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Astronomy Picture of the Day | Westerlund 2

Image credit: NASA/CXC/Univ. de Liege/Y. Nael et al.

This Chandra X-ray Observatory image shows Westerlund 2, a young star cluster with an estimated age of about one or two million years. Until recently little was known about this cluster because it is heavily obscured by dust and gas. However, using infrared and X-ray observations to overcome this obscuration, Westerlund 2 has become regarded as one of the most interesting star clusters in the Milky Way galaxy. It contains some of the hottest, brightest and most massive stars known.

This Chandra image of Westerlund 2 shows low energy X-rays in red, intermediate energy X-rays in green and high energy X-rays in blue. The image shows a very high density of massive stars that are bright in X-rays, plus diffuse X-ray emission.

An incredibly massive double star system called WR20a is visible as the bright yellow point just below and to the right of the cluster’s center. This system contains stars with masses of 82 and 83 times that of the Sun. The dense streams of matter steadily ejected by these two massive stars, called stellar winds, collide with each other and produce copious amounts of X-ray emission. This collision is seen at different angles as the stars orbit around each other every 3.7 days. Several other bright X-ray sources may also show evidence for collisions between winds in massive binary systems.

Noble Wisdom

Maxims of Rochefoucauld:

  • “Few men are able to know all the ill they do.”
  • “We are never made so ridiculous by the qualities we have, as by those we affect to have.”
  • “In every profession, every individual affects to appear what he would willingly be esteemed; so that we may say, the world is composed of nothing but appearances.”
  • “We like better to see those on whom we confer benefits, than those from whom we receive them.”
  • “Everybody takes pleasure in returning small obligations; many go so far as to acknowledge moderate ones; but there is hardly any one who does not repay great obligations with ingratitude.”
  • “In misfortunes we often mistake dejection for constancy; we bear them without daring to look on them, as cowards suffer themselves to be killed without resistance.”
  • “None but the contemptible are apprehensive of contempt.”
  • “We want strength to act up to our reason.”
  • “We easily forget crimes that are known only to ourselves.”
  • “It is as easy to deceive ourselves without our perceiving it, as it is difficult to deceive others without their perceiving it.”
  • “We are sometimes less unhappy in being deceived than in being undeceived by those we love.”

And “Those who apply themselves too much to little things commonly become incapable of great ones.”