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Direct detection of a microlens in the Milky Way

Alcock, C.; Allsman, R. A.; Alves, D. R. +22 more

The nature of dark matter remains mysterious, with luminous material accounting for at most ~25 per cent of the baryons in the Universe. We accordingly undertook a survey looking for the microlensing of stars in the Large Magellanic Cloud (LMC) to determine the fraction of Galactic dark matter contained in massive compact halo objects (MACHOs). Th…

An auroral flare at Jupiter

Desai, S.; McComas, D. J.; Young, D. T. +8 more

Jupiter's aurora is the most powerful in the Solar System. It is powered largely by energy extracted from planetary rotation, although there seems also to be a contribution from the solar wind. This contrasts with Earth's aurora, which is generated through the interaction of the solar wind with the magnetosphere. The major features of Jupiter's au…

Discovery of X-rays from the protostellar outflow object HH2

Maeda, Yoshitomo; Bally, John; Feigelson, Eric D. +3 more

Herbig-Haro (HH) objects have been known for 50 years to be luminous condensations of gas in star-forming regions, but their underlying physical nature is still being elucidated. Previously suggested models encompass newborn stars, stellar winds clashing with nebular material, dense pockets of interstellar gas excited by shocks from outflows, and …

Gravitational microlensing by low-mass objects in the globular cluster M22

Casertano, Stefano; Livio, Mario; Albrow, Michael D. +4 more

Gravitational microlensing offers a means of determining directly the masses of objects ranging from planets to stars, provided that the distances and motions of the lenses and sources can be determined. A globular cluster observed against the dense stellar field of the Galactic bulge presents ideal conditions for such observations because the pro…