The Antennae Galaxies are much closer than previously thought

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Berlin, May 10 : A new research by astronomers using the Advanced Camera for Surveys onboard the NASA/ESA Hubble Space Telescope, has shown that the Antennae Galaxies, which are a pair of interacting galaxies, are much closer than previously thought - 45 million light-years instead of 65 million light-years.

The Antennae Galaxies are among the closest known merging galaxies, and are named for the two long tails of stars, gas and dust that resemble the antennae of an insect.

These 'antennae' are a physical result of the collision between the two galaxies.

The two galaxies, also known as NGC 4038 and NGC 4039, began interacting a few hundred million years ago, creating one of the most impressive sights in the night sky.

They are considered by scientists as the archetypal merging galaxy system and are used as a standard against which to validate theories about galaxy evolution. Studying their properties gives us a preview of what may happen when our Milky Way galaxy collides with the neighbouring Andromeda galaxy in several billion years.

Now, an international group of scientists led by Ivo Saviane from the European Southern Observatory has used Hubble's Advanced Camera for Surveys and Wide Field Planetary Camera 2 to observe individual stars spawned by the colossal cosmic collision in the Antennae Galaxies.

They reached an interesting and surprising conclusion.

By measuring the colours and brightnesses of red giant stars in the system, the scientists found that the Antennae Galaxies are much closer than previously thought: 45 million light-years instead of the previous best estimate of 65 million light-years.

The team targeted a region in the relatively dormant outer regions in the southern tidal tail, away from the active central regions. This tail consists of material thrown from the main galaxies as they collided.

The proximity of the Antennae system means it is the best-studied galaxy merger in the sky, with a wealth of observational data to be compared to the predictions of theoretical models.

The previous canonical distance to the Antennae Galaxy was about 65 million light-years, although values as high as 100 million light years have been used.

The new smaller distance makes the Antennae Galaxies less extreme in terms of the physics needed to explain the observed phenomena.

For instance, with the smaller distance its infrared radiation is now that expected of a 'standard' early merging event rather than that of an ultraluminous infrared galaxy.

The size of the star clusters formed as a consequence of the Antennae merger now agree with those of clusters created in other mergers instead of being 1.5 times as large.


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