Astronomy Picture of the Day . NGC 4603 and the Expanding Universe . 27.05.1999 . ... Its distance has been accurately measured by astronomers using one of the fundamental yardsticks of the extragalactic distance scale - pulsating variable stars known as Cepheids. ... Two weeks ago, the BATSE instrument on the orbiting NASA Great Observatory Compton detected unusually bright flashes of gamma-rays from a point deep in the southern sky. NGC 6872: A Stretched Spiral . ... The Keyhole Nebula . ...

... 2013 August 26 . Bright Planetary Nebula NGC 7027 from Hubble . Image Credit: Hubble Legacy Archive , ESA , NASA ; Processing: Delio Tolivia Cadrecha . ... Studying Hubble images of NGC 7027 have led to the understanding that it is a planetary nebula that began expanding about 600 years ago , and that the cloud of gas and dust is unusually massive as it appears to contain about three times the mass of our Sun. ... About APOD | ... NASA Official: Phillip Newman Specific rights apply . ...

... Comet Tutorial . ... On July 1, 1993 an image was taken with the Hubble Space Telescope (HST) that clearly shows at least 15 individual fragments in one image frame of the train. ... This made an accurate orbit (or orbits) difficult to determine; however, after numerous observations of the comet, astronmers determined that the comet had passed within 96,000 kilometers (60,000 miles) of the center of Jupiter or 25,000 kilometers (16,000 miles) from the cloud tops during the July 8, 1992, approach. ...

... Comet Tutorial . ... On July 1, 1993 an image was taken with the Hubble Space Telescope (HST) that clearly shows at least 15 individual fragments in one image frame of the train. ... This made an accurate orbit (or orbits) difficult to determine; however, after numerous observations of the comet, astronmers determined that the comet had passed within 96,000 kilometers (60,000 miles) of the center of Jupiter or 25,000 kilometers (16,000 miles) from the cloud tops during the July 8, 1992, approach. ...

In this gallery are many images of Low Surface Brightness Galaxies which have recently been discovered and analyzed. ... The central surface brightness of this galaxy is 24.28 . Malin 2 This galaxy is another huge disk galaxy with a scale length of 15 kpc and a redshift of 15000 km/a. The high surface brightness knot in one of its spiral arms actually has the same color, luminosity and H-alpha equivalent width as the entire Large Magellanic Cloud . ... Truly it is a Low Surface Brightness Galaxy. ...

... For more distant stars we must use other techniques. ... Hence if we see a distant galaxy and can pick out any cepheids lying within it, we can calculate its distance. ... Here then is another method to gauge the size of the Universe and there are yet more. volume at high enough temperature a nuclear fusion reaction sweeps across the white dwarf's surface and eventually we will see a spectacularly bright new star (hence nova) in our skies. ... Why is this relevant to the size of the Universe? ...

LBV M33 varC in M33 . This page is devoted to information on Supernova M33varC in M33 . Basic information on this LBV, including the last reported brightness, on this Supernova can be found on the main page . Information on the original web pages for many of these images can be found on the links web page. ... This object, almost invisible for many years suddenly flared back to life in 2013. An LBV in outburst like this have been known flare into supernovae. ... 15.1 . ... Pedro Re' . ...

... The expansion is measured as a number called the Hubble Constant . ... Our value is about 20% lower than the one got with the Hubble Space Telescope in 1994," said Dr Jim Lovell, leader of the team that made the measurement. The Hubble Constant is named after American astronomer Edwin Hubble, who in the 1920s found that other galaxies were moving away from ours. ... The Hubble Constant links the galaxy's distance with its speed." ... A short run-down on the Hubble Constant: . ...

In autumn 1994, two groups of astronomers announced that they had discovered Cepheid variable stars in a distant cluster of galaxies. ... As the term suggests, variable stars change in brightness over time. ... Variable stars are an ideal way to get high-school students doing real science, with real data, from the real sky. ... a sky chart to find the stars . ... Students can use the nearby stars to estimate the magnitude of Delta. ... Locate the star Delta in Cepheus and estimate its brightness . ...