A Spiral Galaxy is Visited by a Trojan War Hero

Wise_wise2010-031_500

WISE_WISE2010-031 September 8th, 2010

Credit: NASA/JPL-Caltech/WISE Team

Its a bird! Its a plane! Nope, its an asteroid tracking its way across the sky with a beautiful spiral galaxy in the background. In the center of this new mosaic image captured by NASAs Wide-field Infrared Survey Explorer (WISE) is the galaxy Messier 74, with its spiral arms seen face-on. The bright reddish object moving across the lower right part of the image is the much closer asteroid 3540 Protesilaos, seen at different points in its orbit around the Sun. WISE observed and detected this previously known asteroid a total of ten times, although only a few of those frames were used in this mosaic.

Also known as NGC 628, the Messier 74 galaxy is between 24.5 and 36 million light-years away, and has a diameter of about 100,000 light-years. It is suspected to have a black hole at its center, with a mass equal to 10,000 Suns. It is one of only a handful of known black holes with masses intermediate between the relatively smaller ones that form from collapsing stars and the supermassive black holes millions of times more massive than the sun, which are more typically found at the centers of galaxies Although it is called a Messier object, Messier 74 was actually discovered by Pierre Mechain in 1780, who then told his friend Charles Messier about it. As one of the dimmest of all Messier objects, this galaxy is a challenge for amateur astronomers to see in visible light, but the WISE cameras captured it clearly in infrared light.

The colors used in this image represent different wavelengths of infrared radiation. Blue and cyan represent light at 3.4 and 4.6 microns, respectively. These colors show both nearby stars inside the Milky Way Galaxy and the combined light of billions of stars that make up Messier 74. Green and red represent light from 12 and 22 microns, respectively. These colors show light from cooler objects and material. Dust in star-forming regions in Messier 74 traces its spiral structure. The coolest object in the picture is the asteroid 3540 Protesilaos.

This asteroid was first seen in 1973 by the German astronomer Freimut Brngen, who discovered more than 500 asteroids while he was researching galaxies. At the time that WISE observed 3540 Protesilaos, it was at a distance of 772 million kilometers from Earth (480 million miles, or about 43 light-minutes). It is classified as a Jupiter Trojan minor planet, which are small rocky bodies that share the same orbit around the Sun as the planet Jupiter. Based on the infrared observations, the WISE team estimates the asteroid to be about 90 kilometers (56 miles) across and to reflect only a few percent of the light that lands on it, which makes it about as dark as coal.

By convention, Trojan asteroids are named after the heroes from the Trojan War. In this case, asteroid 3540 is named after the hero Protesilaos. According to Greek mythology, Protesilaos was the first Greek to set foot on Trojan land during the war. Unfortunately for him, there was a prophecy that the first soldier in the war to step onto land from a battle ship would die. The prophecy quickly came true and Protesilaos was killed by the Trojan hero, Hector.

Image Source: /image/WISE/WISE2010-031

Curator: Wide-field Infrared Survey Explorer, Berkeley, CA, USA

Image Use Policy: Pulic Domain

Image Details

Image Type
Observation
Object Name
Messier 74 M74 NGC 628
Subject - Local Universe
Galaxy » Type » Spiral
Galaxy » Activity » Normal

Distance

Universescale2
30,000,000 light years

Position Details

Position (ICRS)
RA = 1h 36m 41.6s
DEC = 15° 46’ 58.0”
Field of View
41.2 x 41.2 arcminutes
Constellation
Pisces

Color Mapping

  Telescope Spectral Band Wavelength
Arrow_left_blue WISE Infrared (Near-IR) 3.4 µm
Arrow_left_cyan WISE Infrared (Near-IR) 4.6 µm
Arrow_left_green WISE Infrared (Mid-IR) 12.0 µm
Arrow_left_red WISE Infrared (Mid-IR) 22.0 µm
Spectrum_ir1
Arrow_top_blue
Arrow_top_cyan
Arrow_top_green
Arrow_top_red
Wise_wise2010-031_1280
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ID
WISE2010-031
Subject Category
C.5.1.1.   C.5.3.1.  
Subject Name
Messier 74, M74, NGC 628
Credits
NASA/JPL-Caltech/WISE Team
Lightyears
30,000,000
Redshift
0.002192
Reference Url
/image/WISE/WISE2010-031
Type
Observation
Image Quality
Good
Distance Notes
Facility
WISE, WISE, WISE, WISE
Instrument
Color Assignment
Blue, Cyan, Green, Red
Band
Infrared, Infrared, Infrared, Infrared
Bandpass
Near-IR, Near-IR, Mid-IR, Mid-IR
Central Wavelength
3400, 4600, 12000, 22000
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
ICRS
Equinox
Reference Value
24.1733130, 15.7827803
Reference Dimension
1800.0, 1800.0
Reference Pixel
901.0, 901.0
Scale
0.000381916, 0.00038191637
Rotation
Coordinate System Projection:
TAN
Quality
Full
FITS Header
Notes
WCS retrieved using CXCs PinpointWCS
Creator (Curator)
Wide-field Infrared Survey Explorer
URL
http://wise.astro.ucla.edu
Name
Email
outreach@ssl.berkeley.edu
Telephone
Address
7 Gauss Way
City
Berkeley
State/Province
CA
Postal Code
94720
Country
USA
Rights
Pulic Domain
Publisher
Publisher ID
WISE
Resource ID
Resource URL
/image/WISE/WISE2010-031
Related Resources
Metadata Date
2011-08-05
Metadata Version
1.2
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Detailed color mapping information coming soon...

 

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Universescalefull
30,000,000 light years