Related Research Articles
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby galaxies. Galaxy formation is hypothesized to occur from structure formation theories, as a result of tiny quantum fluctuations in the aftermath of the Big Bang. The simplest model in general agreement with observed phenomena is the Lambda-CDM model—that is, that clustering and merging allows galaxies to accumulate mass, determining both their shape and structure. Hydrodynamics simulation, which simulates both baryons and dark matter, is widely used to study galaxy formation and evolution.
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to Earth's. A white dwarf's low luminosity comes from the emission of residual thermal energy; no fusion takes place in a white dwarf. The nearest known white dwarf is Sirius B, at 8.6 light years, the smaller component of the Sirius binary star. There are currently thought to be eight white dwarfs among the hundred star systems nearest the Sun. The unusual faintness of white dwarfs was first recognized in 1910. The name white dwarf was coined by Willem Luyten in 1922.
A proplyd, short for ionized protoplanetary disk, is an externally illuminated photoevaporating protoplanetary disk around a young star. Nearly 180 proplyds have been discovered in the Orion Nebula. Images of proplyds in other star-forming regions are rare, while Orion is the only region with a large known sample due to its relative proximity to Earth.
In the fields of Big Bang theory and cosmology, reionization is the process that caused electrically neutral atoms in the universe to reionize after the lapse of the "dark ages".
An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate objects have been discovered in the Milky Way galaxy and others nearby, based on indirect gas cloud velocity and accretion disk spectra observations of various evidentiary strength.
A rogueplanet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown dwarf.
Photoevaporation is the process where energetic radiation ionises gas and causes it to disperse away from the ionising source. The term is typically used in an astrophysical context where ultraviolet radiation from hot stars acts on clouds of material such as molecular clouds, protoplanetary disks, or planetary atmospheres.
A satellite galaxy is a smaller companion galaxy that travels on bound orbits within the gravitational potential of a more massive and luminous host galaxy. Satellite galaxies and their constituents are bound to their host galaxy, in the same way that planets within our own solar system are gravitationally bound to the Sun. While most satellite galaxies are dwarf galaxies, satellite galaxies of large galaxy clusters can be much more massive. The Milky Way is orbited by about fifty satellite galaxies, the largest of which is the Large Magellanic Cloud.
A sub-brown dwarf or planetary-mass brown dwarf is an astronomical object that formed in the same manner as stars and brown dwarfs but that has a planetary mass, therefore by definition below the limiting mass for thermonuclear fusion of deuterium . Some researchers call them rogue planets whereas others call them planetary-mass brown dwarfs. They are sometimes categorized as Y spectral class brown dwarfs.
The Tolman–Oppenheimer–Volkoff limit is an upper bound to the mass of cold, non-rotating neutron stars, analogous to the Chandrasekhar limit for white dwarf stars. Stars more massive than the TOV limit collapse into a black hole. The original calculation in 1939, which neglected complications such as nuclear forces between neutrons, placed this limit at approximately 0.7 solar masses (M☉). Later, more refined analyses have resulted in larger values.
Active asteroids are small Solar System bodies that have asteroid-like orbits but show comet-like visual characteristics. That is, they show a coma, tail, or other visual evidence of mass-loss, but their orbits remain within Jupiter's orbit. These bodies were originally designated main-belt comets (MBCs) in 2006 by astronomers David Jewitt and Henry Hsieh, but this name implies they are necessarily icy in composition like a comet and that they only exist within the main-belt, whereas the growing population of active asteroids shows that this is not always the case.
HD 100546, also known as KR Muscae, is a pre-main sequence star of spectral type B8 to A0 located 353 light-years from Earth in the southern constellation of Musca. The star is surrounded by a circumstellar disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance of around 47 AU.
In physics, the proton-to-electron mass ratio is the rest mass of the proton divided by that of the electron, a dimensionless quantity, namely:
A circumbinary planet is a planet that orbits two stars instead of one. The two stars orbit each other in a binary system, while the planet typically orbits farther from the center of the system than either of the two stars. In contrast, circumstellar planets in a binary system have stable orbits around one of the two stars, closer in than the orbital distance of the other star. Studies in 2013 showed that there is a strong hint that a circumbinary planet and its stars originate from a single disk.
Strategic Explorations of Exoplanets and Disks with Subaru (SEEDS) is a multi-year survey that used the Subaru Telescope on Mauna Kea, Hawaii in an effort to directly image extrasolar planets and protoplanetary/debris disks around hundreds of nearby stars. SEEDS is a Japanese-led international project. It consists of some 120 researchers from a number of institutions in Japan, the U.S. and the EU. The survey's headquarters is at the National Astronomical Observatory of Japan (NAOJ) and led by Principal Investigator Motohide Tamura. The goals of the survey are to address the following key issues in the study of extrasolar planets and disks: the detection and census of exoplanets in the regions around solar-mass and massive stars; the evolution of protoplanetary disks and debris disks; and the link between exoplanets and circumstellar disks.
Triangulum II is a dwarf galaxy close to the Milky Way Galaxy. Like other dwarf spheroidal galaxies, its stellar population is very old: the galaxy was quenched before 11.5 billion years ago. It contains only 1000 stars, yet is quite massive, having a solar mass to light ratio of 3600. This is an unusually high mass for such a small galaxy.
HD 169142 is a single Herbig Ae/Be star. Its surface temperature is 7650±150 K. HD 169142 is depleted of heavy elements compared to the Sun, with a metallicity Fe/H index of −0.375±0.125, but is much younger at an age of 7.5±4.5 million years. The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star.
A circumplanetary disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. They are reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.
GRB 221009A also known as Swift J1913.1+1946 was an extraordinarily bright and long-lasting gamma-ray burst (GRB) jointly discovered by the Neil Gehrels Swift Observatory and the Fermi Gamma-ray Space Telescope on October 9, 2022. The gamma-ray burst was around seven minutes long, but was detectable for more than ten hours following initial detection, and for several hours was bright enough in visible frequencies to be observable by amateur astronomers. Despite being around two billion light-years away, it was powerful enough to affect Earth's atmosphere, having the strongest effect ever recorded by a gamma-ray burst on the planet. The peak luminosity of GRB 221009A was measured by Konus-Wind to be ~ 2.1 × 1047 J/s and by Fermi-GBM to be ~ 1.0 × 1047 J/s over the 1.024s interval. A burst as energetic and as close to Earth as 221009A is thought to be a once-in-10,000-year event. It was the brightest and most energetic gamma-ray burst ever recorded, being deemed the "BOAT", or brightest of all time.
References
- ↑ Ellingsen, Simon Peter (1996). Class II methanol masers in star formation regions (phd thesis). University of Tasmania.
- ↑ Ellingsen, S. P.; von Bibra, M. L.; McCulloch, P. M.; Norris, R. P.; Deshpande, A. A.; Phillips, C. J. (11 May 1996). "A survey of the Galactic plane for 6.7-GHz methanol masers -- I. l = 325 -335 ; b= - 0Formula53-0Formula53". Monthly Notices of the Royal Astronomical Society. 280 (2): 378–396. arXiv: astro-ph/9601016 . doi: 10.1093/mnras/280.2.378 . ISSN 0035-8711.
- ↑ Ellingsen, S. P.; Sobolev, A. M.; Cragg, D. M.; Godfrey, P. D. (1 November 2012). "Discovery of Two New Class Ii Methanol Maser Transitions in G 345.01+1.79". The Astrophysical Journal. 759 (1): L5. arXiv: 1209.5744 . Bibcode:2012ApJ...759L...5E. doi:10.1088/2041-8205/759/1/L5. hdl: 10995/51230 . ISSN 2041-8205. S2CID 118344109.
- ↑ Ellingsen, S. P. (10 February 2006). "Methanol Masers: Reliable Tracers of the Early Stages of High‐Mass Star Formation". The Astrophysical Journal. 638 (1): 241–261. arXiv: astro-ph/0510218 . Bibcode:2006ApJ...638..241E. doi:10.1086/498673. ISSN 0004-637X. S2CID 13889056.
- ↑ Ellingsen, Simon; Voronkov, Maxim; Breen, Shari (29 December 2011). "Practical Limitations on Astrophysical Observations of Methanol to Investigate Variations in the Proton-to-Electron Mass Ratio". Physical Review Letters. 107 (27): 270801. arXiv: 1111.4708 . Bibcode:2011PhRvL.107A0801E. doi:10.1103/PhysRevLett.107.270801. ISSN 0031-9007. PMID 22243297. S2CID 28086251.
- ↑ Ellingsen, S. P.; Voronkov, M. A.; Breen, S. L.; Lovell, J. E. J. (1 March 2012). "First Cosmological Constraints on the Proton-To-Electron Mass Ratio from Observations of Rotational Transitions of Methanol". The Astrophysical Journal. 747 (1): L7. arXiv: 1201.5644 . Bibcode:2012ApJ...747L...7E. doi:10.1088/2041-8205/747/1/L7. ISSN 2041-8205. S2CID 118465837.
- ↑ Gray, Robert H.; Ellingsen, Simon (20 October 2002). "A Search for Periodic Emissions at the Wow Locale". The Astrophysical Journal. 578 (2): 967–971. Bibcode:2002ApJ...578..967G. doi: 10.1086/342646 . ISSN 0004-637X.
- ↑ "Supporting space infrastructure growth". Department of Industry, Science, Energy and Resources. Archived from the original on 10 October 2021.
- 1 2 "Simon Ellingsen - Profiles". University of Tasmania, Australia. 16 April 2012. Retrieved 16 April 2021.
- ↑ "ICRAR welcomes new Executive Director". www.uwa.edu.au. Retrieved 9 April 2024.
 | This article needs additional or more specific categories .(April 2021) |
| Academics | |
|---|---|
| People | |
