Evidence for Densest Nearby Galaxy

[Waspie_Dwarf]

NASA's Hubble and Chandra Find Evidence for Densest Nearby Galaxy

The densest galaxy in the nearby part of the Universe may have been found. Packed with an extraordinary number of stars, this unusual galaxy is providing astronomers with clues to its intriguing past and how it fits into the galactic evolutionary chain.

The galaxy, known as M60-UCD1, is a type of “ultra-compact dwarf galaxy”. It was discovered with NASA’s Hubble Space Telescope and follow-up observations were done with NASA’s Chandra X-ray Observatory and ground-based optical telescopes.

Observations from the W. M. Keck Observatory on the summit of Mauna Kea, Hawaii, characterized it as the most luminous known galaxy of its type and one of the most massive, weighing 200 million times more than our Sun.

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[Waspie_Dwarf]

Tour of M60-UCD1

Astronomers may have discovered the densest galaxy in the nearby Universe. The galaxy, known as M60-UCD1, is located about 54 million light years from Earth. M60-UCD1 is packed with an extraordinary number of stars and this has led scientists to classify it as an "ultra-compact dwarf galaxy." This means that this galaxy is smaller and has more stars than just a regular dwarf galaxy. While astronomers already knew this, it wasn't until these latest results from Chandra, Hubble and telescopes on the ground that they knew just how dense this galaxy truly is. M60-UCD1 has the mass about 200 million times our Sun and, remarkably, about half of this mass is packed into a radius of just about 80 light years. That translates into the density of stars in this part of M60-UCD1 being about 15,000 times greater than what's found in Earth's neighborhood in the Milky Way. Astronomers have been trying to determine where these ultra-compact dwarf galaxies fit into the galactic evolutionary chain. Some have suggested they start off not as galaxies but as giant star clusters. The latest results on M60-UCD1 challenge that idea. The new Chandra data indicate that there may be a supermassive black hole at the center of M60-UCD1. If that's the case, then it's unlikely this object could have ever been a star cluster. Instead, the X-ray data point to this galaxy being the remnants of a larger galaxy that had its outer stars ripped away by tidal forces, leaving behind the dense inner core of the galaxy. Other information about M60-UCD1 including its large mass, point to the same conclusion. Regardless, this galaxy is a fascinating object that astronomers will be studying for a long time to come.

Credit: NASA/CXC/A. Hobart

Source: Chandra - Photo Album

[Drayno]

54 million light years away?

Geeze.

I don't think I'll ever get to go there on vacation.

[Taun]

Very interesting...

I know that in our part of our galaxy stars are roughly 3 ly's apart on average (1 parsec), and from other databases I have, I know that within 20 ly's of Sol there are 81 star systems (some are multiples so there are 115 actual -known- stars)

80 Ly's is 26.667 Parsecs... so:

(on the off chance that my math is right)

using the formula (4pi/3) * 26.667³ we are looking at about 111,699 star systems within 80 ly's... Assuming that about half are multiple systems (binary's and trinary's) we come up with 167,548 stars...

If they truly are 15,000 times denser (i.e. 15,000 times closer together) and my math is correct then the average distance between stars is ~1,173,139,000 miles… That is just slightly inside the orbit of Saturn!...

The night skies there must be stunning…

Edited September 26, 2013 by Taun

[Waspie_Dwarf]

If they truly are 15,000 times denser (i.e. 15,000 times closer together) and my math is correct then the average distance between stars is ~1,173,139,000 miles… That is just slightly inside the orbit of Saturn!...

A far simpler way of doing the calculation. If the density is 15,000 times denser then it follows that the average distance between stars is 15.000 times less.

Using you figure of 1 parsec and converting it into miles gives us a figure of 19,173,511,600,000

19,173,511,600,000/15,000 = 1,278,234,106, which is not far off what you got.

The night skies there must be stunning...

What night skies???

Edited September 26, 2013 by Waspie_Dwarf