Monicks: Unleashed

Tag: astrophysics

  • 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.

  • Astronomy Picture of the Day | Hubble snaps heavyweight of the Leo Triplet

    Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration. Acknowledgement: Davide De Martin and Robert Gendler

    Hubble has snapped a spectacular view of M 66, the largest “player” of the Leo Triplet, and a galaxy with an unusual anatomy: it displays asymmetric spiral arms and an apparently displaced core. The peculiar anatomy is most likely caused by the gravitational pull of the other two members of the trio.

    Those three galaxies are close enough together that the gravity of each affects the other two. See how the spiral arm at the bottom appears to be wider, messier, less organized than the one near the top of the picture? That’s no illusion. It’s thought that a recent pass by NGC 3628 may have bonked M66 pretty hard, disturbing it and messing around with its structure. The core of the galaxy — usually a smooth and symmetric blob — is all weird and misshapen. The pink glow in the image (emitted by hydrogen gas) is where stars are being born, and the deeper red is where they’re being cranked out en masse. Many times, when a galaxy passes near another one, the gas clouds get all riled up, collapsing to form lots of new stars.

    That’s more obvious in the Spitzer Space Telescope image included here. Spitzer sees far-infrared light, which is emitted by warm gas and dust. You can see how wide and weird the lower spiral arm of M66 is, as if it’s been tugged and pulled, like a piece of taffy.

    In this Spitzer image, gas and dust emission is also colored red, and starlight is blue (seen as a fuzzy glow since individual stars are not visible). You can see the stars are not distributed evenly: instead there’s more to the right; a good sign that another galaxy is affecting M66. Also, since red is gas and dust, that’s where stars are being actively born, and there’s a lot of that going on just outside the central region of the galaxy. That’s yet another sign that this galaxy was disturbed; the gravity of a passing galaxy can push the gas toward the center where it circles the core and forms stars.

    And the clincher? In most galaxies, you see one star exploding at the end of its life every century or so. In the past 20 years, M66 has had three! Hot, massive stars don’t live long, only a few million years. So if a galaxy is making more stars than usual, you’ll see more supernovae than usual. Clearly, M66 has been pretty busy lately!

    The unusual spiral galaxy, Messier 66, is located at a distance of about 35 million light-years in the constellation of Leo. Together with Messier 65 and NGC 3628, Messier 66 is the member of the Leo Triplet, a trio of interacting spiral galaxies, part of the larger Messier 66 group. Messier 66 wins in size over its fellow triplets — it is about 100 000 light-years across.

    This is a composite of images obtained through the following filters: 814W (near infrared), 555W (green) and H-alpha (showing the glowing of the hydrogen gas). They have been combined so to represent the real colours of the galaxy.

  • A Dying Star

    NGC 2440 is a planetary nebula ejected by a dying star, but it has a much more chaotic structure than NGC 2346. The central star of NGC2440 is one of the hottest known, with a surface temperature near 200,000 degrees Celsius.

    A Dying Star. Credit: NASA/ESA and The Hubble Heritage Team (AURA/STScI).

    The complex structure of the surrounding nebula suggests to some astronomers that there have been periodic oppositely directed outflows from the central star, somewhat similar to that in NGC2346, but in the case of NGC 2440 these outflows have been episodic, and in different directions during each episode. The nebula is also rich in clouds of dust, some of which form long, dark streaks pointing away fromthe central star. In addition to the bright nebula, which glows becauseof fluorescence due to ultraviolet radiation from the hot star, NGC 2440 is surrounded by a much larger cloud of cooler gas which is invisible in ordinary light but can be detected with infrared telescopes. NGC 2440 lies about 4,000 light-years from Earth in thedirection of the constellation Puppis.

    The Hubble Heritage team made this image from observations of NGC 2440acquired by Howard Bond (STScI) and Robin Ciardullo (Penn State).