Images by Date
Images by Category
Solar System
Stars
White Dwarfs
Supernovas
Neutron Stars
Black Holes
Milky Way Galaxy
Normal Galaxies
Quasars
Galaxy Clusters
Cosmology/Deep Field
Miscellaneous
Images by Interest
Space Scoop for Kids
Multiwavelength
Sky Map
Constellations
3D Wall
Photo Blog
Top Rated Images
Image Handouts
Desktops
High Res Prints
Fits Files
Image Tutorials
Photo Album Tutorial
False Color
Cosmic Distance
Look-Back Time
Scale & Distance
Angular Measurement
Images & Processing
AVM/Metadata
Getting Hard Copies
Image Use Policy
Web Shortcuts
Chandra Blog
RSS Feed
Chandra Mobile
Chronicle
Email Newsletter
News & Noteworthy
Image Use Policy
Questions & Answers
Glossary of Terms
Download Guide
Get Adobe Reader
More Information
Normal Stars & Star Clusters
X-ray Astronomy Field Guide
Normal Stars & Star Clusters
Questions and Answers
Normal Stars & Star Clusters
Chandra Images
Normal Stars & Star Clusters
White Dwarfs & Planetary Nebulas
X-ray Astronomy Field Guide: White Dwarfs & Planetary Nebulas
Questions and Answers: White Dwarfs & Planetary Nebulas
Chandra Images: White Dwarfs & Planetary Nebulas
Related Podcasts
A Tour of Flame Nebula
Download Image

More Information



Related Images
Nova Aquilae
Nova Aquilae
(06 Sep 01)
V471 Tauri:
Star Shows It Has the Right Stuff


V471 Tauri
Credit: NASA/CXC/SAO/J. Drake et al.

The V471 Tauri system comprises a white dwarf star (the primary) in a close orbit - one thirtieth of the distance between Mercury and the Sun - with a normal Sun-like star (the secondary). The white dwarf star was once a star several times as massive as the Sun. Chandra data on this system provide the best evidence yet that a star can be engulfed by its companion star and survive.

The illustration shows X-ray spectra made by Chandra's Low Energy Transmission Grating Spectrometer of two individual stars and V471 Tauri: a red giant star (Beta Ceti, top panel), V471 Tauri, and a Sun-like star (Epsilon Eridani). The peak in the spectrum due to carbon ions is much smaller in the giant star than in the Sun-like star, whereas the carbon peak in V471 is intermediate between the two. These differences provide important clues to the different evolutionary histories of the stars.

Nuclear fusion reactions in the core of such a star convert carbon into nitrogen over a period of about a billion years. When the fuel in the core of the star is exhausted, the core collapses, triggering more energetic nuclear reactions that cause the star to expand and transform into a red giant before eventually collapsing to become a white dwarf.

The carbon-poor material in the core of the red giant is mixed with outer part of the star, so its atmosphere will have a deficit of carbon, as compared with Sun-like stars, as shown in the figure. If a red giant is part of binary system of closely orbiting stars, the evolution of the secondary star can be dramatically affected.

Theoretical calculations indicate that the red giant can completely envelop its companion star. During this common envelope phase, friction causes the companion star to spiral inward rapidly where it will either be destroyed by the red giant, or it will survive when much of the envelope is spun away.

If the companion star manages to survive, it will bear the marks of its ordeal in the form of contamination by carbon-poor material that it accreted while it was inside the red giant envelope. The X-ray spectrum of V471 Tauri in the middle panel shows just this effect - the carbon peak is intermediate between that of a Sun-like star and an isolated red giant star. The data indicate that about 10 percent of the star's mass has been accreted from the red giant.

In the future the companion star can return the favor. It will expand and dump material back onto the white dwarf. If enough material is dumped on the white dwarf, it could cause the white dwarf to explode as a supernova.

Fast Facts for V471 Tauri:
Credit  NASA/CXC/SAO/J. Drake et al.
Scale  Image is across.
Category  Normal Stars & Star Clusters, White Dwarfs & Planetary Nebulas
Coordinates (J2000)  RA 03h 50m 25.00s | Dec +17° 14’ 47.40"
Constellation  Taurus
Observation Dates  January 24-25, 2002
Observation Time  24 hours
Obs. IDs  2523
Instrument  HRC
References J. Drake and M. Sarna, Astrophys. J. Letters, 594, L55 (2003)
Distance Estimate  150 light years
Release Date  January 30, 2004