Anne’s Image of the Day: Spiral Galaxy IC 2560


March 27, 2014

IC 2560, a barred spiral galaxy in Antlia

IC 2560, a barred spiral galaxy in Antlia

Image Credit: Nick Rose, ESA/Hubble & NASA

IC 2560 is a barred spiral galaxy with a diameter of about 121,000 by 78,000 light-years, located over 110 million light-years away from Earth in the southern constellation of Antlia (the Air Pump). It is speeding away from us at approximately 2925 kilometers per second.

The constellation of Antlia was originally named antlia pneumatica by French astronomer Abbé Nicolas Louis de Lacaille, in honor of the invention of the air pump in the 17th century.

However, IC 2560 is a relatively nearby spiral galaxy, and it is easy to spot its spiral arms, its dark dust lanes and barred structure in this image. This galaxy is part of the Antlia Cluster, a group of over 200 galaxies held together by gravity. The Antlia cluster is unusual; unlike most other galaxy clusters, it appears to have no dominant galaxy within it.

IC 2560 is classified as a Seyfert II galaxy, a kind of spiral galaxy characterized by an extremely bright nucleus and very strong emission lines from certain elements, such as hydrogen, helium, nitrogen, and oxygen. The centers of Seyfert galaxies have active galactic nuclei (AGN), and usually contain supermassive black holes with masses between 10 and 100 million solar masses. Seyferts are classified as Type I or II, depending upon whether the spectra show both narrow and broad emission lines (Type I), or only narrow lines (Type II).

Indeed, the bright center of IC 2560 is thought to be caused by the ejection of huge amounts of super-hot gas from the region around a central black hole.

This image is taken with the Wide Field Planetary Camera 3 onboard the Hubble Space Telescope using an infrared, an optical and an ultraviolet filter. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Nick Rose.

Anne’s Image of the Day: Spiral Galaxy NGC 3244

July 15, 2013

NGC 3244, a spiral galaxy in Antlia 

NGC 3244, a spiral galaxy in Antlia

Image Credit: ESO

NGC 3244 is a spiral galaxy of about 25,000 light-years across (only a quarter of the size of our own galaxy), located about 100 million light-years away from Earth in the southern constellation of Antlia (the Air Pump). It is receding from us at approximately 2761 kilometers per second.

This galaxy – discovered on April 22th, 1835 by the British astronomer John Herschel – has a small, dense core and open, well-defined spiral arms, of which one arm slightly protrudes, what makes NGC 3244 somewhat asymmetric. The arms are dotted with bluish regions of active star formation, and the galaxy also shows dark dust lanes along the spiral arms.

On 27 June 2010, a supernova, now known as SN 2010ev was discovered in NGC 3244, which is still visible as the — now faint — blue dot nestled within one of the thick spiral arms just to the left of the galaxy’s nucleus. At its brightest, SN 2010ev reached an apparent magnitude of about 14, making it about 1000 times dimmer than the naked eye can see, but it was still the third brightest supernova observed in 2010.

To the right of the galaxy, a foreground star in our own Milky Way, TYC 7713-527-1, shines brightly. Although the star seems a great deal brighter than SN 2010ev, this is actually an illusion created by the large difference in the distances of the two objects. In fact, if the supernova had been as close to Earth as TYC 7713-527-1, it would have been easily visible to the naked eye, unlike the aforementioned star.

The image was taken using the FORS2 instrument on the ESO Very Large Telescope (VLT), through three color filters, which were colored blue, green and red respectively. It was taken with the help of the President of the Czech Republic, Václav Klaus, during his visit to ESO’s Paranal Observatory, on the night of 6 April 2011. Therefore the galaxy is sometimes referred to as The Czech President’s Galaxy. The Czech Republic joined ESO in 2007, and this was the first visit of the country’s President to an ESO site. A framed print of the President’s Galaxy has been presented to Václav Klaus, as a memento of his visit to Paranal.

Anne’s Picture of the Day: Dwarf Galaxy ESO 318-13

June 3, 2013

ESO 318-13, a dwarf galaxy in Antlia

The Glitter Galaxy

Image Credit: ESA/Hubble & NASA

ESO 318-13 (also known as the Glitter Galaxy) is an oval-shaped irregular dwarf galaxy located roughly 20 to 30 million light-years away from Earth in the southern constellation of Antlia (the Pump). It is receding from us at approximately 720 kilometers per second. In this image, we see the galaxy along its edge.

Despite its distance, the stars captured in this image are so bright and clear you could almost attempt to count them. However, little is known about this small galaxy and the image doesn’t show us much of the galaxy’s structure. There are a few small blue-looking clumps of stars in the left part of the galaxy that look like young clusters. Judging from its brightness it’s only about 1 percent or less the mass of our Milky Way, and it’s mostly made up of stars. There’s not a hint of gas or dust.

We can also see many distant galaxies with distinct spiral and elliptical shapes scattered throughout the image, as well as several stars, near and far. One that particularly stands out is located near the center of the image, and looks like an extremely bright star located within the galaxy. This is, however, a trick of perspective. The star is located in our own Milky Way galaxy, and it shines so brightly because it is so much closer to us than ESO 318-13.

Peeking through ESO 318-13, near the right-hand edge of the image, is a distant spiral galaxy we see face-on. This is another indication that the galaxy is mostly stars and doesn’t have much gas and dust, otherwise that more distant galaxy would be heavily obscured, but as it is we can see it pretty well.

Galaxies are largely made up of empty space; the stars within them only take up a small volume, and providing a galaxy is not too dusty, it can be largely transparent to light coming from the background. This makes overlapping galaxies like these quite common.

This false color image was taken with the Advanced Camera for Surveys on the Hubble Space Telescope. The astronomers used two filters, one that lets through only orange/red light (shown as blue), and another that lets through only infrared light (shown as red).