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The cosmic distance ladder (also known as the extragalactic distance scale) is the succession of methods by which astronomers determine the distances to celestial objects. A direct distance measurement of an astronomical object is possible only for those objects that are "close enough" (within about a thousand parsecs ) to Earth.
Instead of working with Hubble's constant, a common practice is to introduce the dimensionless Hubble constant, usually denoted by h and commonly referred to as "little h", [29] then to write Hubble's constant H 0 as h × 100 km⋅s −1 ⋅Mpc −1, all the relative uncertainty of the true value of H 0 being then relegated to h. [46]
The WFPC-1 was replaced by the WFPC-2 during Servicing Mission 1 in 1993, which was then replaced by the Wide Field Camera 3 (WFC3) during Servicing Mission 4 in 2009. The upgrade extended Hubble's capability of seeing deeper into the universe and providing images in three broad regions of the spectrum. [54] [55]
Selected distance estimates to the Pleiades Year Distance Notes 1999 125 Hipparcos [66] 2004 134.6 ± 3.1 Hubble Fine Guidance Sensor [58] 2009 120.2 ± 1.9 Revised Hipparcos [2] 2014 136.2 ± 1.2 Very-long-baseline interferometry [62] 2016 134 ± 6 Gaia Data Release 1 [63] 2018 136.2 ± 5.0 Gaia Data Release 2 [64] 2023 135.74 ± 0.10 pc
This video clip shows a visualization of the three-dimensional structure of the Pillars of Creation. Closer view of one pillar. Pillars of Creation is a photograph taken by the Hubble Space Telescope of elephant trunks of interstellar gas and dust in the Eagle Nebula, in the Serpens constellation, some 6,500–7,000 light-years (2,000–2,100 pc; 61–66 Em) from Earth. [1]
Since galactic redshift is proportional to distance, NGC 7320 is only a foreground projection [2] and is ~39 million light-years [2] from Earth, making it a possible member of the NGC 7331 group, versus the 210–340 million light-years of the other four. [8] NGC 7319 has a type 2 Seyfert nucleus. The galaxies in the vicinity of Stephan's Quintet.
1.4 m – length of a Peel P50, the world's smallest car; 1.435 m – standard gauge of railway track used by about 60% of railways in the world = 4 ft 8 1 ⁄ 2 in; 2.5 m – distance from the floor to the ceiling in an average residential house [119] 2.7 m – length of the Starr Bumble Bee II, the smallest plane
In 2003, using the infrared surface brightness fluctuations (I-SBF) and adjusting for the new period-luminosity value and a metallicity correction of −0.2 mag dex −1 in (O/H), an estimate of 2.57 ± 0.06 million ly (162.5 ± 3.8 billion AU) was derived. A 2004 Cepheid variable method estimated the distance to be 2.51 ± 0.13 million light ...