Astrophoto Lab
--- your online source for astronomical & satellite images ---

Rings Upon Rings
General Information
Special Galleries
Deep Space
Stars, Supernovae
Solar System
Earth from Space
NASA Space Programs
Other Astro Images
Space Image Gallery
Useful Links
Credits & Useage
Name: NGC 2273
Description: Spiral galaxy
Position (J2000): RA 6h 50m 8.02s Dec 60° 51' 3.26"
Constellation: Lynx
Distance: 95 million light-years
Visual magnitude: 11.7
Angular size: 3.65 x 2.1 arcmin
Field of view: 2.59 x 2.01 arcminutes
Orientation: North is 6.8° left of vertical
Image Credit: ESA/Hubble & NASA, J. Greene
Release date: April 6, 2020

Click the image to buy a print


At first glance, the subject of this NASA/ESA Hubble Space Telescope image looks to be a simple spiral galaxy, with two pinwheeling arms emerging from a central bar of stars and material that cuts through the galactic center. In fact, there are rings within these spiral arms, too: spirals within a spiral.

This kind of morphology is known as a multi-ring structure. As this description suggests, this galaxy, named NGC 2273, hosts an inner ring and two outer "pseudo-rings" - having so many distinct rings is rare, and makes NGC 2273 unusual. Rings are created when a galaxy's spiral arms appear to loop around to nearly close upon one another, combined with a trick of cosmic perspective. NGC 2273's two pseudo-rings are formed by two swirling sets of spiral arms coming together, and the inner ring by two arcing structures nearer to the galactic center, which seem to connect in a similar way.

These rings are not the only unique feature of this galaxy. NGC 2273 is also a Seyfert galaxy, a galaxy with an extremely luminous core. In fact, the center of a galaxy such as this is powered by a supermassive black hole, and can glow brightly enough to outshine an entire galaxy like the Milky Way.

From Wikipedia:

NGC 2273 is a barred spiral galaxy located in the constellation Lynx. It is located at a distance of circa 95 million light years from Earth, which, given its apparent dimensions, means that NGC 2273 is about 100,000 light years across. It was discovered by Nils Dunér on September 15, 1867.

NGC 2273 has a multiring structure. The galaxy has an inner ring and two outer pseudorings formed by two sets of spiral arms. The galaxy is seen with an inclination of 41 degrees. The galaxy hosts about 1.1×109 M of hydrogen gas (HI), with most of it lying at the outer pseudoring. The galaxy also hosts large amounts of molecular gas, as indicated by the CO lines, which is regarded as an indicator of active star formation. The total infrared luminosity of the galaxy is 1010.25 L. The galaxy has a bar whose radius is 40 arcseconds.

Observations of the central 20 arcseconds of the galaxy by the Hubble Space Telescope showed spiral arms that corresponded to the inner ring. The central ovoid of the galaxy was found to feature a bar-like structure and two arc structures that form a partial nuclear ring. Its emission is associated with the presence of HII regions. Around the nucleus lies a dusty ring-like structure, with a radius of 7 arcseconds, better seen at its northwest part. Another dusty ring is observed at 20 arcseconds radius. Based on the emission lines that are present in its spectrum, the nucleus of NGC 2273 has been characterized as active and it has been categorized as a type II Seyfert galaxy. Also, a water kilomaser has been detected in the nuclear region of the galaxy. It could be created either by the active nucleus or by a prominent site of star formation.

Observations by BeppoSAX, XMM Newton, and Chandra X-Ray Observatory suggested that the nucleus of NGC 2273 is obscured by a Compton thick column, with high column density, estimated to be 1.1×1024 cm-2 as measured by ASCA, or 1.5×1024 cm-2 as measured by Suzaku. The harder X-Rays manage to get through and are dominated by reflection from cold material, as the Fe-K line indicates. The spectrography of the nuclear regions is weakly polarized, more prominent in H-alpha. The broad X-ray spectrum of NGC 2273 has been found to be composed of a thermal or scattered soft component, a reflected component, and an absorbed power law component. The 2-10 keV X-ray flux of the galaxy is estimated to be 1.7×1042 ergs-1.

The nucleus also emits radiowaves. The radio source has been found to be linear and is composed of two unequal radio features separated by about 170 parsecs. These two radio features have been identified as radio jets. A linear jet-like feature extending for 2 arcseconds east of the nucleus was observed in [O III] λ5007 images. It is aligned with the radio jets and is possibly of nuclear origin.

The most accepted theory for the energy source of active galactic nuclei is the presence of an accretion disk around a supermassive black hole. The mass of the black hole in the center of NGC 2273 is estimated to be between (7.5±0.4)×106 M based on kinematics of the water maser circumnuclear disk. The disk appears warped.

NGC 2273 is the brightest galaxy in a galaxy group known as the NGC 2273 group. Other members of the group include the galaxies NGC 2237B and UGC 3504. NGC 2237B lies 40 arcminutes to the south.