA Web Privacy Policy and Important Notices A service of: [30]ASD at [31]NASA / [32]GSFC & [33]Michigan Tech. U. References 1. https://apod.nasa.gov/apod/archivepix.html 2. https://apod.nasa.gov/apod/image/2205/Abell_7-2022-02-20-HOO-1600.jpg 3. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 4. http://www.waid-observatory.com/index.html 5. http://www.allthesky.com/constellations/big/lepus28vm-b.jpg 6. http://arxiv.org/abs/1210.6226 7. http://www.waid-observatory.com/abell-7-2022-02-20-HOO.html 8. https://apod.nasa.gov/apod/ap111013.html 9. https://apod.nasa.gov/apod/ap100506.html 10. http://en.wikipedia.org/wiki/Planetary_nebula 11. http://www.futuretimeline.net/beyond.htm 12. https://www.nasa.gov/feature/goddard/2019/citizen-scientist-finds-ancient-white-dwarf-star-encircled-by-puzzling-rings 13. https://apod.nasa.gov/apod/ap220520.html 14. https://apod.nasa.gov/apod/archivepix.html 15. https://apod.nasa.gov/apod/lib/apsubmit2015.html 16. https://apod.nasa.gov/apod/lib/aptree.html 17. https://antwrp.gsfc.nasa.gov/cgi-bin/apod/apod_search 18. https://apod.nasa.gov/apod/calendar/allyears.html 19. https://apod.nasa.gov/apod.rss 20. https://apod.nasa.gov/apod/lib/edlinks.html 21. https://apod.nasa.gov/apod/lib/about_apod.html 22. http://asterisk.apod.com/discuss_apod.php?date=220521 23. https://apod.nasa.gov/apod/ap220522.html 24. http://www.phy.mtu.edu/faculty/Nemiroff.html 25. http://www.phy.mtu.edu/ 26. https://antwrp.gsfc.nasa.gov/htmltest/jbonnell/www/bonnell.html 27. http://www.astro.umd.edu/ 28. https://apod.nasa.gov/apod/lib/about_apod.html#srapply 29. https://www.nasa.gov/about/highlights/HP_Privacy.html 30. https://astrophysics.gsfc.nasa.gov/ 31. https://www.nasa.gov/ 32. https://www.nasa.gov/centers/goddard/ 33. http://www.mtu.edu/