Hubble zooms in on double nucleus in Andromeda galaxy

Jan 11, 2012
This is a Hubble image of the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy. The compact cluster of blue stars is surrounded by the larger "double nucleus" of M31. The double nucleus is actually an elliptical ring of old reddish stars in orbit around the black hole but more distant than the blue stars. Credit: NASA, ESA, and T. Lauer (National Optical Astronomy Observatory)

(PhysOrg.com) -- A new Hubble Space Telescope image centers on the 100-million-solar-mass black hole at the hub of the neighboring spiral galaxy M31, or the Andromeda galaxy, the only galaxy outside the Milky Way visible to the naked eye and the only other giant galaxy in the local group.

This is the sharpest visible-light image ever made of the nucleus of an external galaxy.

The , the closest region around the black hole where light can still escape, is too small to be seen, but it lies near the middle of a compact cluster of blue stars at the center of the image. The compact cluster of blue stars is surrounded by the larger "double nucleus" of M31, discovered with the in 1992. The double nucleus is actually an elliptical ring of old reddish stars in orbit around the black hole but more distant than the blue stars. When the stars are at the farthest point in their orbit they move slower, like cars on a crowded freeway. This gives the illusion of a second nucleus.

The blue stars surrounding the black hole are no more than 200 million years old, and therefore must have formed near the black hole in an abrupt burst of star formation. Massive blue stars are so short-lived that they would not have enough time to migrate to the black hole if they were formed elsewhere.

Astronomers are trying to understand how apparently young stars were formed so deep inside the black hole's gravitational grip and how they survive in an extreme environment.

The fact that young stars are also closely bound to the central black hole in our Milky Way galaxy suggests this may be a common phenomenon in spiral galaxies.

Tod R. Lauer of the National Optical Astronomy Observatory in Tucson, Ariz., assembled this image of the nuclear region by taking several blue and ultraviolet light exposures of the nucleus with Hubble's Advanced Camera for Surveys high-resolution channel, each time slightly moving the telescope to change how the camera sampled the region. By combining these pictures, he was able to construct an ultra-sharp view of the galaxy's core.

Lauer is presenting these Hubble observations this week at the meeting of the American Astronomical Society in Austin, Texas.

The image of the was taken on Jan. 13, 2001, with the WIYN/KPNO 0.9-meter Mosaic I by T. Rector, University of Alaska in Anchorage.

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User comments : 14

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Phaze
3 / 5 (3) Jan 11, 2012
There seems to be a blue red split along the axis. Left is redder than the right. Wonder if its like a Doppler thing
Vendicar_Decarian
3 / 5 (5) Jan 12, 2012
I don't buy the explanation. The difference in distances is not great enough to produce the observed double nucleus effect.

It could be the result of an elliptical orbit around the central mass or a real second nucleus inherited from an absorbed galaxy.

GuruShabu
3.8 / 5 (10) Jan 12, 2012
Phaze, the Doppler effect does not turn the light red. Its is the entire spectrum that shifts so you would not notice any change in the perception of the colour. What you would perceive is that the absorption spectral lines are shifted towards the red.
As the electromagnetic spectrum is continuous all colours will shift towards the red or the blue so nothing is perceptible in the colour of the light itself.
Eoprime
4.7 / 5 (3) Jan 12, 2012
Cant wait to see JWST pics from the nucleus...
Phaze
4.5 / 5 (2) Jan 12, 2012
Thanks for the info. in ultrasound we turn everything either red or blue, makes it simple. it is interesting that the right side looks more blue than the left.
yyz
5 / 5 (2) Jan 12, 2012
"I don't buy the explanation. The difference in distances is not great enough to produce the observed double nucleus effect.

It could be the result of an elliptical orbit around the central mass or a real second nucleus inherited from an absorbed galaxy."

Currently the best explanation for the double morphology is that the two lobes result from an eccentric disk of stars ~2 pc in diameter that is bound to the central BH: http://arxiv.org/...12v1.pdf

An interesting feature of the model is that it requires a central BH to reproduce the observed light minimum between the two lobes.

The paper describing these new observations has more detailed images of the remarkable central blue cluster, composed of young, blue stars and extending only a few parsecs in diameter: http://arxiv.org/...19v1.pdf

One of the "stars" visible in this cluster is thought to be the (blended) image of the SMBH in Andromeda itself.
Callippo
3 / 5 (2) Jan 12, 2012
The double nucleus may not be so rare feature at the case of galaxies. Our Milky Way has some remnant of another black hole at its center too. http://www.space....ter.html
Deathclock
3.4 / 5 (5) Jan 12, 2012
DOUBLE NUCLEUS ALL THE WAY ACROSS THE SKY OMG WHATS IT MEAN!

(look up double rainbow on youtube...)
Graeme
5 / 5 (3) Jan 12, 2012
"only galaxy outside the Milky Way visible to the naked eye" - untrue, the Magellanic Clouds are also galaxies and even more visible.
yyz
not rated yet Jan 14, 2012
"Our Milky Way has some remnant of another black hole at its center too. http://www.space....ter.html"

The Space.com article references the stellar complex IRS 13E, located very close to Sag A*, which was postulated to contain an IMBH(and might help explain the presence of this young massive stellar complex near the central SMBH).

But the paper cited in the article finds that while an IMBH cannot be totally ruled out as being involved with IRS 13E, the required high mass and observed lack of X-ray emission make the MBH scenario unlikely: http://iopscience...L111.pdf

A 2005 study (cited in the previous paper) also found that an IMBH was unlikely in this stellar complex due to dynamical concerns: http://arxiv.org/...43v1.pdf

While double nuclei in galaxies are somewhat rare (but are being increasingly discovered), the case for a double MBH system in the Milky Way galaxy has yet to be convincingly made.
350
not rated yet Jan 15, 2012
I just realized something, if two black holes were spinning in a binary system inside the event horizon, the gravity difference in-between the two would essencially allow light to escape allowing us to see what a black hole looks like perhaps.
350
not rated yet Jan 15, 2012
What I meant was in-between the two black holes, not some compounding effect from having two.
350
not rated yet Jan 15, 2012
If that's the case it should look like a lighthouse beacon as well.
Callippo
not rated yet Jan 15, 2012
I just realized something, if two black holes were spinning in a binary system inside the event horizon, the gravity difference in-between the two would essentially allow light to escape allowing us to see what a black hole looks like perhaps.
Yep, this system is close to toroidal Kerr geometry with holes at its even horizon at poles. Such black hole would radiate the light through polar jets.

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