APOD: Trio Leo (2015 May 09)

[APOD Robot]

Trio Leo

Explanation: This popular group is famous as the Leo Triplet - a gathering of three magnificent galaxies in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but they tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628 is seen edge-on, with obscuring dust lanes cutting across the plane of the galaxy, while the disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have also left telltale signs, including the warped and inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans about one degree (two full moons) on the sky. The field covers over 500 thousand light-years at the trio's estimated distance of 30 million light-years.

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[Wayne Jepson]

Is that a linear dust lane crossing almost all of M66, above the nucleus? Almost looks like another spiral approaching edge-on from behind it!

[Boomer12k]

And some long far off day...a single galaxy?

Wonderful Shot. Very nice. Hope to get out the scope tomorrow night.

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[Boomer12k]

Dueling Galaxies...fighting over the Star?? OK...probably not...but they look "perturbed" at something...

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[Boomer12k]

Looks like a star stream below M66...and maybe another to the right "above" the core...


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[Chris Peterson]

Dueling Galaxies...fighting over the Star?? OK...probably not...but they look "perturbed" at something...

The star is quite nearby, in our region of the Milky Way. The galaxies are thousands of times farther away. From their perspective that star is probably lost in the general glow of a billion Milky Way stars.

[Ann]

This is a fascinating group of galaxies, and they are definitely perturbed! Except M65, that is. That galaxy looks remarkably serene and symmetric. Not too much is going on inside it, either. There are some young stars in it, but no pink emission nebulas, to the best of my knowledge. Unsurprisingly, this galaxy is a full magnitude fainter in far infrared light than in blue light, which is typical of dust-poor (and inefficiently star-forming) galaxies. By contrast, richly star-forming M66 is a full magnitude brighter in far infrared than in blue light.

But there was a supernova in M65 in 2013, and fascinatingly, it was a Type II supernova, resulting from a massive star undergoing core collapse. So M65 is not totally devoid of young massive stars.

M66, on the other hand, is absolutely contorted by the tidal forces working on it. Interestingly, all the star formation takes place in the dusty inner parts of it, while at the same time there are huge relatively bright smooth outer features that appear to be made up almost entirely of old stars. Thee is a tendency in some galaxies to show star formation and dust only in its inner parts. M64 is an extreme example of this, but M66 may be evolving towards to a similar state.

NGC 3628 is seen so (almost) perfectly edge on that there are not too many other bright galaxies rivaling it. NGC 891 is the only even better example I can think of. But unlike NGC 891, NGC 3628 has extremely puffed-up disk endings. Also, unlike NGC 891, NGC 3628 has a spectacular tidal tail.

Nice APOD!

Ann

[N Hash]

The star is probably in the foreground possibly in our own Milky Way. Love to see the merge of those three.