Astronomy Picture of the Day 2-09-03

NASA ^ | 2-09-03 | Robert Nemiroff and Jerry Bonnell

[petuniasevan]

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2003 February 9

COBE Dipole: Speeding Through the Universe
Credit: DMR, COBE, NASA, Four-Year Sky Map

Explanation: Our Earth is not at rest. The Earth moves around the Sun. The Sun orbits the center of the Milky Way Galaxy. The Milky Way Galaxy orbits in the Local Group of Galaxies. The Local Group falls toward the Virgo Cluster of Galaxies. But these speeds are less than the speed that all of these objects together move relative to the cosmic microwave background (CMB). In the above all-sky map, radiation in the Earth's direction of motion appears blueshifted and hence hotter, while radiation on the opposite side of the sky is redshifted and colder. The map indicates that the Local Group moves at about 600 kilometers per second relative to this primordial radiation. This high speed was initially unexpected and its magnitude is still unexplained. Why are we moving so fast? What is out there?

[petuniasevan]

Something is out there. Dark matter makes up a percentage of the physical universe (what it is or how much there is is not known). A stream of galactic clusters at least 200 million light-years in length (including our own Milky Way) is being pulled in the direction of the "Great Attractor" (about 250 million light-years away in the constellation Centaurus) at a speed of 400 miles per second.

This "Great Attractor" is thought to be a mass concentration on the order of 10¹⁶ solar masses. We can find less than 10% of the matter required to account for the attraction. Thus the search for dark matter (and its nature) continues...

This is the galactic cluster ACO 3627, also known as the Norma Cluster. It is near the center of the Great Attractor.

[petuniasevan]

[BossyRoofer]

The work your doing is so great. My daughter is asking questions that I can't answer, so we explore the answers togather. Good job APOD!

[petuniasevan]

Thank you. It makes it worthwhile to know my work is helping someone learn more about the universe.

[mikrofon]

Another fascinating pic -- thanks for the "sonogram" of the universe ;^)

[RightWhale]

The Great Attractor. This might not be good. We better get our space program geared up to investigate, and right now we are short of capability by a few orders of magnitude. Complacency seems to be the order of the day.

[boris]

"The Great Attractor. This might not be good."

The Great Attractor sucks.

--Boris

[petuniasevan]

Freeper Amateur Astronomers Image Thread
My photos | 2-9-3 | Joe Hadenuf