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Therefore, the X-ray flux at the peak of the burst should correspond to Eddington luminosity, which can be calculated once the mass of the neutron star is known (1.5 solar masses is a commonly used assumption). This method allows distance determination of some low-mass X-ray binaries. Low-mass X-ray binaries are very faint in the optical ...
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
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]
Distance measures are used in physical cosmology to give a natural notion of the distance between two objects or events in the universe.They are often used to tie some observable quantity (such as the luminosity of a distant quasar, the redshift of a distant galaxy, or the angular size of the acoustic peaks in the cosmic microwave background (CMB) power spectrum) to another quantity that is ...
A cosmological horizon is a measure of the distance from which one could possibly retrieve information. [1] This observable constraint is due to various properties of general relativity, the expanding universe, and the physics of Big Bang cosmology. Cosmological horizons set the size and scale of the observable universe. This article explains a ...
23 Tauri is the star's Flamsteed designation.The name Merope originates with Greek mythology; she is one of the seven daughters of Atlas and Pleione known as the Pleiades.In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) [21] to catalog and standardize proper names for stars.
It relates the proper distance (which can change over time, unlike the comoving distance which is constant and set to today's distance) between a pair of objects, e.g. two galaxy clusters, moving with the Hubble flow in an expanding or contracting FLRW universe at any arbitrary time to their distance at some reference time . The formula for ...
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 ...