Astronomy Picture of the Day [1]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. 2025 November 23 [2]A diagram is shown depicting various parts of the universe that are observable. In the middle are the parts closest to Earth, and around the far edges are parts furthest from Earth. Planets, galaxies, and the CMB are illustrated. Please see the explanation for more detailed information. The Observable Universe Illustration Credit & [3]Licence: [4]Wikipedia, [5]Pablo Carlos Budassi Explanation: How far can you see? Everything you can see, and everything you could possibly see, right now, assuming your eyes could detect all types of radiations around you -- is the [6]observable universe. In light, the farthest we can see comes from the [7]cosmic microwave background, a time [8]13.8 billion years ago when the universe was opaque like thick fog. Some [9]neutrinos and [10]gravitational waves that surround us come from even farther out, but humanity does not yet have the technology to detect them. The [11]featured image illustrates the observable universe on an [12]increasingly compact scale, with the [13]Earth and [14]Sun at the center surrounded by [15]our Solar System, [16]nearby stars, [17]nearby galaxies, [18]distant galaxies, [19]filaments of early matter, and the [20]cosmic microwave background. Cosmologists typically assume that our observable [21]universe is just the nearby part of a [22]greater entity known as "the universe" where the same physics applies. However, there are several lines of popular but speculative reasoning that [23]assert that even our universe is part of a [24]greater multiverse where either different physical constants occur, [25]different physical laws apply, [26]higher dimensions operate, or slightly [27]different-by-chance versions of our standard universe exist. Explore the Observable Universe: [28]Random APOD Generator Tomorrow's picture: stellar shell game __________________________________________________________________ [29]< | [30]Archive | [31]Submissions | [32]Index | [33]Search | [34]Calendar | [35]RSS | [36]Education | [37]About APOD | [38]Discuss | [39]> __________________________________________________________________ Authors & editors: [40]Robert Nemiroff ([41]MTU) & [42]Jerry Bonnell ([43]UMCP) NASA Official: Amber Straughn [44]Specific rights apply. [45]NASA Web Privacy, [46]Accessibility, [47]Notices; A service of: [48]ASD at [49]NASA / [50]GSFC, [51]NASA Science Activation & [52]Michigan Tech. U. 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