More intriguing (yet indirect) evidence for extrasolar
planets
Circumstellar disks look to Hubble like Saturn's rings,
indicating planets at work
Observations with Hubbles near-IR NICMOS camera have shown new details
in the dusty disks around two stars that can only be explained by the
gravitational action of - as yet unseen - planets. The disk around
HD 141569 seems to come in two parts: a dark band separates a bright inner
region from a fainter outer region. This could be darker dust, but more
likely a real gap.
And the disk around the star HR 4796A (which has already been
discussed in Update #78) turns out to be a
remarkably narrow ring - a novel type of structure seen in space. The
only comparable features to these circumstellar ring systems are the
rings of Saturn - and they can only stay in shape because tiny moons act
on them. Thus the conclusion: Freshly formed planets keep the
circumstellar rings in shape.
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STScI Press
Release and stories from
ABC,
BBC and
CNN.
2 or 3 new planet discoveries by radial velocity, microlensing:
Stories from
ABC and
BBC.
Stars with planets are special: They have more
heavy elements. A
Press Release.
Dangerous Suns?
Flares from Sun-like stars have been
found
in some cases - but not our own Sun. Also covered by
CNN and
ABC.
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Lots of intergalactic stars in the Virgo cluster
The discovery of 130 planetary nebulae between the galaxies in the Virgo
cluster - a task facilitated by the narrow line emission from these nebulae
around dying stars - leads to the conclusion that at least 22% of the
overall light from the galaxy cluster should actually stem from
intergalactic stars. Most of them are not seen individually (except for the
brightest ones, already
spotted by Hubble),
but from the sheer number of planetary nebulae one can extrapolate their
number. How did they get there? Collisions between the cluster galaxies
ripped them out of the galaxies where they were born.
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Press
Release from Penn State
Related Stories: Three new dwarf companions of M31 were identified
- here's one and
here are two more.
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Dwarf Stars dominate a galaxy's extended halo
Long-exposure infrared images of a small portion of the faint halo of the
galaxy NGC 5907, an edge-on spiral galaxy 39 million light years away, do
not show as many individual stars as expected: This halo must be composed of
a weird population of stars, mostly dim dwarfs too faint to see from Earth.
Most galaxies contain a mix of bright giant stars and dim dwarf stars, with
about half of the light coming from each group. If the halo of NGC 5907
contained a mix similar to that in our own galaxy, one would have seen
hundreds of bright giants in the field of view.
Instead, only a handful were
there. The best explanation: At least 20 times more light comes from dwarfs
than giants in the halo of NGC 5907. Such a population has been invoked in
the past as a constituent of the enigmatic dark matter making up galaxy
halos and influencing the galactic rotation curves. And even if
the dwarfs don't have enough mass to account for the dark matter holding
this galaxy together, the fact that the dwarfs have the same profile as the
dark matter means some formation mechanism may well tie the two together.
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Press Release from Berkeley
ABCNEWS Story
Another galaxy discovery: There are
dust grains and silicates within superheated gas in the center of
ancient elliptical galaxies - the first direct observation of how
mass lost by aging stars evolves in a hot, exotic environment.
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