Astronomers theorize that a collision with a smaller companion galaxy near the core of the main galaxy could have led to the unusual spiral structure.

Astronomers estimated that the visible fragments of SL9 ranged in size from a few hundred metres to two kilometres across, suggesting that the original comet may have had a nucleus up to acrosssomewhat larger than Comet Hyakutake, which became very bright when it passed close to the Earth in 1996.

Astronomers had expected to see the fireballs from the impacts, but did not have any idea in advance how visible the atmospheric effects of the impacts would be from Earth.

Astronomers have determined that it is between 6, 000 and 8, 000 years old ; it is approximately one light-year in diameter.

* Astronomers have reported that spectral class T brown dwarves ( the ones with the coolest temperatures ) are colored magenta because of absorption by sodium and potassium atoms of light in the green portion of the spectrum.

Astronomers have made great efforts to find and analyse brown dwarfs in the Pleiades and other young clusters, because they are still relatively bright and observable, while brown dwarfs in older clusters have faded and are much more difficult to study.

Astronomers do believe that the Ordovician – Silurian extinction, the third most destructive extinction on Earth, might have been due to a GRB.

Astronomers think that the sun had about 70 – 75 % of the present luminosity, yet temperatures appear to have been near modern levels even within 500 Ma of Earth's formation, which is puzzling ( the faint young sun paradox ).

Astronomers have long believed that the Magellanic Clouds have orbited the Milky Way at approximately their current distances, but evidence suggests that it is rare for them to come as close to the Milky Way as they are now.

Astronomers have been conducting surveys to locate the NEOs, many ( as of early 2007 ) funded by NASA's Near Earth Object ( NEO ) program office as part of their Spaceguard program.

Astronomers have directly observed protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars in the nebula.

Astronomers have long thought it was quite likely that many undiscovered dwarf stars exist within 20 light years of Earth, as stellar population surveys show the count of known nearby dwarf stars to be lower than otherwise expected and these stars are dim and easily overlooked.

Astronomers have speculated that either intense star formation regions or active galactic nuclei ( which contain supermassive black holes ) may be responsible for the intense dust heating that produces this emission, although the general consensus is that both may be present in most ULIRGs.

Astronomers have paid particular attention to whether earthshine measurement can detect the red edge, a spectral feature that is due to the plants.

Astronomers have postulated that this fluctuating emission comes from the first known intermediate-mass black hole, of roughly 200 to 5000 solar masses.

Astronomers using the Hale Telescope have discovered distant objects at the edges of the known universe called quasars and have given us the first direct evidence of stars in distant galaxies.

Astronomers announce this as evidence that the theory of the cosmological constant proposed, but later discarded, by Einstein may have been right after all.

Astronomers usually express distances in units of parsecs ; light-years are used in popular media, but almost invariably values in light-years have been converted from numbers tabulated in parsecs in the original source.

Astronomers have a number of observational tools that they can use to make measurements of the heavens.

Astronomers have dubbed this object as the Twin Jet Nebula because of the polar jets believed to cause the shape of the lobes.

Astronomers in societies which have alternate traditional names for the planets may use those names in scientific discourse.

* 1957, Mathematician Donald B. Gillies, Physicist, James E. Snyder and Astronomers George C. McVittie, S. P. Wyatt, Ivan R. King and George W. Swenson of the University of Illinois used the ILLIAC I computer to calculate the orbit of the Sputnik I satellite within 2 days of its launch.

Astronomers have used the Bortle Dark-Sky Scale to measure skyglow ever since it was published in Sky & Telescope magazine in February 2001.

* A small building on the site is used by the Haleakalā Amateur Astronomers.

Astronomers used this instrument to study chromospherically active stars, binary stars, and pre – main sequence stars.

Astronomers continue to investigate the astrophysics of a large scale feature of the Milky Way to which he called their attention in 1877, and honor him with its name, The Gould Belt.

Astronomers use Gyr as an abbreviation for Gigayear .< ref name =" sel07 ">< cite id =" Selsis "></ cite ></ ref > Specifically, one Gyr is equal to 10 < sup > 9 </ sup > years.

Astronomers did not observe large amounts of water following the collisions, and later impact studies found that fragmentation and destruction of the cometary fragments in an ' airburst ' probably occurred at much higher altitudes than previously expected, with even the largest fragments being destroyed when the pressure reached, well above the expected depth of the water layer.

Astronomers were surprised by these " hot Jupiters ," since theories of planetary formation had indicated that giant planets should only form at large distances from stars.

Astronomers predict that the four interacting galaxies will eventually merge to form a large elliptical galaxy.

Astronomers organized a large observing campaign which included every available ground-based ( e. g. CCD optical photometry ) and space observatory, including major observations with the Hubble Space Telescope, the Chandra X-ray Observatory, the INTEGRAL Gamma-ray space observatory, and the Very Large Telescope.

Astronomers analysing old data found that Ulysses ' instruments had detected a large drop in the number of protons passing, as well as a change in the direction and strength of the local magnetic field.

Astronomers anticipate an increase of activity in the region of the black hole, giving opportunity for further study, in mid-2013, as it is expected that a large gas cloud will be disrupted by close approach.

Astronomers were surprised at this as the Moon is the only large object in orbit around the Earth and anything else would have been ejected long ago due to perturbations with the Earth, the Moon and the Sun.

Astronomers had long wished for a way to photograph large swathes of the sky quickly for the purpose of surveying the visible contents of the universe and seeing large-scale structures.

Astronomers inferred that the star had been a red supergiant, and had shed a large amount of matter into space, before evolving into a blue supergiant and exploding.

* 2003 – Astronomers Michael E. Brown, Chad Trujillo, and David L. Rabinowitz discover 90377 Sedna, a Trans-Neptunian object.

Astronomers have detected an object traveling through space at half the speed of light, and it is predicted to impact Earth within 30 minutes, wiping out human civilization.

Astronomers believe that centaurs are recent escapees from the Kuiper belt, a zone of small bodies orbiting in a cloud at the distant reaches of the solar system.

* 2002 — Astronomers at the Max Planck Institute for Extraterrestrial Physics present evidence for the hypothesis that Sagittarius A * is a supermassive black hole at the center of the Milky Way galaxy

*" Latitude, How American Astronomers Solved the Mystery of Variation " by Bill Carter and Merri Sue Carter, Naval Institute Press, Annapolis, MD., 2002.