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Spiral galaxy seen in a new light

Infrared view of NGC 1365

An infrared view of NGC 1365, a beautiful barred spiral galaxy in the Fornax cluster of galaxies, about 60 million light-years from Earth.

  • Galaxy NGC 1365, the Great Barred Spiral Galaxy
  • 200,000 light-years wide, with two huge spiral arms
  • Located 60 million light-years from Earth

A new image taken with the powerful HAWK-I camera on the European Southern Observatory’s (ESO’s) Very Large Telescope in Chile shows the beautiful “barred spiral” galaxy NGC 1365 in infrared light.

NGC 1365 is a member of the Fornax cluster of galaxies, about 60 million light-years from Earth.

NGC 1365 is one of the best-known and most-studied barred spiral galaxies, sometimes nicknamed the Great Barred Spiral Galaxy because of its strikingly perfect form…a straight “bar” or middle section and two prominent outer spiral arms.

Closer to the centre there is also a second spiral structure, and the galaxy as a whole is laced with delicate lanes of interstellar dust.

Astronomers consider it an excellent “laboratory” for studying how spiral galaxies form and evolve.

The new infrared images from HAWK-I are less affected by the dust that obscures parts of the galaxy than images taken at visible light wavelengths, and they reveal very clearly the glow from vast numbers of stars in both the bar and the spiral arms.

The images were acquired to help astronomers understand the complex flow of gas within the galaxy and how it affects the reservoirs of gas from which new stars can form.

The huge bar disturbs the shape of the gravitational field of the galaxy and this leads to regions where gas becomes compressed, triggering the formation of new stars.

See the full-size, high-resolution version of the image (suitable for PC wallpaper) here.

Visible light and infrared views of NGC 1365

This comparison shows a visible-light image (left) of NGC 1365 along with the new infrared view (right). The infrared view "peels away" the veil of dust to reveal more stars beneath.

Black hole hidden in the core

Many huge young star clusters are visible in the main spiral arms, each containing hundreds or thousands of bright young stars that are less than 10 million years old.

The galaxy is too remote for single stars to be seen—most of the tiny clumps visible in the picture are really clusters of stars.

While the bar of the galaxy comprises mainly older stars long past their prime, many new stars are born in stellar “nurseries” of gas and dust in the inner spiral close to the core. Over the whole galaxy, stars are forming at a rate of about three times the mass of our Sun per year.

The bar also funnels gas and dust gravitationally into the very centre of the galaxy, where astronomers have found evidence for the presence of a super-massive black hole, well hidden among myriads of intensely bright new stars.

Here’s a video that zooms in on NGC 1365, alternating between visible wavelength and infrared wavelength views:

NGC 1365, including its two huge outer spiral arms, is around 200,000 light-years across. Different parts of the galaxy take different times to make a full rotation around the core, with the outer parts of the bar taking about 350 million years to complete one circuit.

NGC 1365 and other galaxies of its type have come to more prominence in recent years with new observations indicating that our Milky Way galaxy could also be of the barred spiral type.

Such galaxies are quite common—two thirds of spiral galaxies are barred according to recent estimates. Studying them can help astronomers understand our own galactic home.

Adapted from information issued by ESO / P. Grosbøl.

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